I am building a 357 sbc for my 1992 Pontiac firebird.
I am using flat top pistons with 4 valve reliefs, and I want to use GM vortec heads. I plan to use an edelbrock performer intake. I am also going to spray a 150 shot of nitrous through it. My big question is what cam and carb should I use to get the most power for my money?

 

Welcome aboard thirdgen.org.

"Most power" isn't a static target. Most power for the strip? Most power and still reasonable for street driving? Two different answers.

I'd say go for a Performer RPM intake. Better RPM range.

Vortec heads stock can't handle much valve lift. What are you planning on doing about that? Most popular choices are having the tops of the valve guides cut down, or using beehive springs. Personally, I'd go for the cut down guides because your valve spring choices are much better.

As for the cam, go for a dual pattern type that has a power band up to 6500 RPMs. Is your block roller lifter ready, or an older one? Hopefully roller.

150 is a pretty healthy shot. Hope you're building everything to handle it.

 

I guess I probably should have specified a little more.
I want it to be a fast street car but also a fast track car. I only plan to use the 150 shot a few times on the track and never on the street.

The block is a non roller block, I was originally searching for a roller block but a friend of mine just gave me this one.

As for the heads . They are going to get a multi angle valve grind, I'm having the press in rocker studs removed and having them machined for screw in studs, and I plan on matching a set of valve springs to the cam I get. I don't really plan on using beehive springs.

And the intake is a performer rpm, we were going to use a super victor, I read that single plane intake isn't a great idea for nitrous?

 

For the work that you are going to put into the heads, why not buy a good set of aftermarket ones? Cost is more, but you have more potential....

 

Actually, a single plane intake IS a good idea for nitrous. With a plate system, the straighter shot to the heads gives less chance for fuel separation and rich/lean cylinders. But it will be OK with the Performer RPM with just a 150 shot.

Since you're using a non-roller block, stay conservative with your NA power goal. Higher spring pressures needed for a cam that revs to 6500 rpm are not going to play nice with flat tappets on the street using conventional oils.
Build a torquey NA setup for the street with about a 262-268 cam and still have 500 hp on the 150 shot.
The Vortec style Performer RPM manifold comes only in square bore, so that pretty much rules out a Q-jet carb. I think I'd run a Holley mechanical secondary anyway to prevent distribution issues with the nitrous on the hit.

 

I assume you're going to use forged pistons for the build. Nitrous and hypereutectic pistons don't play well together. Cast are fine for a 150 shot, but you'd better not let it go lean.

Single plane intake and nitrous are fine together. Just isn't as good on the street. And, Vortec heads start fading when you get over about .550" lift and 6500 RPMs without porting by a Vortec-knowledgeable porter.

Screw in studs is a good idea. There is a guide/spring seat cutter that will do the job in one pass that allows you to use better springs.

Since you won't be using roller lifters (unless you go to the expense of retrofit rollers), use an oil that has the old levels of ZDDP like this - http://www.amsoil.com/shop/by-produc...tic-motor-oil/

 

Edelbrock-s RPM AirGap doesn't have any great problem with mixture distribution. I'd use that with Comp's 12-560-4. I'd probably install the cam retarded and get a reinforced loose torque converter. Then run 3.73:1 gears.

 

Do NOT give any consideration to a little 150 shot when picking cam profile. With a "nitrous" cam in this application, you'll lose much more NA power than you will get back on the nitrous, so your net effect will be a loss in total power on the spray.
I agree with the "268" cam size, but it should be something like a 110 LSA installed at 105-107 ICL.
Yes, the RPM AirGap is perfect for this combo.
Are you running an auto trans? If so, choose the TC for best NA operation (not necessarily best NA ET). For sure nothing over 3600 for a mild combo like this.
What's your CR and quench?

 

The overlap of the non-nitrous cam WILL do more to screw up mixture distribution than the extra 10 ft-lbs off-nitrous is worth. You may be starting with a 150 shot, but it won't be long before you're spraying 250, probably with a 2-stage if not a progressive controller. HP is addictive. You get bored and need more. Build for the 250-shot, not the 150 shot. 3600 stall is very loose, I was thinking of a 2400-stall, which can also be loose if you choose a 12" instead of a 10" converter. Either way, you will balloon any non-reinforced converter if you keep hooking up on the bottle.

 

WHoa.....easy now! We're not making recommendations for a 250 shot here!
I can assure you from experience that a 110 LSA with the little 268 cam we're talking about will NOT affect nitrous mixture distrubution ONE IOTA. You don't engage nitrous at idle! A 150 shot should be brought in about 3000 rpm, at which point there is no reversion going on from the overlap.

I wouldn't waste the time with a 12" converter, unless money is really tight and you're not so concerned with performance. Those units are not very efficient as the stall rpm is raised.
Yes, a 3600 is the upper limit, but perfectly reasonable if you go with something efficient like a Yank SS3600. Better yet would be their PAS3400, basically a SS3600 with a different stator giving it a higher STR and couples up quicker; flashes to 3600 but drives more like a 3000, and nice n tight for the nitrous.
If you're going with a cheaper converter, 3000 rpm in a 9-1/2" unit would be a sensible upper limit, but with cheap you'd probably not get the anti-ballooning front cover mentioned above