64 Fuel Injection Timing

[Larry M.]

I know I ask some dumb question but I learn a lot from what you experts say. So here we go. After points/plugs/rotor/cap, etc. I checked the timing. At RPM 8-900 (book says 850) I get approx 10 degrees - great. When I raise the rpm to about 1100 (which I recall seeing a note from Duke Williams that this was a good idle speed for FI) it appears the centrifugal advance adds "roughly" another 10 degrees. Then if I connect the vacuum advance it adds a whole bunch more....timing mark almost on top of the balancer so I'd guess thats another 20 degrees, maybe more. Car is running and starting great - no preignition on 93 octane ethanol free - but I was surprised by the magnitude of the advance. Does this look like a normal situation or, said differently, do my advance mechanisms seem to be working as designed?

[Jerry G.]

Re: 64 Fuel Injection Timing

This motor likes approx. 38 degrees total advance, all in all components.

[William C.]

Re: 64 Fuel Injection Timing

But under light load conditions, with a lean mixture it will provide better mileage with even more timing due to the lean mixture. That's why the vacuum advance is used to provide extra timing under light load conditions. So on a '65 FI car running down the road @ 2500 rpm under light load (cruising) your total timing would be 12 degrees initial plus 24 degrees centrifugal, plus 16 degrees vacuum advance, or 52 degrees of total advance! Remember this is under light load ONLY! As soon as you hit the "Go Pedal" the Vacuum advance drops out and you are down to 36 degrees advance which under load is considered near optimal for the smallblock production engines for performance.