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Author Topic:   cam timing question ?
regal 22
Dirt Full Roller

Total posts: 30
posted November 27, 2005 05:40 AM  
I recently built my first motor,I used a cam from a 377 that lasted 10 laps and melted the rings, I installed the cam straight up. the problem is the motor will start at correct ignition timing (12 deg) but labors severly untill timing is advanced (38 deg), but absolutley will not attempt to start at 38. This cam did the exact same thing on the 377, by the way the new engine is a 350 and the cam is a 500 lift, i do not have cam card. The 377 did ran very fast with that cam but i don't know if I melted rings with poor ingnition timing.Will advancing or retarding the cam make any diference for my problem. I am a novice at best any help would be greatly appreciated thank you!

Eljojo
Dirt Forum Champ
Total posts: 983
posted November 27, 2005 08:03 AM  
cam timing (degreeing) affects the valve opening and closing events. It has no relationship to ignition timing.

Normal Sullivan
Dirt Full Roller

Total posts: 57
posted November 27, 2005 10:50 AM  
It does affect cylinder pressure tho'. If you're having detonation problems, it might be a good place to look.

tlkdlw
Dirt Full Roller

Total posts: 44
posted November 27, 2005 11:06 PM  
It sounds like you have a timing problem. Not cam timing problem is ether in timing procedure or possibly a bad harmonic balancer
that the outer ring moved. Take and find top dead center of number one and check to see if mark is correct.

Terry

Normal Sullivan
Dirt Full Roller

Total posts: 57
posted November 28, 2005 03:17 AM  
regal 22: I'm assuming the only part of the 377 that you decided to re-use was the camshaft? Same balancer? What sort of cylinder pressure are you developing? Is your distributor indexed correctly? points? HEI? I certainly don't mean to disagree with these other fellows, it sounds as if you have an ignition problem, but how much ignition advance would you have to run in order to melt down an engine if everything else was correct? More than 38 degrees I think.

Who made the cam, and what grind number? Even if it has nothing to do with your other problems, there is ABSOLUTELY NO WAY to correctly install a camshaft without the timing information. You might get lucky, but at the very least you'll be leaving free power on the table.

regal 22
Dirt Full Roller

Total posts: 30
posted November 28, 2005 05:20 PM  
thank you everyone for your responses! Yes the balancer is the same one from the 377 the camshaft is a comp cam again i have no specs. Lasat night I ran the motor for about 20 min. the timing was set at 14 deg at 1000 rpm the water temp never rose above 160 degrees, then I noticed that the cast iron exhaust manifolds were literally cherry red. i shut it down then fired it back up with no problems, then set timing at 24 deg shut it down, and it would not turn over. the front runners at my track say they set timing at 36 deg weld mech advance crank motor with ignition off then switch ignition on with no problems, Thers is no way I could do that. any suggestions.

MOD 4s
Dirt Roller

Total posts: 18
posted November 28, 2005 11:32 PM  
Make sure you set your timing 36' at full advance that should probably be over 1000 rpm
depending on your distributor

nine finger
Dirt Forum Racer

Total posts: 93
posted November 29, 2005 04:40 PM  
regal you need th check your starting system you may have a problem if it wont crank over at 24 degrees. have one of your fellow racers come over and help you with the ignition, it really needs to be split up so you can crank the motor and then hit the ignition.

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