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I am rebuilding a 400M because after 500 miles it loss oil pressure and took out all the bearings. I have tank the engine and cleans out all the oil passages, found a lot of junk in them. I have 2 problems 1.I am unable to find any flat top pistons at a reasonable price. I want to increase the C/R, the engine is a 1981 with 2V heads. The other problem is when installing the cam it fit very tight in the last bearing you have to use a bar to turn it. Has any one seen the cam problem before.
 

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Try T. Meyer racing (I think) for the pistons, they know 351M/400 engines. As for the cam, it should turn freely. Check the size of the cam journels, if they are in spec, get new bearings installed.

Nathan
 

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im pretty sure that numerous 351C pistons will work with the 400m, however the compression will be slightly less. you can now get australian 2v heads with small chambers for a reasonable price used on ebay.
 

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351C pistons have far more options, but the wrist pin diameter is different, so it would be rather expensive to adapt them. This is one reason for the low popularity. If you're going to spend money, I'd put it into aftermarket heads. Smaller chambers and better breathing right out of the box. The Aussie 2V heads have smaller chambers for compression, but don't even breathe as well as a cheap set of Windsor aluminum heads, and will choke your peak HP on 400 cubes unless well-ported.

To top it off, the pistons ride roughly .060 in the bore, and so you can't raise compression much without getting detonation. Although the Aussie 2V has a closed chamber, the piston is not designed to use it, and effectively has no quench without heavily decking the block. This is one reason for the very weak factory compression ratio. This is the second reason the 400 'factory stroker' was never popular for performance upgrades.

Yes, you can make excellent power with them, but you'll either need high octane fuel or lots of machine work and good parts to get much over 400 hp on a good day. If 350-400 hp on pump gas is OK, then no worries. Have E85 available? Then bump the compression and push it!
:D
David
 

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TMeyer sells a stepped dish piston which works pretty well with the stock heads raising comp. to approx. 9.5:1 Lots of info on 400's at Ford-trucks.com Been running these pistons since they became available and would definately use them again.
 

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There is nothing wrong with the 351M/400 Series engines. They are very reliable and are popular in the light truck circles.

And there is no 400M... It is a 400.
 
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