Are motors balanced from the factory???? I bought a virgin 350 2 bolt main. it is still factory bore and the crank has factory specs on the journals, I am going to rebuild the motor which doesn't need boring just a light hone and the crank is in great shape. I plan on reusing the dished factory pistons and factory rods. will I need to have the rotating assembly balanced by a shop??? I don't plan on turning the motor past about 6000 or 6500 rpm.

I am going to be running a set of home ported 416 heads which have alot smaller chambers so the dished pistons won't hurt compression too bad ( I don't think).

by the way, what was the factory compression ratio with the 76 cc 882's that were on there, and what will it be with the 64 cc 416's???

thanks guys.

 

Yes, they are. But not the same way you would do it at a machine shop.

As rods come out of the manufacturing process, they go into an n-dimensional array of boxes if you will, sorted by big end weight, small end weight, overall weight, length, etc. When a box gets 8 in it, they match a crank to them and build a motor with it.

I always like to rebuild with a set of rods, not just 8 rods, when possible, for exactly that reason.

The CR was somewhere in the 8¼-8½:1 range. It should be somewhat over 9:1 with those heads.

 

thanks RB, the rods are a factory set so they should be OK. I was hoping for more compression than that since I will only be running race gas in it after its built. I quess that will have to do until I can put some flat-tops or domes in there and bring the compression up to par.

 

Are you running them with the factory crank they came with? If so, you're probably good to go; if not, they should be balanced.

 

Yes, its the factory crank. I couldn't believe the condition of the motor when I opened it up, looks like it has hardly been run. not too bad for $100.00 I don't think. huh??