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Question about decking the block and timing cover


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Got all my engine parts back from the machine shop.  Their mill head was too big to shave the lower timing cover when they decked the block.  The block is a donor from a '75 engine, timing cover is from my 74tii engine.  After decking, both the old and new blocks appear to be same height, so maybe it'll fit.  When I attach the lower timing cover, it looks like a good fit, but I can feel a little lip with my finger, about the thickness of a piece of paper.  See pic.

 

Is this acceptable, or do I need to find a machine shop that can machine that area next to the tensioner? I'm not trying to be cheap, I just don't have many machine shops near me, other than the one I used for the rest of the engine work.

20220111_180328.jpg

Edited by bergie33
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  • bergie33 changed the title to Question about decking the block and timing cover

Sounds like your offset is small, so maybe alright, but I had a similar problem with the upper chain cover when the head was decked, and its been weeping ever since. Its been decades, so I don't recall the details.

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As was pointed out to me by another member, I forgot about how this seemingly minor step might effect the fit of the upper timing cover, which was machined with the head.  I guess I will have to check that and make sure it isn't shifting the upper cover up as well.

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You need to get the timing cover to another machinist. First get the amount removed from the block from the original shop, and take that number along with the lower cover to a shop with an end mill and have that amount removed. It’s a very basic request for a machine shop. If not, you will be fighting leaks regardless of how much rtv you use. 

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1 hour ago, Furry Camel said:

You need to get the timing cover to another machinist. First get the amount removed from the block from the original shop, and take that number along with the lower cover to a shop with an end mill and have that amount removed. It’s a very basic request for a machine shop. If not, you will be fighting leaks regardless of how much rtv you use. 

 

I wish it were that easy.  The lower timing cover came from a different block. So, knowing how much was removed from the block that I am using isn't relevant to shaving the timing cover. Tomorrow I'm taking the block and timing cover to another machine shop to see if they can do it.

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2 hours ago, bergie33 said:

 

I wish it were that easy.  The lower timing cover came from a different block. So, knowing how much was removed from the block that I am using isn't relevant to shaving the timing cover. Tomorrow I'm taking the block and timing cover to another machine shop to see if they can do it.

Unless the timing cover has been cut before (very unlikely), and your previous shop just cut the block, I don’t know what the challenge is. Get the deck spec and have that much removed. Stop fighting good advice from people who know. 

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4 hours ago, Furry Camel said:

Unless the timing cover has been cut before (very unlikely), and your previous shop just cut the block, I don’t know what the challenge is. Get the deck spec and have that much removed. Stop fighting good advice from people who know. 

 

4 hours ago, Furry Camel said:

Follow up question..

You do realize you are putting a Tii front cover on a non Tii block. Just checking. 

 

I am not fighting good advice, I am taking every word here into consideration.  There has been lots of good advice.  I cannot afford to make assumptions about a block and timing cover, both of which I don't know the history.  And yes, I do know that the Tii front cover is going on a non Tii block, won't be the first time its been done. 

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Well, I took the block and timing cover into another machine shop I found.  While the last shop took 0.003" off the block, the front timing cover needs 0.006" taken off the top and 0.002" taken off the bottom.  Crank cover also needed 0.002" taken off.  Glad I took it all in so they can be sure all the surfaces match.  Now I shouldn't have to worry about any future leaks.  Thanks to all of you for your input.

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Follow-up question about the head gasket.  I am putting in new factory 9.5:1 piano top Tii pistons, stock cam.  With block and head both being decked, should I go to a 1.8mm head gasket?  That's what I ordered, but the more I think about it, I wonder if standard size would work and give a little extra compression (don't want too much as best gas here is 91).  The shop took 0.003" (0.076mm) off of the block (don't know it it was decked previously) and the head currently measures in at about 128.7mm.  What do you think, standard 1.5mm or 1.8mm gasket?

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