Boring Flat Head V8 block .060
Fleet Owner
Joined: Jul 2004
Posts: 27,294
Likes: 1,055
From: NM
Guess it depends what bore it is to begin with. It "usually" is quite safe, but sonic checking never hurts.
If you are going that far for cubic inches, not because you need to, I'd save that metal for later and just go .030"
If you are going that far for cubic inches, not because you need to, I'd save that metal for later and just go .030"
Lead Driver
Joined: Oct 1999
Posts: 6,776
Likes: 553
From: Kalispell, MT
.60 or .80 is just getting started on a late series (48-53) flathead V8. These castings are regularly bored a common .125 to reach 3 5/16" bore. Often they have no trouble going to 3 3/8" which is a whopping .250 over. Back in the day, more than a few guys even found blocks that would open up to 3 7/16".
Cargo Master
Joined: Nov 2004
Posts: 2,858
Likes: 3
From: Friendswood, Texas
Wow Tim..... The rule of thimb I'd always heard/read was 0.125" over. I wasn't aware they could go 0.25" inches or more. I wonder if the chances of death cracks are significantly enhanced at the larger bores. My guess would be yes but I've been wrong before.
Lead Driver
Joined: Oct 1999
Posts: 6,776
Likes: 553
From: Kalispell, MT
Hold the presses - my math was off. 3 3/8" is .188 over, not .250 - sorry about that! Stock bore is 3 3/16"
Biggest problem with the larger bores is keeping them from running hot. You just need to keep wall thickness at least .100"
I honestly haven't heard on anyone cracking a block in the past 8 years I've been messing with flatheads. Someone on msn suggested once that they believed that all the cracks in the flatheads happened as the cores were stabilizing and settling out. If they crack as easily as we hear, you'd think it would be happening every day. There's a lot of guys driving these daily. FWIW
Biggest problem with the larger bores is keeping them from running hot. You just need to keep wall thickness at least .100"
I honestly haven't heard on anyone cracking a block in the past 8 years I've been messing with flatheads. Someone on msn suggested once that they believed that all the cracks in the flatheads happened as the cores were stabilizing and settling out. If they crack as easily as we hear, you'd think it would be happening every day. There's a lot of guys driving these daily. FWIW
Last edited by mtflat; Mar 24, 2007 at 01:23 AM.
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