daughter has a 66 coupe with 289 edelbrock 4 barrel. discovered that vacuum advance had a hole in diaphragm so replaced it. now the engine starts fine like before, but as soon as accelerator is increased, the engine starts to buck and surge. disconnected and plugged tube coming from passenger side of carb and it seems to run fine. not sure whether carb, distributor or timing problem. any help appreciated.
Vacuum Advance Problem
- Thread starter healeymanjim
- Start date
tos
Founding Member
Sounds like its advancing way to early or easily. Check your springs? Make sure your wires aren't getting pinched when advancing. You can operate that advance with the dist cap off by putting a hose on the dist port and sucking on it to see whats going on. Is it backfiring thru the carb
Edster
Founding Member
Passenger side is ported vacuum, so when the throttle is opened it puts vacuum to the distributor. Ser the timing with the hose disconnected at the minimum spec per manual and start from there.
Sent from my C6606 using Tapatalk
Sent from my C6606 using Tapatalk
Some aftermarket vac canisters are adjustable. Check your base timing like above, then see what the total mechanical advance at rpm is from there. If the canister has been bad long enough, it could be tuned for advance without vac. You'll want it for highway and cruising. So third, make sure what the total advance is with the canister plugged into the right port. If an Allen wrench in the tube (like on an HEI) does not do it, they are sometimes marked with how many degrees and can be swapped. Or a blocking plate allowing partial advance can work.
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