The motor in my sig was just finished up being rebuilt. There is no 1/4 around here and I have not dynoed it yet. My question is about the horsepower production. The guy who built the motor with me said it should make about 425hp. Is that possible with only .480 lift? I was under the impression that I would need a more aggressive cam. The C/R is about 10.8 if that helps.

 

Looks like a very nice motor but I do not see 400+ hp at all.

To be completely realistic with you I would say if you are lucky then 300 RWP.

400 is not as easily attained as everyone thinks. Even 300 is sometimes tough. You diffenately need some more lift.

 

I see several power-robbing mistakes in there.

An old cam, a low-performance street carb, and what might possibly be the worst intake you could use.

Lift, by itself, doesn't control HP. That is, just to look at a cam and say it has "only" however much lift and so won't make power, is wrong. Just as wrong as seeing a BIG lift number and automatically assuming that it WILL make power.

That said, HP comes from flow. Flow comes about through a time-proportioned valve in 3 ways: make the valve bigger, open it farther, hold it open longer. Youve got nice big valves, so #1 is taken care of. Your cam fails miserably on #2 & #3.

A 383 will make about 450-475 ft-lbs of torque at its torque peak. It would be reasonable to expect the torque to be down 10% from that at peak HP; call it 400-420 ft-lbs at the RPM where peak HP occurs. That means, since HP = torque x RPM ÷ 5252.11, that your peak HP will have to occur somewhere around 5200-5500 RPM.

I don't see that in your combo.

I'd suggest either this cam or this one.

Get rid of that crappy intake. NO CAR will ever run its best with that thing. It wasn't any good when it came out, and hasn't got any better in the last 25 years. Get a Performer RPM or Air Gap.

Use a Holley carb; I'd recommend a mechanical secondary 750 or 800.

Also, lose the "triangle of death" air restrictor you've got on top of your carb, before it catches fire and drips into the carb, or the screen gets sucked out of it and ingested into the motor. That thing isn't a "go fast" part; all it is, is for winning a "sq in of chrome" contest, and for 8-yr-old kids to ooooh and aaaaah about in a parking lot somewhere behind a rope.

 

I don't use that air cleaner and as you can see if you look closely in the pic it was just set on for pictures, there isn't even a hold down on it.

Thanks for all the advice.

Nelapse, the motor ran a 12.9 as configured now, before the rebuild, if that helps.

 

I would guess that the cam intake & carb swap could net you .4 sec; maybe more, depending on your torque converter and gears. Or maybe less, if it's a stock converter and 2.73 gears. But if it's some sort of more appropriate combo, like 3000-3500 stall and 3.73 gears, or something along those lines, then there's major room for improvement available. Especially if the car hooks and lays down good short times.

 

What was used on it when it went 12.9?
That would be pretty close to 400HP right there wouldn't it?

I agree, that intake manifold needs to go.

I don't know what heads those are, as far as CC of intake port, or flow characteristics. That cam you've got is a bit small and old, but I think sofakingdoms choices are a bit on the too large side. It'd make the car quite hard to drive with a 248/248 or 260/260 @.050 cam. And why a straight pattern cam?

I think you might be close to 400HP at the crank now, but it's certainly not optimized, that's why the suggestions are to replace the intake and carb and cam. Those would really unleash what it has in it.

 

I've been seriously considering the cam/intake/carb swap. I got the car out of storage yesterday and I have a little extra cash laying around. I appreciate all the help and advice for sure. What exactly do you mean by "too hard to drive" idle quality? I didn't pick a stright pattern cam thats just what it came with.