pinging

[stroked windsor]

I really don't know..

[blykins]

Three peaks is right.....unless you have 20 cc of piston volume, you likely don't have 10.5:1.

[blykins]

Originally Posted by stroked windsor

I really don't know..

That's the variable.

If that cam wasn't degreed, or was put anywhere further advanced than 106-107, it's gonna make it on the touchy side.

Until you figure out exactly where it was installed, we really can't do any more.

[stroked windsor]

I know. they never told me when they made the cam change on this motor just dyno and that was it. I wish I had left the bigger cam in. I still have it..

[stroked windsor]

i can call them.. but it was 2 years ago. so i don't know if they will remember the install.. but ill ask if they did..

[blykins]

Both of them are universal cams, essentially designed for Chevy engines. You'd be better off with a custom, that's designed specifically for your engine and its use. The compression ratio is one of the most major specs when a new cam is spec'd for a street car.

The XTreme Energy lobes are noisy and in most cases are too aggressive for the application. It's easier to do more with less.

[stroked windsor]

was a custom cam with the AFR 205 heads well know guy on the forums..

[stroked windsor]

pistons were fly cut..

[blykins]

Originally Posted by stroked windsor

pistons were fly cut..

Without any firm measurements, there's no way of knowing what the actual compression ratio numbers are.

[Three Peaks]

If all else were right, that cam or one similar in a custom grind (but better specs as Brent is referring to) would be terrific on the street. Should have better street manners than my XR 294 but about the same horsepower and torque readings- but at more street friendly range.
Where do you live? Maybe you could have someone close by come over and show you how to determine Head and piston volume measurements, degreeing a cam, and if it were me, I would be checking your piston to valve clearance while you're at it. All things you could do yourself with a little technical guidance in a weekend.


Still, a piston dish measurement is just about mandatory before doing anything else.

Bob

[jhv48]

What do your plugs look like. Post a pic if you can. If you’re getting pinging, they should be on the white side.

[blykins]

Originally Posted by Three Peaks

If all else were right, that cam or one similar in a custom grind (but better specs as Brent is referring to) would be terrific on the street. Should have better street manners than my XR 294 but about the same horsepower and torque readings- but at more street friendly range.
Where do you live? Maybe you could have someone close by come over and show you how to determine Head and piston volume measurements, degreeing a cam, and if it were me, I would be checking your piston to valve clearance while you're at it. All things you could do yourself with a little technical guidance in a weekend.

An old school trick I've heard of, but haven't tried myself is to increase combustion chamber volume by doubling up on your head gaskets. Of course, this won't work with metal gaskets, but worth a try to see if it addresses the problem without completely removing the engine. Also, some manufacturers make double thickness head gaskets just for this purpose but I wouldn't know which ones to recommend. Hopefully, someone here can help out or call bull**** on my idea, whichever is appropriate...
Still, a piston dish measurement is just about mandatory before doing anything else.

Bob

Doubling a head gasket would be a big no-no.

Increasing the quench distance can cause just as many problems by itself as a high compression ratio.

[Three Peaks]

Went back and took it out. I wouldn't have thought .040 thickness would have caused a quench problem, but I'm quite often wrong according to my wife....

Bob

[blykins]

We married to the same woman?

[Three Peaks]

Lolol

[stroked windsor]

hey don't steal my thread. lol

[stroked windsor]

I think what that engine guy did was throw in a comp cam for better street manners. that's what I was told. bring down that curve a bit. im sure they either called comp cams up or just looked one up for my 402w street car. they never asked me about what stall I had or gears etc. they just stuck that cam in a dyno it..

[HighPlainsDrifter]

hi,
Comp grinds their cams 4 to 5 degrees advanced so it is too far advanced when installed straight up. Get a bushing kit and retard the cam 4 degrees.Also check the total advance of timing at 3500 rpm, it should be 32 degrees. You can put a advance limiter in the distributor if needed.
Perry.

[stroked windsor]

ill tell my mechanic Monday thanks.

[blykins]

Originally Posted by HighPlainsDrifter

hi,
Comp grinds their cams 4 to 5 degrees advanced so it is too far advanced when installed straight up. Get a bushing kit and retard the cam 4 degrees.Also check the total advance of timing at 3500 rpm, it should be 32 degrees. You can put a advance limiter in the distributor if needed.
Perry.

Hold on a second now....

A camshaft installed straight up means that it doesn't have any retard or advance in it at all. Comp Cams does grind most of their stuff 4 degrees advanced. You can adjust it with the timing set from there. Installing it straight up wouldn't be too far advanced....

Also, a "bushing kit" is a Chevy thing.....not a Ford thing.

Different engines need different amounts of timing. A 3500 rpm total ignition timing rpm is a band-aid for what's wrong, and in reality will make the car extremely lazy. Cobras need a 2500-2700 rpm total ignition timing rpm.