I recently aquired a 335 series engine I say 335 because I have almost no Idea what it is. I was told that it was a 351m but when I pulled the heads off IT had flat top pistons I don't think a stock 351m has these. So I began to think it was a 400 or a 351C. I'm going to try to check the stroke distance tonight, the only problem is that it hasn't been ran ever apparently it just had a fresh timeing gear and chain gas saver cam put in it ans a valve job done to it. Two new pistons were also put in it. Which makes me think the other six are stock pistons. I know that on casting numbers a D7 means it was made in the seventies and tha following digit is what year It was made in. how can I tell from the block casting what engine it originally is? Also do any of the 335 engines have stock flat top pistons?

 

Find the block casting ID and compare it with the codes listed on this page:

http://home.earthlink.net/~bubbaf250/parts/parts02.html

Or find the crankshaft casting ID and compare it with the codes on that page.

Are the pistons really flat tops, or do they have a very shallow dish? Stock 351M truck pistons had a shallow dish, as shown in the following pic:

 

Very easy to measure the stroke with the heads off.

3.5" = 351
4" = 400

 

Hey guys thanks for the info I'll go to bubbas first nex time Bubba the pistons do look like that so I was wrong. If the pistons are as flat as they are what makes the 351m have such poor compression? btw Bubba not to rush you or anything but when are you going to up date your web site ?(if you haven't done so already)

 

Combine that big dish in the middle of the piston with a 78cc combustion chamber and you end up with C.R. of the 351M.