cam timing

[cliffsgt]

Car: 1972 Vega with 2300 (140ci) motor.
My problem is cracked rings - On back roads I test and adjust my ignition timing a little at a time by advancing the timing and about when the motor is really starting to run strong the motor busts a ring(s).
I can't hear any detonation, probably cause of the after market solid lift cam. It's a mild cam, cut to run with stock pistons, headers, HEI distributor and a larger carburetor. I'm running 1-Weber 45 Sidedraft.
I have since purchased a timing light with the built in advance function so I can tell exactly how much total "advance" I'm giving the motor so I'm not busting rings anymore.
But now I wonder if there isn't a "rule of thumb" in regards to ignition timing and cam shaft timing, as in - if the motor runs better with 34 degrees total advance at 3500 rpm's - would "advancing" or "retarding" the cam by means of an "off-set" bushing help me optimize horse power/torque. Not sure how much ignition advance the motor can take, but I feel comfortable that a total 34 degrees is safe - beyond that, I ain't so sure, but the motor would like more.
My thinking is, by using an "off-set" bushing to adjust the cams timing, I'd be able to move my ignition timing around to get the extra horses without "advancing" the ignition timing too far.
I'm probably way off in my thinking on this, but you never know.

I know a lot of the folks on here have plenty of experience putting motors together and tuning them - I'm a big car enthusiast, but I don't have a lot of experience tuning out motors with performance parts in them.

Thanks,
Cliff

[77nighthawk]

If you advance your valvetrain timing, you gain low end, if you retard your valvetrain timing, you gain top end. Not for sure if that's what your asking, but it may help. As far as your breaking rings, if you are detonating, run a compression test, you may be in need of more octane. Some cam grinds can increase compression, some can decrease compression, just by changing when the valves open and close.

[77nighthawk]

Sorry, typical me, skip step 1, go right to 5. Check your timing advance mechanisms first. Vacuum advance on distributor, vacuum source to vacuum advance, and mechanical advance in distributor.

[cliffsgt]

Yes, that's exactly what I needed to know.
I didn't ask the right question but you were able to read between the lines so to speak.
I will see about bumping my cam back some. I always thought that the problem was in my ignition advance - so I've been over that a bunch.
But it makes sense - I had the head milled and didn't add a spacer to the head gasket to make up for the difference so the cam is advanced.
Wow, I can't wait to get the cam retarded and see what she'll do.
Did a compression test with oil added to each cylinder and came up with:
#1-140, #2-138, #3-145, #4-130
While not optimum, I think the compression is OK.

Thanks!
Cliff

[77nighthawk]

Hey Cliff, glad I could help. Summit and Jegs offer a degree wheel for degreeing your cam in. It would take all the guess work out of your situation. I think the inexpensive ones go for about $30. You would probably have to do some research on your particular engine as far as how exactly to degree it in, but it is well worth it. plus when your done you have a cool tool, and the knowledge. Check your cam card, it should have a recommended setting for the degrees. Brad

[Monza Harry]

Hi Cliff Here is a link to a Canadian Company that sells theirs for CHEAP, if it is here (Canada) at this price it is even cheaper in the US. This company often swaps trends with Harbor Freight, So I would check them out often. Harry http://www.princessauto.com/en/detail/p ... -p8514721e

EDIT" Hey here's the ticket check this out: http://www.flatheadv8.org/degree.htm

[cliffsgt]

Yeah, degreeing the cam in would be best but I don't have the specs on the cam anymore. Long story short, I got the cam back in the early 80's, it was a "custom grind" not from a big name maker, and all I really know about it is that the Intake adjusts to 10 and Exhaust adjusts to 22.
So I'll just have to fly by the seat of my pants on it. The valve settings have always seemed kind of crazy considering that the valves adjust in 3-thousendths increments - I think that's right. All to say is you'll never get the valves settings to hit those specs. I've always run 'em kind of on the loose side.

Thanks for helping me guys - I'll update in a few weeks when I get the stuff together and drill out the cam sprocket.

Cliff