LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

PM rod question

Old Sep 18, 2009 | 08:21 PM
  #1  
94zgreenmachine's Avatar
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PM rod question

From what I have read PM rods weren't in use till late 94 and were in all 95 and up lt1's. The lt4 has PM rods but has a cracked cap and the lt1 rods have a machined cap.

The rod on the left is from my original z28.It is a 94 z28. From what I can tell, it is a plain old forged rod. I am assuming this based on how it looks and the pad on the big end of the rod. This rod has GM cast onto the rod. Here are the pics:
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The rod on the right is from a Corvette with a 4-bolt main, as all are. Is that what a PM rod looks like? It certainly is different than the one on the left and it is from a 96' engine. This rod has no GM markings. The rod is NOT an LT4 rod, no cracked cap.

I want to reuse these rods , if they are indeed PM rods.
Old Sep 18, 2009 | 09:06 PM
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You are correct - the one on the right is the PM rod, GM didn't use cracked caps until the LS motors.
Old Sep 19, 2009 | 05:15 AM
  #3  
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Originally Posted by MachinistOne
You are correct - the one on the right is the PM rod, GM didn't use cracked caps until the LS motors.
I have seen from several sources that the LT4 uses a cracked cap:
http://www.enginebuildermag.com/Arti...t1_engine.aspx

I think this is a ditto of the above link:
http://www.lt1.org/lt1tech.html

Thanks for the rod id!
Old Sep 19, 2009 | 11:25 AM
  #4  
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Originally Posted by 94zgreenmachine
I have seen from several sources that the LT4 uses a cracked cap:
http://www.enginebuildermag.com/Arti...t1_engine.aspx

I think this is a ditto of the above link:
http://www.lt1.org/lt1tech.html

Thanks for the rod id!
you're right - I forgot about that one.

Cracked cap rods are a joke, they get thrown right into the trash when building a motor.
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