Tmadd1018

So I have an 89 f150 efi to carb swap and I set the timing without the vacuum advance on it like I was told to but when I plug the vacuum advance back on the dizzy it immediately kills the truck, the truck idles and drives fine without it connected but I know it should be connected.... it seems to go against everything to plug it in if the damn truck won't run... should I re adjust the timing with the advance on? Where do I go from here?

Matthew Burr

you probably have it on the wrong vacuum plug, ported vs manifold, try the other and see how it works, also some engines run a little differently, how did you set your timing? with a vacuum gauge or with a timing light? i would recommend using the vacuum gauge, it will provide a more accurate tune for your engine than just using factory spec

Tmadd1018

I set it with a timing light and I'll check the vacuum on the carb? Right?

Tmadd1018

I unplugged the vacuum from the intake a plug that hole and then plugged it into the carb and not much changed

Chris_1

iTrader: (1)

Is it possible you're using the wrong timing mark ?
You should also try keeping the light hooked up and watch how far the timing advances when you plug in the vacuum.

Matthew Burr

yes, do what chris mentioned.

reason why i say not to even bother with the light though is two fold,
1. the harmonic balancer slips with age eliminating it's usefulness for timing.
2. as your engine ages and wears, getting the best performance doesnt necessarily happen at factory spec timing. using a vacuum gauge and adjusting for highest vacuum without pinging will give you the best results, and it's only way to do it if your balancer has slipped without replacing it.

when using vacuum to tune the engine, use manifold vacuum