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Engine block: do I machine it?


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Hi,

 

I am in the process of replacing the head gasket in my L28E engine for my 1975 280Z. I will have the head cleaned and inspected and slightly milled. I don't plan on freshening up the block with new pistons or rings or bearing as I think it still has a ways to go before I need to rebuild.

 

My question: Do I have to get the blocks' mating surface to the head milled/machined or can I get away with just bolting the head back on?

 

I raise this question because I don't know how I can get the block surface milled without taking it apart, or can I?

 

Your comments will be appreciated.

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Unless your block was heated up really bad, chances of it warping are far slimmer than the head. Aluminum is far more subject to heat than cast iron. So, unless your block is warped from a previous mishap, chances are it is ok now. May want to check with a straight edge. You can do that with it in the car. As far as decking the block, you'll have to pull it out and get it apart and take it to the machine shop. No way to do it with the block in the car.

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If your head is not badly warped, your block should be fine. They rarely warp. I have a steel ruler here that is NOT straight....you can put it on a flat surface and fit a thin feeler gauge under the middle. Just be aware that a cheap "straightedge" can deceive you when you are checking for warpage!

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Unless your block was heated up really bad, chances of it warping are far slimmer than the head. Aluminum is far more subject to heat than cast iron. So, unless your block is warped from a previous mishap, chances are it is ok now. May want to check with a straight edge. You can do that with it in the car. As far as decking the block, you'll have to pull it out and get it apart and take it to the machine shop. No way to do it with the block in the car.

 

Thanks .. Do I have to pull the pistons/chain/oil pan etc out if I want to get the block decked? Or can I just take the complete engine block with the pistons/chain/oil pan intact and have the machine shop deck it. That was my original question.. sorry if I was not clear..

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Yes - when they deck the block, it creates metal shavings. That stuff can get down in your motor and ruin it if you were to attempt to do it with all the internals in it. You'll have to completely dismantle the motor down to the block and take the machine shop just the block. Don't know how the machine shop would even be able to mount the block on the lathe table with the oil pan on it! So yes - it must be completely disassembled.

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