I'm sure this topic has come up a bunch and I tried finding existing threads about it but was not super successful (maybe because I'm a forum newb). I know you can advance the base timing on the efi 460 to improve power but have not been able to find any guidance on how much advance works best or found anything documenting other folks results at which degree of advance and what they found to work best. Thanks for any input. Btw the truck is an 89 f250 4x4 5spd with the efi 460.

 

As much as you without pinging would be my advise. Just go 2 degrees at at time. I predict you won't get far without it pinging on you.

 

The initial ignition timing the distributor is set at is only a part of the equation. Where it ends up at - around 2,000 to 3,000 RPM - and how quickly it gets there, where is the timing at during steady highway cruise, all that is what really counts. So you have to check it. The vacuum advance port has to be disconnected & plugged, and you first want to verify the crank balancer ring hasn't slipped, which will hork the timing marks giving inaccurate results.

Most every OHV V8 ever made wants somewhere around 34° to 36° BTDC ignition timing when spooled up. This would be without vacuum advance. The exact number depends on compression ratio, weight, gearing, elevation, fuel quality etc. That's what you're looking for. The amount of internal centrifugal advance is not ordinarily adjustable in a convenient method, so you're kind of stuck with whatever the distributor provides if you're unable or unwilling to change it. Verify and or adjust the distributor housing so as to get 34° at say 2500 RPM.. Maybe 2800 RPM ...with the vacuum advance disconnected and plugged. Make sure it's done advancing all the way. Let the initial timing fall wherever it may, so long as it's less than about 20° should be OK.

It won't run better with less "total" advance than it is designed for, it will only lose power and efficiency and tend to run hot. With vacuum advance you'll see somewhere close to 50° timing on flat ground steady cruise. This is how they are spec'd from the factory.

 

My efi engine wouldn't be vacuum advanced would it? It would be computer advanced.

 

Maybe, but the exact same principles apply. It needs to be set correctly, and measure that the timing curve is optimal. It will be ping city with more than 34° to 36°, or if it comes in too fast, or crap fuel, etc.

 

Right, I understand

 

No


Correct

 

I put in 10 deg. adv.just right

 

The procedure to set base timing on these EFI motors is pretty simple, with the engine warmed up and idling and with the timing light connected, find and pull the spout plug to disable computer advance(in the distributor wiring harness on this vintage truck) and then rotate the distributor clockwise to advance timing. The factory setting is 10deg BTDC and most SD engines will tolerate 2-4 deg additional advance depending how they are used, just driving around unloaded it will take more, towing heavy it might not take any extra. When done lock down the distributor and reinsert the spout plug.

There isn't a single timing curve with an EFI system there is a 2D map in this case, the timing will vary up and down at any given rpm based on engine load which the driver can alter in real time with throttle input. There is no way to see or reprogram the timing map without a tuner so I only mention this as a point of interest, I'll just add that there is more than enough timing advance available to get maximum power from the engine at all rpms, this is something you will discover if you alter the base timing setting.