1967 Camaro for OUSCI

[clill]

Thats it ? Two pics ?

[coolwelder62]

Two pic's.Two

[formula88]

Originally Posted by clill

Thats it ? Two pics ?

Haha... Guess you need to bug Stielow to get more work done

[preston]

Would sure like to hear as many details on the engine as you want to share.
All I know is that it is a "ZR1" supercharged 427 LS.

Heads ? Cam ? Idle vacuum ? Compression ?
Mods ?

I usually assume that even the modern compression style blowers are still only about 5% efficient (including drive losses), which means at 882 whp the base engine is making 550 to the wheels ?

[camcojb]

Originally Posted by preston

Would sure like to hear as many details on the engine as you want to share.
All I know is that it is a "ZR1" supercharged 427 LS.

Heads ? Cam ? Idle vacuum ? Compression ?
Mods ?

I usually assume that even the modern compression style blowers are still only about 5% efficient (including drive losses), which means at 882 whp the base engine is making 550 to the wheels ?

Huh???!!!!!! I will guarantee it makes way more than 550 rwhp. 5% efficiency seems just a bit low................ I remember when they were first starting the dynoing of the ZR1's their first dyno pulls were making close to 700 rwhp. They definitely backed it down for the production cars.

[preston]

Well if it is more efficient than 5% than the base engine power number is lower than 550. I know you understand that - IF the blower is 6% efficient than the base motor would make 512 whp. This assumes 12 psi of boost.

550whp is about the max I've seen for the 427Ls motors that are in what I would call the "streetable envelope", and Mark has always setup his cars to have reasonably tractable drivetrains. So I don't think it is "under rating" it to arrive at 550, that is a huge number, somewhere north of 650 on the motor dyno. That's why I'm always very curious about idle speed and vacuum, its the only way I know of to get some idea of how aggressive the engine is.

Not trying to be "one of those guys", I'm just genuinely curious about what went into such an amazing engine.

[camcojb]

Originally Posted by preston

Well if it is more efficient than 5% than the base engine power number is lower than 550. I know you understand that - IF the blower is 6% efficient than the base motor would make 512 whp. This assumes 12 psi of boost.

550whp is about the max I've seen for the 427Ls motors that are in what I would call the "streetable envelope", and Mark has always setup his cars to have reasonably tractable drivetrains. So I don't think it is "under rating" it to arrive at 550, that is a huge number, somewhere north of 650 on the motor dyno. That's why I'm always very curious about idle speed and vacuum, its the only way I know of to get some idea of how aggressive the engine is.

Not trying to be "one of those guys", I'm just genuinely curious about what went into such an amazing engine.

I think you and I have a different definition of efficiency. If I say a blower is 5% efficient then that means it's 95% inefficient, it costs nearly as much HP to run as it makes.

Since the stock ZR1's dyno in the 540-550 rwhp range (Dynojet) and make 638 flywheel HP, I'm not sure how you'd add 240+ flywheel HP and still dyno at 550 rwhp.

Yes, the blower costs HP to run. If he's making 880 HP he's probably using fuel for 1000 HP+ to cover running the blower.

[camcojb]

To answer your question on engine specifics, we'll wait on Mark. I do know that Red Devil idled like a stocker at 600-650 rpm, so the cam doesn't have a lot of overlap..............

[preston]

Yeah my mistake - I'm totally using the phrase "blower efficieny" incorrectly. By that I mean you gain 5% power per psi of boost. The max "efficiency" possible is 7% (100 % / 14.7) which is close to what turbos get. Blowers (especially PD style) usually dip down to 5% per psi of boost.

When I say the "base engine makes 550whp" I mean with (theoretically) no boost or blower restriction the base engine makes 550

I was under the impression those dyno results I saw were chassis numbers, but I went back and those are engine dyno numbers. So if I run my little rule of thumb -
5% * 12 psi = 60% more power

875/1.6=550 base engine power at the flywheel. That actually makes more sense to me as a 550 hp Ls 427 is well within a streetable, tractable envelope.

Either way a tour de force, especially as we know the work has been done so it can live under track abuse.