I'm building up a 400 and I've been looking all over for forged pistons for the stock 5.565" rods with the compresion ratio I want. I think I found a set that will work, but I need to figure out what my deck height needs to be before it goes to the machine shop. The pistons are TRW forged L2352 w/ a 1.555" compression height.

Now to calculate the height of the piston in the hole, you would do this correct?

(Stroke/2) + Rod Length + Compression Height of Piston = Height

If that reasoning is correct then,

(3.75/2) + 5.565 + 1.555= 8.995

So the deck height would need to be 8.995" plus whatever qeunch is needed.

That brings me to the second question, what is the reccomended quench on a street/strip motor? I've heard anywhere from .005 above the piston height all the way up to .025". I'm confused now as to what the correct quench height should be.

 

I can't help you with your first question but as far as quench area, I've been told to shoot for around .04 including the gasket. I've also been told you should mill no more than .035 off the decks which normally would'nt be a big deal unless the pistons your buying sit .05 or more down in the hole ( taking for granted the block has never been decked ). With that being said you should also leave .01 from the top of the piston to the deck to allow for variance from piston to piston, rod to rod and journal to journal ( or mock it up and measure to see how close you can get to zero deck on all eight ).

 

Stock 400 pin height is 1.56". A stock block usually has a deck height of around 9.025", but there's a fair amount of variation.

Best thing to do is measure your block, and go from there. With most heads, zero-decking the block and running a standard .039" head gasket works fine, assuming you use pistons with the correct volume to match the heads you're using (flat-tops, D-cup, etc.)

 

So if I zero decked the block to 9.000" that would give me .005" piston to deck clearance, plus a .039" head gasket would make for a total .044" quench. Does this sound good?

 

That should work out perfect, as long as you can get heads & pistons to make the compression yo need, with that gasket & clearance.

 

I've got AFR 190's with 64cc chambers (milled from 68, not by me though) and TRW forged .083 dished pistons which yields 10.7 compression.