FULL DYNO RESULTS ON THE L78 396, OVERRATED AT 425 HP OR UNDERRATED AT 375 HP? WHAT DID IT MAKE?

HOW MUCH POWER DID THE L78 375-HP 396 REALLY MAKE? WAS THE 1965 L78 425-HP 396 CORVETTE OVERRATED? WAS THE 375-HP L78 396 CAMARO OR CHEVELLE UNDERRATED? HOW MUCH POWER DID CHEVY'S LITTLE BIG BLOCK REALLY MAKE? AFTER FINDING LEAKING HEADS IN PART 1, WE REPLACED THE HEADS FOR A SECOND TEST. I INSTALLED NEW 858 HEADS IN PART 2, ALONG WITH AN ELGIN REPRODUCTION FACTORY L78 CAM AND STOCK ROCKERS. I RAN THE 396 BOTH WITH LONG TUBE HEADERS AND STOCK, CAST-IRON BBC EXHAUST MANIFOLDS. CHECK OUT THE POWER DIFFERENCE THAT HEADERS MADE ON THE BBC. FINALLY WE HAVE DYNO RESULTS ON THE L78 396!

[@rogerharris907]

Have experience with those engines in the 70,s, I agree with the engine builder. We didn't have the carb and ignition technology back then I would like to see a set of 350 horse oval port heads dynoed on that engine.

[@buzzwaldron6195]

Carb. and ignition tech was fine in 1970...

[@eflanagan1921]

@@buzzwaldron6195 you may have my share of points and solid lifters 1

[@kevinvannoy]

awesome Richard.. so cool to see these factory deals on the dyno.. i think you nailed the factory numbers with factory exhaust..in my opinion there’s no way that factory carb will make more power. like you said the venturis and over all sizing are damn close.

[@PeggyParrow]

I had 1 ,they actually came with a 780 vacuum seccondary carb. Everbody calls them 750s but measure the primarys verses the secondarys, the secondarys are noticably bigger, therefore , the 780 rating. The prim. And sec. In a 750 are the same size !

[@1967davethewave]

Thanks for another classic engine test Richard! People will argue and claim this and that but marketing was responsible for selling cars and embellishing a little helped to push that. It also helped to bring about the change to the "Net" rating that started in 1971. Cars seemingly lost 50hp or more overnight. I figured the 396 would be closer to the higher number as I always figured the 427 with the same heads was around it's 425 rating. Now build one of those and lets see. I know Pontiac 400/455's will make about the same horsepower if they use the same heads just like your 302/327/350 test. But of course different torque numbers and peak rpms. No matter what it's cool to see actual numbers and not just good campfire stories and hyperbole! An actual 375hp in the late 60's is nothing to be ashamed of. Those cars were very fast with minor mods in light cars like the Nova and with a set of slicks bolted on the back. They can still embarrass a lot of the new muscle that has the benefit of 50+ more years of technology.

[@recoilrob324]

I had a 350 horse 396 out of a Chevelle in a Camaro and it took no crap from 375 horse motors. They have 10.25:1 CR, oval port heads and Q-Jet spreadbore manifold and it was running a small 204/214 @ .050" with slightly less than .500 lift. On pump gas and properly tuned the heads flow enough to feed the displacement just fine and the larger heads actually take away torque below 5000 rpm where much of a race is run. We did lots of top end pulls against 375 horse motors and never had one keep up. Of course..I'll take a little credit for this due to tuning but if you look at the dyno graphs the 375 doesn't exceed the 350 until well over 5000 rpm...so on the street I don't think the 11:1 CR helps very much as they're detonation limited on pump gas today and actual power of the lower CR motor able to match or even exceed it due to better timing advance being used. Love the old Big Blocks! :)

[@gordocarbo]

@@recoilrob324 Ive always preferred ovals over rectangle ports on these With a little bowl work even 20 deg cam timing these really woke up!

[@1967davethewave]

@@recoilrob324 I bought a 70 Corvette in 1995. It had a 454/4speed of unknown vintage, definitely not the original engine. I pulled it apart after the summer cruising was over and it had rec port heads. I decoded it and turns out it was a 70 LS6 someone had ground the numbers off of, restamped and tried to pass off as the original engine (very poor work and very obvious it wasn't). After reading a couple of articles by John Lingenfelter about the superiority of the oval port heads I pulled the rec ports off, sold them in local classifieds (this was the 90's) and used the money to build a set of oval ports built to Lingenfelter's specs. I went from low 13's in the quarter with the rec ports to well into the 12's with a best of 12.51@110 and the car just felt like it had more torque. The oval port heads from what I have read over the years just superior on engines under 700hp or so. Of course if you have a 1200hp Pro Stock car I'm sure you want those rec ports!!

[@williepelzer384]

I street raced everything in those days, and I can tell you headers made a BIG difference on those big blocks. 😊

[@harleysgarage327]

Glad to finally see this, impressive for a stock engine, no matter how you rate it. Keep in mind your testing done on the L79, LT1, DZ were all run with headers, so I think this is a great comparison to those engines. Thanks for doing it with manifolds and headers!

[@jeffwebb-eb5hg]

I bought a '70 SS, El Camino, years ago, it had 42k miles. I put an Edelbrock performer intake, 750 CFM , HEI headers. Dyno showed 412 HP , 422 # .

[@williamhaynie4229]

There is NOTHING like a big block chevy at full song.

[@holeshot1721]

Gives real meaning to chevy thunder!

[@lollipop84858]

Prove it

[@antilaw9911]

Hemi at full song 😃

[@antilaw9911]

440 at full song

[@OxBlitzkriegxO]

Except, literally any other big block engine. 🙄 All big blocks are awesome.

[@allankwiatkowski8217]

you are forgetting one thing,as a 66 chevelle owner with the 360 horse 396,i noticed that the horsepower rating for the chevelles was at 5200,corvettes 6200,and using your graph it is basically as gm said chevelle 5200 375,corvette at 6200 425,so if you wanted 425 horse in the chevelle just rev higher

[@richardholdener1727]

the 425 hp rating was only in 1965

[@garywilson7992]

It’s not that simple, to just raise the rpm’s, although that’s true many times for the factory manipulating horsepower ratings for the same engine. But for a 66 Chevelle 360 hp or a 67 Chevelle 350 hp or say a 69 Chevelle 325 hp, those engines had hydraulic lifters where the peak horsepower was typically under 5500 rpm; while the same CI engine with a solid lifter cam, higher compression and hi rise intake manifold, along with usually a bigger cfm carburetor, developed its peak horsepower around 6500 rpm, and they usually had 4 bolt main bearings instead of 2.

[@laughton57]

Great - Thanks Richard. I've been waiting for this. Make sure the kids at Engine Masters as well as Steve Brule know this! LOL.

[@brianhicks9568]

i think you are really close on that but the original 1965 vette motor supposedly ran 425hp out at 6400 "according to book" and the 375 hp L78 supposedly got the rating at 5600. i guess 800 rpm might make a difference if it honestly went there from factory, but like said might just have been marketing on them to help sell corvettes can't have them making the same as normal joe blow sedans. love the dyno numbers they don't lie.

[@craigchiddo2794]

I would like to see what it would make with ported 049 oval port heads l-88 cam and single plane manifold

[@georgeperillo6421]

Back in the day (1971-72) I owned a L78 396 Corvette Sting Ray Coupe. My engine upgrades were Hooker headers, A set of Crower racing valve springs and a Mallory dual point distributor, which was more trouble than it was worth, as I spent alot time at Reath Automotive getting the points calibrated on their Sun distributor machine. But that engine was very stout. That throaty idle sounds familiar. Thanks for the memories.

[@h2oskiaddict]

Reath Automotive in Long Beach? Is it still there?

[@georgeperillo6421]

@@h2oskiaddict Nope, it's gone along with Lion's Drag Strip.

[@garywilson7992]

@@georgeperillo6421 I think 1965 was the only year that Chevrolet offered the 396 L-78 425 hp in the Corvette. In 1967 & 68 I had the same factory 396 L-78 in a SS Impala. And I assume you already know what that Vett would run in the qtr, and you obviously would’ve been faster than my full size Impala, being lighter, and Vetts were known to hook up better than most with a good pair of slicks. But I could turn consistently in the mid 13s in the qtr with slicks and a 4:88 rear end.

[@michaelfercik3691]

@@garywilson7992 Yes, 1965 was the only year the L78 396ci was put into the Corvette. I had a March built 1965 Corvette L-78 396ci / 425hp engine (only) that was rebuilt with what we called a full race cam and the compression ratio was bumped from 11 to 1 to a 13 to 1 compression ration and stock heads, intake, carbarator. It was put into my Slit Bumper -1972 Camaro RS/SS (Sun-flour Yellow) with a stock turbo 350 transmission, and 373 ratio rear end. Never made the Drag Strips that were long distances away, but our County Sheriffs Office held street racing down by allowing us to race using two way radios for shutting down all traffic on the seldom used roads, with letting any traffic go through between races. Sometimes we talked a couple of Sheriff Deputies into sitting at the end of our measured off quarter-mile for giving accurate trap speeds, along with stop watches used at starting and ending lines, which were visually and radio communicated starting of the stop watches. We we crazy, so there was no pretty ladies flag starting the races, instead it was men with big brass balls and were usually intoxicated, and yes all of us drank beer while racing with everyone policing each other for someone being "too intoxicated could not race". "How stupid and young immature we were". I used to power brake the transmission while popping wheelies coming off the line with ETs in the mid-tens at over 135mph. Back in the 1960's and 1970's, the cops would always tell us to take our drinking and parting off main street. We were told to either "take your drinking out of town, or go home". Most of us were underage drinkers, but, back then most people figured if you was near the age of being drafted into the Vietnam War, you are old enough to drink, especially if your life was to be taken in Vietnam.

[@garywilson7992]

@@michaelfercik3691 Quite an upgrade to the L-78 with a higher lift cam & the 13:1 compression, but to be honest, I wonder how accurate whoever it was that was doing the 1/4 mile timing claiming mid 10s, seems just a little faster than I would’ve guessed. I did something similar in 1969 with my 67 Chevelle factory L-78 engine. Had it rebuilt with the L-88 cam, 12.5:1 compression pistons, etc, along with the 4:88 ring & pinion I had taken out of the 65 Impala before I sold it. Anyway, with 10” slicks, I was around 2 seconds faster in the 1/4 than the L-78 Impala. Of course to a layman that doesn’t sound like much difference, going from mid 13s to mid 11s, but that translates to a huge difference at the end of the 1/4, when every 1/10 of a second is around one car length give or take. And so if you ran mid 10s and I ran mid 11s, I’d of lost by around 10 car lengths. And yet it sounds like we had fairly comparable engines, and so that’s why I question the accuracy of the timer?

[@CrankAddict]

I had to pause the video to say that the carb cam is freakin' awesome. Nice editing!

[@brad3139]

I like that you keep bolting manifolds on with these tests 👍

[@terrypikaart4394]

The 1965 L78 was 425hp+ and had a 7200 red line, that first yr engine was quite special. After that the engine was detuned...

[@richardholdener1727]

engine specs are identical (including springs and rpm potential)

[@terrypikaart4394]

@@richardholdener1727 That is correct, but if you owned a early 65 ss impala or a vette with the L78, engine was clearly different.

[@richardholdener1727]

how can it be identical and clearly different at the same time?

[@terrypikaart4394]

@@richardholdener1727 Easy, the factory specs for that first early engine were not for it, they were for the 66 375hp.. Hence the 65 said 425 on air cleaner and the 66 said 375. The 427 came out in 66, didnt need two engines at 425hp.

[@playlist55]

LOL, Engine was identical except for the exhaust manifolds. L78 is an L78.

[@ericreimer6627]

I like that you ran it with manifolds and headers. I'm a little surprised at how much it lost with manifolds. The guys at Horsepower Depot (red 67 L88 clone that runs FAST series) run 9.10s with stock manifolds, or should I say "stock" manifolds. I know better than to think they're truly stock, and even still, they admit they're a restriction, yet with as much power as they make (555ci engine running 7,500 rpm), I kind of expected less difference on an engine putting out so much less power.

[@mrho4speed]

Great video and this takes me back to 1978 where "Popular Hot Rodding" magazine did several articles on a 396 rebuild = called "Project Engine" and what happens to torque and horsepower when different speed parts are used on an engine. The most significant part is of course the camshaft selection and to make a long story short = these guys coaxed 502 horsepower out of this 2 bolt engine. The last test was in the volume 18, number 9, September 1978 issue = truly great stuff!!

[@garywilson7992]

Very interesting, and I wish had a time machine, because I’m about 57 years too late to take advantage of anything. In 1967 I bought a very low mileage 1965 SS Impala 425 hp L-78. And I regret not putting headers on it, not realizing how much restriction there was with the factory exhaust manifold, although for what it’s worth, I did install exhaust cut outs at the manifold collectors, that I only opened if it was a serious enough race for enough money. And I don’t know how much it actually helped, bypassing the mufflers, but it was intimidating, and with a rev could sound like all hell was waiting to break loose. I also removed the 3:31 ring and pinion rear end, and installed a 4:88, that with the 7000 rpm shift point allowed me to approach around 6500 rpm in 4th gear near the end of the qtr mile. And of course I also would put on my good pair of slicks, or all I would’ve accomplish was destroying tires and creating a massive smoke screen. I was 19 years young and hadn’t yet had enough experience, and I won so many 1/4 mile street races with that car, that I didn’t think I’d ever come across anything on the street that could out run it. Until I finally did, and I was shocked, because it wasn’t even close, and I think I even suffered from PTSD for quite awhile. And I still remember 57 years later and counting, my best friend at the time, haunting words to me after the race was over, he looked at me and laughed, and said, “hell Willy, you might as well been on Hoover vacuum cleaner”.

[@michaelfercik3691]

That is a $300,000 car, or more when restored to factory specs. That car only had a few hundred produced compared to 2,200 Corvettes with the same 1965 L78 engine,

[@mattrohr1266]

The corvette also used a 14lb steel 10.5 inch clutch and it had the same cam and heads as later 427 cars, but it felt just as strong, I have owned them all. Corvette 396 cars had 4.11 gears standard with an m21, and were rippers.

[@alexbrown4820]

I think we all kinda expected the results from what we saw with the sbc 302, 327 and 350lt1 testing. But now im curious what it does with a modern valvetrain and edelbrock rpm air gap.

[@robking9857]

HioSSilver1999 said: "I would love to see what some general improvements would do to this engine. Stuff like a better balancer, better oil control, roller rockers, better intake, e85. Do that with the stock cam and heads!" I would like to see the same tests... and then add a rowdy street/strip cam... and then add NOS to see how you can take one on a "relative budget" and up it in stages. Or, do the upgrades HioSSIlver1999 suggested and add NOS with a stock cam... or both. Keeping in mind a hot street driver to the dragstrip and toss on slicks type of sportsman deal.

[@Imnotyourdoormat]

So the 325 probably made 350, the 350 made 375, and the 375 horse made 425?...Right? hahaha LOL

[@d48mclain]

Just a daily driver street racer, but a serious one; n got sponsored by a couple speed/dyno shops. Seen about anything you can think of actually dyno. The 60’s muscle cars were overrated . Not by a ton, but certainly so. Had the opportunity to not only see a COPO 69 425hp hp with 2000 original factory miles get tuned on the dyno but also rode in the car afterwards. I believe it first made 344 rwhp and about 355 after tuning. Really need to look again at the dyno sheets but if off, very little. My car at the time made a little over 500 at the wheel with a 300hp progressive nitrous. Maybe I was spoiled, but I had a hard time figuring out if he was 100% on the throttle. Looked close… he was. Kinda busted my bubble. Was expecting to not be able to grab a 20 on the dash. 😀 amazing how urban legends spread n how they get busted by new tech. Denny

[@barbarycoast3972]

I guess I was born at the right time. I was looking to buy a new Chevy when the 375/425 L87 became an option on the Chevelle. Unfortunately I didn't know much about it, except it was more HP. A 66 396 SS Cevelle. The car was beautiful. Now I consider it Chevy's 1st big block muscle car. Only had a couple of years with it when I had to go into the USAF. Never saw it again. Still think about it all the time

[@jayb9687]

Loved the 396. So simple so strong so easy to work on.

[@stevenbean9706]

had an Ls3 396 that was definitely underrated! torque to the moon

[@DortonFarb]

With the correct 3310-type vacuum secondary "780 cfm" carb, no overbore, stock valve job, typical as-produced deck height, typical as-produced combustion chamber cc's, a full stock dual exhaust system, engine-driven water pump, engine-driven alternator, engine-driven radiator fan, stock air filter & housing, full operating temperature, etc., the quarter-mile terminal velocities of numerous period road tests of L78-powered cars, reveal an ACTUAL power output of no more than about 300 horsepower, which is less than any new stock base-model 4-cylinder 2023 Mustang..

[@dclug1]

Nice to finally see the finished product. I have a 1969 396 in a corvette. Has 215 oval port heads, 10.25:1 compression. Only changes from stock are a comp cams 268 and a chevy performance dual plane intake with a 750 vacuum secondary carb. With headers and running the manual water pump it made 435HP and 465TQ on the engine dyno. Your 396 above with a simple cam swap would make high 400's in power.

[@dclug1]

@@kevinseybert5795 I’m not comparing my motor to his. I know they aren’t the same. I was just putting out there what my motor did on the dyno. I’ve done my research. I know these 396 motors quite well.

[@dclug1]

@@kevinseybert5795 I’ve only got the numbers I have to go by. Didn’t run on any other dynos to verify. And that would have been a pain. The shop that broke my engine in and tuned it for me builds high end BBC for race boats and such. Still working to get the car fully driving. Seat of the pants will really tell the story. It no doubt will have a lot more power than the crappy small block it did have. Nothing made HP in 1980.

[@DanClayton-fo6wt]

I dynoed a 1969 L78 396 that had a hydraulic flat tappet 238°/242° @.050 cam and weiand stelth intake with 850 carb and on my dyno it barely made 400hp with dyno headers.

[@mikewillett5076]

Were you at high altitude or was the compression particularly low? Not trying to be smart, really asking because it just seems like it'd make more, even ground at less than optimal LSA.

[@DanClayton-fo6wt]

@mikewillett5076 Engine had been rebuild at some point quite some time before it came to me to dyno. Still had the std bore TRW forged 11:1 pistons. Cam had been switched to a hydraulic flat tappet as mentioned. Leak down test was fair at 16-24% it just didn't make any power. I played around with timing and a/f ratios but it just never really responded well. Think it made 405hp @ 6000 rpm. I got a chance to drive the restored 70 chevelle the engine went into and it ran well. I think there are so many inflated dyno numbers out there most people would be surprised what an honest 400hp actually feels like.

[@mikewillett5076]

@@DanClayton-fo6wt . Thanks for the reply. You know what? You are right about how powerful and honest 400 horsepower engine can feel. We tend to think of a 400 HP factory engine as powerful but not when we build one ourselves. But that is a good number!

[@JViello]

Engine dyno or chassis? That can make all the difference in the world! Same if you are using any correction factors - everything has to be SPOT ON for them to not skew the results. I used to develop turbo kits for my own company and then the company that purchased us for a couple/few years after. Everything from diesel side by sides to muscle cars to exotics. I've literally got thousands of hours of dyno time. I know people like to bag on results and whatnot, but 400hp to the tire is healthy in just about any car less than 3500lbs.

[@keithw372]

would that be a L78 with a hydraulic lifters?

[@mikegreer9041]

Numbers are all bull. The only way to campare anything is with the same dyno. Huge grey area in hp, sae net, gross, and finally the calibration of the dyno.

[@thetype85]

Stock ignition with points, full exhaust with restrictive mufflers, air conditioning compressor, alternator, water pump, power steering pump all hooked up with a load on them. Air cleaner with stock filter housing. Now you're seriously looking at 350 horsepower if you're lucky! The ratings were a joke back then, they weren't even close!

[@jamesbosworth4191]

Many speed freaks in the 60s frowned on things like AC, power steering, automatic, etc. Power steering doesn't hurt much in a drag race, but if you are deviating much from a straight line, puts a drag on the engine. AC, unless switched off, puts a big drag on the engine, and automatic transmissions also reduce performance potential somewhat.

[@brucesmith5426]

No air in my 65 coupe.

[@jamesbosworth4191]

Most people didn't have AC in 65. It exploded in popularity in about 69. Suddenly, everybody wanted it, and more than a few sports car people disliked power steering. They felt that it made the car a girl's car.

[@brucesmith5426]

@@jamesbosworth4191 No power steering either in the 65 coupe I owned. Just a huge teakwood wheel! My dislike of power steering is years ago you lose the feel of the road.

[@jamesbosworth4191]

@@brucesmith5426 Very true! You have better control of the car with conventional steering. Ditto for power brakes. Conventional brakes are easier to modulate, especially in comparison with power brakes of the 50s and 60s - many were light-switch like, either full on or full off. If you so much as breathed on the brake pedal, you were almost thrown through the windshield. I never like that.

[@michaelangelo8001]

I test drove a 69 Chevelle back in 71, that had a 396/375 w/a three speed manual floor shift transmission. It was *very* strong. Made a lasting impression on me.

[@eflanagan1921]

If built that way , very rare package !

[@rudyjhughes]

I would like to see this with only change a set of pro maxx heads

[@joseiracheta3817]

Im guessing just over 400

[@NobilityandLoyalty]

I know how badly you wanted to get this project done. I believe your findings are spot on , especially when one factors in the necessary factory accessories, carburetor and exhaust manifolds. Thank you for building the engine as close to stock specifications as possible. What were the camshaft's specifications? Well done Richard!

[@craighansen7594]

I will add that even in a restoration using the original engine, i would choose a new cam grind. The cars owner could specify the repro cam but why?

[@gordocarbo]

Agree...one could keep the same @050 numbers but tighten cam timing up a bit to make power but still not kill lobes. Love me some solid lifter engine sounds! Better than solid roller to be honest.

[@Damothedevo]

Mine feels good from seat of pants tuning, blocked off secondary powervalve, which is a weird thing and complicates tunning. Love you've followed up on earlier build. Have original carb.

[@ht24d64]

I’d be curious to see the difference in power between Camaro / chevelle manifolds vs Corvette exhaust manifolds. I know neither are as good as headers but would be neat to see if the vette manifolds/exhaust system flowed better hence Chevrolets better rating in the Corvette. I’ll also bet the Corvette rating numbers were done with headers

[@jamesblair9614]

I recall the MkIV being introduced part way through the 65 model year, the first part of the year being the 409, but single 4 barrel only. For a very brief period, the L78 was rated at 450hp, before they dialed it back to 425. Chevrolet was in a difficult position, their new improved big block had to be seen as an improvement over the 425hp W engines of the year before, and the factory knew there was a 427 Mk IV being released in a short few months. If their 396 was already rated at 450 or 425, what would they have to rate their 427 at. That’s the problem when you play fast and loose with the numbers, it wasn’t the first time the Chevrolet division got themselves in this trap, and it wouldn’t be the last.

[@benjaminwatson7868]

No that was the 427 rated at 450 then derated to 425

[@jamesblair9614]

Kevinseybert5795 I was mistaken when I said the L78 was briefly rated at 450hp, it was 425hp, then reduced to 375hp. However, the L72 was rated at 450hp early in 1966, before being dropped to a 425hp rating. A Google search of early 1966 L72 horsepower ratings explains it, and you can see the air cleaner sticker on early 66 corvettes. Chevrolet just had too many variants of their engines with minor differences in the case of the small block. In the case of the MK IV, they seemed to be hung up on maintaining 25hp differences between the different variants, and since their early hp ratings were extremely optimistic to start with, it quickly got silly.

[@mattrohr1266]

The 1966 reduction to 425 hp was insurance and corporate related only.

[@dannyfritts9706]

My “L-78” has “HIGH PERF TRUCK” on the back of the block it’s a 4 bolt main with factory aluminum heads and intake bored .60 over with 12.5:1 pop top pistons, what would the displacement be now? This engine was in a 1969 Camaro I bought, I bought the engine rebuild parts for it. Also the engine number on the back of the block comes back to a 1968 Chevelle.

[@richardholdener1727]

the aluminum heads are the l89 option and your displacement is 408

[@dannyfritts9706]

@@richardholdener1727 thank you Richard. I bought a 1969 Z-28 in 1978 the 302 had been blown up from racing it, the BB was in it when I bought the car

[@anythinggoesgarage5943]

that's pretty much spot on... I saw them squirters having fuel pulled thru them.. looked like the primary may have been leaking at the gasket? I've got the 325 hp version in my 68 Chevelle SS 4 speed. It has oval port semi closed chambers that makes great torque. Crane 270 old school car. Its a tire fryer with 3.31 gears.

[@gordocarbo]

Saw that also

[@otisbailey5455]

Thanks Ritchard, I have been waiting impatiently. I will ride with the 425 rating on mine as it has the proven upgrades that work. The 67 SS best release of 612 units.

[@joshuashuck3994]

It’s funny how people refuse to believe common sense, proof and logic when they have constructed an alternate reality like their uncle could tune a 750 double pumper to make 500hp

[@scottsigmon926]

We ran a 396/375 on the engine dyno with the stock 780, stock solid lifter cam and manifolds but it had an electric water pump and made 378 on 110 octane gas!

[@JViello]

If you don't NEED it, (I.E. optimal timing and A/F ratios on pump without knock) race gas will actually make less power. Slower burn rate and other factors.

[@scottsigmon926]

@@JViello a 396/375 has 12.5 compression!!! And it’s supposed to be ran on leaded fuel.

[@JViello]

​@@scottsigmon926 12.5!? For the L78? You mean 11:1 right? I don't know what any of what I wrote has to do with your comment. It was just a factual statement about fuel octane. We were talking about what the engine produced from the factory in 1969 and you were using an example using fuel that had a MUCH higher octane than what was available in 1969, higher specific gravity etc etc etc. If you are saying the engine YOU ran had 12.5:1...that might have been your problem right there. Race fuel isn't some magic bullet. Head design is much more complicated than "compression vs octane". There are designs that are optimised for a certain compression ratio and any attempt to raise it is met with less than great results. Again, just a stated fact, not saying your engine had this issue or that the L78 did.

[@playlist55]

@@scottsigmon926 LOL, no, L78 396/375 has 11/1 compression

[@oldschoolmotorsickle]

Did you verify the CR with the replacement heads? That engine seems to need every bit of compression possible. Cam timing verified and on the nose? I enjoy these affectionate retro factory look-backs!

[@crownironman]

I just finished a full bone stock restoration on an all original 1970 L-78 from a Nova, motor was untouched and I was the first to open it up. I have the original 780 carb on the original "low rise" 3963569 manifold with the TCS system installed. Heads are all original, new valves of course. I used the original distributor (even the cap) but I replaced the points with a Pertronix kit. Dyno testing showed the best HP at 420 and the torque at 428 through headers. I did not do the "hero run" as you did so maybe there was more in it. Also, I was a litter conservative on the valve lash, but I at that point I was out of time and I was happy with what it was showing. kzbin.info/www/bejne/l2TIl3quoddrbsU

[@AlanRoehrich9651]

The 396/425 in the Corvette was rated with an 850 vacuum secondary carburetor. Chevrolet removed all of those any time one came to the dealer, and replaced it with a 750 vacuum secondary. The insurance companies went insane when the first big block Corvettes were released in 1965.

[@richardholdener1727]

this wasn't carb limited at 425 hp.

[@benkrom2737]

11 to 1 solid lifters, yeah 425 hp

[@thegdfp6447]

780 came on them. Any verification of the 850 used for ratings?

[@nmbr3fan]

Absolutely wrong…..every 396/425hp and 396/375hp came with a 780 vacuum secondary carb from the factory (Tonawanda). Only the 427/430hp L88/ZL1 came from the factory with an 850….and that was a double pumper.

[@richarddahmer4474]

The main resign that all engines of big block or small block for that matter is back in the 60's to early 70" insurance companies would not insure a car if it made more HP then cubic inches!! I lived through that time and Ford or Chevy the 427 ford and 427 chevy where 424 HP rated if you look at the old test results, they did dino testing at way low RPM! like if you're a Chevy guy you know what a DZ-302 made way more then 296 HP! For me it was Ford back then, I build and race both now days, but the 289 HP "K" Engine was rated at 271 HP Yeah right! LOL!!! if you had to buy a new car on time you had to have insurance to cover the loan so a 435 HP Corvett or a 308 HP GT 350 Shelbey Mustang had to be bought cash! or get your own loan!! Definitely not like today where HP sells cars and insurance companies don't care? I built plenty of L-88's back in the day and with all GM parts 12.5 to 1 and the off road only Cam "Snowflake Aluminum Heads" They all made really close to 600 HP! some over! 289's with the same setup from ford 12.5 to 1, La Mans cam! made over 400 HP! etc. On pump gas! But we had 105 to 110 octan pump gas with real lead in it back then! LOL! @@richardholdener1727

[@MultiHotrod74]

Glad to see this finally completed. Thank you Richard!

[@coreyshort9461]

I agree with the marketing being the reason for the difference in HP. In 1965 Chevy still offered the 375hp 327 and with it also having 11:1 advertised compression and a similar solid flat tappet cam I can see why chevy may not want two engine options rated at the same power especially since the small block was so much smaller in cubic inch.

[@mylanmiller9656]

If you put he stock Mufflers Carb water pump and Fan with alternator it would be hard pressed to pull 375!

[@leighfisk1344]

The corvette used a better exhausr manifold

[@doctorcountersteer6580]

Dyin to know, Richard, how we didnt see any oil applied to the pushrod cup in those rockers? Plus you didn't use 'Vette manifolds....

[@richardholdener1727]

you weren't looking close enough

[@lostallmymoney2082]

My L34 396 with a 750 Holley, hydraulic roller camshaft, Edelbrock airgap and headers made 399.5 HP on the dyno. I think the numbers for the L78 were pretty accurate for the 375HP. 425 HP was marketing. Edit: MY 1970 so it was a 402. But it was bored 40 over which made it a 410 cid.

[@danmyers9372]

Wow, I would have expected a bit more than 400 with the upgrades you list. Guessing you weren’t thrilled with the result?

[@lostallmymoney2082]

@@danmyers9372 was happy with it.

[@jefflilyea4669]

Back in the day,400hp was a lot. I built a 327 w/ fuelie heads Lt1cam and 12:1

[@alanmeyers3957]

And it was probably stronger than this and it would last longer as well.

[@bengagnon6947]

Yeah it's funny how it varied from engine to engine. This one possibility slightly overrated then look at the L88 for example which said it had 435HP but actually had roughly 580HP from all the dyno testing I've seen. So it just depends on marketing from the competitors it was built for or tricking insurance companies lol thanks for the video very cool!!!!

[@naughtmeenaym869]

The 425 HP was only available in the Corvette one year. '65 was the only year for a 425 HP 396. The '66 Vette had a 427 (big block option). It was rated at the same HP. That convinces me it was GM Corvette bias on the 425 rating in 1965. Did Impala come with the 425 HP 396 in '65? Nope. The first few big gun big cars had the 425 409 then the 425 427. Chevy let the L78 loose on the rest of the carlines in 1966. The REAL anomaly is the 1965 Z16 375 HP 396 with similar intake and carb as the L78 but with a hydraulic cam. WEIRD. It's the only 375 HP 396 without a solid cam. New test?

[@MonzaRacer]

First of all one really trick way to get a drop booster 3310 to run is swap on an 850 CFM base plate and do a little clean up where they met. Losing choke horn isn't much in flow numbers but the blade and shaft really change it's characteristics. Now most racers with 375hp 396/402 swapped in headers and bigger exhaust nearly right away. Another trick is playing the cam advance or retard AND some would swap on different intakes but no internal mods to start. These little beasts could push past 450+HP and really did good in 1/4. Only thing better was swapping to a 427!

[@SpringVinMoto]

That overhead carb shot makes me proud to be an American! Really great series of videos. I may have to get an ultra xp for mine

[@thomasalair5861]

Yeah but even while watching it on my phone I have an uneasy feeling anticipating the pop and a ball of fire in my face.

[@buzzwaldron6195]

Like to see the 2 1/4" rear barrels of a Q-Jet...

[@alexcorona]

All the engines were overrated back then, just to sell more. Look at how much they dropped when they started net testing, some went down 100HP despite having the same specs.

[@oldsranch]

Its uncanny how many cars' HP rating was very close to curb weight divided by 10...Corvette excluded.... go down that rabbit hole sometime.

[@clevlandblock]

Nicely done. This video addressed one of the Chevy BB mysteries of that era in no-nonsense fashion.

[@Wilson-cp4gx]

Thanks for coming back to complete this with the right cam. Nice test. These were hard to beat in a chevelle with headers and a 411 or 456 gear.

[@gordocarbo]

Had a fake 68 SS in the mags back in the early 90s..Loved that 396. Close ratio M21 tall fwy gear lumpy hft cam headers it never quit pulling. Was always surprised at how much torque it put out. No need for OD

[@davidkirkham6497]

Yes, I purchased new in 1969 Chevelle L78/ 396/375 HP, m22 rock crusher. I ordered it with 3:73 rear end bears which were not near low enough for street racing. These had lots of power & always regretted not getting at least 4:10 or 4:56 gears to unleash the true potential of these high reviving mills. I had a lot of valve spring peoblems, probably from over reviving the engine! I used to speed shift it @ 7000 rpm.

[@Paulster2]

I didn't think they started using "net" horsepower ratings until 1972? If so, then this engine would have been tested without all of the accessories.

[@richardholdener1727]

it would have been tested with a water pump-that wasn't the only change from gross-net

[@mikewillett5076]

Right. Net started in '72. I used to look back and forth at '71 and '72 engine specs in books and thought they went way down in HP until it was explained the different test method.

[@milojanis4901]

​@@mikewillett5076 Net started in 1971. It's why the LS6 BB went from 450hp to 425......

[@mikewillett5076]

@@milojanis4901 . Actually not the case. '71 was still gross HP. The 25 HP drop from '70 was mainly from lower compression. If you look up several '72 engines a lot of their specs are the same as '71 but a big HP drop as it was net. Example: '70 LT1, 360. '71, 330 (lower compression). '72 had the same compression as '71 but rated at 255 NET.

[@paulk5311]

0:32 you inaccurately stated it had a 3.75 inch stroke. it should read 3.76 instead.

[@richardholdener1727]

yes

[@impalaSS65]

Thanks, the first video, and this one together are the reality for anyone doing the hands on themselves. Also great to see an L78 perform as intended. Love any big block that is this close to stock. Those OEM style chrome valve covers are the best looking ones. Even though I'm not crazy about the ad hoc solution with the dent for the vacuum reservoir.

[@thman6453]

Carb cam is pretty cool 😎 👌 👍

[@richardholdener1727]

agreed-the squirters are adding plenty of random fuel

[@nerradnosnhoj5122]

There was a test done on one of these that made 425 HP with manifolds and up to 450+ HP and 465 Torque with headers , might have been in HOT ROD awesome engines the 396/402 BBC

[@alanmeyers3957]

Awesome? They usually won’t go 100,000 miles and those are the ones that don’t throw rods, I’ll take a small block anyday.

[@nerradnosnhoj5122]

@@alanmeyers3957 You are correct , most performance engines do not make 100,000, a lot do not make 5,000 miles without wounds being repaired and I am talking about performance engines in cars that are being pushed hard , dragstrip etc . both small and big blocks.

[@fridgeopener236]

Everybody's papaw is going to be trying to fight in the back yard when they get shown this video over Christmas dinner😂😂 Hop a coke can I swear!😂

[@alonzahanks1182]

putting on smaller carb and saying its new and improved and would compensate for 200 cfm smaller carb is like a restrictor plate

[@patbateman6729]

I believe back in the day Chevy exaggorated on all there motors, especially the BB's. Chrysler had a CI advantage until 1970 and the horespower wars was huge for car sales. With all the dyno's out ther today there are many video's proving this.

[@HioSSilver1999]

I would love to see what some general improvements would do to this engine. Stuff like a better balancer, better oil control, roller rockers, better intake, e85. Do that with the stock cam and heads!

[@robking9857]

I would like to see the same tests... and then add a rowdy street/strip cam... and then add NOS to see how you can take one on a "relative budget" and up it in stages. Or, do the upgrades and add NOS with a stock cam... or both. Keeping in mind a hot street driver to the dragstrip and toss on slicks type of sportsman deal.

[@mattrohr1266]

That was not a stock Corvette left exh man, did not see the right side, but they dont flow as well as the Corvette, the TI factory ign was fantastic also.

[@danielduvall4154]

That thing sounds good!!

[@DaveyHo69]

I've got THE carb for that: 3959164-GE List-4346 2872 1969 big block 396/375 & 427/425 high performance models. 780 CFM Original GM part # 3959164 Holley list number 4346 on air horn, original. Exact fit for all 69 , 396/375 & 427/425 models. PART NUMBER: ENC-844

[@shanefrericks2070]

Chevrolet needed up their horsepower in the 396 just to beat the Little GTO it was on the 360 horse 389 or the new 400 that year that was rated at 366 horse. But then again Chevy needs to get 425 horsepower 396 to get enough torque to beat the Little GTO

[@Thumper68]

My old man taught me to oil bath lifters overnight before installing.

[@armcchargues8623]

Very surprised the stock cam was that lopey at idle. I guess the factory exhaust hides a lot of the chop.

[@zachattack2016]

they did it for emissions. and i believe they tested all engines with long tubes and open carb. correct me if im wrong

[@randyphillips559]

To bad you didn't have the Corvette manifold. Still might not have made the 425hp or would it?

[@ericuncapher9922]

They are variances between dynos. Yours might be off. Or there's. Who knows.

[@simbanugz2906]

My uncle has several L98 swap vehicles, with a turbo 400 and 3.08 gears in a 89 camaro with Holley 750 in a pretty much stock L98 on 93 octane. Full assesories without ac. Put down right at 330 whp. Runs low 12s @110 mph. He has a L98 swapped in his 92 Silverado drag truck runs mid 11s 112-115mph. My uncle has at least 3 L98 engines sitting on stands. Mention LS swap around him and be prepared to get into a heated battle.

[@richardholdener1727]

L98 TPI motor?

[@hugieflhr03]

Love the Carb Camera!

[@danlaperuta6916]

Would you consider putting a 454 crank (4 inch stroke) in a 396 to create a square engine 4 inch bore, 4inch stroke ? Keith Black makes the pistons for this combo.

[@richardholdener1727]

NO SIR

[@mikef-gi2dg]

@@richardholdener1727 I am looking at those same KB 396/402/434 pistons. I am curious why you wouldn't consider it. If there is an unseen (by me) problem with this, I would like to know before dropping some cash down the drain. Very good test by the way.

[@richardholdener1727]

My point was that this 396 is staying a 396 (actually 402). If you are asking if you should do it, then the answer is yes-bigger is better. Or just go get a cheap 454 from the junkyard for less than the cost of those pistons.

[@mikef-gi2dg]

@@richardholdener1727 Thanks for the reply, it means a lot. I've had 2 402's for a long time, and in my area 454's have turned to gold $$$ lately. Time do do something with them. Thanks again.

[@godblessamerica99]

So the engine makes 434, but you think 375 rating is more accurate. Ok got it.

[@bdugle1]

I love the sound it makes! Looks to me like the peak hp was waiting for you at 6100-6200 with headers. Nice re-creation, thanks Richard!

[@duradim1]

Chevrolet wasn't known to under rate their engines overall.

[@PatandDoopypoopy]

Thank you. Been waiting to see this. Very cool test. You tuned much better than o.e. and definitely a superior carb and ign. Be well.

[@lancelanphier9509]

In addition; running the factory pulleys without the Meziere electric water pump would have reduced horsepower even more, so I would have to agree with you on the original rating of 375

[@TractorWrangler01]

I love this kind of testing.

[@realbogus]

SAE gross HP did not have any engine driven accessories. Run this using SEA net rules.

[@annelarrybrunelle3570]

Interesting comparison would be a '62 421 Pontiac, nominal 405HP. The BBC was supposed to have a lot more going for it . . .

[@geneparadis7888]

375HP for sure in the car because the full exhaust air cleaner and accessories that run off the fan belts.

[@robertbergstrom9287]

I will be rebuilding a stock 69 396/350 hp engine for my SS Chevelle. Would roller rockers and roller cam jump the hp and tourqe up? It will have stock exhaust manifold.

[@richardholdener1727]

yes-depending on cam specs

[@notinterested8397]

I would love to see how much weaker the 325hp 396 was. 275? Less?

[@Lagrange1186]

I think we need more carb cam! Awesome video Richard thanks again.

[@richardholdener1727]

agreed

[@benkrom2737]

SHP, 11TO1, SOLID LIFTERS, 4BOLT MAIN CAPS. YEAH 425 HP I had a firebird RAIV AND MY BUDDY HAD THE CAMARO WITH L78 WITH HEADERS AND POWER WAS SOO MUCH MORE THAN MY RAIV AT 370 HP. AND YEAH I MODIFIED THE SECONDARIES ON THE FIREBIRD 🧐

[@dannytravis7118]

I think that 375 was probably closer to the truth but end of the day seat of the pants in a vette torque was the real story. That much torque in a light vette was probably a like a rocket taking off

[@michaelfercik3691]

Can't compare apples to oranges like you always do, with excuses for everything different being the same. They made close to 440 hp if you researched all information and car magazine tests from the 1960's when original parts were used with no exacuses.

[@richardholdener1727]

no

[@DaveyHo69]

Back in the '70s, my friend had a built L78 in his stock car, sold it to me. In my '68 Camaro, it would peg the right turn indicator in L2, Drive WAS the Millenium Falcon!!!

[@MrSpartanPaul]

I wish you would test the big car big blocks (non-hi perf 454,455,500) which all claimed to make 360-375 hp, but in reality made closer to 300 or less.

[@alanmeyers3957]

Huh?

[@Demoralized88]

After having seen some seen some revivals with those engines (Cadillac 500, Lincoln 460 (?), GM 455 and 454) from the 'peak' HP years in luxury landyachts it's actually shocking how overrated their 'gross' HP ratings were and how obvious it is that they're well over 100HP less than advertised. They all have torque, obviously, but are slow as shit from a roll despite being rated around 400HP. Very few engines were actually built like the one in the video to flow and rev to make anywhere near the rated HP, yet they barely lowered the rated HP for the severely detuned engines that went in the vast majority of them. Crazy.

[@MrSpartanPaul]

@Demoralized88 Absolutely correct! The advertised HP for the luxury cars was total BS. Richard Holdener's channel has dyno results for a lot of bone stock V8s and the HP is nowhere near 375 or 400. More like 320 HP for a 472 and 330 HP for a 500. Muscle car HP ratings are close to reality usually.

[@timothybruggeman9332]

Mostly just curiosity, but why, when you are dynamometer testing, don't you set the engine up in the configuration it will have when it is in the car? E.G. air filter, water pump running off the shaft pulley, mufflers? Maybe it's as simple as being able to directly compare other engines output, apples to apples, without having to know what the end user is going to use for those accessories?

[@richardholdener1727]

I have accessory tests up too

[@jamesbosworth4191]

Because the manufacturers test them without accessories, so he is duplicating THEIR test to see if he will get the same power figures that they did. If he puts the accessories on it, it will make about 12% less.