91 5.7 Roller engine intermittent knock at idle

[Hipster]

No clue ...once I connected the vac advance I never measured it... I just ran my idle screw down....Im running 13 initial now disconnected.

You need to know the inititial, total, and how much advance the cannister pulls in to get it dialed in. When you bump the initial you need to shorten the slots in the advance plate to limit the total advance. Spring kits only change the speed at which the advance comes in not the total. Then go to the vacuum advance can. You can get them in different Hg. ratings for different distributors or adjustable ones depending on what you have.

You don't always hear detonation at higher rpm but it can kill some bearings in short order.

 

[kenh]

OK.... I know I'm WAY late to the party here but a vacuum advance dizzy should have ported vacuum. In other words no vacuum at idle. Find another port on the carb that only supplies vacuum at off idle only. there should be one.

Or I completely misunderstood what the OP was saying.



Ken