Can someone explain this to me please

[soCalTA]

Can someone explain this? Why would the main seal being one vs. two pieces make any difference in installing the flywheel? They are talking about a 305 motor.



" weren't able to get the spare motor installed in his car - forgot the flywheel. We were willing to use the existing flywheel even though there could be some balance issues. Unfortunately, we didn't figure out that the existing flywheel would not fit until 1:00 in the morning. One piece rear main vs. two."

[DeWynter]

Can someone explain this? Why would the main seal being one vs. two pieces make any difference in installing the flywheel? They are talking about a 305 motor.



" weren't able to get the spare motor installed in his car - forgot the flywheel. We were willing to use the existing flywheel even though there could be some balance issues. Unfortunately, we didn't figure out that the existing flywheel would not fit until 1:00 in the morning. One piece rear main vs. two."

The difference lies in the fact that two peice main seal engines (55-86) are internal balanced so have a neutral balance flywheel (except 400), and the one piece rear mains have an external balance flywheel. This is true for all 305 and 350 engines in small block gen 1 form. A 305 wheel does not work on a 350 either.

[soCalTA]

Sorry to ask but ok so if I have a 86 305 what am I ..internal or external?

and thank you for the answer .. its help me understand better ....

[DeWynter]

Being an 86 it could be either as they do the change over half way through the year. You can look on the back of the block just below the head on the drivers side for a marking on the lip of the block where the trany bell housing bolts to the block. If it is the newer one peice rear main seal it will have the engine size labled in liters eg. 5.0L or 5.7L, if it is the older two peice rear main it will just have the engine code stamped there eg. 355909 Being an 86 it is most likely a one peice rear main block.