Here's One for dist. guru's

I had a points dist. in my 91 302 & was told to put a steel gear on it which I did. There's this really nice hill on hwy. 22 when you come down to the Symcoshakedown & let your pipes rap. Mine used to, but now that I put a Duraspart dist. in it no longer will rap going down that hill. Both dist. are set up to be fully advanced at 2300 rpm. Why the difference?

 

The Duraspark is electronic.
If the timing is the same, the only difference I can think of is dwell time.

 

I've also noticed at local round-d-round race tracks how some cars just slow for the corners with no rapping noise & some rap & back fire. I didn't do anything different with the motor. Just went from points to electronic.

 

Just a WAG but even though you said they both have full advance at 2300 rpm, that would be centrifigal.There may be a difference in the vacuum advance unit calibration. My experience has been that engines tend to cackle and pop more when backing off with more timing. So if your curve is the same, and your base timing is the same, then try swapping vacuum advance canisters and see if that does it. Some are adjustable too, by removing the hose and inserting an allen wrench through the hose nipple on the canister.Just a thought.

 

There would be tons of vacuum when you let off the gas at 5 grand in low. Next time I come down that hill I'll bring my allen wrench along. I'll see how many turns are set in the old vacuum canister & match it to the Dura-spark. Thank guys for the info.

 

Was the original distributor vacuum retard too?

 

Yes noboD

 

Are you using the same vacuum port?

 

That was a pisspoor design to meet smog laws. I'd say that's why it used to backfire. When running correctly it should not backfire on decelaration. My '70 302 truck does and has been violent enough to blow the muffler up.