351M/400 Ignition
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351M/400 Ignition
Ignition trouble in my 1979 F-250
First of all, thanks to all that have helped me with my '67 project... haven't gotten into it very deep yet, but thanks anyhow.
OK, New question for you all: Got a '79 F-250 with a 351M in it. The engine died and I bought another parts truck from a guy who claimed it had a 351M in it (turned out to be a 400). the 400 came originally from an old car, and I am not sure what type of car that was. I swapped engines and have had very little luck since. I replaced all of the electrical parts in the truck, including the box on the inner drivers side fender. Now I am told that there were different boxes for different series of 400 and 351M engines. I have a box with a dark blue plastic piece on it, and I have 2 (an old spare) that are light blue. I am told that these are how you tell the difference. Does anybody know what color I am supposed to have? The truck will fire here and there, and backfire once or twice, but not run. Timing is good, plugs are new, and carb is adjusted and not sticking. Thansk for any help that you can give me.
--Ryan
First of all, thanks to all that have helped me with my '67 project... haven't gotten into it very deep yet, but thanks anyhow.
OK, New question for you all: Got a '79 F-250 with a 351M in it. The engine died and I bought another parts truck from a guy who claimed it had a 351M in it (turned out to be a 400). the 400 came originally from an old car, and I am not sure what type of car that was. I swapped engines and have had very little luck since. I replaced all of the electrical parts in the truck, including the box on the inner drivers side fender. Now I am told that there were different boxes for different series of 400 and 351M engines. I have a box with a dark blue plastic piece on it, and I have 2 (an old spare) that are light blue. I am told that these are how you tell the difference. Does anybody know what color I am supposed to have? The truck will fire here and there, and backfire once or twice, but not run. Timing is good, plugs are new, and carb is adjusted and not sticking. Thansk for any help that you can give me.
--Ryan
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351M/400 Ignition
Question, Did you replace the sparkplug wires?
I bought a '78 F-250 W/400, and gave it a tuneup.
That was a mistake! I pulled of the wires and didn't look to see how they were routed. After putting every thing back to FACTORY specs, it had the same symptoms as your motor. I chased that problem for 2 WEEKS!!@! Finaly decided the timing chain had trimmed off the factory nylon teeth on the timming gear. WRONG!! The prior owner had put in a gear set 180 deg. out.
Fixed that and it ran fine!
I bought a '78 F-250 W/400, and gave it a tuneup.
That was a mistake! I pulled of the wires and didn't look to see how they were routed. After putting every thing back to FACTORY specs, it had the same symptoms as your motor. I chased that problem for 2 WEEKS!!@! Finaly decided the timing chain had trimmed off the factory nylon teeth on the timming gear. WRONG!! The prior owner had put in a gear set 180 deg. out.
Fixed that and it ran fine!
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351M/400 Ignition
when you put your engine in time, did you make sure that the #1 cylinder was on tdc of the compression stroke? kinda sounds like it might be timed on tdc of the exhaust stroke. when you installed your plug wires, did you you make sure that you installed them in the correct order and in the correct direction according to distributor rotation?- I kow this sounds stupid, but I've seen sevral mechanics install them in the right firing order, but opposite of distributor rotation. this is where I'd look first
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351M/400 Ignition
I timed it with a timing light and to be sure I also made sure #1 was TDC. Is it possible that I am timing to the exhaust stroke? I don't think I can turn the distributor very much farther. the plug wires are good - I have checked them multiple times and they look good. It ran perfect for a while, then the carburetor got all flooded and I had to tear it apart and rebuild it. I ended up buying a new carb for the truck, and I know it is tuned to run with a 400. I thought that the trouble obviously was in the carb, but both myself and a mechanic (a "professional") looked at it and neither of us canb find anything wrong. this is why we thought it may be the ignition box. Let me ask you this: are there different versions of the box? Do the colors of the plastic pieces mean anything? I'll get the serial# from the engine and see if anybody can tell me what it originally came out of. Maybe I have the wrong box?
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351M/400 Ignition
Just checked both my '78 trucks. Both have blue tabs on the ignition box. The only time I had a box go out, it wouldn't fire at all.
Look at the intake valve (valve cover removed and no sparkplug in #1) as you rotate it around to TDC on #1 cylinder. Intake should be just closing on TDC approach, fully closed on TDC. Piston will be at top of travel. Timing mark aligned.
If all this doesn't happen in that sequence. Look at my earlier reply.
Look at the intake valve (valve cover removed and no sparkplug in #1) as you rotate it around to TDC on #1 cylinder. Intake should be just closing on TDC approach, fully closed on TDC. Piston will be at top of travel. Timing mark aligned.
If all this doesn't happen in that sequence. Look at my earlier reply.
