butler

I recently purchased a 383 forged rotating assembly from scoggin dickey with the 227.00 upgrade to balance it. I took it down to Bob Morton Enterprise to hone the motor, check the deck and align bore if necessary with arp studs. He checked the balance and the crank was 5 grams off and each rod and piston was a different weight from the other. I emailed John Ginter at scoggindickey and he said the way a motor is balanced is that you take the rods and pistons and try to get it close on opposing sides of the crank. The problem I had with that was the the rods were sealed in plastic and the rods and pistons were not numbered to pair them up and what journal they should go on. It was my understanding that you weigh the rods and pistons come up with the lightest rod and piston and equalize them. The bearings and rings are generally close in weight. Add that weight which gives you your bobweight then add or take away from the crank to get it zero balanced. What are your thoughts, please.

KCS

iTrader: (20)

5 grams isn't much, especially considering it's from one machine to another, with two different operators. The way you setup the bobweights on the crank can make that difference. Then there is oil. Some shops add weight to the bobweight to account for oil, some don't. Who is wrong? Once oil gets all over the rotating assembly, it will change it anyways. Who knows how much it will change? I say run it.

Usually, numbering the rods and pistons is up to the machinist/builder. It's not relevant to the balance of the crank, more like the clearances. In my experience, aftermarket rods are almost always within a gram or two from the maufacturer. Stock rods are the only ones I've seen that would need to be worked on to balance. How far off where the rods and who made them?

butler

Scat h beam rods, forged manley pistons, forged scat crank. Don't know the variances yet but will find out. This builder is a perfectionist. He said he bought 12 sets of manley pistons the same ones that came with my kit when they first came out and they were all different as far as the wrist pin alignment to the crankshaft. He knew the owner and called him when he was on vacation and told him about it. They conferenced called and got it straightened out. I never realized that there were so many variances in the weights till I did a little research. He talked about x y and z stuff. He definitely is a perfectionist. Said diamond makes the best and most accurate pistons. I really just wondered what is the correct way to balance a motor since I am not a machinist.

SKI

iTrader: (9)

I would like to know also ...