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Old 01-26-2019, 11:35 AM   #7
Flathead Fever
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Join Date: May 2010
Location: Yucaipa, CA
Posts: 1,091
Default Re: head bolts or studs

The last thing you should do is to "chase" the threaded holes in the block with a regular tap. It will ruin the special thread pattern that Ford machined into these blocks. I use an 8BA headbolt with grooves cut in them to "chase" the threads. :

You may want to check out this thread to see how I keep the heads from moving around : https://www.fordbarn.com/forum/showt...light=aluminum.[/QUOTE]

He is absolutely correct don't run a tap into your block of any kind!!!! I did it on my first flathead engine. I know two other people that did it and all of our studs leaked, even with gobs of Permatex on them. Not just with the engine running but just sitting there in the garage. It would leave puddles of coolant on the finned heads. I finally used blue Loctite on mine to seal the threads.

I was a mechanic for 30-year's and I never knew there were different classes of threads? Very few bolts on modern engines screw directly into coolant passages. There are some water pump bolts that do but that's about it. A flathead is a whole different beast.

I "think" there are three different classifications of threads? There are loose fit threads, like the regular grade five hardware bolts. Then there are really tight threads. you will never find for for sale. Those are specialty bolts, probably manufactured for special applications. The threads are so tight they create an interference fit. Its like running a lock nut onto a bolt. The studs have resistance screwing them into the block. That is why they are so hard to get out and they can break off. That resistance is what makes your seal so the studs do not leak. All the old books tell you to run a tap into all the holes when rebuilding all engines. Don't do it on a Flathead Ford head stud hole!!! Run a tap into the block and you have removed the metal that made it an interference fit. I'm beginning to thing the more rust and junk I leave in the stud hole the better chance I have it won't leak.

If you look at a factory photo of them installing the studs. It appears they just grab a stud and run them down with a impact with no sealer on them. That thread fit is so tight they can't possibly leak.

Last edited by Flathead Fever; 01-26-2019 at 11:41 AM.
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