heres what i have so far 427 marine block with new 13.5:1 dome top pistons, a set of fresh not sure what valve size yet oval port heads (freebie from brother-in-law) gonna get a steel crank, so i was wondering what length piston rods would be best wwith what i already have and what size cam also? dont want anything to nuts!! the 13.5to 1 pistons are bad enough ha ha this is my fist big block build so im not real familiar with things! any help or ideas would be great thanx!! Tony

Imho, I would think .400" longer since that is the deck height difference..

But in doubt measure..

pdq67

Tony,
You are going about this in the wrong sequence. Usually, the rod length is determined, then pistons are ordered according to the rod length, stroke, deck height, etc.

Best bet is to check your piston compression height and determine what size rod you will need to put the piston at, or close to, the deck surface.

engine guy said it. You got started backwards. The pistons are the last thing you get. Are they correct for the stroke of the crank you will be running with a stock pin location? If they are a .400 long rod should work if they aren't you need to figure out what you need.

That and "your first big block" is not the place to use 13.5:1 pistons anyway.

thanx everyone! the reason i have the pistons already is i got the block and the new pistons for 150$ so i wasnt about to turn the package down!! machine shop bud of mine selling out and movin to washington. i`ll check with him about the rods and thanx again

If its gonna be a street motor, sell the pistons, choose rods, and then get new pistons to match what you are doing....

Other than that.... if they are pistons for a regular 427 (stock stroke,standard deck, stock rod length) then +.400 is right.

I thought .400" longer was right...

pdq67

thats alotta compression, what stroke crank are you going with? I just used standard pistons with the 6.535" rods.