331 Stroker Pistons .. Does it matter if pistons are dome, dished, or flat top?

RebelRouser · 12-11-2002

OK, guys!
I'm putting together a 331 stroker and going with a nodular iron crank, forged H Beams... now I'm stuck at the pistons. I am trying to make about 375hp n/a, but I want to keep my options open for a blower and nitrous. My question is, does the pistons have to be specifically for a 3.25" stroke? Or does it not matter as long as the size is for a 4.030" bore? I'm want to go with Keith Black, if possible. Also, I haven't decided with what heads to go with... it's either Edelbrock RPMs or TFS TW... so how much does it matter if the pistons are dome, dished, or flat top? I want to run a compression of at the most 9.5:1. One more thing, what 3 size piston rings do you guys recommend?

Thanks!

EZBNME · 12-11-2002

Pistons have to match bore, stroke, and rod length vs deck height. As for pistons my opinion is to use forged with what your trying to do. Keith blacks are good but are still cast plus require unique ring gaping. Forged pistons can tolerate engine knock better as where cast pistons are quicker to break if your tune up goes sour. I could go into much more detail but i am giving you the idea. Compression ratios are not so much an issue with nitrous as it is with blowers. Blowers compress air creating more heat as where nitrous is 125 below zero when injected. Flat top pistons or dish are all around better for power if you can hit your target compression through machine work or correct cylinder head cc. You don't need domes for 9.5 compression with your set up. Talk with a piston manufacture for help on figuring your compression, correct piston height, ring size, and intended use of piston for placement of rings. I would use a standard tension oil ring on the street with any kind of power adder along with correct ring gap. As for heads I like Edelbrocks better. Twisted wedge heads are prone to premature valve guide wear due to valve angle and qaulity of parts used. TWs could be better today as I have never used them again.

86Cobra · 12-11-2002

You really should decide which power adder route you want to take before building your motor. Nitrous likes compression. For a street nitrous motor with aluminum heads 10.5:1 is a good target. For a blown application 8.5:1 - 9:1 is a good target cr.

TFS TW valve guide problems are no longer an issue. They stopped making pedestal mount TWs years ago as they could never get the geometry to work right. Stud mount TWs have no valve guide issues as long as you use the correct length pushrods (usually 6.7-6.75") and good rockers.

RebelRouser · 12-12-2002

Thanks!
I found some Probe 3.315" rods and matching 3.315" pistons for a 347. Is it true that the only difference between the 331 and the 347 is the crankshaft (3.25 vs. 3.40 stroke)? If so, can I go with these shorter rods so that I won't have any oil burning problems?

RebelRouser · 12-13-2002

Anyone?