Thread: 383 500 Hp! No Juice

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I'm hoping to get someones help, hopefully help from experience. I did post on this earlier, but now I have a more concrete route I want to go, to get to the 500 HP mark...no boost no juice.

500 is just a benchmark, I'd ideally like to run flat 12's in an 81 camaro,stock weight, retain decent mileage, and some reliability to drive on the weekednds 50 miles to the track on PUMP GAS

WELL, I am buying the short block from a friend. It's got 12.5:1 compression,

This block was machined 2 seasons ago very well, zero decked, I dunno what else, because HE had it done. But I know he paid an arm and a leg, had it blueprinted etc.

its obiously a 383 (actually a 385ish, bored .040 over), 5.7" rods

I will replace the pistons with forged flat tops to achieve roughly 10.0 or 10.5 compression. Can I go higher and still run pump gas?


the cam is 250.260 and .533/.555 @ .050. Not sure about lash or lsa, i'll ask him for the card on the cam if he has it. Its a solid flat tappett.

Heads are up in the air. DEFINATELY want AFR's, not sure on 195's or 210's, any suggestions?

Dart, single plane intake

holley 750 cfm , mech secondary(im assuming, havent bought one yet to replace my 650, any sugg?)


msd ignition, mech water pump, new edelbrock fuel pump (cant remember spec,more than sufficient tho)


I want to run pump fuel, no doubt. But I want to get close to 500, and YES, to pad my ego. :-). Or say, 380-400 rwhp :-).

I was thinking of using a 3200 rpm stall tc i have, but i hear i may need a higher stall?

built th-350 with shift kit

3.42 rear end, posi (not a good match with the cam?)

1 3/4" headers to 2 1/2" pipe, thru 2 flowmasters no x or h pipe

What more info can I provide? any suggestions?

Desktop Dyno shows 425 hp. seems kinda low.
How are these companies making 515 hp on 93, with afr 195's, 9.5:1 compression etc? (AFR,CHEVY HI-PERF) With a much more tame came.

thanks!

Most engine simulators rely on a engine volumetric efficiency number to calculate hp. You need to figure out your volumetric efficiency in order to get an accurate hp prediction. Most desktop dyno's default around 80%, these other manufacturers might be able raise their VE a little. Adding boost increases the VE past 100% Don't ask me how to calculate it, I'm sure the calculations are very involved.

12.5:1 compression on pump gas? 10.5:1 is starting to get high for pump gas. Above 10.5:1, I strongly recommend computer controls for fuel and timing. You'll need a cam with a tight lobe seperation angle (more valve overlap between intake and exhaust stroke) to bleed off cylinder pressures in the lower rpms to help combat detonation. Because you'll have to run some big cam with a tight LSA to get the hp you want without detonation, you're going to be pushing a lot of fuel through the cylinder and right out the exhaust because of the amount of time both valves are open. Your fuel milage is going to be bad. Maybe 7 or 8 mpg? The car wont idle well either.

NO, HE WAS RUNNING RACING FUEL AT 12.5:1.

AS FAR AS "NOT IDLEING WELL",WHAT O U MEAN? HAVE TO GAS IT WHILE AT A STOP LIGHT?

IS THIS BASED ON THE CAM I TOLD U WAS ALREADY IN THERE?

I APPRECIATE UR RESPONSES IN THIS THREAD AS WELL AS THE OTHER.

DO U HAVE ANY RECCOMMENDATIONS AS FAR AS WHAT COMBO WOULD WORK BETTER WITH THOSE AFRS, IN THIS SHORT BLOCK (MAYBE A DIFF CAM?), STILL PUSHING THE HP TO 475+?

tHANKS AGAIN

With everything right on. The math says you can go as high as 11.35:1SCR/8.50:1DCR if the cam you have has 73*ABDC IVC.

Ruff est. 488hp @6000rpm 457Lbft @5000rpm

them #'s are with small tube headers and muffler

503hp @6500rpm 471Lbft @5000rpm large tube headers and muffers

536hp @6500rpm 487Lbft @5000rpm with large tube open headers

3.73 rear gears would give you 6500rpm @140mph with 28" tire (27 actual)

4:10 rear gear If yur trying for 127mph @6500rpm

thats my point. u say 500, i say 450, another guy says 400.

what sim software r u using?

Sounds like you are leaning towards spinning this thing pretty good. If you want to go with a 3600 stall converter, I would go with AFR 215's, change the rods to 6" units, less stress on the pistons. With the single plane intake manifold, you will lose a little in the lower RPM range, but look out on the top end.

I've been figuring the same with that cam. It aint gonna run worth a darn. What cam might u suggest? something in the 240 range with max lift?

I HAVE looked at those afr combos BUT none even come CLOSE in an EA or Desktop dyno. Wonder why?

If I end up changing pistons AND cam, I dont think I'll even be buying the short block, since it'll cost the same to have one machined to my specs with cam and pistons.

This combo will get you 11.90's in your 81 with a 3.55 rear gear and a 383

383 with 9.5 to 1 with a .005 deck ...sportsman 200cc heads 2.02-2.05 valves / cam 230 duration @ .050 with .495 lift degreed in!....7qt pan....thin oil /good pump...headers and a 2 1/2 exhaust ...and a 2500 stahl( if auto trans)

This will run all day long and idle in traffic and will run the number if you tie it good...and this runs a 10in street tire....

If you use a aluminum head and/or a roller cam or anything above and beyond what I listed will only help....especially a Asymetrical cam with slightly more lift and duration on the exhaust side if you use a smaller head....This yeilds approx 450hp

bumping the CR to 9.7 (thinner gasket) and a 240@ .050 roller cam may put you over 500-550hp but then it will dance all over the starting line.....

I might also add that 500hp with 12.5 to 1 is easily obtainable but this is racing compression ( no street use) used on the street you may very well exceed the fuel and this melts stuff (usually pistons) you can use this but you would have to severely "over cam" this to work and it wold not be responsive for a daily driver and you would be disapointed.....If this is going to see a daily grind...stay conservative you will be so happy you did....

You can run 500hp with 9.5 to 1 ALL DAy
you can run 500hp with 12.5 to 1 20 seconds at near max rpm's before cylinder pressures start exceeding the fuel!

so dr bowtie, do u speak from experience? that sounds like an easily attainable combo. Is that cam u quoted a solid flat tappet?

Would slightly more lift help (more than 495?). It seems like a mild cam to make so much power. I WILL be running ALUMINUM AFR 195's. You suggest an asymetrical cam for that?

Yes I do....That cam was a cam dynamics (crane) it's a hydrolic flat tappet....

Yes....but depends on what exactly you want to do with the combo.....all out or driver...I personally would opt for a roller cam in anything but that cost some paso's.... an Asymetrical will always get you the most power.....I only use a symetrical cam when I need to bleed off some torque to get it off the line consistantly!

Just one question. Why are you going with that gear ratio?

If you are asking me, I got the rear end from an old 79 camaro and it had the 3.42s in it, better then my 2.xx.

Id like to be able to cruise at 60 at a decent rpm, so i feared going over say 3.73's.

the motor is the major concern

I want a somewhat consistant flat 12 second car i can drive on the highway and only burn a gallon every 9 or 10 miles. I will maybe goto the track 5 or 6 times/season. thats all.

other than that, I'd like to be able to do a 100 ft burnout if i want to while going 25 and dropping it into 1st. TORQUE!

what DISADVANTAGE would come from having more lift than ur combo, Dr. Bowtie?

Fed....

That 342 rear will be fine....pick a stall converter acording to the cam....but that 3500 will do fine....

Really come on....100ft burnout @ 25mph when goin back to first? do you realize what you are saying.....

although this is practical...quite easy actually.....if you want to impress girls...well it doesn't..well maybe a little...but in a race you want it to "hook and book" if it does what you want it to your going to get spanked every time.... plus buy lot of tires....been there done that....

3rd....minimal if any as long as you don't go overboard....but lift isn't what your after..... duration is the whole key....