So, I have a 72 cutlass with a 455. I just rebuilt it and got it running pretty good without a timing light. I want to time it with a light now! I locked out my distributor because I'm going to run efi, so there is no advance anymore. I've been reading reviews and don't understand what all in means. Can someone pleas explain how to time it and what to time it as with vacuum advance blocked? Thanks in advance!

 

I'm guessing your EFI controller will be controlling your spark? If not, you should not have locked out your distributor. I would not have locked it out UNTIL I did the EFI swap, though.


Each EFI system will have a certain initial timing setting that you will need to set the distributor at, in order for the system to accurately control the timing. Some systems will require that you phase the rotor, but that is a topic for another thread.


"All in" means the timing value when the mechanical advance is fully extended. Since yours is locked out, your "all in" is where ever you set the timing at. With the advance un-locked, you would have to run your motor at higher and higher rpm, until the timing stopped changing - that would give you the "all in" value and the rpm at which it happened.


Since your distributor is locked, the timing should have the same reading at idle as it does at 5,000rpm (assuming vacuum advance is disconnected).


With it locked, you are either going to have a LOT of timing at low rpm, or not nearly enough at higher rpm - until you let the EFI computer take over the timing chores. You will probably need a dial-back (adjustable) timing light, to set timing on your car. If you want 36 degrees, you will set the dial at "36" then adjust your distributor until the TDC mark on the harmonic damper matches up to the "0" on the timing tab. If your efi system needs the timing at 20, then you turn the dial to "20" and again match the damper mark to "0" on the tab.

 

"Locked" refers to the mechanical advance (controlled by the weights and springs) and NOT the vacuum advance that is controlled by the vacuum canister connected to either ported or manifold vacuum.

I find it odd that you locked out the mechanical advance but you still want to run vacuum advance.

 

As the others said, locking out your distributor eliminates the mechanical advance. However, it was my understanding that EFI systems which control timing need the vacuum advance eliminated as well. What type of EFI system are you running and what type of distributor do you have? You will DEFINITELY need a timing light to set your base timing.

 

I suspect that's because it makes no sense, unless one plans to run the engine at one continuous speed, as in a race car running from 5,000 to 6,000 RPM for the whole race.
Of course, in that case, running mostly at full throttle, you'd eliminate your vacuum advance as well.

- Eric

 

Locked timing is very common especially for radically cammed engines. It helps with idle and does not really effect drivability. The only issues you may run into is starting a heat soaked engine. Most use a switch to power up the ignition once the engine is spinning to fire it off. Another route is to use an ignition box with a timing retard for start.

 

Ahh, Eric, that's timing mentally challenged for start.