So I get to installing the #7 piston and I realize the piston is damaged. Something whacked the side of the piston and crimped the ring land. Pretty sure it wasn't me, as I pulled the piston out of the factory box and realized the rings wouldn't go on.

So I call the supplier and they send a new set of speedpro hyper pistons. I weigh all of them and the closest one is 7 grams (almost 1/4 oz) lighter than the damaged slug. mothertrucker....

How significant is 7 grams? Do I need to pull the rotating assy back out and have it rebalanced? Do I just throw all 8 lighter pistons in? Can I just swap out the 1 damaged slug? Try to get a heavier piston from the supplier?

I'm gonna call the machine shop, but I suspect he'll tell me to run it.
thanks......

 

The problem is not just the piston weighing 7 grams lighter. You need to know what the rod piston and rings weigh as a package like when the balance them.

Lets say your shop shot for within 5 grams on all of them. I believe Stock is within 10 Grams. Was #7 on the light or heavy side???

In a stock type rebuild it probably won't matter but in a performance application you might feel a slight vibration throughout the RPM range.

 

the pistons are a weight matched set +/- 1 gram. He didn't balance the rods. He weighed 1 piston/pin/ring/rod/bearing and used that to establish a bobweight for the crankshaft.

Current piston/pin is 586g and new piston/pin is 580g. I tried to call him today but the shop was closed. the saga continues...

 

I swapped some pins around and got it down to 5 grams. I put the light piston at #7 and we'll see what happens. It's a truck motor that tugs around at 2,000 RPM or lower. Deck height was within .003" of the other slugs so it won't affect compression or P to V.

Next question- At what valvespring pressure do you upgrade from stock retainers and locks? I'm using the PAC 1211X spring that has about 325# over the nose at 510 lift.

 

Not sure on the springs and locks.


I usually go with what the manufacturer recomends if I don't buy a kit that already has them.

 

What is the torque value for the Scoggin dickey reusable balancer bolt?

 

I would call or email them to be sure.

 

I'm so busy during the day I don't often have time to call about stuff. I did get up with the PAC spring guys. They said I'd be fine using the stock retainers and locks with the 1211X springs. They said many of their beehive springs were designed to be used with stock hardware.

Do you guys use ARP lube or locktite on your balancer bolt threads?

 

Nobody on the balancer bolt?

I'll help the next schlub. 240ft/lbs with ARP lube.

 

http://arpinstructions.com/instructions/234-2503.pdf

Kit #: 234-2503 ARP Recommends:
Tighten the balancer bolt to 235 ft-lbs using ARP ULTRA TORQUE FASTENER ASSEMBLY LUBRICANT.

I could not find any info on the SDPC bolt and they do not have any specs listed that I was able to find online.