BeepBeepRR
Well-Known Member
Couple ounces here, couple there.. whats the difference? Tell ya what go to a ceiling fan and tape a 1/2 inch nut to one blade and fire it up.. See what happens.
Couple ounces here, couple there.. whats the difference? Tell ya what go to a ceiling fan and tape a 1/2 inch nut to one blade and fire it up.. See what happens.
Why risk it, it's not worth it to me. The engines already apart. Seems like a no brainier.
Built many we did not balance. It would probably be fine. But it is cutting a corner...and I am glad to here you are balancing it. When they do the calculations for the bobweights for balancing the crank they use 100% of the rotating weight and 50% recipricating. The piston end accounts for 50% of the bobweight. So let's say your pistons are 50 grams heavier...it amounts to 25 grams on your bobweight. For most street builds it would be hard to tell the difference when your sitting behind the steering wheel. Some of the cheaper forged pistons are pretty heavy compared to the original cast piston...the only to know is find the weights of both pistons and compare.
I just wrote out a check to balance 2 mopars yesterday. 150 bucks per engine. Imo really reasonable. But I've paid $400 to have one done that they had to add Mallary metal...because the new assembly had heavier rods and pistons then stock. Imo...its a common mistake buying rods and pistons. If you purchase lighter rods and pistons...they will have to lighten the crank which involves drilling holes in the counterbalances and is inexpensive. If you skimp and add heavier pistons or rods it's more expensive to balance if they have to add weight instead of drill. Some of the heavy metals are expensive. But...it all depends on how heavy or how light.
Yes... they tapered the inside ends of the wrist pin...and went from like 220g to 180g. Pretty trick set of pins back in the day.Actually, It's starting to come back to me. Those weights for the TRW/Sealed Power/Speed Pro pistons used to be published. I think the domed pistons were actually a little heavier, but they took weight out of the pin so that the balance would match the factory piston as well.
The ceiling fan analogy posted above isn't quite correct. You are adding/subtracting weight equally to each blade. Weigh the 2 types of pistons. How much difference? This biggest deal is that all 8 are similar. My bet is the TRWs are at least as close (piston to piston) as the factory parts. Different weight pins can sometimes help. Lighter pin with a heavier piston. Engines can be built with over balance and under balance. What does this mean? Basically they take a percentage of the calculated balance weight that would be bolted on to the rod journals during balancing. So if your pistons are lighter, it would be under balanced, heavier would be over balanced. Now as far as cylinder to cylinder? The factory job has a pretty wide tolerance. We all know factory motors all broke, nope. Save your dollars and get your build done.
Doug
Back in the day I was a dumb kid. My 1st car 68 Road Runner 4 speed. It had a transplanted 440, Cast iron 6 pac. Racing it at Milan Dragway, it lost about 15psi oil pressure. I could hear a ticking. Drove it home 45 miles. Puled the pan in my dads garage and found #5 rod spun. Crank looked fine. I pulled the head and piston/rod. Polished the crank with 400 grit. Then went to the dealer and ordered one new rod, $45 in 74. Who knew you could get used rods or have them resized? I didn't. When it showed up (10 days) it was much larger than the rest. In it went. Ran that motor for years after. Eventually I "rebuilt" it and put it in a Dart. By now I knew that it had one 6 pac rod and 7 LY rods. Swapped the one rod turned the crank, new rings, bearings, valve job.
Doug