Gary Z

I want to assemble an NA 347 that can safely touch 7200 rpm or so without the expense of a forged (3.622) crank. I want parts that will simplify (avoid Mallory metal) balancing the stock crank. I want flat top pistons with valve reliefs. I am willing to invest in expensive 6.125 rods that could be reused later in a stroker. Are there forged piston/rod combinations that have a lower-than-stock bobweight?

KCS

iTrader: (20)

Have you researched how much the difference in price is between a stock and aftermarket crank is? Usually, a 4.00" forged crank will only add about $500 to the cost of the build. With a nice "lite" rod and then forged pistons, you will probably end up paying the same if not just a little less.

Just don't get a forged 3.622" crank. I've balanced a few and everytime the counterweights are WAY too heavy. I had to cut the counterweights down on a lathe and then drill up to 13 holes to get it to balance out.

But whatever the case may be, I would go with a Mahle piston for a low bobweight. They use a 4032 alloy, instead of a 2618 like most other piston manufacturers. The benefit is that I have seen a Mahle piston weight 60 grams lighter than a comparable 2618 piston. The disadvantage is that the 4032 is supposed to be weaker than the 2618.

WeberRacingEquipment

iTrader: (4)

We have noticed that most of the 5.7 cranks require heavy metal because of the heavier bobweights. There really is no way around it. This is why we use the 6.0L crankshafts because they have solid rod journals and we usually have to take weight out of them.

Give me a call or shoot me a PM and we can go over some pricing for your build.

Thanks,
Leo

Gary Z

Thanks for the information. I've decided to stick with my stock internals for the time being. I'll upgrade my rod bolts and flycut my pistons. I'll call Weber when I'm ready to go bigger.

GrannySShifting

iTrader: (10)

Is this Gary that used to live around here?

Black Plague

iTrader: (13)

Manley rods Weisco pistons!!

SEMI-RETIRED

Carillo rods, JE pistons with stock crank plan on shifting at 7800

ChiTownHustler

iTrader: (3)

K1 Technologies Lightweight rods and Mahle Motorsports PowerPak would be my choice. That is about as light as you are going to get.