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Old 02-20-2013, 06:06 PM
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Help with 305 crankshaft

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?

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Old 02-20-2013, 07:20 PM
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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
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Old 02-20-2013, 09:28 PM
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I have compared the cranks and they are different. I upload some pics in the members gallery if you search my name they are the only two pics I have uploaded.

So would a flywheel from autozone be ok?
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Old 02-20-2013, 09:31 PM
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If that shows up, the left is a one piece seal. The right is a two piece (pre-87) crank. If it's the one on the right, a standard zero-balance flywheel will work. I think "zero-balance" is the phrase I'm looking for.

Matt
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Old 02-20-2013, 09:41 PM
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Found the pics. Yes, an autozone flywheel for a pre-87 small block would work, as long as it's not a 400 engine flywheel.

Matt
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Old 02-20-2013, 09:50 PM
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its apart,balance everything,lol.
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Old 02-20-2013, 10:00 PM
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thanks for taking a look at pictures still have to figure out how to upload them I read the tutorial but still think I'm doing something wrong but I appreciate the advice.
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Old 02-20-2013, 10:17 PM
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Originally Posted by vinniekq2 View Post
its apart,balance everything,lol.

That's crazy talk!!
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Old 02-21-2013, 07:11 AM
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Quote:
Originally Posted by kiaser001 View Post
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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