This is the second of two posts and discusses mods I have actual done on my cars or on friends cars and SEEN the dyno tests myself. All #s given are on the same Dynojet dyno and corrected using the SAE correction method dynojet uses:
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Here are the results of modifications and tests I have participated in and witnessed myself over the past years, on Corvette or Corvette-type drivetrains. All numbers are RWHP

346 cubic inch LS1 in a 1998 Camaro Z28 M6
A. Stock, as from the dealer, 2800 miles: 294
B. Stock but dyno-tuned for max power: 302
C. with short-tube headers, sealed cold air box and ram air scoop, LS6 manifold, ported MAF and throttle body, “mid-range” aftermarket cam: 349
D. all of C above but with long-tube headers instead, 358
D with catalytic converters removed, 365
D with cats removed and open exhausts, 360
E. all of D plus “75 shot” of NOS: 403
and a “100 shot” 425
and a 175 shot 470

346 LS6 in a 2002 Corvette ZO6 M6
A. Stock, as from the dealer, 2500 miles, 357
B. dyno tuned but otherwise stock, 363
C. with long-tube headers, air box, retuned: 385
D. C with Magnusen SC kit, no intercooler, 6.5 lbs boost,450
E. D with a lot of fiddling and fine tuning, higher pressure fuel, 465

346 LS1 in a 2004 Corvette M6
A. Stock, from the dealer, 1980 miles, 309
B. Returned on the dyno, 314
C. Long tube headers, halltek air box, aggressive street cam, Magnusen w. intercooler, 7.2 lbs boost, 485
D. As C above but a smaller-than recommended SC pulley, 8.3 lbs boost, 514
(This engine blew up spectacularly only 500 miles after this mod)

408 LS6 (bored and stroked cast iron block from a 6-liter Silverado/Escalade)
A. With AFR 225 heads, 11.25:1, radical cam (255/265/.670 lift, lumpy @ 1200),
all forged internals and APR, LT 1 7/8 LT headers, 3 inch exhaust, no cats, LS6 manifold and stock throttle body, cold ram air, etc. 465
B. With FAST 90 mm, 512
C. With 175 NOS, 648 (and 700 ft lbs of RW torque at 4100 RPM)

427 cubic inch “LS1” (GMPP C5R block)
A. Patriot III heads ported by Justin Engineering (347 flow @ .6 inch rise), 10.2:1 c.r., custom grind Crower cam (232/236/.594 lift), Blackwing airbox, 1 7/8 LT headers, largest size cats available, 3” H pipe, 2.75” GHL catback, LS6 intake manifold and throttle body, underdrive pulley 485
B. A above with FAST 90 mm: 507
C. As B above but with an ATI Procharger at:
4.5” pulley: less than 1 lb boost, 470 HP
4” pulley, only 2.5 lbs boost – 510
3.75” pulley, only 3.5 lbs boost – 535
3.4” pulley, 4.5 lbs boost – 565
3.4” pulley, 4.5 lbs boost, no cats, open exhaust, 594
3.25” pulley – slips about 5250 RPM, test not completed.
The engine has been built with forged internals and only 10.2 c.r. so that it should take up to 10 lbs boost at which it should be around 700 RWHP. The problem I have is that I am driving the SC with a under-drive (small diameter) crank pulley and not spinning it fast enough, but below 3.4” on the SC can’t get enough traction to power the SC (it takes about 85 HP at full RPM). I can’t add a stock diameter pulley on the crank because only the underdrive aftermarket pulleys will clear the double roller timing chain I added to handle the big cam. I’m having a new crank pulley custom machined when I can afford it).

 

Wow, an awesome post. Have you ever seen any dyno results for the ZZ crate engines? I have one I literally took out of the crate (it really came in one) and dropped in my car: it started and ran just the way you'd hope. Never dynoed it thought. Supposed to be 355 HP.

 

I have not seen a ZZ crate engine dynoed but I have been told that one in a 64 Nova with a 4-speed and a big, custom Magnaflow dual exhaust here abouts did right at 295 RWHP.

Ive always been under the impression that the "355 HP" ZZ crate engine was similar or identical to the 335 HP factory-rated LT4, and like many crate engines, has its HP rating given as what it would register on an engine dyno (I mean, it IS out of the car when you buy it in the crate, isn't it?) than actual installed-in-the-car flywheel factory rated HP, which accounts for the 20 HP difference.

Maybe somebody else knows more . . . .

 

What about just cubic inches? GM Performance Parts sell 572 and 620 crate V8s up to 620 HP.

 

Well, the GM crate engines are great, except, the 573 and 620 are based on the big block (rat) motor 454 of old, with new heads, etc. They are big - too big to fit in a modern corvette or Camaro (at least on the street) and too heavy. Also, I think they are carburated (although it would not surprise me if there were fuel injected models) and carbed engines that big get about 8-9 mpg.

These crate engines are also rated on engine dyno values (the 620 HP is probably about 575-590 HP flyshweel when in the car, and about 500-520 at the rear axle would be my guess).

 

Thanks for the post Lee, this is really going to help me out, with trying to figure out what mods to do first.

 

Hey, CaptVette, why don't you post what it took for your car to get 521 HP?

Anyoneelse with a C5 and mods, please post what you got and what you did to get it.