REVIEW: Everything Wrong With A GM 6.5 Detroit Diesel

What could possibly be wrong with the 6.5 GM-Detroit diesel?
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[@DEBOSSGARAGE]

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[@trolltime1862]

no

[@mckjew]

I wish rich lived closer, I love this channel

[@tomlucasrccrawlers9108]

Kinda odd an old 6.5 needs to meet smog.

[@calholli]

On the smaller valves having "more torque" -- I think they just mean that the engine is set to run at a lower max RPM, which gives you more TIME with the valve open, so it's already sufficient in making the max torque. When you jump to higher RPM's, the valves open and close much quicker, so then you need to maximize the air flow itself, because you're racing against the clock. It's not that a bigger valve gives you more air--- the cylinder volume is the same either way; it's going to pump what it pumps either way. But again, the larger valves allows you to open and close them in a shorter time frame and still sufficiently fill the bore.. which lets you rev higher, since it can fill faster now............... So again, link your valve size to the TIME it takes to fill the bore, not that it adds more volume; it adds the same volume in a shorter amount of time. cheers

[@Desert515]

Would you be interested in putting a 5.9 into a Hummer H1

[@shadymaint1]

Most impressive thing I've seen out of a 6.5 was when we had a HMMWV engine run away. Some guys were messing with the injection pump trying to get more power out of it. When they fired it up it ran away and wouldn't shut down. Figured they would just let it blow up and put a new motor in it. Insulation in the transmission tunnel caught fire and it didn't take long for the whole thing to go up. Have to give the 6.5 credit. It never shut down until the aluminum intake manifold melted and got sucked into the motor.

[@MrGGPRI]

When the injection pump cover is installed and the he lever does not connect properly with the rotating shaft, the engine runs away.

[@jonathanwright5550]

Thats pretty impressive

[@wes11bravo]

Vehicle not fully mission capable if it's on fire.

[@PNW_K5DIESEL]

If the shut-off solenoid lever doesn't get put back right, it pushes on the governor wrong. You can shut it off by clamping the fuel return for the injection pump and making it so fuel cannot return to the tank.

[@shadymaint1]

@@PNW_K5DIESEL we tried shutting off the fuel. Didn't help. Was running off its own oil at that point.

[@seansouth1556]

The 6.5 does have a cross over tube that feeds back up the bottom of the exhaust manifold and out through the turbos down pipe feeding the turbo from both banks

[@whatsBF3]

yeah not sure what they thought the pipe casted into the manifold did at 5:50

[@dadi2450]

31:02

[@kenleppek]

​@@dadi2450yep

[@shaun.h.barlow]

Just talking out there a$$

[@ryanhoover7661]

kind of hard to watch the rest of the video if they honestly thought the turbo was fed by one bank lol

[@radradR0bot]

The idea behind smaller valves giving more torque has to do with air speed. Smaller port means higher air velocity, so you actually get slightly more air at lower rpm. I used to tune motorcycles, and you could get more bottom end torque with a slightly smaller carburetor

[@calebthompson1657]

Higher pressure with smaller ports, but less air. Larger ports lower pressure, but more air. Kind of like how a pressure washer has a ton of pressure that can get more work done with less water than a hose can do at a lower pressure with more water flow. That's how it was explained to me. Anyway. Makes sense So does your explanation

[@thegodfreyspecial423]

I believe this is the answer - velocity and better mixing in the combustion chamber at low RPMs.

[@exoticcreature3059]

Not so with diesel. There is no mixing air and fuel together. There is no atomization of fuel with the incoming air. That is done by the injector and tips. Air movement and velocity can impact flame front behavior in diesel engines, which may help. I'm no expert. But air velocity is not beneficial to diesel engines for those first two mentioned purposes simple because it doesn't work that way.

[@zf9903]

This theory applies primarily to engines which introduce fuel prior to the intake valve. The closer to the valve, the smaller the benefit. High velocity improves fuel atomization. Diesels can get away with smaller valves because 95% of them came with turbochargers, meaning air is crammed rather than drawn into the cylinder, rendering valve size largely irrelevant, and smaller valves are easier to package and cheaper to manufacture. To illustrate this point, 1982 HD 6.2’s came with “large valve” heads. This was a single-year feature that was dropped because every one of the large valve heads cracked and became scrap metal. Smaller valves remedied this for the most part. If the large valve heads hadn’t been problematic, they probably would have become the standard for HD 6.2/6.5’s. Bear in mind that aftermarket turbo kits were prevalent from their inception, but GM only turbocharged the 6.5 starting in ‘93, so 6.2’s were never mass-produced with a turbo. Wouldn’t be surprised if dealers installed Banks kits before then, but it wasn’t something GM/Detroit designed for. Now, I’m not saying smaller valves wouldn’t have some benefit. I’m sure the velocity would still help some with mixing, but diesel is a relatively heavy fuel and these engines have relatively low injection pressure, so the atomization is relatively poor compared to what would come later. The IDI design helps account for this in the precombustion chamber design, which induces swirl using the injected fuel. Intake air velocity plays a relatively small role in this, most of the work is done by the 18-21.5:1 compression ratio squeezing the crap out of everything in there. I guess what I’m saying is the small-ish valves in these engines is a byproduct of multiple unrelated aspects of the design, as opposed to a special feature. It may help, it may not, but I don’t think it was intentional because there’s evidence to suggest GM/Detroit would have done otherwise if they could’ve.

[@robertmason8341]

@@zf9903excellent explaination and analysis backed up by thoughtful examination of the evidence to gm’s engineers engineers design/intent. Gale just did a video where he’s talking with the older guy, his friend from Garrett I believe about the history behind his kit for these engines and the marketing and involvement directly with GM and their dealerships. Pretty interesting video. Long format but it’s in there. Actually he’s done a few with the guy I’m talking about, can’t remember his name off the top of my head. IMO Gale Banks is the man when it comes to diesels. And funny too. His reaction to some of the youngsters work/videos hilarious!

[@victorrobison5069]

Rich, I used to maintain a fleet of 6.5 turbos in a fleet that belonged to a tree service. All of the diesel pick-ups were purchased used, with mileage that ranged from 189,00 to 260,000 miles. We would do a ring and bearing service, send the turbo out for bearings and seals, and check the heads. They always got the pump mounted driver relocated, and usually the board in the module connector was replaced also. This seemed to solve most of our fuel problems, but hard acceleration in the middle of an Arkansas summer was still going to produce a little smoke. The heads would crack in every cylinder between the exhaust and the intake valves, ( very fine cracks, cracks nonetheless )but whether we sent the heads out for repair or just re-installed them with new gaskets, the engines ran well. Two things to know is that the end of the push rod with the pink ring around it belongs at the top, and the thick fat clunky washer is the spacer between the camshaft timing sprocket and the end of the cam. To put the wrong end of the push rod up causes rocker arm failure at about 700 miles after re-assembly, and to leave out the cam spacer causes timing chain damage about 1,000 miles after assembly. My service truck was a cable throttled 1991 3/4 Chevy (no PMD required) and was very reliable. The big weak spot on these trucks was the lift pump, and it would be folly to blame that on what turned out to be a pretty good engine.

[@turbotaco3244]

This guy 6.5’s. I’m partial to the 6.5’s and have a 94 truck I’ve been slowly upgrading. I love them. I think they’re underrated but most of all misunderstood. The thing about a 5.9 is you can neglect it and still get half a million miles from it. The 6.5’s do not take abuse. And really that’s where the bad reputation comes from. Dirtbags neglecting their trucks and complaining they’re junk. Certainly there’s something to be said about a motor that can survive abuse. But the 6.5 is a classic sounding engine.

[@stkcattleandhay]

​@@turbotaco3244I have seen plenty of blown up/worn out 5.9's in pickups that have had their guts pulled out of them. That said, my case tractors have 5.9L cummins engines and they easily last 10k hours.

[@PNW_K5DIESEL]

@turbotaco3244 facts, kinda surprised my friend's 92 k2500 was still running with a melted piston and cracked cylinder wall on cylinder 8. He pulled it because of the coolant consumption. Both the 6.2s in my 84 c20 and 88 k1500, and the 6.5 I swapped into my 82 k5 have been very reliable. My k5 even has a hx40wii turbo that's hit 20 psi of boost (at roughly 1000 degrees EGT), maxed out db2 4911 injection pump, airdog lift pump, and a few other minor things. She's very fun to drive, but she's currently getting manual swapped.

[@bryanst.martin7134]

I'm retrofitting an 86 Coachman from 460/C6 to the 6.5/4L80E. Should be a plus to the fuel economy. Only mod will be an intercooler and improved intake pipe. I may go with the Ford electric vacuum pump for turbo control. I used to think it was "rattely" till I heard the Ford 7.3 at idle. :-) Forget drive thru's. Not many places worth driving through anymore. And with the RV, you can't anyway. I would hear people saying "ooh I have always wanted to get one and go cruise!" When I tell them it gets 5 mpg, they tell me I crushed their dreams! Not my fault. They just need much deeper pockets. ;-) Hopefully I will see a major improvement. 3x would work.

[@MrPoogman]

Hahaha as a mechanic I love how exact you are on the distance to failure if incorrectly assembled 😂😂 (I won’t ask how you know)

[@vikipapa179]

On valve sizing in a nutshell: smaller valve and smaller intake: higher air velocity on lower rpm, but chokes out on high rpm, bigger valve and intake: slow initial (low rpm) air speed, but higher rpm it starts to "flow"

[@skonky]

vtec on a diesel

[@Mountain-Man-3000]

Yep. No need for large valves on small ports.

[@persistentwind]

Thanks for this explanation - this makes sense to me.

[@ericmorin9613]

Well said

[@tnrancher3913]

No, the 6.2 had big valves and ran well. however, sometimes they would crack between the valves, so they put smaller valves in so more material was around the valve to help prevent cracks, the 6.5 got even smaller valves for this reason. Later redesigns would fix the problem without using smaller valves. Even so the cracks that can develop are usually not a problem even though it isn't ideal. We've had big valve 6.2 j code engine go close to a million miles with cracks

[@aarontuerk7829]

Ive had an lb7 duramax , 5.9 p-pump cummins but my favourite will always be my GM 6.5. its that crisp idi idle clatter that is ingrained in my ears for life.

[@robertwarren110]

Same I've had an LLY and I have an LML now and I still love to hear one clatter as it goes by.

[@yourfriend9048]

im still driving my 1995 Chev K2500 with a 6.5L i take good care of it. it always gets the job done. SOLID ENGINE! the 6.5L TD needs to be brought back. less power = more reliability and fuel efficiency.

[@johnroethel5527]

Had a 1993 GMC one ton dually with a 6>5. Heads were changed when new cause of a recall. Truck went 778000 Miles before it went bang. Miss that truck to this day. Merry Christmas to all

[@stevebuttrum]

Got a 93 with nv4500 and 34k hoping to double it

[@stevebuttrum]

340k

[@katiejameson]

Uh, ok, this is going to be a bit long but... I have worked on and owned a LOT of these 6.5 powered trucks and a few 6.2 trucks. These engines are very robust, we're built for fuel economy and longevity, though many say they are junk and I like to say, just like people who day Subarus are junk, you just need to do maintenance, especially preventative maintenance. A few of the best upgrades for these are the Duramax fan (sing heat kills these) and a Flight Systems PMD (purchased from Quadstar Tuning) with a relocation kit and a #5 resistor. Getting it down in the bumper where the heat sync can get fresh cold air is best. DO NOT continue to use Dexcool in these are that causes issues. There is a cross over pipe that links that drivers side exhaust manifold to the passenger so no, the turbo doesn't feed off only one side. Currently, Quadstar Tuning and Leroy Diesel make/sell some of the best products for these engine. John Faddis is the owner of Quadstar Tuning and actually makes tunes in house that will maximize the efficiency and longevity of these. With his help, 6.5s can now push over over 500hp. Also, there are no such thing are injectors that make more horsepower for a 6.5. It's all a myth!! The fuel is controlled by the injection pump. The marine injector is designed to run longer and more efficient at higher rpm

[@tonywimbish8410]

I have a 6.2 M1008 military truck I want to turbo it

[@gorak9000]

You missed a big one - at one point he's talking about shiny spots on the cylinder walls and says "that's where the injector sprays" - the 6.5 is an indirect injection engine - it injects into the pre-cumbustion chamber in the head, not into the cylinder at all. Like a [hand smack forehead] moment there - clearly this guy is pretty clueless

[@DjWhitehead-rv8ki]

I think it's funny that he made the Video about a 6.5 but anybody who owns a 6.5 knows they have a crossover pipe so both sides feed the turbo. Nice to see 6.5 getting some attention in 2023 though

[@waynebinky]

Mine's in a 1994 gmc with 114,000kms. She just turned 30 years old. Inherited it about 4 years ago from my Dad. Never winter driven so no rust at all and stored indoors since it was 2 years old. Oil lines replaced with SS, Pump module relocated to behind the bumper, manual turbo dump installed, and exhaust recirc plugged. Not much for power but I haul soil and wood during the spring and summer then park it in the garage again til the next year. Only diesel engine around that has amber oil for it's annual oil change. I have a Carter lift pump for it but haven't gotten around to installing it.

[@jeremykamel9655]

I worked on a LARGE fleet of generators with Yanmar and Kubota diesels. They ran at low loads for weeks on end while powering 40’ refrigerated can going cross country on the railroad. They carbon up and wouldn’t pass compression tests. So we’d run marvel mystery oil in them and run them at 100% of their rated load for 15-30 minutes. 95% of the time they’d clean up. Then when we pull the injectors to run compression we’d run the injectors through a sonic cleaner. Oh, pro tip. If you can’t get injectors or glow plugs out due to carbon build up. Get it running and mist water into the intake. It’ll steam clean the upper cylinders and remove carbon deposits allowing the injectors and or glow plugs to come out.

[@iamthesargent]

One thing I didn't hear mentioned is that these blocks (6.2 and 6.5) LOVE to break starter bolts, and you have to use the specific GM type as a replacement after extracting the old ones. I love my 1989 6.2 J code engine except for that problem. From the story I was told by the original owner's fleet mechanic, it was on its second set of bolts before those also broke and they decided to auction it off. A few days in my driveway with a couple new creative words and it had new bolts along with the support bracket being tightened up correctly. I began having problems again a few weeks ago when i heard the starter grinding when starting and found the brace bolt rattled off and the main two bolts were starting to work loose. Checked the bolts for cracks and then tightened them down along with a replacement brace bolt and its been working fine again.

[@johnolver3217]

Yep with good batteries both engine would snap those bolts off. That bracket was very important to save a lot of heart ache. I have a 6.2 with 800000km on it an a 6.5 with 500000km on it. 6.2 I’ve changed oil pan and rear main seal, timing chain at 450000km few glow plugs an updated the fuel filter to the 6.5 along with the 6.5 grey glow plug controller other then that nothing internal

[@doughboy1966]

Biggest issue with breaking starter bolts was the absence of the support bracket that many had removed.

[@rileymcfadden6382]

And even the “upgraded” arp starter bolts brake too I’ve seen that a few times as well

[@grindersandgears3445]

@@rileymcfadden6382 I find that hard to believe, unless the brace is missing....

[@PNW_K5DIESEL]

Bolts breaking are cause by that missing bracket, a loose bracket, worn knurled part on the bolts, missing washers, or over tightened bolts. Any of that can also cause a piece of the block to break off, too. I've seen that happen on the old 6.2 from my k5 with a previous owner. The knurled part on the starter bolts are also used to hold the starter better, and if the starter is replaced, it's better to replace the bolts, too. Missing washers for the bolts also allow the bolts to bottom out in the holes and cause the starter to not be bolted down all the way.

[@59MackB61]

We did a lot of 6.2s and 6.5s for folks back in the day. Agree on all fronts! The 6.2 had big valve heads in higher GVW and smaller valves in lower GVW when it was introduced. The big valve heads were more prone to cracking and GM ended up with a smaller valve in everything. The big valve head did not have much material between the valves. I have one with about 300,000 on it with big valve heads, it has never been overheated and it has not bothered. GMC offered a Banks Turbo 6.2 when you ordered a new truck. My uncle had one in ‘92 and it was better than the 6.5 on all fronts! Mr. Banks got it right on intake and exhaust. We saw broken cranks in 6.2s, they always had a cracked block that let the crank flex and you know the rest. Timing chains were a common problem on 6.2s if folks did not change their oil. If it was a truck we serviced, it had a two quart filter, 30W in summer and 15W-40 the rest of the year. We saw lots of them go over 200,000, rust got them by then. Being a pre-chamber engine they would run at higher RPM. In a 2500 or3500with 4.56 gears they were singing all the time. This is hard to imagine now, but when the 4L80 came out it was not what folks needed. If the truck was trailering or working hard in overdrive things went south quick. The aftermarket did a great job fixing GMs transmission issues. As good as the Turbo 400 is, these diesels needed an overdrive. Great Video and Thanks for sharing! Merry Christmas !

[@Shiftyspeedshop]

I have told people for years that the 6.2 and 6.5 like a little RPM. In the military trucks I have driven, we certainly gave them the RPM, and they did pretty well for what they are.

[@Wingnut353]

@@Shiftyspeedshop The exceptions is the M1009/K5 blazer but its really just for putting around the base, and it does sing pretty good at interstate speeds still with only a 3 speed on it .... an overdrive would still be usefull on it with a 3.08 rear end on it. The problem then is just not enough gears at the low end for towing.

[@59MackB61]

GM built lots of 1/2 ton 2WD and 4WD trucks with 3.08 axles, a 700R4 and a 6.2. If the 6.2 ran good it would detonate the overdrive cluster in short order. Not unusual to get 22-24 on the highway with a 4WD 1/2 ton 6.2 back in the day. Most folks left them out of OD unless they were on the interstate. They had a side loader 4 speed with the same ratios as a 700R4. That was a good combo with 3.42 axles and a 1/2 ton truck with 15” tires. Anybody else remember when trucks had 15” tires?

[@ChrisHarding-lk3jj]

​@@59MackB61What do you mean by overdrive cluster in the 700r4? The only difference between 3rd gear and 4th gear in a 700r4 is the application of the 2-4 band.

[@ChrisHarding-lk3jj]

About 2 years ago I was at my local pick a part yard and there was a 6.2 powered suburban with the banks turbo kit. I purchased the entire turbo system and I have had many people try to buy it from me.

[@scottymoondogjakubin4766]

I had 2 gm 6.2's in my fleet ! They both had over 650,000 miles ! They both still ran like a champ but got retired and sold at auction !

[@pling501]

YES! This is my favorite sounding diesel i've had a few of them throughout the years.

[@rangerismine]

I have had a few military chevy pickups with the 6.2. The first things to do when buying one were 1. New balancer, 2. Check for a starter brace, 3. Change the oil cooler hoses. Besides that, I never had a problem with the 6.2. It eats used motor oil, kerosene, atf and diesel without issue, and moves the truck pretty good since I turned the fuel screw 1/4.

[@richardcoombes5292]

I’ve done a nv4500 swap to mine and it works great on 37s

[@1oldskoolluvr]

New balancer & the starter brace are both well known points of failure on the six2, but the oil cooler lines is a new one. Was the reason for changing the cooler lines due to lines being clogged over time?

[@Anubis78250]

@@1oldskoolluvr They always end up leaking over time. The problem is that they are not a standard thread, so it becomes more involved than just swapping in new lines. You either need to go with adapters/custom lines/re-cut threads, or pray you can find a set of new old stock somewhere as they were long ago discontinued by GM. It's just an issue you're better off dealing with upfront instead of the side of the road.

[@1320fastback]

I drove a CUCV in the early '00s and it was great, until the balancer let go and broke the crank.

[@Anubis78250]

@@1320fastbackThe original design by Detroit Diesel called for a forged crank. GM decided to go with case hardened instead to save money. It usually isn't an issue until you add a turbo, or as you found out, the balancer deteriorates. Most recommend fluidampr as a replacement. I looked into an aftermarket forged crank some years ago (maybe a decade) and I was able to find one company making them, but I don't recall the name or have any current info.

[@DDescalchuk57]

I have a soft spot in my heart for the ol Detroit diesel 6.5 have had a few of them and really enjoyed them. Was substantially more reliable then my lb7

[@southernyankeehomestead3230]

If I remember correctly the 6.2 had some insane compression on it too. Something like 22 or 23:1 if I remember correctly severely limiting the amount of boost you could run. I think the 6.5 dropped to the 18:1 range so a turbo was more viable. I had both and liked both for different reasons. In my 82 K5 Jimmy I had the 6.2 which was not great for towing but with the suburban 42 gallon tank and a top speed around 70 if I was cruising flat land I could get almost 1000 miles to a tank. I would regularly get 25+mpg ... not quickly...but for cruising it was great and super reliable. The 6.5 that I had in my 2001 suburban 2500 was a great tow rig/camper. I would go to the mountains with my Toyota once or twice a month and the burban would fit a twin air mattress in the back. One of those propane heaters and I could sleep in freezing weather with the windows cracked and not need a sleeping bag! Plus it towed really good and got respectable fuel mileage empty. Too bad the PMD tried to kill me by shutting off the engine on the interstate. Manual brakes suck when the hydroboost stops working.

[@johneckert1365]

The 6.5 had very high compression ratio as well. All pre-combustion chamber diesels do.

[@Anubis78250]

21.5 to 1, I still get about 22-24mpg in mine, that's with the original TH400 3-speed 3:08 rear and 33" tires.

[@killstrees]

I love the sound of the 6.5. Have a buddy from high school who still has his and it has a 5 inch turbo back exhaust and you know where he is when he's driving because you can here it a long ways away. It's awesome!

[@taylorsutherland6973]

They sound like marbles rolling down a staircase.

[@richardfitzwell6579]

Hahahaah

[@zombienectar]

I have a 1992 6.5 in a 1985 Chevy K10. 599 block with db2 4911 pump. No pmd. Mechanical of course. 24 MPG ( 10 litres per 100 k ) . 750 lbs. Love my 6.5. Love the sound of it. Not a stump puller but she will take you anywhere you want to go and then bring you back.

[@compressorhead02]

So glad to see you actually take a look at this engine so many people just dismiss this engine as junk just because it doesn't make 400hp, if you understand where it comes from and if its in the right application these are fine motors and i love learning about them

[@gadsdenconsulting7126]

My son told me they are throw away engines. My response to him was pretty much what you posted. It's no 5.9 Cummins like my '04 sled-puller truck, and it's no 6.7 Cummins, like my '21 2500. But it was never meant to be. It does a fine job in its role!

[@nou8257]

And they are much cheaper to work on then most more modern diesels.

[@RTDragonCommando]

We had a 2001 Chevy Express 3500 that had the PMD go on the highway. It shuddered, the engine light came on, and then it started accelerating on it's own and blowing a huge cloud of black smoke. Did the research when we got home, found out about the relocation kit, but my father decided he trusted the dealership more than me. So it went again less than a year later, also on the highway, and then finally got the relocation. Only other problems we had with that truck weren't engine related. Tail light wiring went bad on one side, and the diff exploded on the highway.

[@rotorhead5000]

Good to know, a friend of mine has a similar vintage van chassis short bus that had a runaway shortly after I helped her through the misery of valve cover gaskets. I'll have to pass this on.

[@southernyankeehomestead3230]

You were luckier than I was... when my PMD went bad on my 2500 suburban the engine would shut off! Not fun on the interstate with a 7000 pound vehicle! That's when I learned to hate the hydroboost. 2 feet on the brake pedal lifting my butt off the seat trying to manually get that burban to stop!

[@johnhinston958]

Chevy trucks have horrible wiring issues my 2000 express box truck with the 6.5 is always blowing out lights in the back

[@Tuchodi8004]

I’m omfg finally !! I daily a 6.2 na a lot. Thing is gutless but very reliable and good on fuel.

[@skstibi]

I got rid of the DS4 pumps and went to mechanical DB2 on my 6.5 trucks. They don't make big power but a few tweaks and they perk up considerably and turn into REALLY nice running trucks.

[@stevebuttrum]

I've got a db2 is it worth cranking up the fuel?

[@sam49921]

One of the first engine jobs that I got to do myself was changing a 6.5 in a gmc van cab box truck, it had a rod cap hanging out of the oil pan. Took almost a week but when i finally went to start it the sound was wonderful, and the first test drive without the doghouse scared the hell out of me with that turbo screaming right next to my leg. I kept that rod cap and even see the rig around town every few months. Not too bad for a 17 year old kid

[@seancollins9745]

The 6.5 was a good engine, for the time in which it was designed and for the design objectives it had, cheap to produce, uses big block chevy acessories etc, light weight " it is a light engine, and cheap to produce. The optimizer 6.5 version from general dynamics was a beast mode version of the 6.5 and had many upgrades.

[@paullucas3]

Is a good engine, I’m running my shop truck 99 till the frame breaks in half. Nice fuel economy and love how it just runs…

[@mdwdirect]

Best “Everything wrong with” video ever. The dynamic and dialogue between you and Scott is fantastic to watch.

[@ShadowOppsRC]

There is a cross over pipe from the left bank for the turbo.

[@juanfo7307]

You can see the manifold on the tray at the biginning of the video.

[@stkcattleandhay]

6.2L engines were cast in 660, 599, and 929 castings. 599 castings came out in 89 and in 92 they bored the 6.2L to the 6.5L. In 1994 the 6.2L was no longer available but there were GM crate 6.2's through 95 with the 929 being the last yr. 6.5's could be had with 599, 529, 141, and 506 castings. In '00 the 506 casting right was bought by Navistar and the casting was improved. The turbo on the 6.5L was too restrictive and the back pressure held heat which caused head gasket failure and head cracking. The hx35 and hx40 turbos work very well on a 6.5L. Failed harmonic balancers will result in cracked mains and cracked cranks. There are fluid dampners and billet crank pulleys that help this issue. The 6.5L will never hold up to the same power as a 5.9L cummins but they can be made reliable and to have decent enough power for daily driving and being a solid work truck.

[@deltafreshrelics1660]

Everyone listen to this guy. All good info here. I would add to watch the oil cooler lines, starter brace, and relocate pmd on 94+ models. 6.2/6.5 are great engines. Check the stats for the 97 model year big 3 trucks and you’ll see that the 6.5 was right on par with Cummins and power stroke for output if you can believe it. 200 HP and 440 ft/lb in a smaller lighter footprint and better mpg. I’ve loved every one I’ve ever owned. I’ve had 3 6.2/6.5 trucks and more engines than I can remember just to mess with. Right now I have an optimizer in a 95 k2500 suburban with a low mileage 599 6.5 on the stand running in the shop. A love affair.

[@carlthor91]

The center web cracks where also in the 6.5, that was supposedly cured by a stiffener plate. The AM General version 6.5, called a 6500, used in the later HMMWV, had a deeper block skirt. That cured the center web cracking issue.

[@sixstringsid]

Nope, they still crack. both the 6500 and the p400. Lock and Stitch make a repair kit that is 100% permanent, about $400

[@carlthor91]

@@sixstringsid Yeah, when my 1994 K2500 Turbo was new, the local farmers would haul 30,000 lbs of hogs to the packers, with their's. They would leave the trans in top gear. Four or five trips like that would do them in. Mine lasted because it was a long distance highway machine, not pulling any weight, just +80 mph, the 1800 miles round trip to work, every month.

[@haydenpearson7203]

@@sixstringsid does the repair kit also prevent future cracks from arising?

[@sixstringsid]

@@haydenpearson7203 I would just buy a brand new block from China. The machine work is very nice and has higher nickel content. $1000 plus shipping

[@F3ST3Rfilms]

You coulda told me y'all had a 6.5 Detroit video in the works when i was telling ya about mine haha! Thanks again for stopping by the shop! Was great getting to meet y'all in person! -Harley

[@normancurd8719]

the humor between the both of you makes you feel like we're there. feels like I'm hangin with my boys as well.

[@2ndMomentumGarage]

Just turned 300,000 on the 6.5 suburban I’m daily driving in 2023.

[@E_L12]

I love the candid-ness of this video. The jokes about the KZbin comments & banter, excellent

[@DDescalchuk57]

When looking for a 6.5 the L65 was the best but the marine application 6.5 is pretty dang good and obviously the 6.5 was good enough to be the standard option for the US military. There’s a twin turbo 6.5 that ran 190 mph in the boniville salt flats. 5000 rpm redline 80% of the water jacket filled with block hardener. God do I love ‘‘em lol

[@shaun.h.barlow]

Military grade equals cheapest bidder aka pile o shite ask any military mechanic.

[@jdrok5026]

​@@shaun.h.barlowthey still have to pass some basic standards tho

[@Livetowrench]

Buddy!!!! Thanks Scott for showing how to engrave rods instead of hard to read stamps... wicked

[@nickdevost]

What a great side convo about towing ad turbos. I'd love to see more content just chatting about stuff like that

[@larryreece1403]

Great discussion! Reminds of being back at Tech School a million years ago! Torque is the answer! Regardless of the question!

[@Pinehollowmechanical]

I enjoy the6.2 6.5 stuff a lot. Hope to see more of that rebuild

[@jpl57210]

Only thing i ever repaired on these(mostly) were the fuel systems. Stanadyne pump, rail pump, etc. These were bullet proof. GM tech here.

[@cbr600rx7]

I did video on my little channel going over the 6.2/6.5 a few years ago on the pros/cons of them and agree with you. Just a few small points. The 6.5 uses a cross over tube from the driver to passenger side. They only produce like 8psi stock but can support mid teens fairly reliably. Head studs for a 6.5 from ARP are fairly cheap compared to many others. My personal experience working on military and civilian versions is they tend to be fairly reliable. I am personally owned a 6.5 turbo with close to 400,000 miles on a stock bottom (received heads at 330,000) and worked poor military 6.2/6.5 M998/M1151/M1114/M1097s to death. The only real issues that came up regularly with the military versions were fuel injection issues and this mostly because of JP8 fuel on top of extremely high temperatures (110F+ running WOT for hours). On the 1151s that had sorry rear mounted turbo set up we would turn the injection pump 2-3 flats, straight pipe the exhaust, and pin/weld the wastegate shut. These trucks were close to 14,000lbs fully loaded and you could add another 4000lbs if they a mine roller up front. They needed all the help they could get. Operators would literally just keep the throttle pined to the floor running up and down route Irish or route Utah depending on the country. Still we didn’t see really any engine failures it was usually the mechanical lift pump or injection pumps failing and once again JP8 vs diesel fuel. I have wondered however what life would have been like if the military had adopted a 4BT vs The 6.2/6.5 and before some one in the comments says something about the 4BT being underpowered keep in mind that the first 6.2 M998s only came with like 135hp and 260tq. And honestly in a soft skin that had no problem going everywhere it needed to. Any way good video and rant over.

[@troyadams1076]

Man love when u an Scott talk about engine great information

[@vtwinaddicted5852]

Would love to see the bullet proofing video on one of the 6.5's

[@fastinradfordable]

There is no such thing. You just created an amalgam of power choke and Detroit/gm

[@billhackley3540]

you two are a great pairing. i learned a considerable amount that had nothing to do with the 6.5

[@benderisgreat1469]

Love this channel, , an with all the good shops you sho around my area , will be going to him soon hopefully

[@darthgator639]

This is why BMW made the Valvetronic heads. By opening the valves less at low RPM you get the torque that you would not get on the normal cam profile. Ath higher RPM the valves are lifted higher on the cam allowing more air in the cylinder, sort of the best of both worlds but more maintenance intensive in the long run.

[@lawrencepage2682]

Love the insight of the engine tear downs with professionals.

[@germanjesus]

I’ve owned and worked on hundreds of 6.5s and next to the 12 valve it’s the only other diesel I’d ever consider driving/owning

[@daniandreotti3892]

Mechanical injection, NO PMD, would be best, correct?

[@Jeep5point9]

I remember when he first appeared on the show-wasn’t too fond of the camera lol but it’s nice to see him open up and enjoy it 👍 super cool

[@mikecox3659]

Enjoy these videos the most ... all the best from Arkansas!!! Got a best friend in Belmont, Ont.

[@MikefromMOMichaelTurner227]

So true on the valve size talk!!! Remember the 351 400 M the aftermarket manifold runners were half as big to increase velocity 😆

[@janamo70]

On a diesel engine (wich does not need to suck in a fuel mixture) valve size has not much impact on low end torque. Only cam profile. It probably has to do with cracks between the valves, like the other comments suggest. Keep up the good work. Love your channel!

[@ricardoauerbach4092]

That mod is a must, I had issues with my k1500 Suburban cutting off at parking lot speeds, and only then. Relocated the PMD to the cavity in the bumper maybe 10 years ago and never had an issue since.

[@Remingtonrestoration]

love these vids...... I've got a 2000 7.3 excursion....... Over 320k...... Still running perfect w basic maintenance & regular oil changes...... Gonna keep it forever if I can

[@daddyodylan8902]

Awesome video. Loved my 6.5. Thanks for the content Rich

[@parksfrei]

Quadstar Tuning and leroy diesel are the place to go for any aftermarket and performance parts for the 6.5.

[@josephernest91]

Holy shit! That intake and exhaust valve size conversation just blew my mind. Thanks for the lesson guys!

[@niio111]

The "star pattern" of wear you saw in the cylinder is not from injector nozzle spraying fuel there. This engine uses prechamber combustion so the nozzle isn't even in the cylinder.

[@RP-hq4ec]

For my business I have a 24 valve, three 7.3 IDI trucks and bought a 6.5 last year The 6.5 truck is excellent and if I find a nice 6.5 Suburban I will definitely buy it.

[@johnhead8567]

It's a Venturi effect over the stack drawing air out of the exhaust. If valves are in overlap, it will draw air in the intake and through the motor and out the exhaust, slowly turning the turbo. It is a thing for sure.

[@TheBrokenLife]

I think the turbo spinning in the wind is a combination of things. If you create a venturi of the exhaust by blowing air over it you're creating a low pressure behind the turbine. If you are also pushing air on the opposite side of the wheel you're creating a high pressure. Once those two get working together, it seems like it would be pretty easy to get the wheel to spin. I imagine this would also vary wildly on the machine in question and the conditions.

[@thisguy7254]

Wouldn't air still have to travel from one side to the other to cause the spin? That was Casey's main point. There is no air going from intake through to the exhaust side (or reverse). Say something is moving forward on a flatbed. Air might be pushing on the intake blades, but none of the air is really moving past the impeller through to the exhaust side (due to pistons and such), it's simply blowing around the intake. IDK, seems like it makes sense that it would not spin. But people say they have seen it happen.

[@TheBrokenLife]

@@thisguy7254 Some valves in the motor will always be open and an amount of air will always be able to move through. I didn't see any particular video, so I don't have any bone to pick with anyone, but it is a thing that _does_ happen. I do imagine it has to be a pretty ideal condition for it to happen though. I've most commonly seen it in race cars. You have a giant turbo with a giant motor and giant exhaust and the turbos will sit there and gently spin just from the wind. Cranked up to 80 on an open trailer? I could see a problem.

[@kingduck3192]

@@TheBrokenLife the only way it can happen if both the intake valve and exhaust valve are open at the same time which is why you see it a lot on race cars because they usually have long duration of overlap. On my tractor i trailer a lot I cut off the front facing spout and put a flapper cap on it because I know it can ha even if it is rare.

[@tangydiesel1886]

An open or stuck egr valve could also be attributed to it.

[@thisguy7254]

​@@TheBrokenLife That is a good point about valve overlaps. Would certainly be more common in race cars like you said. Now I am curious as to how often engines stop at the right location for that to happen. Don't engines tend stop at the some locations due to natural engine braking. Probably more opportunity with an 8 cylinder vs a 4 cylinder. Need to get Project Farm or Mark Ropper in on this to test.

[@odelldickey2218]

I had a 1992 Gimmy C 1500 half ton pickup with a 6.2 diesel and an NVG 4500 transmission. It was a very reliable and fuel efficient machine . Thanks for the video. American Iron all the way!

[@SV867]

The Banks Sidewinder kit was okay for getting boost on a non-turbo 6.2 or 6.5 but it was not much better than a stock setup. I love my 6.5, it does great just chugging at 70 mph on the highway. I've got a lot of custom work into it, so it's a fair bit better than stock (custom water/air intercooler, HX35, 3 inch downpipe, 4 inch exhaust, marine injectors, tune etc). I never see over 1000 EGT even flooring it up a grade... time to find a way to get more fuel in it.

[@CorwinBos]

Scott is such a big dude from lugging that Mastercraft impact around!

[@nickd.4512]

The whole turbo thing i agree with casey. in 20 years of towing i never once covered the stack, never had any issues. Not enough pressure coming down the stack to turn it. Even if there was, with everything sealed up it cant spin, nowhere for tbe air to go. The only equipment thathad it covered was because we found a bird stuck in the exhaust of a loader. And that was a volvo with a huge rectangle exhaust

[@JuiceSpringsteen88]

Yeah, I would've argued with Casey but he has a solid point. There isn't enough overlap between the exhaust and intake valves to allow air to flow freely through the engine. Maybe if the turbo is super worn out and the hot and cold side aren't sealing properly?

[@c0le_798]

I love my 6.5 y’all got most of it right but 6.5 does have a cross over pipe it does run both banks through the turbo they have cranks snapping cause the balancer will rot away sometimes break cams and lifters pmd definitely an issue common turbo swap hx 40 hx 35 and super 60/54 And definitely will the 6.5 and 6.2 do your maintenance you can’t beat on these will no maintenance like you can a Cummins and the 6.2 was n/a unless someone purchased the banks turbo kit (as far as I know) love y’all’s videos guys keep it up 👍

[@user-yt7np9ik3h]

I found this very informative. I’m not a diesel guy but I understand them. Thank you.

[@richard3141592638]

Casey Ladelle gets a mention!

[@kenleppek]

Hard to believe a fella that makes a living building engines doesn't have a set of number stamps to number bearing caps... But I guess seeing his preferred brand of cordless tools it makes sense

[@scottturner1434]

I dont use stamps because it can impact a rod especially on thin walled rods like kubota. So don't keep them in the shop . Engraving is not aggressive and faster .. thankx for the comment 👍

[@kenleppek]

@@scottturner1434 Ahh. Makes sense. I'm just used to playing with old junk 350s.

[@JLCmike4014]

I worked on a fleet of school buses with those engines and the main things that i saw that went wrong on them were injection pumps, thermostats, and water pumps. Every now and then the damper would rip the rubber apart and the engine would have a weird knock to it. Put a new damper on and it would be happy again.

[@JREACHER1954]

Bought mine new in 94. Still driving it. It may not be the best but it's the only one I know.

[@upperroomtoo]

I had a last year (1993) 6.2 in a 1500 that I loved. It was smooth and reasonably powerful. It would get 22mpg on the highway. Rich, you need to build one like the one in the video opening. That is one from Oz built with Peninsula Diesel parts.

[@Nwem111]

Thanks for doing this video us 6.5 daily drivers thank you

[@oneoldmansgarage7880]

Rich, I have a late 94 k1500 Z71 with the 6.5L turbo diesel. You were correct about the crossover pipe feeding the turbo. It does get pressure from the left bank, and then both exit thru the right manifold. The PMD is a real problem, mine is mounted on a heat sink in the front bumper. The biggest down side is the big timing chain you saw. It runs the cam and injection pump. GM recommends changing it every 25,000 miles, not sure how many kilometers that is. I have 332,000 miles on mine and it is very in need of a rebuild, but it still runs. I have learned a lot about this engine and how to upgrade stuff since I have owned one. Like SS Diesel and other places offer a water pump upgrade for a bunch of money, but the 97 and up had an upgraded water pump. They are cheep to maintain and repair. Rant over! On a side note Scott was absolutely right about the vale sizes. Great explanation Scott!

[@darrellbobyk6363]

25,000 miles = 40,000 kilometers. A kilometer is 5/8 of a mile.

[@Firebird400]

Good series, I find them all informative.

[@kennyspry5189]

He's absolutely CORRECT about Smaller lntake Valves for torque !!!!

[@chrisl7511]

He's right about the valves, same is true for carbs on old engines, the trucks always had 2bbl stock for the most part, muscle cars or more performance versions would get the 4bbl. Usually different intake manifolds too. Love the vids

[@kingpuff10]

Intake runner length has a massive effect on torque curve specifically, there are multiple intake designs on factory engines that adjust the intake runner length at different RPM's to increase low end Torque. His description on RPM/ VS horsepower delivery was pretty spot on.

[@douglasmayherjr.5733]

I have been around the 6.2L / 6.5L since the early 90’s. I had a 1982 K20 that was a reliable truck. I bought a 1986 K20 from California and rebuilt it from the ground up installing the 82 6.2 engine in it. I didn’t want to do all that work without rebuilding the engine, long story short. It never ran the same and was a problem immediately after the rebuild. After many hours of troubleshooting and money spent I found the problem and it’s a design issue. There is no valve adjustment after machining has been done. Mine original engine block and heads was machined too much. As the engine builds oil pressure and the hydraulic lifters pump up, it would hold the valve slightly open, dropping compression, making it very hard to start. I’m hoping a new set of heads solves the problem. It’s something to watch out for. Thanks for the Videos, Rich.

[@EliasEklund]

Have a 1995 6.5 thats done 340000 miles still working. Brings equipment and fuel to a truck and loader servicing and building logging roads. A very appreciated piece of equipment at the company. Have had to change the computer two times, even with it being relocated behind the front bumper. Even prefere these compared to nissan navara and Mitsubishi L200 whom have been really quite troublesome with lots of irritating faults for us.

[@jontest5718]

Stupid question, is there any air flow behind the bumper?

[@garykirk1968]

Instead of blowing directly into the exhaust, try pointing the blower direct across the exhaust exit to create a venturi effect. May be drawing air through the charge system and causing the turbo to rotate unoiled?

[@Watchyn_Yarwood]

My thoughts too. Intake air comes into the system because not all valves are closed at the same time, not all pistons are at TDC at the same time, creating a passageway for air through the intake, through open exhaust valves, through the turbo, out the exhaust pipe due to the venturi effect.

[@bobbyfoard79]

That’s cute you guys are giving each other manicures with the piston rings. 😂😂😂. Love the content learning a lot keep it coming 👍🏻

[@hughjarse4627]

I converted one of these to a genset with a db2 pump it’s still running to this day that was 15 years ago

[@rick3090]

i had the pleasure of learning the hard way on these with my tow truck, 2 versions of this engine were available, 1 for the van had the turbo in the middle of the V of the engine, 2 the truck version turbo on the passenger side, and yes it had a crossover pipe feeding the turbo from both sides, these 2 were not completely compatible as the van had the intake bolts drilled at 90 degree to the head and the pickup was 45 degrees, they could be made to produce more power by doing a pcm swap but also needed reworking of the waste gate spring , i get 15 psi out of mine pulling hills, i use a modified air filter from a cummins for mine to breathe, the pcm upgrade i did was from HEATH diesel , it helped bring more power out .

[@ClearComplexity]

Built a 6.5 turbo for a G20 panel van in the mid 00s when I was around 14-15 as my first diesel project and conversion. Basic mods like marine injectors, better exhaust/turbo setup I had to do to make it fit properly, relocated the module, head stuff, basically everything mentioned. I got the engine free running that had been taken care of until the truck got hit. For a kid that price was hard to beat, I couldn't get a 4bt for that. Eventually I got a full mechanical 6bt from my dad for free off one of his propane trucks that wasn't propane and 454. The 6.5 does what I need it to do still with no problems, I'm not cutting up the van just to swap in something I don't need.

[@alexmatthews2332]

I completely agree with what Scott says about the RV heads that used to be a very common practice with 440 dodges etc. Makes perfect sense nobody is going to rev the crap out of an rv engine but it has to have useable power at low rpm to be able to move heavy weight comfortably.

[@kameronkoerbitz8733]

You talked about the head gaskets being common… from my experience, the heads themselves are usually the problem. Either cracking between the valves and/or warping. Also, the cooling systems were poorly designed for these engines in the non marine and military applications. Once the proper upgrades are done to these engines, they’re not bad at all.

[@roughneckmp]

My grandfather splurged on the Banks upgrade when he bought his ‘88 C2500 with the 6.2, he absolutely loved that truck. He was diligent with oil changes & maintenance, it served him & my grandmother well until someone struck him & insurance totaled it out.

[@anthonywilson6611]

My friends dad had a 2 wheel drive 6.2 that was turbo charged from the factory. It was a 93. I think that was the only year they came turbo charged. It was an extended cab short box half ton. The thing had 530,000 kilometers on it before the saskatchewan backroads out to wiseton and back to rosetown every day, five days a week took its toll on the frame and it had to go to the junk yard. It still ran though. And it towed trailers and all kinds of stuff. Still have fond memories of sitting in the back of that old truck.

[@marvz71]

Banks discontinued the Sidewinder turbo kits for the 6.2L engines a few years ago. There are a few options for upgrading the turbo without having to add an intercooler.

[@katiejameson]

Quadstar Tuning make a 54mm and a 60mm turbo for the 6.5

[@taylorsutherland6973]

Smaller valves, and smaller runners means higher velocities. If it is all tuned to a certain RPM, it will act like a ram air in essentially supercharging the engine. Torque would be a peak then. But breathing suffers so HP will be low.

[@detroitdiesel-vu3ig]

Had a 6.2 and a 6.5, loved both, currently on the search for another 6.2 but they’re starting to get rare unfortunately

[@charbvin]

Love these types of videos!

[@samspezza8328]

Smaller valves are about controlling air speed. The bigger the valve, the slower the speed for a given volume. Because the 70s/80s smog heads had such low-lift cams to avoid fuel consumption, they needed smaller intake valves to maximize low rpm air speed.

[@HuckThis1971]

I bought a 2000 k3500 this summer with 122000km. Supposedly former city of Hamilton dog catcher truck. It does have a bit of blow by, but cap doesn't blow off. Has 2 high idle switches. I brought 2 chords of hardwood up in the laurentiens with it. Made it work hard. Seemed to be better after for power. I then towed a Ford escape on u haul flatbed for 20km and wasn't easy on the go pedal. Much better now.

[@oldfarmer4700]

As a previous owner of a 6.5 in a 93 dually from new to 2003 it was good on fuel, and only the injection pump ever gave me a problem but was mechanical and no electronics on that year. As far as work was concerned light loads and don’t expect to win races is all you can expect. I bought a 38 foot enclosed gooseneck and when I picked it up and started for home it was all it could do to pull it empty. Everything passed me on the 500 mile return trip home and my foot was in it the whole way.

[@CollinWeis]

I love how the phrase“they probably used synthetic/conventional oil” has become the inside joke of this channel. Keep ‘em coming!

[@joeg7755]

Scott is basically correct about valve sizing but forgot to include port runner size that goes hand in hand. Smaller valves and runners usually means higher port velocity for cylinder fill at a given low to moderate rpm. This is great for the street but somewhat restrictive at higher RPMs. Larger valves and runners of course have the opposite effect, work extremely well at high RPMs, kind of suck in performance at the lower end. But Today's engines are not the same as the 60's and 70's, they now use variable valve timing, variable port runner adjustments etc, and can achieve amazing power levels at almost any rpm. Sorry Rich, we need to chuck one for Scott on this one.

[@joeg7755]

I stand corrected, Scott actually mentioned the smaller runners for high velocity cylinder fill at lower RPM's. Good for you Scott!!!

[@AJ-wj9ij]

This will help what steve was trying to explain an it the valve lift and size I sent you the link hope this helps thanks