timing affect compression?

[aga]

sup!

as whoever has read my build thread knows, my car before i bought it has been built by monkeys :wackit: in a dark cave using only hammers.

now, here's the deal. i ve had problems with running proper ignition advance on the car, and after doing some research i was lead to believe that the previous guy had fuc*ed up something on the head. either took too much off the head, or timing is wrong , i dunno.

i bought an untouched head, and all the necessary parts to swap a head. told my mechanic to check everything as he is dissasembling, specifically do a compression test and check the timing. so here's the data:

compression 105 in all cylinders. (but the car doesnt burn a drop of oil, so it can't be piston rings)

the intake cam was 1 tooth off

as i write this , he didnt have time to correct the timing and do another compression test. when he does, if the compression doesnt change, i'm taking the head off to go deeper.

here's the question: can 1 tooth wrong timing on the intake cam affect compression so much? (if at all)

cheers :goyou:

[[email protected]]

1 tooth off will affect compression in my opinion..say the intake cam closes by one toothoff. By the time cam lobe is closing, the engine is already onto the compression stroke and the intake valves are still open for a split second, causing some pressure to escape.

[aga]

yeah i believe too that it is possible, because 1 tooth in our chain driven system is a lot of degrees... like 10+

[aga]

RESULTS:

as i said, apparently the intake cam was 1 tooth off. like this, it had 105 compression.
we correct it, set it on it's marks, the crank correctly at TDC. compression = 95

this can't be right i say, doesnt make sense. The only way it would make sense is if the guys who built the engine misplaced a tooth on the crank side gear. so we put the intake cam as it was, 1 tooth "wrong" and we put the exhaust cam 1 tooth wrong too. measure compression, 120. we are on the right track. so i look into our compression tester. is it reading correctly? we measure another car, an NA car with more compression than my SR, it spits out 150. very low for that car. should be near 190-200. a friend lends me his, which was recently tested. i measure the SR, 180. ok that's too high. but whatever, the engine is ok.

so , does timing affect compression? you bet.

case closed. miller time.