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FFCobra Craftsman
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1,297 Posts
Discussion Starter · #1 ·
I have a line on a 1970 302 that has been bored .30 or .40 over. What is the danger zone before there is a thin water jacket?

Mike O.
 

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Senior Member
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2,860 Posts
Interesting question, old motor. The 302 was first offered in 1968. My 1989 is bored .040 over; which is quite common. Hummm... :confused:
 

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The Never-Ending Builder
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5,329 Posts
You have reached the danger zone at .040 over, especially if it's a stroker.

Hank
 

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section 8
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5,136 Posts
We do a lot of Jasper engines at the shop . I'm a nosy guy so I always look in the plug holes and what I see alot is 040 over pistons. I'm a fan of as little boring as possible . The EFI302 engine runs such a perfect mixture that bore wear is minimal . So you can clean it up with as little as 010 but can't find pistons. Unless its running and guaranteed I'd be care ful. bob
 

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FFCobra Fanatic
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1,092 Posts
0.40 is the limit without sonic testing the block.
I have seen a .60 over 302 in a mustang I bought a few years ago. It had a rebuild engine from a local shop. The owner told me the head gaskets needed to be replaced, that water was getting into the oil. I thought it was the intake gaskets, I would fix it and turn it around real fast and make some money. Anyway as I tore it down I found a small crack in the block in the middle of # 3 cyl then I looked at the pistons to find 60 over.
 
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