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Old 07-16-2007, 11:25 AM
oldbogie oldbogie is offline
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Quote:
Originally Posted by KNanthrup
Oldbogie,

Thanks for the detailed information. Cam timing may be my problem. I did degree the cam when I installed it, however, at the time I did not know that Comp grinds them with 4* advance already. I put 3-4* advance in it when I installed it. So it must theoretically be at about 7-8* total. How much cam timing is excessive, where do you draw the line? It sounds like I may have a real issue if the cam wants timing farther in but the piston timing doesn't. I don't know if it would be safe to run it hard like that... which means I need to figure out the quickest and easiest way to get that cam back in place.
Advancing the cam is a way to recover bottom end and mid range torque. This is an effective trick where too much cam is used in an engine that can't be run toward its power peak RPMs. Manufacturers recognize that most buyers over cam their engine so many grind advance into hot street sticks to reduce complaints about a weak bottom to mid power band.

In the real world of race engines it may be necessary to advance or retard the cam to tune the engine to specific track and weather conditions. This is usually not more than 4 degrees either side of a straight up setting. Competition engines usually include an adjustable cam gear rather than bushings. There is a two piece timing case cover where the cam gear and its adjustment can be quickly accessed for between round tweaking.

In your case, putting a 4 degree bushing in addition to a cam with 4 degrees advance built in is 8 degrees advance, by any standard this is too much advance and will make the engine ping prone regardless of distributor settings.

I'd go back to a straight up configuration using only Comp's built in 4 degrees. If the engine still pings than take it back with a 4 degree retard bushing to straight-up timing.

Bogie
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