Timing issues...distributor advance?
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Freshman User
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Timing issues...distributor advance?
OK guys, I've been lurking for a while and searched without any real direction so here goes. I have a 1978 Ford F250 with the 351M and a 4 speed. I have been doing some upgrades and cannot eliminate my timing issues. So far I have replace the stock cam and lifters with an Edelbrock performer cam lifters and timing chain set. A performer intake and Edelbrock carb. I have a rebuilt distributor and a new module. new fuel pump and all the basic tune up items. I cannot get this thing to stop backfiring either through the carb or exhaust. I cannot run any vacuum advance due to this. If I disconnect the advance it runs Ok but misses a little on initial acceleration. Then it runs OK at best unless you floor it and then it runs like a race car! Can anybody give me some direction?
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From: Alabama
Just a thought... maybe the wires are one space off, not letting you get/remove enough timing? Happened to me several times, I had to rotate all the wires in the direction that I couldn't turn it far enough.
I hope you get it going.
I hope you get it going.
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Freshman User
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I don't think thats the problem. I can move the timing way advanced or retarded. It just has that miss right when you crack the throttle. but only under load. If I hook up the vacuum advance it backfires immediately when you accelerate under load. When you disconnect the vacuum its not near as bad. Coould the new cam have a different rate of advancement needed to run correctly. I saw one vendor here stating that factory distributors are EGR friendly and do not advance properly when EGR parts are removed or modifications are made to the valvetrain.
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I think you are right about the recurve. How is this done? Another thought is can i replace the dist. with one from an earlier year engine to get a "pre" EGR curve? More interested in how to recurve the distributor.
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From: Wingo, Ky
Never done it before, but I need to do it on the dizzy for my 79 Bronco. There is a kit available and I think you just change out the springs on the mechanical advance. Maybe somebody has done it and will know specifics.
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From: Alabama
Does your dist. have a mag pickup? My last one was not stock but had a bad mag pick up, it did a similar thing yours is doing, I may have had the gap wrong also? I just switched it for a GM style HEI and it has been good since. Just thinking out loud hoping you get it.
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Freshman User
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distributor is the second "new" rebuilt unit I've had. I think we are in the right ballpark with the recurve. I read a little about how this is done but can i get this recurve kit at a auto zone or another local parts store? I'm willing to try this.
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From: Big Sky Country
Postmaster
Joined: Dec 2008
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From: Southern Oregon Coast
On my 400, I installed a distributor for a 460 - it seems to be curved differently than the 400 distributor and helped a lot with my pinging issues... Since the 351M and 400 are the same block, maybe this will help...
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OK, I got the recurve kit ordered. Now can somebody who has some experience with an Edelbrock performer cam 2172, tell me what they used for initial timing? Cam card says 10-14 degrees. Is this pretty much where I need to be? Also, what will be my target total centrifical advance once i get the recurve kit? I know all engines are different but I just need a ballpark or somebody who has experience with these engines and know what kind of timing they like. I'm assuming from research I want this at full centrifical by 3000 rpm's?
New User
Joined: Nov 2009
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From: Wisconsin
Well i for sure am not an expert on the recurving. Just that i also had a lot of issues with the distributor in my 400 and after different issues here and there i just switched over to and HEI dizzy and what a world of difference elimiates all the little things that usually drive a guy mad. LOL truck ran like a champ ever since.
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Joined: Mar 2008
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From: KS
When you re-connect the vacuum advance hose to the carb with the engine running, does the vacuum advance pull all the way at idle? Not sure on the V-8s but this was the case on my I-6 and found out that I was missing an inline vacuum restrictor pod. Or possibly that the vacuum advance should be hooked up to a delayed vacuum port on the carb. Just an idea to try.