Distributor Advance Discussion
Posted: Wed Oct 26, 2022 11:39 am
In an effort to resolve an overheating problem, I recently replaced the distributor vacuum advance canister, then ran some tests to determine the distributor advance characteristics. I did not have a tachometer, so my estimates of engine RPM is estimated.
At idle, 7.5" vacuum, 5 degree BTDC with no vacuum canister plugged
At idle, 11" vacuum, 23 degree BTDC with vacuum canister working
2500 rpm, 14" vacuum, 16 degrees BTDC with vacuum canister plugged
3500 rpm, 14" vacuum, 42 degrees BTDC with vacuum canister working
From this data, I surmise that the distributor vacuum canister is contributing 18 degree advance at idle and the centrifical advance is contributing 11 degrees. I've read that the total advance should be 52 degrees at wide open throttle and that the vacuum advance canister should be worth about 15 degrees and the initial advance is 7.5 degrees. I'm thinking that my centrifical advance is not working properly and should be providing an additional 10 degrees of advance by 3500 rpm.
Does anyone know what the total advance should be on our 425 engine?
Marty
At idle, 7.5" vacuum, 5 degree BTDC with no vacuum canister plugged
At idle, 11" vacuum, 23 degree BTDC with vacuum canister working
2500 rpm, 14" vacuum, 16 degrees BTDC with vacuum canister plugged
3500 rpm, 14" vacuum, 42 degrees BTDC with vacuum canister working
From this data, I surmise that the distributor vacuum canister is contributing 18 degree advance at idle and the centrifical advance is contributing 11 degrees. I've read that the total advance should be 52 degrees at wide open throttle and that the vacuum advance canister should be worth about 15 degrees and the initial advance is 7.5 degrees. I'm thinking that my centrifical advance is not working properly and should be providing an additional 10 degrees of advance by 3500 rpm.
Does anyone know what the total advance should be on our 425 engine?
Marty