Ford 390 (piston in the hole)

goatman-68 · #1 (**permalink**) 01-13-2003, 04:50 AM

We have a 1968 390 Ford engine that we are assembling and noticed the piston to be .135 in the hole. The old ones had a larger dish than these but were only .050 in the hole. What is the preferred stock distance in the hole supposed to be with a factory deck height?

mstngjoe · #2 (**permalink**) 01-13-2003, 05:08 AM

According the the Steve Christ book "How to Rebuild Big Block Ford Engines", the stock deck clearance on a 68 390 was .0005. In other words, damn close to zero.

VanL6 · #3 (**permalink**) 01-13-2003, 05:18 AM

.050 in the hole would be better than .135.I have yet to mike one from the factory to be at ".0005". You have to deck the block to get it to ".0005".You obviously could not machine the deck that much goatman;so,How about another set of pistons?

goatman-68 · #4 (**permalink**) 01-13-2003, 05:41 AM

Thanks for your replies, I think I found the problem. They thought they had a 390 and the block is stamped 352***** I am not a Ford man and didnt look in the book, but they must have the same bore size??

Biggarmike · #5 (**permalink**) 01-13-2003, 05:50 AM

Many FE series castings have 352 cast into the block, left side under the timing cover.

KULTULZ · #6 (**permalink**) 01-13-2003, 05:51 AM

All early FE's had 352 cast into the block.

What was the origional bore/stroke? It sounds like you might have a stroker or stroker piston (360/410).

mstngjoe · #7 (**permalink**) 01-13-2003, 04:45 PM

After doing some more checking, Pat Ganahl's book "Ford Performance" lists the deck height clearance at .010-.030, which sounds more reasonable.

I'm guessing the Steve Christ book is mis-printed.

goatman-68 · #8 (**permalink**) 01-13-2003, 05:31 PM

It appears that 1971 390 uses a different compression height (about .090 difference) They ordered the wrong pistons. The right ones should solve the problem.
Thanks to all who responded.........

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