Flathead Bore Size ?

[1934calkid]

This is for a street rod,34 coupe, flathead 8BA bore size favorite !

[JWL]

+.030, .060, .080 or .125. Just wherever it will clean up.

[deuce_roadster]

It is determined more by block condition then your wishes/favorite size.

[rotorwrench]

If you want to bore one from standard all the way out to max, you will lose a lot of potential use of the block. If you are already at 3 5/16" then that is a good size for a hot rod. A person can go to sleeves though and use larger if you have a mind to. It just depends on how much you want to spend and how long you want it to last.

[tubman]

I did my first a 3 5/16 (276 with a Merc crank) and it worked well. I just bought another set of 3 5/16 pistons (this time for a stock stroke). Pistons, rings, and pins were $100, which is a heck of a lot less than a merc crank (if you can find one) for a comparable increase in displacement.

[OLD...BILL]

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I'am at 3-5/16 with my build and one four inch merc. crank. 276 inch ?? at my age (82) I saved some for the next build ....?? and here I sit with two more complete engines with 59 on the bell ... I just like saving some for the next build or the next guy, and a JWL says just what it take to clean it up ?? Yes the grandkids will have a big yard sale someday ??......OLD.....BILL

[Mike51Merc]

255 is stock with a 4 inch crank.

[texas webb]

Well I have a 51 merc eng(255 stock for now)for my Av8.May go a bit over in the future.

[Seth Swoboda]

Originally Posted by JWL

+.030, .060, .080 or .125. Just wherever it will clean up.

I agree with JWL.

[Walt Dupont--Me.]

I like 276, 1/8'' bore. If you wear that bore out they make ,030 over 3-5/16 and probably .040 and .060 Walt

[Walt Dupont--Me.]

Originally Posted by tubman

I did my first a 3 5/16 (276 with a Merc crank) and it worked well. I just bought another set of 3 5/16 pistons (this time for a stock stroke). Pistons, rings, and pins were $100, which is a heck of a lot less than a merc crank (if you can find one) for a comparable increase in displacement.

Tubman, where did you get 3-5/16 pistons and rings for $100.00 Walt

[Ol' Ron]

Egge makes light 3 ring piston in 3 5/16, + .020 and .030. With the thin Metric rings. Saved a 276 with the .020" and rings from a Volvo truck. I now have a 280 (279.4) Milled EAB heads 8.2CR and a stock EAB cam. Talk about torque??? I think even JWL would like it.

[Ralph Moore]

I've got a 265 by my calculations, I just think, why bore it bigger than you have to, after all they aren't making them anymore.

[tubman]

Originally Posted by Walt Dupont--Me.

Tubman, where did you get 3-5/16 pistons and rings for $100.00 Walt

Speedway's garage sale section. About a year ago thay had a lot of piston sets (some were advertized as being made by Offenhauser) on closeout. I posted it here and on the H.A.M.B. The pistons came in a "plain brown wrapper", so they may be Chinese. but I took a chance on them. They look real nice and I went over them with a mic and all appears well. We shall see.

(Edit : Just for kicks, I checked the Garage Sale page again; there are still a few sets of pistons, but the prices I paid are long gone,)

[Tony, NY]

Originally Posted by Ralph Moore

I've got a 265 by my calculations, I just think, why bore it bigger than you have to, after all they aren't making them anymore.

That's what I have too.

[rotorwrench]

Speedway had some hypereutectic flathead pistons for a while that were cast for them. They must not have sold too well but I haven't really heard anything about how they worked out. It would be interesting to know. I always wondered why the piston makers didn't go that route. The expansion factors for those pistons allow for a tighter bore clearance than with forged ones. The cost might be prohibitive in a niche market. How strong they are would be the big question for me.

[Old Ford Addict]

Flathead bores are tougher than some of you give them credit for … part of the reason there still here.
The truth is you’d have a hard time wearing one to the point of needing a rebore in the time any of you have left.

Bore it out all the way ... you cant take it with ya

[1934calkid]

The main question was WHAT IS YOUR FAVORITE BORE SIZE FOR A STREET ROD ...

[OLD...BILL]

Originally Posted by 1934calkid

The main question was WHAT IS YOUR FAVORITE BORE SIZE FOR A STREET ROD ...

Hey Calkid; looks like you got your answer 3-5/16...276, hands down, or 75 per/cent .........not good enough for you, ?? all this talk about it, make me want to do it again, all I need is someone to make the "HOLE"
And find me a pieeeekup 39 or 40 I'll do it........OLD.....BILL

[37fordtruckguy]

3 3/8