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Old 06-16-2010, 07:04 AM
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400 Ford Questions

My cousin recently bought a 76 Ford F100 4x4 in good shape that has a 400 dropped in it. He and my nephew are close and do a lot of mechanic work together so my nephew`s asked me some questions on it and I`ve told him what I knew of it since fords aren`t my strong point. My cousin was driving, doing about 35, when the truck started coughing, back fired through the carb and few times and shut off, he said it acts like it jumped time. Years ago, someone else I knew had a 400 ford that would jump time anytime you nailed it, it would break or twist the distributor shaft. A real good mechanic I know told me later that when the oil pumps bad it breaks or twists the distributor shaft. My cousin was told by the former owner he just installed a new oil pump but I`m guessing it didn`t fix the problem so he sold it.
My nephew told me the distributor is still turning, but he hasn`t checked to see if it was still in time. He said if you try to start it all it does is spit back through the carb. Anyone have any insight on 400 Fords that eat distributors? Any helps appreciated.

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Old 06-16-2010, 07:17 AM
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They will twist the oil pump drive if there's anything that gets into the pump- I had occasion to remove the pan and pump from a 351C that had a tiny piece of gasket material that hadn't been cleaned out of the pump, it wedged the gerotor gears and stopped the pump dead in the water- or oil in this case.

This can put enough stress on the gear to shear the roll pin of the distributor gear. This, in turn, will cause the timing to go away, but can actually run that way if the timing is reset- at least for awhile- until something causes the gear to again slip, causing the timing to go out yet again.

The gear can still look fine- both sides of the gear will still have the ends of the roll pin in place, so you need to be sure the pin actually hasn't sheared off.

Something worth checking, anyway.
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Old 06-16-2010, 10:15 AM
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They will twist the oil pump drive if there's anything that gets into the pump- I had occasion to remove the pan and pump from a 351C that had a tiny piece of gasket material that hadn't been cleaned out of the pump, it wedged the gerotor gears and stopped the pump dead in the water- or oil in this case.

This can put enough stress on the gear to shear the roll pin of the distributor gear. This, in turn, will cause the timing to go away, but can actually run that way if the timing is reset- at least for awhile- until something causes the gear to again slip, causing the timing to go out yet again.
Took the words outta my mouth. Another common issue is the umbrella seals on the valves get brittle, and break apart. Then that hard chunk of crap jams the oil pump, and twists the dist gear, shearing the roll pin. Every time you try to start it the timimg will change, and it will cough and backfire like a b*stard. Change the oil pump, pump drive and dizzy roll pin, re time and it should be good to go.
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Old 06-16-2010, 11:50 AM
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Originally Posted by sbchevfreak
Took the words outta my mouth. Another common issue is the umbrella seals on the valves get brittle, and break apart. Then that hard chunk of crap jams the oil pump, and twists the dist gear, shearing the roll pin. Every time you try to start it the timimg will change, and it will cough and backfire like a b*stard. Change the oil pump, pump drive and dizzy roll pin, re time and it should be good to go.
Don't forget to replace the pickup screen as well.
The VERY WORST thing you can do is to attempt to clean it, as that just dislodges some of the krap that gets trapped in there where you can't see it.

Also ... get the correct roll pin from the dealer, not just some random spring pin. They're *designed* to shear, rather than bust the teeth of of the cam.
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Old 06-16-2010, 12:39 PM
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Thanks guys, I`ll pass the word to my nephew. Hopefully they`ll be able to get it straight. I asked my cousin if anything else had been did to it, he said the heads are fresh reworked. The former owner did install a performer intake and a holley 750 double pumper on it. I mentioned to my cousin he may want to replace the cam with a edelbrock performer cam, a new timing chain and a set of headers. That long stroke 400 should be a stump puller afterwards. I had heard many years ago Ford retarded the cam timing on these engines in order to pass emissions, so I thought a cam and timing chain may wake it up a little.
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Old 06-16-2010, 05:39 PM
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Quote:
Originally Posted by sbchevfreak
Took the words outta my mouth. Another common issue is the umbrella seals on the valves get brittle, and break apart. Then that hard chunk of crap jams the oil pump, and twists the dist gear, shearing the roll pin. Every time you try to start it the timimg will change, and it will cough and backfire like a b*stard. Change the oil pump, pump drive and dizzy roll pin, re time and it should be good to go.
took the words out of my mouth X2, good call cobalt..
this is very common on 351Cs, 351Ms and 400Ms. unlike other oil pumps the gerator pumps in these engines will NOT tolerate any debris, the roll pin on the dist gear is designed to shear, both to save the cam gear and to shut down the engine so no damage is done due to loss of oil pressure. to us 351C racers this is a well known weak point. i have even seen the roll pin shear just from high oil pressure on 351C race engines. a common fix is to run 2 roll pins, this is done 2 different ways-1 drill out the dist. gear and shaft for a larger roll pin then insert a smaller roll pin inside the larger roll pin. 2-drill a second hole in the shaft/gear just under the origonal hole at 90 degrees and install a second pin the new hole...

SBcvev, i have also seen the rock hard umbrella seal debris both in the heads and in the pan.
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