Estimated Horsepower (Just Curious)

[Justasgood]

Curious if the group can play a guessing game regarding what HP my engine may produce. Not interested in exact numbers and don’t have access to a Dyno. So here are the details:

Block - 1969 383 HP
Bored -.040
Heads - 906 worked by Indy heads
Cam - comp cams extreme energy 477 lift
Compression - 11.5 -1
Intake - Edelbrock dual plane aluminum
Carb-Holley 850
Torque converter - stock

Is it even possible to make an educated gues at horsepower?

Thanks in advance,

Kurt

 

[Don Frelier]

My guess 450.

But I don't think you'll be able to run it on pump gas.
Once you get a little carbon in the chamber you'll need race fuel.

 

[Justasgood]

My guess 450.

But I don't think you'll be able to run it on pump gas.
Once you get a little carbon in the chamber you'll need race fuel.

The previous owner mention race fuel would make it come alive. I have access to high octane, non ethanol fuel. Is that a bad thing? Can I add anything to the tank of non ethanol to get good performance?
Thanks for the reply.

 

[lewtot184]

I think horsepower estimate is irrelevant. 11.5:1, non-quench head, and short cam will put the engine into detonation rapidly. I don't think race gas will save it. If the engine has been ran with this combo there'd have to be some engine damage. The only saving grace would be a lower compression ratio than stated.

 

[Justasgood]

I think horsepower estimate is irrelevant. 11.5:1, non-quench head, and short cam will put the engine into detonation rapidly. I don't think race gas will save it. If the engine has been ran with this combo there'd have to be some engine damage. The only saving grace would be a lower compression ratio than stated.

Can you clarify this for me(non professional )

Thanks

 

[WileE]

You're running iron heads with a high comp ratio, with that type stock cyl head chamber and cam, you'll be fighting detonation

 

[DanielSlocum]

i wouldnt expect to run it on any pump gas. are you running a quench dome type piston? if so.... then no need to worry about quench.
i think you can expect an honest 400-425 hp. perhaps a good octane booster will work with pump fuel?
as long as it gets enough octane to avoid detonation it will be happy and run plenty strong. ignore the worry warts and run it.

 

[4mulas]

If you can confirm that indeed they are 11.5 to 1 compression pistons I’d expect around 415-425 horsepower. That said I don’t think I’d want 11.5 to 1 pistons with your combo far all the detonation reasons everyone else mentioned.
‘if the pistons are around 9.0 to 1 comp pistons which would be more friendly for the combo I’d expect around 365 horsepower ish

 

[Dave6T4]

I think you have too much carb and compression for the cam you are using. I think I would install a second head gasket on each side to get your compression down to run available fuel, if this is a street car. I think 9.5-10.0 compression with iron heads and today's fuel is about all you can go. Somewhere around 400 horses. That 850 cfm. double pumper is more a race carb, than street one. I would go 750 Edelbrock.

 

[68-500]

Personally I’d like to know if more about the pistons. If they’re not in quench pad type you may need to run ethanol fuel ,E-85. Race gas in a street car is just not practical unless you’re bank account is very large. As far as HP id guess 400 that cam isnt much different from factory advertised duration.

 

[oldkimmer]

435 with a mix of race gas and pump gas. He can step up the cam then it will bleed off some compression. But he would need a higher stall converter. Kim

 

[PRHeads]

I’m going with:
“Somewhere around 400hp”

If you get more curious, bring the car to a chassis dyno for a few pulls.

 

[33 IMP]

I have "11 1/2 to one" trw's in a 440 with iron heads, and I can run 91 10%. BUT! here's the explanation. ACTUAL measured c.r. is really 10.5, and I'm running a LOT more cam than you.
IF you really have 11.5, iron heads, and such a short cam, it WONT run on pump gas. You have a couple alternatives.....
1. lower the compression ratio. Four head gaskets would be the easiest way. A pair of thick cometics would be better.
2. Buy a carb and run E85, if it's available in your area. Other problems might result.
3. Run straight Avgas, or a mix with pump 91.
I run a few gallons of avgas as a sweetener in my car, cause I have access, and I can. The avgas I buy is slightly less costly than california 91 10% cat pee.

 

[4speed68rt]

400 ish... is this a new motor, or have you run it already?

 

[lewtot184]

You need to find out exactly what pistons are in the engine; no guessing or fudging the numbers. I say less than 350hp at the crank.

 

[Justasgood]

400 ish... is this a new motor, or have you run it already?

Little over 4,000 miles on motor but new to me

 

[dadsbee]

420 and you're gonna be running at least 33% AV100LL mixed with the best premium you can find. Ask me how I know.. LOL

 

[4speed68rt]

Well it must run ok if it has 4000 miles on it. I was going to ask you if you like how it feels to you. That's what is important. Does it make you smile or pissed off when you drive it?

 

[lewtot184]

If the engine has made 4000 miles intact I have some doubts about 11.5:1 compression. Keep in mind that a stock 335hp 383 only netted 280hp to start with. I drop my horsepower estimate to 325 at best, and that's probably too high.

 

[Justasgood]

Well it must run ok if it has 4000 miles on it. I was going to ask you if you like how it feels to you. That's what is important. Does it make you smile or pissed off when you drive it?

It stumbles and has no power from a dead stop. From a 10-20 roll, it downshifts and burns the **** out of 2nd gear and runs hard.

I am thinking the car was set up for a bigger CAM( prior owner mentioned his wife drive it mostly and didn’t like the way it shook the car) so he put the current cam in.

I have a Carter Competition series carb with a square flange mount and electric choke. This is a model #9636 rated at 625 CFM.

Not sure if this is the answer or go back to a bigger cam and upgrade the heads.

I am about to change the rear end gear from 3:73 to 3:21 to enjoy driving it a bit more.

Just want to sort the power out first.