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Discussion Starter #1
Here is my combo. It made 355 hp at 5600 rpm and 369 ft/lb torque at 3700 rpm at the wheels :

342 (eagle, eagle & SRP)
11.0:1 compression (flat tops)
Canfield heads with minor port work
X Cam 4* retard w/ 1.7 roller rockers
SysteMax intake
70mm throttle body
Pro-M 77
30# injectors
255 lph pump
42# fuel pressure (static)
1 5/8 shorties
2 1/2" Bassani X w/ cats
2 1/2" Super turbo mufflers

I then changed to and made 370 hp @ 5700 rpm and 371 ft/lbs torque at 3700 rpm:

Comp Cam XE282HR straight up (234/240 duration and .565/.574 lift)
1.6 roller rockers
1 3/4 BBK Long tubes
2 1/2 Dr. Gas X pipe w/o cats

All runs made w/ timing at 10* due to detonation with pump gas. All runs with Autologic chip custom tuned.

What is the restriction here?

Horsepower is 300 at 4250 and falls to 300 at 6300 rpm.
Torque is relatively flat from 3500 to 5300 and over 350.
No ignition problems or missfires. All in great tune.

Any suggestions?

Thanks, Mickey
 

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One word

INTAKE!!! I bet U change to a shorter runner intake (eg Victor 5.0), U will be able to run more timing and make more power in the higher RPM range. It seems to me you are making good torque all through the lower RPM range, but it is falling a little fast.
 

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Discussion Starter #3
Will the Victor 5.0 hurt the low end torque at all? This is a daily driver.

Anyone else have any ideas?

Thanks, Mickey
 

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You may loose a little, but who knows until you try. I can almost guarantee it will pick up though. You also need to do something about the exhaust if you really want it to make the power. If you haven't opened up those bbk's yet tot he full 2 1/2" hole (they are 2 1/4 how they come), then there is some power in that, but swapping the collectors to a true 3" and the rest of the exhaust would be the best idea along with the vic 5.0 swap.
 

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Intake,
That long runner is building too much cylinder pressure that is why you are detonating.

I think you need to lower the cr a little if you want to stay with that intake on pump gas. Or put some 105 unleaded and see what it can do with the Holley.

I would think the victor 5.0 would work better with a nice solid roller.

Mike89lx,01 Cobra
 

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mike89lx,

detonation is not a function of long manifold runners. It's caused by lean mixtures, hot spots in the chamber, high c/r's & high cylinder pressures. Cam timing also has a great effect on detonation.

Mickey,

what are the spec's on the valve springs you are running? A bad spring caused my 331 to nose over after 5300 rpm.

Mark Lowry
 

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Discussion Starter #8
Mark,
The springs are 135# on the seat and 350# at .550 lift. I recently checked them when the head gasket gave up.

I think detonation is undercontrol now. I just expected more power at a higher RPM. Maybe this is all it will make and still be driveable.

Thanks, MIckey
 

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Mlowry,

The long runners manifolds in concert with shorter cams and high static compression are a sure fire recipe for detonation. You can only have so much cylinder pressure on pump gas and many other common Corral builds even make this worse with the way things are setup. The shorter runnered setups will allow more static compression because of the reduced lower rpm cylinder filling and help to make more power up top where the shorter manifolded and longer cammed stuff starts working. You have less peak cylinder pressure but can keep it longer and make more power.

With too much compression and shorter cams the long runners will always detonate worse because they allow more pressure to be built down low where detonation has more time to occur. Of course bad chamber design or mixture homogeneity will make it worse along with no quench etc.

From what I've seen the long runners that actually breath can't take much compression or they will make too much pressure in the middle. They have ungodly specific TQ numbers sometimes due to the supercharging efect of these long runner designs but it kills you up top and then you have the double bogey of having to run low compression also so you lose twice up top. You can run the bigger cams in the long runners too but they still won't make big power up top anyway and just lose more down low.

You have to manage cylinder pressure in most engines when you have a detonation limit as we do with pump gas.
 

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One thing I think may be hurting you is that 70mm throttle body. Most of the combos I've seen like yours were using an 80mm. That means your going to have to go bigger on your MA as well.

Like some others have said also, that intake is probably too restrictive. A victor jr would be a much better choice.
 
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