hi guys, here is my problem. i have a 1977 f150 with the 302 and auto trans. when i went to set the timming, before i touched anything the timming was way off. it was retarded about 20 degrees from where it should have been with constant vac advanced ran to it. i knew this wasnt correct so i hooked up the correct ported vac advance. then unhooked it from the dist and pluged it so i could set the timming. i put it at 6degrees btdc like it calls for. it pings so bad it couldnt be drivin. i figured something must not be right. so i pulled the #1 plug, and used a micrometer guage to make sure the piston really was at tdc. well when it showed tdc the timming mark was also at tdc. so thats all good, but to make the truck run good the timming must be set at 6 to 8 degrees after tdc. i cannot figure this out and its driving me nuts!!! it has a fresh tune up, fresh carb rebuild that was tuned on the emissions machine. it runs very smooth and has no hesitation, however the timming doesnt make any sense. i checked the vac advance line from the carb and it pulls about 6 inches of vacuum. the electronic pick up is free and working, checked it with a vacuum pump and when i rev the engine. what could alter the timming from where it should be to 6-8 degrees after tdc? that is over 12 degrees off. also the truck doesnt run hot, only about 190 degrees or so. if anyone can tell me why this is like it is i would be greatfull. thanks.

 

Maybe the distributor gear is off by a tooth or two.

 

Did you check the mechanical advance in the distributor? Pehaps it's frozen in place.

Does it appear to have the stock heads on it? (Not that it's easy to tell). Maybe at some point in time someone bumped up the compression, possibly by putting earlier heads on it. Might require the use of premium fuel to get the timing up where it belongs without pinging. Have you had this truck for a while or is it a recent acquisition?

 

i just bought the truck about a month ago. im not sure which one, but either it is not the stock engine or the heads have been replaced. i say this because when i recently did a tune-up i bought the stock motorcraft plugs but they would not fit into the heads. they had the correct threads but they tappered out just a bit too much to fit. so i took one of the old plugs to the parts store and they matched them up for me. so im really not sure what was done prior to me buying it. i will do a compression test at some point to see if its higher than it should be.