Need More HP!

[COBRAIIW]

I got my '77 COBRAII dyno'd sat.
At 5500 rpm it had 280 torque and 260 hp.
It's a 86 HO roller motor(302),with 58cc heads,larger valves,1.6-1 rockers,
10.5-1 pistons,street/strip cam,edelbrock dual plane manifold,headers,dual exhaust(no cats),flowmasters,hi volume fuel pump and a Holley 650 double pumper.
Where do I go from here?I can't spend too much right now.
I figured with this set-up I should have been close to 300hp.
Any ideas?

 

[Gael]

what heads, what cam? you could always put on a nitrous kit. i doubt you can do much for cheap power to get up up to 300rwhp. what size valves are the heads?

 

[Power Surge]

Did you get the A/F on your dyno pulls? If so, let us see it. You could be losing a ton of power in your carb jetting.

 

[77sleeper]

your peak is at 5500? then you might consider grabbing a single plane manifold

~$300 ed curtis will make a cam that will breathe fire into that thing

 

[1badII]

I'd say you're doing pretty good with stock unported heads.

 

[Eos]

I'd say you're doing pretty good with stock unported heads.

Yay theres hope. lol I wish I was making 260 hp!

 

[COBRAIIW]

The heads were "home ported" by the previous owner,no idea what size valves, just larger.
I was running rich on the dyno,have since leaned it out a little,(1/8 turn clockwise)
I set my timing using a vacuum guage,since the marks are off.
I am also running a unilite dist.,blaster coil, and MSD-6.
Maybe just a little peaking and tweaking could get me to 275hp?
I did not go max RPM on the dyno,since it's my daily driver,I wanted to be safe enough to get home.
When I looked at the dyno printout,it looked as if the hp wanted to keep going higher.
I will post it as soon as I can find a scanner.

 

[Eos]

Oh well theres no real way to tell then...

 

[Blue Thunder]

Fine tune the fuel and timing curves!
Most people seem to leave their motors in a rough state of tune, without realizing how much power can be had by the "little things". Even a perfect combination of expensive parts will still run like crap unless you make sure it's tuned perfectly.
Also, Demon carburetors are worth some hp over any other carb. They're amazingly efficient.
I don't put much faith in home porting, because it's more complicated than most do-it-yourselfers can handle, and those stock head castings are the primary limiting factor.(5500 rpm is about right) Better heads are your best bet.

When you say you leaned it out a little, (1/8 turn clockwise?) I assume you're talking about the idle mixture needles on the sides of the front metering block?
That's only leaning out your idle mixture, which is irrelevant to the fuel curve of the main jets. You will need to buy yourself a jet kit, then remove the primary and secondary fuel bowls on your carb, and install smaller jets. (I usually only go 2 jet sizes at a time.) The 650 carb is slightly too big for your current engine setup,(the 225hp 302 HO came factory with a 585 cfm holley) so the 650 carb jets will no doubt be too large.

A race demon 650 carb would run a lot better, as they're far more efficient than holleys, and they respond quicker with a lower vacuum signal, such as when the motor is overcarbed. (that's why they require such small accelerator pumps. They almost don't even need them)
A 650 demon would still need to be re-jetted for your engine, but when done, it would easily outperform a perfectly tuned holley, both in low end torque and top end hp.

 

[Mstng2]

...except Blue Thunder's advice is good advice not stupid...

 

[1badII]

My Speed Demon was a piece of ****. I'll never run a Demon again. You couldn't go full throttle without it stumbling, no matter what I did. When I had my 78 Bronco, I stuck the Demon on it while I rebuilt the Holley 4160. It ran better and had more power when I put the Holley back on. It couldn't even do a one wheel peel with the Demon on.

 

[COBRAIIW]

I have a 600cfm holley from my 351w car,I'll give that a shot.

 

[Blue Thunder]

My Speed Demon was a piece of ****. I'll never run a Demon again. You couldn't go full throttle without it stumbling, no matter what I did. When I had my 78 Bronco, I stuck the Demon on it while I rebuilt the Holley 4160. It ran better and had more power when I put the Holley back on. It couldn't even do a one wheel peel with the Demon on.

Defective Demon.

Don't give up on them, I've installed Demons(one on a 1971? MOPAR Demon. ha.) on a few of my friend's cars after my own great experience with them, and they're all very happy with the carbs. They kick ass!

 

[1badII]

Defective Demon.

Don't give up on them, I've installed Demons(one on a 1971? MOPAR Demon. ha.) on a few of my friend's cars after my own great experience with them, and they're all very happy with the carbs. They kick ass!

Well, Barry Grant's customer service sucked. When I first got it, the secondary venturi's would leak gas. After many calls to them, and sending it back to them for a rebuild, they finally sent me new bowl assemblies. After this, it ran good, except for the full throttle stumble, which I tried everything to fix but couldn't. After about a year of driving it, my gas milage just went downhill. I used to get great gas milage, but then it went down to big block milage. I rebuilt it again, it didn't help. Doesn't matter now, the engine's out, waiting to finish building my 408. I'll be using a BIGGS custom Holley.