I've got an 89' iroc with a 5.7 tpi. Motor is stock with just over 82,000 miles. I am planning on pulling the motor out and doing a rebuild/worked motor. I've been a diesel mechanic for many (10 yrs) and I don't know alot about gas engines. I would like the motor when complete to put out 400-450 hp and be able to accept a 100-200 shot of nitrous. What should be done? 355,383? Heads? Cam? Intake? Forged vs. non-forged. HSR? Super Ram? The car now has a cat-back 3" and hypertech chip. Thanks for the help.

 

This is an E.F.I. combo that has been dyno tested:

Bore and stroke to a 383, use 5.565-6.000 rods if clearance permits, a set of pistons that will put you around 9.2-9.5:1 compression, clevite bearings (my preference), a single pattern cam with 219 duration, 0.503 lift on the intake, 0.525 on the exhaust with 112 degree lobe seperation angle. Use a set of A.F.R. 180 heads. They're pricey but worth it. Use 1.6:1 rocker arms. Use the Accel Super Ram and 58 mm throttle body and a set of 1 3/4 hooker super comp headers. The power output was as follows with a little more compression, which wouldn't be good for your nitrous set up:

Tq Hp
1600 363 110
2000 375 143
2500 411 196
3000 424 242
3500 466 310
4000 476 362
4500 481 412
5000 458 436
5250 446 442
5500 416 435
6000 372 425

As you can see, this is a pretty torquey motor that would be very responsive on the street. With a 200 shot of nitrous you're looking at around 642 hp. Not too shabby. Hope that helps.

 

So you are wanting 600 hp...

Splayed Main caps, Forged Pistons, 6" H-beam rods, Forged Crankshaft, balance and clearance. There are a lot of little things you can do like lifter valley vents and windage trays. The stroke is like this, 3.48 revs to 7300 all day with those HD parts, 3.75 probably 6800 all day.

So depending on your heads and cam will find your power range. Your shift point is usually a few hundred RPMs past your peak hp. Do you have Desktop Dyno?

The 5.565 rods are a joke, don't do that.

A diesel engine should have a very similar long block, I think the only difference are the heads and fuel system.

 

A very important thing to remember is that excessive rpm's are more likely to cause engine failure than power. Stay around 6500 rpm's if you want longevity from that motor. 7800 rpm's is for a track only car that hardly ever sees street duty. Heads and cam do determine your powerband, but if this combo is destined for the street you don't want to run a cam with too much duration. People who do that usually wonder why their engine is such a turd when they're leaving from a stoplight or going through stop and go traffic. The 200 hp shot of nitrous that you want to use will make your 600 hp number, so keep the engine build mild. 5.565 rods are not a joke if you don't want to spend the money for clearancing, but the longer the rod the better. That's why I suggested a rod between 5.565 and 6.000.

 

I will attest to the high rpm on the street/engine failure. Try to keep it lower and you will be happier. Slugs until 4 grand are no fun.