I had my 502 dynoed today. It made 371RWHP and 367TORQUE. It is a GM 502 crate motor. Are these numbers pretty normal. Drivetrain is a TH-400 with 3500 stall converter and 3.73 rear gear.
Scott

HO 502 or ZZ502 crate engine?

It is a ZZ502

Typical HP loss through the drivetrain is thought to be from 20% to 25% of what the total HP is at the engine's flywheel.
If you apply the 25%, the figure comes out pretty close to your actual reading....25%= 377 RWHP
20%= 402 RWHP .Of course these numbers are based on a theory and you could use any percentage between 20 to 25 for HP estimates.

Scott..I am also waiting to hear from the zz502 crowd regarding chassis dyno #.s.The general usually underrates its power levels.If you go with the 20% powertrain parasitic loss..you could expect over 400 rwhp out of the zz502.The variables lie in the chassis dyno itself and the somewhat loose 3500 converter.I am not a chassis dyno fan for hp #,s.More of a tuning tool in a controlled environment.I would not sweat the numbers at all.The mph at the track would be a better indicator of rwhp.What facility did you use out of curiosity and how much did they charge you.?.if you do not mind me asking,.

That seems low. I remember an episode of horsepower tv where the ZZ502 made over 400 HP and I think 467 Tq. thru a th 400 trans.

I had Baker in Nunica dyno it. I did five pulls in about and hour and it cost $125. They charge $125 for the first hour and $75 for every hour after the first. Nice guys. I wasn't real concerned with the numbers just curious. Hopefully I can get it to the track next month.

Those numbers look good...better than most stock 502's I have seen. Your car with traction should run in the 11's no problem.

Your horsepower is pretty close to what a friend of mine recently got from his 69 camaro with a ZZ502. His car has the TKO-600 5 speed and he pulled 376 hp on a chassis dyno. What amazed me was on the same chassis dyno at the same car show on the same day another friend of mine put his brand new Z06 Corvette with 400 miles on it on the dyno to see what it could do. The result was 452 hp, I would have never guessed there would be that much difference between the two cars as the vette is rated at 505 hp and the ZZ502 is rated at 502 hp. Both cars were manual transmissions so I would have thought the losses would have been about the same. I guess Chevrolet has really done their homework with the newer car. Or someone is fudging the true horsepower numbers.

Were the Z06 and ZZ502 motors rated in the same way? The 502 doesn't come in any production cars that I'm aware of, and maybe they measure the production motors differently.

Hi there 6D9,

How do find that XS274S...solid flat tappet ?
What is the idle like ?
What RPM does it pull to in the 408?

I looking at using one in a 355

I wonder if the Vette @ 500+ hp grabbed them chassis dyno rollers better than the 69.I would like to get on a chassis dyno,but not for hp #,s.I question roller traction = slippage skews the #.s with differant cars.

In all the hundreds of chassis dyno tests I've done I've never seen tire slip.

Thanks for the feedback onovakind.this has been a concern for me for some time.My street rubber is slippery and wondered if they would be the same on the rollers.Obviously not.

The rollers are pretty sticky. It's like using the same 12 feet of track over and over.