main bearing cap question
Thread Starter
Instructor
Joined: Nov 2004
Posts: 162
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main bearing cap question
Are the middle three main bearing caps all supposed to be identical?
When I disassembled the engine, I wrapped them with tape and labeled them with their order to make sure they went back on where they came from (I should of stamped them, oh well). When I got them back from the machine shop after they magnafluxed and measured everything, the tape was gone (of course). So, I looked at an old picture along with the caps themselves and noticed that the three middle ones were slightly different, as shown in the picture:
350 before crank removal
All have number 2482 cast in them, but one has 70N, another 73N and the last 69N. Also, the edges are all shaped a little different.
This is good for me because I can just match them up to the picture, but I was wondering if the prev. owner had them replaced or if each middle cap is supposed to be different.
When I disassembled the engine, I wrapped them with tape and labeled them with their order to make sure they went back on where they came from (I should of stamped them, oh well). When I got them back from the machine shop after they magnafluxed and measured everything, the tape was gone (of course). So, I looked at an old picture along with the caps themselves and noticed that the three middle ones were slightly different, as shown in the picture:
350 before crank removal
All have number 2482 cast in them, but one has 70N, another 73N and the last 69N. Also, the edges are all shaped a little different.
This is good for me because I can just match them up to the picture, but I was wondering if the prev. owner had them replaced or if each middle cap is supposed to be different.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
The 2482 designates a nodular iron cap, that's the best you can have on a production block. I take it yours is an early model block? They're all basically the same, just came out of different casting molds.
Thread Starter
Instructor
Joined: Nov 2004
Posts: 162
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Yeah, it's a #'s matching 1970 L-46.
I'm glad I take so many pictures. Those and the different castings for each cap really saved me this time. Thanks for the info!
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Make sure you check that your crank still freely rortates after you torque down the caps. They are bored on the block, and swapping around even unintentionally, can create a compression. Once you torque them down, make sure you can freely spin the crank before adding piston rods to the mix. If the crank is compressed in the journal by one of the caps being mismatched from it's lower portion you may seize and spin a bearing.
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
Make sure you check that your crank still freely rortates after you torque down the caps. They are bored on the block, and swapping around even unintentionally, can create a compression. Once you torque them down, make sure you can freely spin the crank before adding piston rods to the mix. If the crank is compressed in the journal by one of the caps being mismatched from it's lower portion you may seize and spin a bearing.
I reccomend that you take it back to the machine shop and have it line-bored to eliminate ANY possibility of a problem.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Thread Starter
Instructor
Joined: Nov 2004
Posts: 162
Likes: 0
Yeah, I agree about the order being critical. But, how can I get them mixed up if I use that pic? It's pretty clear which one is which in that picture...just as good as if I stamped them IMO. Also, wouldn't the Plastigage or inability to have the crank spin freely (before pistons in) tell me if I have a problem or not?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Yeah, I agree about the order being critical. But, how can I get them mixed up if I use that pic? It's pretty clear which one is which in that picture...just as good as if I stamped them IMO. Also, wouldn't the Plastigage or inability to have the crank spin freely (before pistons in) tell me if I have a problem or not?
If you have the picture as a good reference and you have no question in your mind which one is which, then you're in the clear.
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Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
The caps all have their successive number cast right into them - it says "1", "2", "3" etc right on the caps... you shouldn't have any trouble putting them back in the right order...
