L72 engine

[68-427]

I see that Barrett Jackson will be selling a 68 Yenko Camaro this January. They describe the engine as 450 HP. I thought the L72 engines for 68 were 425 HP. Which is correct? Were there any significant differences between the 425 HP L72 and the 450 HP L72?
Any thoughts on what this car will bring at the sale??Thanks.

[Keith Tedford]

People love to use the biggest numbers that they can. With headers and tuning an L72 might make the 425 hp and the L78 375. Forget the big numbers. They just won't happen with an as factory built engine.

[68-427]

I was just wondering which HP number is correct for a 68 Yenko 427. In other words, what should the air cleaner decal say?
Is the 68 Yenko Camaro that is listed at B-J correct when the air cleaner decal says 450 HP? I assume this car is the real thing and some of the members here are familiar with the car.
Thanks.

[WILMASBOYL78]

The L72 engine was rated at 450hp for a short time at the beginning of the 66 model year and then "downsized" a little. Most assume it was for insurance purposes, or maybe to balance out the presentation between the L78 and L72.....as for real horsepower....blueprinted L72 with tuning and headers will probably produce 450hp or more...the L78 version can make 415-425 with similar prep.

I seem to remember the article about the Harrell prepared 427 cars being rated at 450hp...you can have any horsepower you want for about $3.00...just buy the sticker!

wilma

[3macs1]

Hi Keith:
I'm suprised that the big engines would not make the rated HP. The dyno graphs Gm published for them at the time clearly show they did and if anything GM derated the actual HP.
I have only had one BB ever on a dyno a oval port 427 390 hp and it produced 431 Hp . I know it was bored 30 over and the engine rebuilder was told to do what they want inside to get the max HP but it has to stay original outside and not be decked to keep the vin. It did have headers installed but it's original reworked quadrajet and points.
Same time the brothers that built it are well known in Nova Scotia for their ability to produce HP. Those who know them will remember their 10 second white camaro with the 292 chevy 6 cylinder which they raced across canada and the US for years.
Great guys. I Really don't know what they did vs stock nor did I ask at the time.
Same time these guys could probally pull 50 hp out of a craftsman lawn tractor.

[Keith Tedford]

I was referring to "as factory built" meaning as delivered from GM. One of the guys on this site had an L72 on an engine dyno and it made something like 429 hp. It had a 2" carb spacer which won't fit under a Chevelle hood. It had dyno headers which don't come on the factory cars. It was running racing gas which isn't practical for the street if you run 3K+ miles a year like I do. I would assume that the carb and timing were also optimized.
Our L78 Chevelle is factory stock except for tuning and headers. It is capable of 13.3s. It has no options to add any substantial weight. That might equate to 320 hp at the rear wheels. There are formulas on the internet where you can roughly figure hp and et. With flowed heads, good streetable cam, headers, and lots of little tricks, a friend's '70 L78 Chevelle runs 11.70s. There is a big difference between "as delivered" and tuned. Not that I have a lot of faith in the old magazine road tests, but the L78 cars were usually mid 14s in the quarter. I road in a few of these back in the day. Our COPO Chevelle came with#68 primary jets and lean surge at highway speed. The advance curve was also for emissions. On top of that 5 cylinders had rings that didn't seat. It was a dog. A re-ring, good valve job, headers and some tuning and it was night and day difference.
I believe that GM tested their engines on an engine dyno without accessories. These numbers will not be indicative of what the engine will produce in a car through the drivetrain. Plenty of losses there.
In the end, the quarter mile is the real test.

[Chevy454]

I tried to emulate an *as delivered* L72 as best I could and it hit just over 425hp on the dyno...crappy TRW pistons, rods, cam/lifters, rockers, etc...no internal tricks, just slammed together like in '69...the only thing that wasn't as it left Tonowanda was the .030" bore. I dyno'd it through the stock exhaust manifolds and air cleaner and points ignition...I later found out the 780cfm Holley I had ran was junk, and when I switched to a decent one I picked up ET/MPH, so there was a little more in the engine...put it in front of an automatic, and it pushed our 3700-3800 pound Camaro to 12.7s @ 108+ [on pump gas], and would have picked up a tenth had I known then what I know now about getting the car to hook.

Our blueprinted L72, on the other hand, put 75+ horsepower onto that number, and has gone, ummm, let's say "really low" 12s @ well over 115, in the same car as above...

[68-427]

So, is the B-J 68 Yenko the real thing? Anybody brave enough to guess what the car might sell at?

[nuch_ss396]

[ QUOTE ]
Hi Keith:
I'm suprised that the big engines would not make the rated HP. The dyno graphs Gm published for them at the time clearly show they did and if anything GM derated the actual HP.
I have only had one BB ever on a dyno a oval port 427 390 hp and it produced 431 Hp . I know it was bored 30 over and the engine rebuilder was told to do what they want inside to get the max HP but it has to stay original outside and not be decked to keep the vin. It did have headers installed but it's original reworked quadrajet and points.
Same time the brothers that built it are well known in Nova Scotia for their ability to produce HP. Those who know them will remember their 10 second white camaro with the 292 chevy 6 cylinder which they raced across canada and the US for years.
Great guys. I Really don't know what they did vs stock nor did I ask at the time.
Same time these guys could probally pull 50 hp out of a craftsman lawn tractor.

[/ QUOTE ]

431 hp on a Q-jot! SWEET!

[3macs1]

Not saying it was not worked Steve. Q-jets are usually ok in the right hands under 500Hp, lose some top end but this motor was not built for racing.
Had no choice had to put the original carb back on.