351 M: what to do?

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The 351M and 400 M are identical with the exception of the crankshafts and the pistons.

351 Cleveland 4V and aftermarket heads will all bolt on. There is a shortage of intakes available for a 4V combo, these adapters make any 351C manifold fit http://www.pricemotorsport.com/html/body_ap-29___ap-30_intake_adapter_k.html and if you have access to a mill, I imagine a set could be made to match gaskets from appropriately sized billet aluminum.

the 351/400 block can be stroked up to nearly 500 CID, though a 434 is the street version

http://www.tmeyerinc.com/400stroker.html

Running a proper timing chain is a huge benefit in the 351M and 400 motors as the attempt to make them emissions compliant included retarding cam timing 4 degrees. The 351/400M was phased out because it did not lend itself to the computerization of the EGR system as the channels were integral and therefore not easily adjustable.

In spite of the taller deck height, 351C exhaust manifolds will bolt up and headers could possibly be altered to work too.

Where the 351/400M fails to meet the performance possibilities of a Cleveland is in the really big heavy crank. Keep in mind that the cleveland crank journals at 2.749 are essentially big block chevy sized 2.748. Why the 351W and M needed a 3" crank journal is beyond me.

I've often thought building a really long stroke 400M with proper breathing, carburation, camshaft timing balancing etc would be a neat project and if I ever have the 10K laying around and all my other crazy projects finished I might give it a try.

There is no economy in building these engines.

 
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