I began my new build today and was talking with my friend about how much power i would end up with. AFR told me I would be around 540-560hp at the flywheel and my friend who knows quite a bit thinks I will only be around 500hp. I am just curious what all of you think? The motor is a 383 with a forged rotating assembly by scat 10.3-1 compression ratio with the AFR 195 eliminator heads, roller comp cam XR294HR, Duration @ .050" Lift: 242/248 with .54/.562 lift. Full roller rocker arms 1.5 ratio. Mighty Demon 750 carb, Edelbrock RPM air-gap manifold, 1 3/4 Hooker longtube headers, flow master 2.5 exhaust with h-pipe. Double strike ignition, B&M 3000 stall, 3.70 gears. I spent a lot more money than I expected and I am really hoping for over 500hp running low 12's in the 1/4 mile....do you think I will be there?

 

I think you will hit 500hp, or be damn close.... Thats enough for 11.50s at least..if not quicker...

My buddy built a 422", 10.7-1,Fully ported AFR 210s(not CNC, locally hand ported), Victor intake, custom hyd roller 238/248, 570/580" on a 110. The engine dynoed 560hp on a well trusted and known to be accurate Superflow 902. That engine in a 3700lb 70 Chevelle with a 4000 flash converter and 3.73s ran 10.90s@120 with a 1.50 60' thru full 3" exhaust and super turbos... He had $10k in that motor...it was a mild street cruiser, didn't sound like much at all.





If I were you, I would do something different with the converter....the converter will make or break you....I would get something custom built so it matches your combo yet is still tight around town....Coan, Edge, Continental, Pro-torque etc....You will want a good flash speed but tight on the big end....

 

Thanks for your reply I will def be happy if I make it in the 11's...lets hope I get there. What do you mean about my converter giving good flash speed but tight on big end? Isn't the B&M holeshot one of the best converters?

 

HP numbers are s crsp shoot until you run it. If you can tune well could be alot, if you have no clue on tuning no may not be able to get out of your own way. Work on the tune get it to run well and then you will know the HP as to how much it takes to run what ever numbers you run, the dyno numbers are just numbers and mean nothing. The dyno is great to show you improvements for changes made but that it. Tune it and run it!

 

Heads will support 550Hp, a well put together motor with matched components and tuned correctly will get you over 500HP I would imagine but you'd have to put it on an engine dyno or see if it makes 400RWHP or more. I always build my motors to make x amount of horsepower and it is always fun to see if you make it or exceed it

 

if you win, you will have enough. But if you lose, not enough....I dont think it`s enough...

 

I would also go with 1.6 rockers, gets you up to near .600" lift to take advantage of the good flowing heads

 

You should be real close to 500 flywheel hp.Consider milling the heads to get the compression up a little more.The cam will like it.Should make good torque to move you out.If you have the holeshot 3000 it is a decent street converter.A custom vert will better it considerably.I like ATI,SMR, and Turbo Action myself.

 

B&M converters are junk....as are most TCIs....9 times out of 10 their converters are pitifully loose around town, may flash to the desired stall speed but never tighten up enough on the big end....or have horrible shift recovery(ie. sloppy)....

If you are on a budget(hell who isn't...), you may look at Hughes, they are reasonably priced and pretty efficient. Other well known and respected brands are ATI(DAMN GOOD), Yank, Vigilante, Neal Chance, Fuddle, PTC....

I actually had mine built by a local guy that owns a transmission shop, mine is a 10", around town it barely feels looser then stock....it actually feels like a 2000 stall when running around town.....It will foot brake to 2500-2600 before it starts pushing and it flashes to 3700rpms from a 1500 launch......It is very tight on the big end of the track...I gain 23mph on the back half... I only paid $350 for it....i gave him all my car's specs and dyno charts....I couldn't be happier with it for a weekly driving street car...

I have had cheapy converters that were either way too loose(inefficient) or way too tight (for their stall rating with a crappy flash speed).....they were all off the shelf....(Boss Hogg, TCI, B&M)...

If you haven't bought the converter yet, do some research....if you already have it, try it and see how it does but don't be suprised if it doesn't launch well OR slips too much on the back half of the track...

 

I've dyno'ed several small blocks with almost the exact combination of parts that you describe. Here are some thoughts:

First, don't be concerned about the peak hp number. Peak hp only matters in racecars operating within a very narrow rpm range. For a street car, you want a flat and brutal torque curve, and you're going to get that with your parts combo.

The only way you're going to get over 500 hp with a 383 is to spin it fast: You'll have to get it into the 6500-6800 rpm range to get those hp numbers, and you'll do it with a sacrifice of low- and mid-range torque. That's not a sacrifice you want to make in a street car. Your cam selection is going to give up above 6000 rpm, especially with the 1.5 rockers, so you're not likely to break the 500 hp barrier with the little 383.

My actual dyno results with almost identical parts selections have produced 530 hp with 420 cubic inches and 496 hp on 407 smallblocks. Both engine sizes with that cam and similar heads stopped making power at 5800-6000 rpm, even with 1.6 rockers. The 407's run best with a 750 Demon, and the 420's produce best power with an 850. But both engine combos produce over 440 ft/lbs of torque starting at 2500 rpm and have a flat torque curve of about 500 ft/lbs all the way up through 4500 rpm - this is what really matters in a street car, especially with an automatic. The torque is what's going to rip your head off and make the car feel brutal.

 

100% everything he ^^^ said....

 

I already bought the B&M holeshot I wish I new they were junk ahead of time. I guess for now i will have to see how it works with the car and hope for the best. How much hp would i gain if I buy 1.6 ratio rocker arms? I just bought the 1.5's last year and they werent cheap so if the power gains are min I will prob just stick with the ones I have.

 

How much power gains would I get if I go to a 1.6 rocker? I just bought the 1.5 last year and they werent cheap but if its worth it I will buy the 1.6 ratio?

 

I wouldn't spend the money on 1.6 rockers if you already have full roller 1.5s. Or you could buy a half set and just put them on the intake side....ofcourse more lift and the +1* of duration "could" help make more power but it would probably be minimal. Remember you also have to consider push rod geometry and rocker arm geometry on the valve stem when changing the ratio of the rockers. Your cam has plenty od duration but it is a little weak on the lift...

 

They might be good for about 10-15 in the 4500-5800 rpm range with a loss of torque from 2500-3500.

 

I like to match the lift with the heads, if the heads are still flowing higher numbers at .600" than .500" then I want the lift to be around .600" but that's just me. If the heads stop flowing at .500 then you want a little over .500" lift. In my experience the more power you make the more power you make both HP and Tq

 

That's true, but added lift and duration tends to shift the torque curve upwards. Peak tq & hp numbers will increase at higher rpm, but with a slight loss at lower and mid rpm.