Distributor swap help
Thread Starter
Registered User
Joined: Sep 2017
Posts: 159
Distributor swap help
Hey guys, I need some advice. On my Cutlass Supreme 67 330 4BBL/ TH350, I swapped back in a reman stock points distributor. Distributor is a Cardone 30-1843 (got a steal on it through my work) with new cap and rotor. It is triggering an MSD 6AL box and coil. I believe it is the high compression engine, but has been rebuilt at some time.
I installed an MSD timing tape on the balancer. The carb is a Street Demon 625. With all carb ports plugged, except the breather hose to valve cover, I set the timing at idle 7.5 degrees per the original manual I have. The vacuum advance is disconnected. I adjusted the carb per the intructions after warmed up. The stock timing tab is intact, and rotating the distributor I can see that 10 degrees distance on the tab matches the timing tape. So, I believe I put the correct tape on the balancer.
When I hook up the vacuum advance to full vacuum, the small port at the back of the carb (instructions say the front of the carb is ported) the timing shoots to around 35 degrees at idle and it is definately pinging. I just shut it down after that. Ive owned other older cars with distributors, but have never actually had one with a vac advance distributor. Only EFI, mechanical only, HEI computer controlled, etc. Am I an idiot, or do I need to put an adjustable advance can in? What's next?
I installed an MSD timing tape on the balancer. The carb is a Street Demon 625. With all carb ports plugged, except the breather hose to valve cover, I set the timing at idle 7.5 degrees per the original manual I have. The vacuum advance is disconnected. I adjusted the carb per the intructions after warmed up. The stock timing tab is intact, and rotating the distributor I can see that 10 degrees distance on the tab matches the timing tape. So, I believe I put the correct tape on the balancer.
When I hook up the vacuum advance to full vacuum, the small port at the back of the carb (instructions say the front of the carb is ported) the timing shoots to around 35 degrees at idle and it is definately pinging. I just shut it down after that. Ive owned other older cars with distributors, but have never actually had one with a vac advance distributor. Only EFI, mechanical only, HEI computer controlled, etc. Am I an idiot, or do I need to put an adjustable advance can in? What's next?
Registered User
Joined: Jan 2010
Posts: 6,105
From: central Indiana
You may need to limit the vacuum advance rate. Sounds like it has a canister with a weak return spring, with lots of built in advance. Crane used to sell a really nice curve kit that included a vacuum advance limit cam, and different springs. Do some reading on recurving distributors. Shoot for 10-15 degrees initial, with another 20 or do with the centrifugal advance. Then tune the canister to add another 15-20 degrees at part throttle cruise. Make sure the vacuum advance is on a manifold source. The idea is to add vacuum advance at low engine load for maximum efficiency, then as engine load increases (causing manifold vacuum to drop) the vacuum advance also decreases to prevent pinging. A LITTLE part throttle pinging is ok, it should disappear as you apply more throttle.
Thread Starter
Registered User
Joined: Sep 2017
Posts: 159
You may need to limit the vacuum advance rate. Sounds like it has a canister with a weak return spring, with lots of built in advance. Crane used to sell a really nice curve kit that included a vacuum advance limit cam, and different springs. Do some reading on recurving distributors. Shoot for 10-15 degrees initial, with another 20 or do with the centrifugal advance. Then tune the canister to add another 15-20 degrees at part throttle cruise. Make sure the vacuum advance is on a manifold source. The idea is to add vacuum advance at low engine load for maximum efficiency, then as engine load increases (causing manifold vacuum to drop) the vacuum advance also decreases to prevent pinging. A LITTLE part throttle pinging is ok, it should disappear as you apply more throttle.
Thread
Thread Starter
Forum
Replies
Last Post
