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Old 11-10-2012, 02:15 PM
Stubbs82 Stubbs82 is offline
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BBC timing and idle problems

I'm having issues with timing and idle on BBC in my beat up blazer. I purchased a motor that was supposed to be rebuilt with less than 5000 miles on it and built to run strong. I plan to use as an operate daily with the occasional play time toy. You will have to bear with me as I am no master mechanic but like to learn and do the work myself. I bought from the second owner after rebuild. Here is what i know about it without tearing it down:

It is a 72-74 454 block with 65-66 396 heads. I ran the numbers and believe it said they were 97cc closed chamber heads. I could be wrong. It has a dual plane intake and Edelbrock carb. Has a "mild" cam is what i was told but no specs on it. It has stock damper on it. Seems to have slightly domed pistons. Accel billet dist w/ vac advance. MSD 6A ignition and accel 8.8mm performce wires. The plugs are NGK. Also has headers. When I first brought home and dropped in, the timing seamed way off. I tried to adjust to no good ending coming from it. Noticed the pullies didnt line quite right to find the damper bolt to be stripped and not on all the way. I retapped the hole and put on all the way. Did not seem quite right again, so i decided to check the timing on the chain and gears. I found that when #1 at TDC the crank gear was line correctly and the cam sprocket was 180 deg out. Havent heard of any reason why it would be that far out intentionally. Timing marks not even close. I spun the cam around and proceeded to turn motor slowly to make sure no valves hitting or stuck and appeared ok. I have since tried getting it right numerous times to nothing that seems to fall into place all at once. Got it to idle at 750 at 17deg. Total mechanical time was set at 37deg. when i hooked up the vac adv, the timing appears to jump off the chart on light. way past the 60deg guage at 3200rpm. Then it seems to have either early detonation or valve tapping or something on passenger side. not noticed until around 2500 rpm.

Any suggestions on things to try would be appreciated. Like i said, i am very green and ignorant to some of the things, but want to learn and get it right. Thanks in advance.
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