- Balancing the L98 -

Little info on what goes into balancing a L98 with a stock type set up. As you can these are stock 5.7 rods and flat top sealed power pistons with a .020 over bore.

First thing you do is weigh the rods, all big ends first, then overall weight. This is the big ends being done.

Once all are weighed you catalog them into the computer.

Then you start matching by taking the lightest rod at the big end and matching the rest to it. This is done by removing material from the weight pad at the bottom of the rod.

As you can see from this picture, the large ends are matched, one rod was left untouched because it was the lightest.

With the rods matched its time to match the pistons, now usually the piston manufacture tries to match the piston weights to one another but this can be upto 5 grams, they also try to match stock replacement pistons to what the stock weights are. Here is the stock piston/pin combo.

as compared to the new combo

Once again after weighing all the new pistons, we match them all to the lightest piston, this is done by removing material from just above the pin on the inside of the piston crown, the old way of doing this was by drilling around where the pin goes thru the piston...some have found to weaken the piston by removing weight here.

All the info of the matched pieces is recorded onto a bobweight card, which then lets me know bobweight to add to the throws of the crank.

After entering the info in I know make up the bobweights. The little washers are the weights that I add to the bobweight.

Here are the bobweights attached to the crank, while this is a L98, at the point that this picture was taken the flywheel is not installed. The flywheel/flexplate must be installed on a one piece rear seal motor before balancing. Even though the motor is considered internally balanced, there is a weight of about 100 grams or so welded to the flywheel.

Here is the out of balance of the setup before I begin to drill on the crank, This setup is actually closer than most, but its still to far out. The numbers in the upper right and left are the grams that the crank is out of balance. I did a Scat crank last week that was 199/126 out, so as you can see this one is pretty close.

This is drilling the weight off the counterweight of the crank, its a bit of drill, spin then drill again to get the weight down to what you want. You can see the weight that I was speaking of on the flywheel in this picture.

Here it is...GOOD PART! After drilling the correct amounts out of each end and spinning the crank one last time.

The cranks are spun at 500 RPM while balancing...little info about balancing, one OZ. of out of balance will equal to 24 pounds at 4000 RPM, that same one OZ will be just over 200 pounds at 8000 RPM.

Balancing not only gains HP and makes a smother running motor, but also saves the motor from trying to rip itself apart!