HOW TO MAKE 305 SBC HP. Q-JET VS TPI-ADD 100 HP TO YOUR 3.73-BORE 305. FULL RESULTS-WHAT WENT WRONG?

[@troymecey]

I'm not a 305 guy but after I burned a piston in my 350 I had in my 86 GMC, my cousin give me a Vortec 305 . I installed a Performer intake , headers and the original Qjet. For an engine that was just supposed to get me back and forth to work temporarily, it's been 10 years and I couldn't be happier.

[@xmo552]

Same story in my brother's 4 door 68 Impala.

[@adammcilmoyl4278]

I've always suspected that the reason the 305 in particular responds so well to the TPI system is because of the ram effect of the long runner TPI manifold. The TPI is essentially a very long runner tunnel ram laid out on its side. You can't rely on a big bore and big valves for cylinder filling with a 305 like you can with a big bore block, but the ram effect of the TPI manifold helps to overcome the small bore and small valves as a breathing restriction, at least within a certain RPM range where it was designed to maximize that effect, which is right in the range where the TPI ran away from the Qjet motor in your test.

[@mistabone3899]

I had an 86 TPI WS6 with the "peanut" cam for emissions.

[@CzechSixTv]

Tunnel rams give air as straight a path as possible from plenum to intake valves. Their height, at least on traditional carb versions, is just a side effect of reducing runner angles. Like individual throttle bodies, they are designed for high rpm power. A stock TPI intake is the exact opposite. Runners in the lower intake go across the engine and are almost parallel to the lifter valley. In effect it is a low rise dual plane intake with really long(small cross section) runners. TPI was designed from the git to produce lots of low/mid rpm torque. Compare a stock TPI lower intake to a Holley Stealth Ram lower intake and you'll see the difference is night and day.

[@buzzwaldron6195]

I suspect the 305 short blocks weren't really the same... the one a 145 netHP LQ4 305 base level flat tappet cam, the other a 230 netHP TPI 305 version of L69 but with the TPI roller cam...

[@xmo552]

Well the tpi WAS designed for the 305....

[@SlingSalsa]

I bet you the qjet will shine brighter(er) on a better intake manifold

[@ryurc3033]

Nice spread bore dual plane aluminum high rise.......I agree.

[@allandrake4426]

TPI Induction has more runner length / Volume and a large raised open plenum (Think air gap). This would appear to be an immediate advantage over a low rise dual plane, and perhaps explain the position of the torque peak.

[@johnpye7177]

I raised a dual plain with a 3/4open spacer. Proformer intake. I do t know what it did but it likes it.

[@CS-oe8og]

I believe it to be runner length as well. Great test though.

[@retheisen]

The performer RPM intake is magic.

[@francoismachine]

I'd love to see you collaborate with a Q-Jet specialist like Cliff Ruggles next time you use one in a A/B test, I'm sure great information would come out of it :) Love the videos, thanks for everything !!

[@clinkerclint]

I think a different intake manifold would wake the q-jet combo up. Sounds like a great test, Richard! ....something tells me, he has already done it :)

[@54inches]

Same is true for the TPI and it has already been done too.

[@chrisreynolds6520]

Looking at the power curve, I believe the engine he tested with the Q-Jet had the peanut 178/194 @ 0.050 cam and the later TPI he tested had the 202/207 @ 0.050 L98 cam. Substantial difference in cam timing between different years and applications on the 305s.

[@54inches]

Not sure why you're responding to me, it's his test.@@chrisreynolds6520

[@adammcilmoyl4278]

That factory Qjet manifold is actually pretty good, it definitely wasn't the bottleneck in this test. It's not on the level of something like an RPM, but it's at least as good as a basic Performer. Lots of testing shows those manifolds to make as much hp as a Performer, and usually more torque too. They're a better manifold than they get credit for.

[@chrisreynolds6520]

@@adammcilmoyl4278 I saw nearly 20 hp switching to the RPM from a stock aluminum Q-Jet manifold on a stock 305 long block in my 83 G20. The stock manifold strangled a ~200 hp engine. The RPM gained power everywhere. More to the RPM than just flow. The runners are longer and straighter which helps add torque. The plugs were more evenly colored as well, indicating a better air/fuel mixture distribution and a cleaner burn.

[@GIGABACHI]

The dry, long runner TPI intake and it's "precise" port injection made the difference. That Dinosaur cast Fe intake and equally woeful Q-Jet left a lot to be desired.

[@190avgdad]

86 Z28 ran 13.4s with 305 world heads, isky cam, Hughes 2200 stall Was pretty solid in the pre-LS days

[@MasterWitchDoctor]

my '87 Monte Carlo K/SA stock eliminator is an 11.60s car running 118 mph with 081 stock heads with nothing more than a multi angle valve job. The intake and carb are stock 14057053 and a Barry Grant (while he was still in business) modified L82 quadrajet. My engine is making 419 horsepower and Im certain that Richard probably use a 416 casting and not an 081 center bolt head. The 081 305 head is by far the best non vortec 305 head Chevrolet cast and @ .400 lift actually out flows any 350 non vortec head with a 1.94 inch intake valve. I can easily get 260 hp out of an L69 305 with an 081 head with nothing more than a 5 angle valve job and orange Z28 springs. Give me a custom ground hydraulic roller cam with 220 - 224 intake duration (a 305 is a whole more more sensitive to cam timing than a 350 is) and 228 - 232 exhaust with a 4/7 swap and 1.5 ratio roller rockers,130 lbs of seat pressure @ 1.75 inches, and ill show you a 305 with stock ports, stock intake, and quadrajet making 325 hp with all the accessories attached.

[@linkloudenback8359]

The difference is that the stock versions of this engine is the reason why GM went from carbs to EFI. They always stated that the switch was for more reliable running engines along with better operating at colder and hotter temperatures and better fuel economy also better control over the vehicle. This was of course better selling points to the bean counters, but what sold the cars and trucks with these engines over the previous carburetor equipped engines was of course increased horsepower out put. The 305 of the carburetor version were great sold engines that were great alternative for the 350 for people on budgets, but with the addition of fuel injection GM was finally able to make the realization of the 1957 fuel injected 283 engine with the affordability and reliability of the carburetor 305 or 350 giving the consumer a choice that the other companies weren’t. Even though they were advertised at a certain output we knew that it was actually a little more. You can thank the insurance companies for this reason.

[@icsamerica]

Becuase TPI, that's why. GM figured out how to get big power from modest heads using just a TPI's good looks and runner length.

[@casamequite]

When I was a Pontiac Technician in the 80's and 90's we would race Qjet HO 305's against TPI 305's and the HO's would usually win. Also, Qjets are at minimum 750 CFM. I am guessing the camshaft in the stock TPI block is more optimal with computerized fuel delivery and spark timing. The carburated HO's had computer comand control Qjets and spark timing. The Qjet 305 you tested had none of these.

[@waikrujudovic]

The factory cast iron Intake manifold used must be a major air flow restriction. The carb may have something to do with it also. If I had to pick the major factor it’s that intake manifold.

[@MarcBchannel]

The manifold definitely, not the carb. That qjet flows around 750cfm. Plenty of carb

[@MrPhukyew]

The difference there between the two stock engines was the cam and the intake manifold runner length and the fuel atomization differences of carburation versus fuel injection. Also the compression ratio and valve sizes were probably different. There's plenty of differences that can play a role in these two dyno results.

[@thetriode]

The 40HP difference was largely spelled out in the L69HO vs the LG4 LO cams, which was 190hp vs 155hp respectively. A 204/214 or 214/224 cam is the best money under $200 you can spend on a 305 in your car if you have the 179/195 cam in it. I had an LG4 in my Astro with a 204/214 in it, was pretty darn fun. :) I'd be sticking a performer RPM or a stealth ram on probably just for ease of service over the TPI. Oh, and power :) Those aftermarket TPI parts are collectors items these days from what I've heard. Lingenfelter uppers or AS&M runners go for bank these days.

[@timtodd6830]

He said both engines were roller cam tpi originally. If the 267hp was out of a manual trans car the cam was (iirc) a 207/214 duration 414/427 lift. The automatic cars had a roller version of the 179/195 cam you mentioned. Basically same concept as the original q-jet L69/LG4.

[@MasterWitchDoctor]

oke let med enlighten you on the cam used in the LG4 and L69. They use the same 14093643 cam 202 duration intake x .403 lift and 207 exhaust x .415 lift with a 114.5 lobe separation. This is a computer controlled cam much like the 1990 - 1992 L98 10111773 which is pretty much the same cam only difference being is its a hydraulic roller with .413 lift intake and .428 lift exhaust.

[@thetriode]

Citations please. Every source I've seen indicates that the LO cam was the peanut cam. I've taken a few apart in my day, and they were the peanut cam. @@MasterWitchDoctor

[@MasterWitchDoctor]

@@thetriode try looking up the part number in a Chevrolet Microfiche like my buddy Larry Hoover did at Alexander Chevrolet where he works in the parts department. I race an '87 Monte Carlo SS in NHRA Stock Eliminator K/SA so I may know something about it.

[@thetriode]

@@MasterWitchDoctor a mcss would be a l69.

[@rajcam80]

Great info. I used to have a Dart headed 305 with a Summit cam exhaust etc, in my 1979 Camaro went 15.1. But I thought it could have been better, so it got a 150 shot of N.O.S. went in the 13's not bad for a 305.

[@hayden6056]

What fuel do you need to not strip a ring land at 15:1 with a 150 shot?

[@rajcam80]

@@hayden6056 15.1 in the quarter sorry for the not clarification.

[@hayden6056]

All good I was just like Jesus that's big comp haha.

[@robertappleyard7053]

I am a 305 Guy! No room in the garage for an engine swap, so the 305 is a keeper. Runner length and volume is your friend with the TPI.

[@bluecollarhotrods9781]

One was an automatic car camshaft. The other was a 5 speed car camshaft. That's my guess, yes they were different to some extent in the 87-92 roller cam TPI 305s.

[@claypaul2012]

Lb9 cam was pretty similar to the vortec 350 camshaft

[@bluecollarhotrods9781]

@@claypaul2012 90-92 305 & 350 = same cam. The 87-89 had the "peanut" cam. Also used in the TBI engines. It's only 179 degrees of intake duration.

[@claypaul2012]

@@bluecollarhotrods9781 tpi and g92 cars did not get a peanut cam

[@bluecollarhotrods9781]

@@claypaul2012 The 87-89 305 TPI automatic cars (non G92) absolutely did.

[@claypaul2012]

@@bluecollarhotrods9781 mine is t5 and g92

[@shadvan9494]

I think it boils down to runner length in the intake track. the Q-jet manifold has shorter runners than the TPI. which changes the harmonics of the pressure wave during induction. those tpi runners are about as long as a tunnel ram. I don't know if it was a factory manifold or what year, but some of those just suck really bad. the best on that I know of is the factory L-82 aluminum corvette manifold 3997771 and 340261 from Camaros, and the 458520 from corvettes.

[@donjohnston4215]

The small bore and inefficient heads benefit greatly from the longer runners and greater velocity crated in the tunnel ram. and helps that particular set up shine.

[@richardholdener1727]

every bore and head combo benefits from the long runners in a given rpm range

[@fiend_metal]

Perfect video for the day. My neighbor just gave me the 60k 305 mile engine out of his El Camino, and I want to use it for a swap.

[@andysteele4056]

The Tuned Port uses a ramming effect with its long columns of air in each intake tract. The high port energy comes from inertia of a narrow column of air, but it has some decent mass due to the long length. At the RPM it is "tuned" for it acts almost like a tiny bit of boost. I have heard claims of 1-3 psi of positive intake pressure at torque peak, but given the small cross sectional area this free boost turns into a restriction past about 4500 rpm in stock form. The Q-jet has no such fancy ramming and therefore less output. With 20 degrees more cam timing in each I think we would see the tpi fall behind. As some others pointed out there was likely a cam and head difference as well.

[@richardholdener1727]

please do a search for reflected wave (and the other two forms of charge filling associated with intake design) Inertial ram and Helmholtz Resonance

[@mistabone3899]

@@richardholdener1727 Like the NACA test MIT did and published in 1943 or 1944,

[@kenrolt8072]

@@richardholdener1727 As in Morrison & Smith book on the scientific design of intake and exhaust systems.

[@trebormcfarland8708]

If I had to guess, I'd say the larger manifold volume in slight combination with the fuel injection helped make up that power gap you're seeing, it could also be the jets are a little small on that q-jet for that long block and manifold but that's purely speculation

[@lb9gta307]

The difference is the TPI manifold's superior ability to fill the cylinders in the rpm range of that cam

[@HSTvids357]

I'm sure the intake plays a part, but aside from that it's gotta be a tuning issue. The qjet is not lacking in cfm capability at all for an engine that size. They've been on 600 hp race cars, and my ~375 hp 350 runs exactly how it did with a holley on it. It's just way more drivable now, too 😂

[@jacobnorth8642]

I put a 91 305 firebird motor (auto) in my 71 chevelle because it was cheaper then a tow dolley when i moved. My stock 350 was trashed, it had one of those 2psp "economy" intakes from late 70/ early 80s and a stock mechanical secondaries qjet, stock exhaust manifolds, small 2 od dual pipes, quit mufflers. I put a summit stage1 roller cam, used performer, headers, 2 id y pipe kit with summit magnaflow copies, car burns out now without using any clutch pop (255/60 r15 tires) with lunchbox no slip. Very happy with my qjet 305 for price, lacks some high end but didn't want to change heads and valve springs. Wish i was getting 25mph, if i pass a gas station I'm walking... need a 2x4 under gas pedal i guess...

[@MP-pz9oe]

I think it will be very interesting comparing a 305 with 307 with the same equipment .

[@craig8187]

At that HP/TQ/Ci and the RPM levels they are produced at by the stock engine combo the TP runners are simply a better match than the dual plane. Any aftermarket dual plane intake would lose even more TQ on the stock combo and at that HP level not make any more peak HP than the stock dual plane either. Probably a very interesting test would be to use the TP intake on either modified combo.

[@Modified1]

That tpi plenum has more available air than the low rise dual plane intake fo sho. Shoulda tried a 2" carb spacer before modifying to see if giving the intake more volume would balance the difference between the 2. Thanks Rich!! Keep testing!!

[@richardholdener1727]

it didn't need more plenum volume

[@larryjones1359]

I believe the factory cam is optimized for the TPI runner length. The Q jet manifold has shorter runners than the TPI and the air flows through it differently.

[@grandmasmalibu]

305 TPI used the same cam as the QJet-equipped L-69 HO 305. Even when they went to a roller cam in the 87-up motors it was nearly a clone of the L-69's flat tappet cam. From memory, the specs were something like 202/206* @ .050 on a 115* LSA. Even the lift was almost identical between the flat tappet and roller TPI cams. .403/.415". The cam profiles were around before the TPI engines even existed.

[@chrisreynolds6520]

​@@grandmasmalibu The 86 TPI cam was 178/194 @ 0.050 and 0.350/0.385 lift on a 109 LSA.

[@timtodd6830]

The automatic cars had the LG4 cam and the manual cars had the L69 in 86 and an even bigger roller cam in 87-92.

[@chrisreynolds6520]

@@timtodd6830 ALL 85 305 TPIs came with the L69 cam. ALL 86 305 TPI engines had the peanut cam from GM, part number 14094097. I have had several of them apart with manual transmissions at lower mileage and they had the small cam. The larger cam for manuals came with the roller cam upgrade in 87. The autos had the LG4/L03 roller cam and the manuals had the L98 cam. At some point GM added the larger outlet manifolds and dual cats to the 350. At that point the manual transmission 305s could also come with the better exhaust as an option. In 1990 and beyond ALL 305s had the L98 cam. The higher HP used the L98s larger outlet exhaust manifolds and dual cat setup. The lower HP version had the L03 manifolds and single cat. All the variations between the various options is why some of the LB9s were dogs and others that seemed identical would fly. I had a 1990 LB9 G92 5spd car that ran 13.90s @ 101 mph bone stock. I also had a 1986 LB9/Manual that was a dog until I put a mild 218/218 @ 0.050 cam and headers on it.

[@chrisreynolds6520]

@@timtodd6830 In the older days when these cars were all factory, the easiest way to tell which cam the F-car 305 came with was to look at the tachometer. If the car has the stock cluster, the redline on the peanut cam starts at 5K. On the hotter cam it starts at 5,500.

[@messix7768]

cam and intake perfectly optimized in the tuned port version. carb and manifold needed different cam lobe separation

[@robertwest3093]

Has to be a cam and or head difference. Everyone says that the TPI setup is so hard to make power up top with. I'm in agreement with the peanut cam theory. I know that even the factory Qjet intake manifold will equal or beat a TPI for hp. The TPI is unbeatable for low and mid range torque.

[@Sabe53]

I've always said GM missed the boat by not putting, offering TPI on their 4X4 trucks and Blazers. Way better truck engines.

[@19504x4]

The qjet manifold has tighter turns than the tpi manifold so it is more inefficient. The tpi probably has better fuel distribution also. Put the qjet on an intake with straighter runners and more volume and it'll be closer to the tbi.

[@keithhamilton8004]

The one that was run as a 305 TPI was probably an engine for a G92 car. Despite still being a LB9, the engines in the G92 cars had a slightly hotter cam with a 500rpm bump in the redline. So no, I do not suspect they were the same long block and I do suspect that cam difference made up the bulk of that 40hp disparity.

[@timtodd6830]

Yes it was definitely the cam.

[@Phantom-mk4kp]

Don't forget outside of the US we can't go to the wrecking yard for a 350. Also there are a lot of 305 boat motors outside US

[@joe-hp4nk]

I replaced the stock iron intake Qjet with a Edelbrock performer 600 holley on my 1985 pickup 305 and I couldn't believe the extra performance. I was very happy.

[@peterfinley8028]

I always loved the 305 very underrated

[@timkox2976]

Some 5 speed 305s(and auto 350s) had 207/213 cam. Most Automatic 305s had a roller version of tbi cam 178ish

[@chrisreynolds6520]

All 90+ speed density 305s and 350s had the bigger cam. The lower power 305 is because of the LG4/L03 exhaust manifolds and single cat.

[@timtodd6830]

Yep

[@user-uq8nl7sq5h]

Hey Richard ! Great video comparison... My 85 Fbody was rebuilt 20 y ago and I went with smog legal Holley intake, but had to keep the electronic Quadrajet - RV cam and banks catback exhaust system. Power went up enough to put the car at high 6's on 0-60 - where it was low 9's before - or about 2+s faster :))) Now I am considering the Lsx, but then I saw your video about cheap M90 supercharger ---wow - what a gem - thanks for that! Happy New Year too.

[@thisisyourcaptainspeaking2259]

I'll keep my q-jet 305 the way it came from the factory, it's fine. Pretty sure it's faster than my 2V Cleveland in 1/4 mile. Runs like a watch, smooth as silk.

[@coreyshort9461]

A flow bench test of both manifolds would answer the question I'm sure. And its not just a flow issue, its a velocity issue as well. But, I'm also sure you know that already...😉 Interesting test! 👍

[@greenbassboosts8872]

Runner length difference too to some extent I'm sure

[@AdinSLaboy]

Love it Your the one also I miss you 4cl Hondas videos I hope get some inf from you

[@pacolicious]

Im not a mechanic but I'm hapy with any 305 vids.

[@looneylonzo28]

1:38 before this starts in your intro I just have to say yes, you can always jump up to the 350 and it’s more power but in today’s market today’s economy, the 305 sips a little less of that expensive liquid gold in the Quadra jet can actually get pretty good fuel economy because of its design. Also, when you come to dealing with Quadra jet’s, there were several different versions he had performance versions for some of the big block engines. I think we’re up around 700 CFM 650 and I know they had some smaller ones that were like 450 and 500 so if you use the smaller Quadra jet on a 305 and you run just on your primaries never opening the secondaries, you get pretty good fuel mileage know if you put a stock Quadra jet from what that particular engine would’ve come out of which would’ve been a GEN three Camaro. Usually it would’ve had a smaller I think 500 CFM carburetor versus the larger big block intended Quadra jets would I do know for a fact is that you can takeoff the intake from both of those set ups and put you a good Edelbrock rpm air gap in a 650 dual feed, double pumper and a little exhaust get rid of the mechanical fan and you an electric fan and it really wakes up that little engine. I’m sorry to say I was once a puppy kick but I’ve come to respect the little, 305

[@chrisreynolds6520]

My guess is the carb engine had the 178/194 @ 0.050 peanut cam and the TPI engine you tested had the 202/207 grind. There was a piston difference, some were dished and others flat tops. A Performer RPM was worth 20-30 hp over stock as well.

[@lb9gta307]

Peanut cam engines (carb, TBI, TPI and both roller and flat tappet) make peak power at 4k rpm. I haven't seen one still gain up to 4500 like this test engine.

[@chrisreynolds6520]

@@lb9gta307 My 310 (0.030 over 305) made peak at 4,700 rpm with the peanut cam and 187s. Edelbrock 3704 manifold bored to 2", 454 TBI unit and old design really long tube Thorley Tri-Ys for a G20 van that had the collectors equal with the 700r4 crossmember. I made 197 whp and 284 wtq with it.

[@lb9gta307]

@@chrisreynolds6520 this was a stock engine

[@chrisreynolds6520]

@@lb9gta307 With headers and a 750cfm Q-Jet, basically a 1987 LG4 that was freed up a bit. GM rated the 87 LG4s power peak at 4,400 rpm.

[@mistabone3899]

I think my 86 5.0 WS6 peanut cammed motor peaked at 3800 on a chassis dyno, damn B&W 9 bolt rear end

[@benkrom2737]

The 305 4bbl came from an automatic car. If it had come from a manual transmission car, it would have had same cam as the tpi engine, which is a hotter cam 🧐

[@artscott2677]

I remember back in the 80's that those factory Q-Jet manifold was horrible for power production. I do not put all of the blame on the Q-Jet, especially the one you had from Murphy as being the best version

[@derekdeckens2559]

If the carb is tuned right then it's all in the manifold. Runner length and volume. There may be a slight variance in cam spec, but my guess is intake manifold.

[@SpecialAgentJamesAki]

Looking at the curves I believe there is a difference in camshaft between the two. From the flow numbers I could find the intake is definitely a restriction if the cam lift was over .400 but I’m not sure if it was enough of a restriction to make THAT much of a difference.

[@65panhed39]

Try a Holley 80555C and see how it does. It is a spread bore, and is vacuum secondary.

[@user-lx1nh7gg8o]

they most likely had different stock cams. One was probably a truck cam vs a police package or z/28 cam. that's my guess anyway.

[@jamielombardo5292]

I think the answer lies in the tuned port length of the runners that gives high torque a dual-plane manifold is much shorter and doesn't have the velocity of the long tube intake

[@scottybasham1020]

Would love to see a shootout of a 059 vs the 175 head. Weather it would be worth your dollar or not for a set of heads vs guide cutting and screw in studs on the 059s.

[@someonehasthisid]

I'd like to see a stock 305 HO from an early Monty Carlo SS on the dyno.I think they were rated at 195 HP. Early as in the ones without overdrive.

[@irocitZ]

I'm curious myself, I have a L69 H.O in my 84 Camaro Z28. I wonder if Chevy played with the numbers in the 80s the way they did back in the heyday? With just some minor stuff it's a pretty decent running car.

[@DBSSTEELER]

The only thing I can think of Richard is that maybe there was some sort of weird mismatch with the cam and intake and carburetor wasn’t getting all the vacuum signal it needed.

[@markbunn8576]

I'm thinking the stock cam may have been different between the two engines.

[@danr9584]

I can’t believe how big the difference is. For carbed 305s, they had the LG4 or l69 which also had better cam and higher compression, and would have been comparable to the LB9 TPI. I wonder if someone had swapped in a base LG4 into that car at some point an lO3 with the terrible swirl port heads.

[@leeselset5751]

I would put money on the difference being the factory heads. As I understand it, you put some decent heads on a 305 and it wakes right up.

[@ralphbraxton510]

Looks like 305s prefer long runners. Though it would be interesting to see the qjet with a performer rpm intake vs the tpi to see how close the numbers would have been.

[@stevenwagner4448]

A short block 305 is a short block 305. A better test would compare carb to tpi with mods. Tpi would take programming and injectors etc but that’s a better test

[@frankartale1026]

The carb 305 originally had a crappier cam and made way less HP than the tuned port motor. depending on the year. Tuned port motor's made as much as 230 hp. and with the carb, as low as 135..... Infact. If you put the quadrajet on the tpi block. it probably would make more power than the tpi did.

[@willsmith8586]

I think the difference on the stockers is the fuel injection seems to be cooling the air better than the carb in this particular setup. Just a guess.

[@lt1z350]

Had you used a set of either stock Siamese runners or something Like slp Siamese runners the tpi would have made more torque and the same hp as the rpm intake and carb or maybe more. Back in late 90s when these were popular we saw upwards of 75whp increase on a 5.7 sbe stock ported l98 heads mild cam car by porting the lower intake upper runner area about 1.5 inches into the port. Then the runners opening them up also so creating a break in the intake so it can suck from both upper runner tubes. We turned these “truck” intakes and turned them into 6600 rpm capable sleepers. My 1992 formula was stomping the hell out of the newer lt1 cars mod for mod with a combo like that. I eventually went to a Holley stealth ram on the car when did a single turbo but that l98 intake was a very good setup when ported correctly. I still own that car today along with my 1994 z28 and 2017 zl1.

[@richardholdener1727]

we had big tube tpis runners and also tried siamezed runners (they make less torque)

[@atheplummer]

Intake runner length on the TPI is much greater than the cast iron version. Also, you didn't mention casting numbers on the stock heads. were they the same valve size & combustion chamber volume? Higher compression ratio on the TPI motor? It would be neat to get ahold of a Smokey Yunik SY-1 intake and see how that compares to current technology. I have a buddy that has one, but hasn't put it on anything for a very long time.

[@homotorsports]

You forgot to flip the air filter lid on the Q/jet setup 😂

[@ahotmess2261]

We'll discuss on your live this evening regarding the huge difference in power. if you ever want to sell the TPI set-up let me know.

[@richardholdener1727]

it was cam

[@ahotmess2261]

@richardholdener1727 I figured it would have been more the longer runner TPI intake over the Qjet dual plane and fuel injection than it was the 2 cams although the one cam did have dramatically more lift like 50 thou'ish, and 3 more degree's of LSA. Bumpsticks FTW

[@Mike-yq7ce]

Difference in intake manifold is part of it. Fuel distribution may not have been as balanced with the 4 bbl intake would be the another factor.

[@takeit2-11]

I like it when you do the weird stuff! turbo magnum! turbo magnum! turbo magnum!

[@looneylonzo28]

kind of off subject I’d like to see a comparison with that tune port injection system that was on the GEN three Camaro for the purest, the Z 28 and the other small block and take the one off of the Corvette. I guess I could Google and see what CFM each one of them flowed because I sure don’t know but I’d like to know which one made more power

[@onehot57]

More questions than answers!

[@mistabone3899]

Ram Effect Tuning, like the old Mopars. There is a MIT NACA paper on the subject 1943 or 44. Same as a 2.25" CAI long intake vs a 3" SRI on a Honda, like you've played with before.

[@richardholdener1727]

three forms of charge filling associated with intake design, etc....

[@turboboy-oq6xe]

Factory quadrajet manifold is terrible sharp edges everywhere. I bet if it was tested with a rpm quadrajet manifold it would have been way better!

[@ToxicBreak13]

TPI I believe was originally designed FOR the 305 from what I have read on the internet (we all know what thats worth). But it makes sense. We all know the tpi chokes at higher RPM but even on the stock TPI 350 and 305 cars I have driven, the 305s hang on longer and just seem happier and hang on longer. You can even see in these graphs, that lb9 never falls off a cliff all the way to 5000 like the l98 does right around 4500. It seems that the port size and velocity was tuned perfectly for the 305 that it gets the perfect amount of cylinder filling and gets all you are gonna get from that engine, with that cam, with those heads. Obviously goes out the window whem modified. But if both long blocks were truly the same, thats the only thing that makes sense. The LB9 honestly is just a display of impressive engineering from GM. It was such a step up from any 305 before it. Also always thought it was funny that the manual LB9 cars (230 Hp version) got within 15 HP of the hottest L98 (245 Hp). The 350 has more torque and area under the curve but not as much as there should be. More evidence the system was really designed for the 305 and adapted to the 350 as well.

[@ricksshop]

GM put swirl port heads on TBI-equipped engines back then. Maybe the TPI heads just don't work well with wet flow intakes.

[@scotthultin7769]

First 👍's up Richard thank you for sharing 😊

[@randydudenhoffer9245]

There are tons of 305's running successfully in stoc eliminator

[@CzechSixTv]

I know you know this but HP = Torque x RPM/5250. Less torque for a given rpm means less HP. For the base numbers, the longer TPI runners simply produced more torque in the 2500-5000 rpm range. That's what the TPI system was designed to do.

[@richardholdener1727]

5252

[@jarvislarson6864]

The tpi was designed for the 305 so it stands to reason why 305tpi performs so well

[@OldDirtGuy]

My guess is that the hot plate in the manifold under the Qjet was, well, hot.

[@joelbrown2242]

I’d say it’s the port velocity difference in the intake runner designs.

[@brentsullenberger4711]

305 ho engines had different cam and aluminum 4bbl intake and flat top pistons

[@BOOT]

TPI was made/optimized for the 305

[@edwardwood3622]

TPI was a good set up at the time and the stock 4bbl intake wasn’t very good. 42 hp gain from the swap isn’t a stretch though I was expecting better from the cast/Qjet set up.

[@looneylonzo28]

i’m going to say it’s all about airflow the primary on a Quadra jet are so small. Also, what size Quadra jet is that they made several different sizes I’m not exactly sure but somewhere down in the low 500s up to ones for the spicy big blocks, which I were told were supposed to be somewhere around 700 either way it still comes down to airflow, even if it is a larger Quadra jet with a small primaries, it’s not gonna flow as much air I believe maybe you should put a hat on both of those combos and see which one is pulling more CFM

[@WVXL64]

I think it's a combination of the stock truck engine intake manifold, and the TPI cam profile. I bet it would of picked up at least half the missing power with almost any modern dual plane intake.

[@chriscochran2984]

The small 5.0 didn't have the breath to signal that carb due to reduced port speed where the tpi is tuned for just that focusing on low speed power via long small runners. I would guess that the plenum of that cast iron manifold was to open with too short of a runner paired with two large of an opening on that quadrajet to really get those ports to work for that small motor??

[@chriscochran2984]

The first-year TPI 305 had a better camshaft in the second year talkin 1985 vs 1986 I want to say the 85 model was rated 10 horsepower more

[@Xxjoker21xX]

The factory Heads and Gaskets make the difference and why the Qjet setup was lower HP from the factory!

[@FeralPreacher]

The two stock motors had to have different cams.

[@leebrady6326]

That is exactly what the TPI was designed for.. Similarly, it is not easy to get 400 HP or more with that TPI..

[@Artis-wq1wk]

Totally open up the pleum on the stock intake manifold....then dyno

[@richardholdener1727]

the plenum isn't the issue

[@tomcoon9038]

The O2 sensor and accompanying CPU tuning on the TPI. Not, camshaft or plenum length etc etc etc... That would not make that big of a jump.

[@richardholdener1727]

there is no O2 and CPU tuning-Both the AF and timing were dialed in for each combo til it made max power

[@looneylonzo28]

tuned port is always going to run better than carburetion on the factory set up but if you figure out the fuel consumption per hour on that tune, port injection, and the CFM, and then get a comparable carburetor and tune it to that same fuel delivery per hour if you can do that then they should be fairly equal but I don’t know how that injection works. Is it batch fire

[@user-kl7kp4bc3t]

Intake runner length + port injection maby minor difference in cylinder heads...

[@Pickleram]

Had a 88 ss monte running high 13s with a non computer qj and just headers

[@Chris-bn1bn]

An iron intake is the obvious culprit. TPI breathes a hell of a lot better than the smog intake. With an adapter, I'm fairly sure that the Q-jet would have been close to the numbers on the air gap intake.

[@robertpatton7442]

Any chance it was formerly a TBI motor with the "high swirl" intake ports? or did they ever use those heads on TPI motors? They definitely had the LG4 cam on certain 305 TPI motor years, which might explain the carbureted motor making so much less top end and midrange. Otherwise, if not some timing or fuel mixture issue, or just a crappy intake manifold, I'd have guess that this Q-jet didn't open the barrels fully, like some stock ones that are configured for low emissions and power.

[@lilpoindexter]

those TPIs sure look good to me, but still I scored an LQ4 this weekend

[@DillonAuto]

The intake manifold can better fill the cylinders above 3000 RPM. We can skip the part about atomizing fuel better.

[@xlr8r3VA]

It seems to me it has to be either compression related 76 cc heads vs 56 cc, or a big difference in the stock cam profiles or both. The cast iron intake runners are extremely small, so maybe that came into play as well. But I am betting more on a compression difference.

[@actippets2307]

I'd agree, if you used a Stealth or RPM manifold it would close the gaps.

[@derekbrookins6853]

i;m going with the consensus and go with the intake manifolds look at the torque difference down low

[@doublek5583]

Back in 1985 I did a test of my own at a Chevy dealer near Seattle WA, with 2 - 1985❤ camaros ( new) one Tpi and the other thoutle body. They may have been similar on paper although the tpi outshines the other ran much better, layer tire better, acceleration was way better and overall performance it was tpi hands down Double k from western pa

[@richardholdener1727]

TPI vs TBI is not as contest-big difference in rated power output