Curious!

[82z96ss]

I understand that the COPO, Yenko, ZL1 etc were given a 427 450hp motor. I have heard that on a dyno that these cars were getting around 560-570 rwhp. Were these engine numbers or rear wheel numbers? Did Chevy purposely down grade the motor that much {i think that would be insane to do}? Or was the 560-570 rwhp numbers just off a ZL1? [img]/ubbthreads/images/icons/confused.gif[/img]

Enlighten Me Please

[Don_Lightfoot]

I certainly can't speak from first hand experience, but my opinion would be those 'rear wheel HP numbers' were not attainable from either the L72 or ZL1. It may seem reasonable for the ZL1, with it's 12.0:1 compression, to come close to those numbers at the flywheel. Maybe somebody can jump in here and be more definitive.

[NEW]

Hi,
I would be amazed if the racing guys back then didnt have at least 550-600 HP in the ZL1, at the flywheel after blueprinting, and peeling of stock exhaust systems, smog etc.

My 355 in a 66 Nova, makes 511 HP on the flywheel and thats also with stock GM parts.


NEWs

[Chevy454]

I think it's possible. If my memory isn't too rusty, I think GM did a test of a stock ZL-1, with a set of headers, that wasn't too far from 600hp. I don't think those kind of rwhp numbers would be too hard to get with a ZL-1 with headers. Pete has some experience with a ZL-1 on a dyno...what do YOU think Peter?

[82z96ss]

I wonder why then that GM would rate the motor so low 450hp. I know they do that on newer camaros as not to offend corvette owners but what about the older cars?

ANy explanations?

[Chevy454]

Actually, the ZL-1 was rated at 430hp from the factory, which was GROSS horsepower. NET horsepower they were probably 370-380...somewhere in that neighborhood. I would say both of those numbers are a bit conservative. Oh, I looked up the GM dyno test, and it was in the 530hp neighborhood with headers. But, more is easily attainable!

[Mr70]

I have a 1970 Chevrolet engines Dyno test catalog.
I know we'd all like to think Chevrolet was conservative with the Horse Power ratings,but
in it shows the graph charts and Gross Horse power specs for all the 1970 engines.
It shows the LS-6 tested at 448 peak HP.Other engines from that year were around what they were advertised or less on their respective Air Cleaner labels.
These were engines with Exhaust manifolds as delivered into the car.

[Seattle Sam]

Mr70,
I have heard that Chevy used horsepower and torque numbers that occurred at less than peak RPM, producing more conservative numbers that they could still claim were accurate. Does your data include the RPM at which the horsepower and torque were produced?
-Sam

[Chevy454]

I would absolutely LOVE to see that dyno catalog! Any chance of you posting it or...?