450 hp L72 rating

[Stefano]

The 427 L72 was released in the 1966 Model Corvette and rated by the factory at 450hp in the early car and 425hp in the later cars. Same engine different rating. The L78 /396 was also rated at 425hp for the '65 Corvette.

While I certainly can't speak for the man, I would speculate that Don Yenko who was very familiar with the Corvette Engine used GM's own marketing specs. and Dyno Results to rate his Super Cars.

It was after all the same L72 over the counter blocks which Yenko Sports Cars Inc. began installing between the fenderwells of their first Camaro Super Cars.

Just My opinion and observations.

[jg396]

Speaking of the 425hp 396. Would you happen to know of where I could get the spec's on this engine? I'm looking to build something similar for my 1969 SS/RS 396 Camaro. I've got most of the parts to build this motor except for the spec's for what cam was used and any other special parts. Your help would be greatly appreciated. Thanks, Jesse /ubbthreads/images/graemlins/biggthumpup.gif

[Chevy454]

I believe it's just standard issue L-78 (396/375hp) stuff. What kind of specs you needing?

[Keith Tedford]

From dyno specs etc that I have seen over the years, I would think that the 396 at 375 hp, the 427 at 425 and the 454 at 450, are probably right in the ball park for stock engines. I think Peter Simpson's motor was somewhere around 430 hp and an LS 6 was somewere around 460. We have had a couple of stock L78 Chevelles, with headers, over the years and they are definitely down on horsepower and torque compared to the L72 motor. Until 1966, most companies were putting some pretty bogus numbers on the breathers. Once everyone started racing, reality set in. /ubbthreads/images/graemlins/smile.gif

[Belair62]

OK so what was on each Yenko Camaro air cleaner lid in 1969 ? 425 horse,450 horse or nothing ????

[Chevy454]

Our last L-72, built EXACLTY as the factory did it (10.2:1 compression ratio) in 1969, made 425hp on the dyno through the stock exhaust manifolds and head pipes.

[Keith Tedford]

The Yenko Chevelle tested in SSDI in '69 didn't appear to have any breather decals.

[jg396]

I was just looking to find out the information I would need to find the correct cam to build 425hp out of my stock 375hp 396 motor. I was thinking if I went with what ever spec's where used on this vette motor. I could possible get the same 425hp. Or something close to that. I'm looking to go totally stock with it on the outside(valve covers, smog, carb, intake etc..). Then as close to stock as possible on the inside. I have the stock dimple rods and correct crank for it. When I have the machine shop get pistons for this motor what kind of compression should I be trying to get to. I've heard that stock was 11:1, but then I noticed that it's been mentioned to be actually 10.2:1 too. Which would be best to go with. I plan on driving this car a far amount (1000 miles or less a year). Also is thier a brand of piston that would be the best to go with that you guys like to use. I want to do this thing once and be done with it. I don't know if this matters or not but I will be putting 842 aluminum heads on it. Any help would be greatly appreciated. Thanks guys. Jesse /ubbthreads/images/graemlins/burnout.gif

[Stefano]

There was an article (I believe he actually wrote it) about Bill Thomas in Hot Rod Magazine Circa Mid to Late 1966 on Blue Printing the L72.

I don't have the actual magazine available. That article was part of the Manual which Bill Thomas wrote on Blue prining the L72.

I seem to recall that the Dyno Hp was well in excess of 450hp when the engine was brought up to mfg. specs.

Does anyone remember the article?

[Unreal]

Keith, is that the definitive answer? Did all Yenkos and COPOs have no any decals? Just have crossed flags decal? or both crossed flags and 425HP decals?

[Keith Tedford]

Don't take anything that I say as difinitive. GM was too good at throwing curves for us to be too sure of anything that they did. However, three of us bought COPO Chevelles from the same dealer and none had decals under the hood other than the Tonawanda sticker on the passenger valve cover. The dealer didn't even know what the horsepower rating of the engine was. Here is a day one shot of one of the engines.

[Keith Tedford]

This was our engine in late '69. I added the 427 cross flags to the breather as well as the Delco CD ignition that had the two ballast resistors mounted to the firewall. With this setup the points were just the trigger and didn't burn out. It worked well and I have the complete setup in the original box.

[T Billigen]

I talked to the original owner of The Chevelle I once owned and he said "to the best of my recollection there was no decals on the air cleaner." How about the Camaros though? Did they have the cross flags and the 450HP decal? BKH, any help on this? /ubbthreads/images/graemlins/scholar.gif

[Keith Tedford]

The COPO Camaro that Nurse Chev-Olds sold didn't have any breather decals. I think you will find that they were added by the dealers or owners. The car was written off in about 1971 in a bad accident.

[Mr70]

Keith
Nice Pictures.
*Is that a metal 427 emblem you put on the Air Cleaner top.
*Is there a CN cardboard tag hanging on your Master Cylinder Vacuum hose,and are your fender well flaps
installed from the road side?
*When did you remove your Smog equip. after taking ownership of it.
Rick

[bkhpah]

The Yenko Camaro's only used the 427 cross flags on every original I have seen. It is popular to add the 450 H/P decal, but I feel that would be incorrect. But it looks nice if you like it...BKH

[bbdon]

I really enjoyed these pictures, Thanks for posting!

[T Billigen]

Thanks for the info, I thought it was just the cross flags but did not know for sure. And that is what I will go with. /ubbthreads/images/graemlins/flag.gif

[Keith Tedford]

The emblem was the same one used on the fenders of the big Chevys. I don't recall any tags on the vacuum hose. Then again, how good are 57 year old brain cell. With the car all apart I'll have to do some digging to find the inner fenders. Both of our cars had the plastic inner fenders. I removed the smog system shortly after buying the car but reinstalled the pump because the belt tended to roll over once in a while at high rpm. Never a problem with the pump on the car.