Originally Posted by david-b
I will do this tomorrow to check. So when the pressure pushes the finger off, that's compression getting raised, correct?
Back fire is coming through the exhaust; exhaust isn't hooked up after the headers, so it's very obvious when it backfires and that it's coming from the exhaust.
As far as mods, I have aluminum heads with roller rockers. I don't have specs on things since I got everything when I got the car, and it was already all torn down to the block/internals. Just got it all checked out, and got it altogether.
Even though it is through the exhaust, the same things can cause the backfire. Check the distributor, it is the most common issue.
Yes you should feel the pressure push you finger off the hole. That is compression stroke starting, You can use a breaker bar and A socket to bring it up to the timing mark. The key is to have the helper just bump the key, and to stop when you are close.