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Help with 305 crankshaft

3K views 8 replies 4 participants last post by  bondo 
#1 ·
Hi all,

I just bought a 1980 K5 Blazer. It has a bad 305 in it and came with a rebuilt 305. I pulled the engine and noticed that the crankshafts were different. I researched and found out that there are 2 piece and 1 piece crankshafts. I determined that the new engine has a 2 piece crankshaft with what looks like a counterweight on the outside of the engine. Also the casting numbers says that this engine came from a 1980-1984 camaro,nova.

My question is if I use the new engine with the two piece seal and I buy a flywheel from autozone. due I have to worry about balancing the flywheel?
 
#2 ·
Is the counterweight that you see part of the mounting flange at the back of the crank? 2-piece rear main seal 305s are all internally balanced and that counterweight that you see is part of that balance.

Have you pulled the flexplate/flywheel off the old engine and compared them directly?

Matt
 
#9 ·
Hi all,

I just bought a 1980 K5 Blazer. It has a bad 305 in it and came with a rebuilt 305. I pulled the engine and noticed that the crankshafts were different. I researched and found out that there are 2 piece and 1 piece crankshafts. I determined that the new engine has a 2 piece crankshaft with what looks like a counterweight on the outside of the engine. Also the casting numbers says that this engine came from a 1980-1984 camaro,nova.

My question is if I use the new engine with the two piece seal and I buy a flywheel from autozone. due I have to worry about balancing the flywheel?
Ayuh,.... They're both considered Internally balanced motors, 'n the bolt pattern is different on the respective flywheels so's ya can't get it wrong...

If ya buy a flywheel for a 305, 2 piece rear main seal crankshaft, Yes, it'll be properly balanced...
 
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