How to time my 351 modified


Asked by Dec 01, 2015 at 05:46 PM about the 1993 Ford F-150

Question type: Maintenance & Repair

5 Answers

Bob Beaman

It is properly called a 351M. Modified Cleveland or 400 it is not. Do you have a timing light? Are you doing cam timing or ignition timing? Why are you messing with the timing? Repairs of some sort? From Wikipedia..........351M/400 naming convention confusion[edit] There exists debate as to what Ford intended the "M" designation of the 351M to refer to. Some claim the "M" stands for “Modified” - being modified from a 400 V8 with a shortened stroke - though others claim that the "M" refers to the Michigan Casting Center, where the 351M began production. There is also some who say that the "M" designation has no official meaning, and it was just Ford's way of distinguishing the 351M for the 351C and 351W.[28] Likewise, Ford's use of the 400 block in the creation of the 351M engine has resulted in the 400 mistakenly being referred to as the "400M" or "400 Modified." This is despite the 400 having been the design basis from which the "modified" 351M was derived and it was in production several years before Ford used the "M" designation. Further confusion arises from Ford printing "351M/400" on the emission stickers for the engine. The "351M/400" referenced the engine family, and some confused this with the engine name. This sticker also listed the engine displacement below the engine family. Ford's official name for the 400 V8 contains no additional designations - the proper nomenclature is simply "400."

1 out of 1 people think this is helpful.

351M, basically a de-stroked 400. I've always heard it referred to as "modified." I have a 75 Elite with one of these. Ford developed these to reduce the compression, a big concern in the era of unleaded low octane gas. A good resource for you to check out is: M-Block Ford V8 Workshop -


Why do you suspect the timing is off? If you do not have a timing light and a distributor wrench just bring it to a shop and ask them to check the timing. Probably will not cost more than the combined cost of the tools, if purchased.

Bob Beaman

I am pretty sure on those engines you have to disconnect the "spout" connector to check the ignition timing.


Haynes and Chiltons have put out good automotive repair manuals produced by make, model and year. Some manuals for older vehicles can still be found in auto part stores or online. Are you looking for the firing order?

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