Could be incorrect spark plug gap? They are now 0.6 as per the book, do you have a good experience with a different gap?
no, i didn't try the conventional dizzy, only the 123 and that's i think the only thing not standard.I'm definitely not an expert but one who often just follows the book. If I'm understanding the situation, it backfires using either the 123 distributor or the M78? The camshaft is the original one and it's installed correctly? The only thing changed from standard on the engine is the 123 distributor?
1. The "banging" in the exhaust on overrun -- how loud is it? Could it just be a leak at the exhaust manifold? Have you tried driving it yet, or does it not seem happy enough?
2. You found that the cam timing was late. In particular, that the inlet valve was opening AFTER TDC. Reporting back you said the chain was right but the sprocket had a different offset so you replaced the sprocket. Perhaps it'd be worth checking that the valves are now both rocking when the piston is at TDC.
Going on from this, it might also be worth checking that the piston is really at (or very close to) TDC when the pulley mark lines up with the TDC timing mark. If a sprocket had the wrong offset, maybe the pulley does too?? Worth a check.
Not of the sort you describe here. Exhaust leaks can give some banging/popping on overrun due to letting air in with hot unburnt fuel.the banging is quite loud, i'm not sure if it happens only after i leave the pedal or also when it's revving.
there was a tiny gap between the manifold and the downpipe which i sealed with a victor rheinz sealnt, can it cause the banging?.
I'm a little surprised you have a 12V coil -- but checking the 123ignitions website shows it's expecting a 12V coil. I guess that's to keep the "standard" look. Anyhow, a failing coil will often be ok at low RPMs but become patchy as the revs get up. If you have another coil, try substituting it. If that doesn't get you anywhere, I think I'd start looking at the carby.
Have fun,
Rob.
Sorry. I do go on. At least I warned you it was optional.now i'm completely lost in the coils subject...
1.6 Ohms sounds low for a 12V coil and reasonable for an HEI. An ohmmeter only gives you a ballpark figure anyway since resistance isn't really what makes a coil tick.2pac said:the original coil is stamped 12V, it has about 1.6 Ohms although the book says it should have less than 0.7 Ohms as it's transistorized system.
Bummer, but at least I was right about something for a change.2pac said:anyway i tried this coil and it didn't fix the problem.
2pac said:don't know if it's related, but oil is coming out of the air filter intake (it's the oil bath type of filter).