I am currently building an 355 shortblock for my new LE2 setup, the block is at the machine shop, i will be buying a rotating assembly soon. I am interested in learning al i can about the 1 piece real seal motors.

LT1 motors are nuetral balanced on the front, and externaly balanced on the rear. I surmise the reason for this is, GM didnt want to change cranks, and flywheels from the 86-92 350 motor. So they used the same crank, and flywheel, or flexplate. Am i correct in assuming this?

I am thinking that as long as the damper,crank, and flywheel are balanced, then if you put, pistons and rods on the crank, (that all weigh the same), then you have a balanced rotating assembly. Even if those are gen 1 rods, and pistons, like the 86-92 TPI motors. Is this assumption true?

 

not completely true the lt1 rototating assembly is lighter then the 350

 

Your post was kind of confusing. A stock LT1 rotating assembly is externally balanced. When you buy a rotating assembly, you have bascially two choices. Have it internally balanced, in which case you can then use any neutral balance flywheel and harmonic balancer. Or, have it externally balanced, which means taking the crank, a piston/rod/ring assembly, and flywheel and balancer to the balancing shop. Before doing this, the pistons and rods each need to be balanced (to the same weight), but they will usually come this way.

A small amount of imbalance in reciprocating weight is ok for a drag race motor, but will cause accelerated bearing wear on a higher mileage setup. Reciprocatring weight is the pistons/wrist pin/rings and small end of the rod. The rotating weight really needs to be pretty close. The rotating weight is the crank/big end of the rod and rod bearing/harmonic balancer and the flywheel.

Rich

 

Yea the rods and pistons, i dont think the crank, and flywheel are?

 

NO MATTER WHAT A CRANK NEEDS BALANCED every crank rod piston even pistons rings can be way diffrent, even if you have the bobweight set up to what the manufacturer stats it was balanced to it can still be off, when there sent out there just "close" most cranks even have tags on them when there sent out that they must be balanced before assembly.

 

Your post was kind of confusing. A stock LT1 rotating assembly is externally balanced. When you buy a rotating assembly, you have bascially two choices. Have it internally balanced, in which case you can then use any neutral balance flywheel and harmonic balancer. Or, have it externally balanced, which means taking the crank, a piston/rod/ring assembly, and flywheel and balancer to the balancing shop. Before doing this, the pistons and rods each need to be balanced (to the same weight), but they will usually come this way.

A small amount of imbalance in reciprocating weight is ok for a drag race motor, but will cause accelerated bearing wear on a higher mileage setup. Reciprocatring weight is the pistons/wrist pin/rings and small end of the rod. The rotating weight really needs to be pretty close. The rotating weight is the crank/big end of the rod and rod bearing/harmonic balancer and the flywheel.

Yea i have seen internally balanced one piece rotating assemblies, but do they sell one piece flywheels that are nuetral balanced?

Rich

 

Sure, they are standard SBC parts. The one piece cranks have a different bolt pattern on the crank flange, so you need to get a flywheel/flexplate with the correct (small) bolt pattern or one that is drilled for both (which many are).

Rich

 

Do you think GM balances every crank, with rods, pistons, rings, flywheel, and damper individualy, with each motor? Or do they make them as close as they can , and put them together?

 

Sure, they are standard SBC parts. The one piece cranks have a different bolt pattern on the crank flange, so you need to get a flywheel/flexplate with the correct (small) bolt pattern or one that is drilled for both (which many are).

I guess as long as its 168 tooth it doesnt matter, what about the pilot bearing hole on the gen one crank, will it work with my trans shaft?

 

What about the damper, is the lt-1 damper going to work?

 

All LTs use a damper on the front and not a balancer. So, yes it will work if the new crank is internally balanced on the front.

WD

 

Are we talking about an LT1? It uses a 153 tooth flexplate/flywheel. It is 12.75" in diameter and has a 3.00" bolt circle. A stock piece has a balance weight. If your motor is internally balanced, you need a neutral balance flexplate/flywheel with the above specs.

Rich

 

Thankls Rkrause, good info, i was looking at 168 tooth flywheels. I am just going to put in a one piece seal, internaly balanced ,355 rotating assembly, buy a new flywheel nuetral balanced, (i need a clutch anyway), and i would like to get a keyed fluid damper setup that will line up with my all my lt1 pulleys. I found this one on EBAY.

http://cgi.ebay.com/ebaymotors/ws/eB...6360&rd=1&rd=1

 

the corvette and Fbody dampers are diffrent, you need one made for an fbody, there spaced diffrent.

 

Yea, but i want a keyed one.