Hi all, I have an old Ford school bus camper conversion that I'm swapping over to efi. It's a 330ci v8 with a worn out Holley 2bbl and points distributor. I have dabbled with some efi stuff before and got the (crazy?) idea to swap this over to a GM tbi system. The ford 330 truck engine shares nothing in common with the factory ford EFI engines so this seemed like the best bet for something simple and reliable. Scavenging all the components from the junkyard was pretty cheap. I think the hardest part will be installing the GM distributor guts into my ford distributor housing but really even that looks pretty straightforward.
I grabbed everything out of a 94 with a 7427 BJYL. One thing I'm having a hard time with is how do the values in the main spark table interact with the main spark bias? The note in the xdf says how the table already compensates for this but I'm not quite understanding what that means in a practical sense. I see "Initial Spark Advance" is set to 0 in the calibration which matches what the initial timing at the distributor was set to at the factory in 1994. "Main Spark Bias" is set to 9.8. The main spark table shows 22.1* at 2000rpm at max vacuum. Now if we assume we were at a steady 2000rpm cruise, so no PE advance, engine at normal operating temperature and EGR & knock systems disabled and zeroed out as far as I can see the only spark table at play should be the main spark table. If I threw my timing light on it at that point , would I see 22.1* or would I see 22.1* + 9.8* = 31.9*? I want to make sure I'm reading this the right way, the last engine I built the old fashioned way ran 16* initial timing + 22* mechanical advance all in @ 2500rpm + 18* vacuum advance = 56* total at cruising speed. Comparatively speaking what I'm seeing in the bin seems super low so I keep questioning myself.
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