Boring a Flatty
Gary
wrote:
:)I was just given a 49-53 Ford flathead that has already been bored .60 over.
:)I plan to use it in my highboy (a steel 27' roadster on model A rails) Does
:)anyone know how much, if any this can be bored again? Is it possible to
:)sleeve a flathead cylinder or is it worth it?
:)
:)Don
:)
IMO the largest bore for a street Flatmotor is .125 over (3.313"
bore). If you punch it out to .187 (3.375" bore) the realistic maximum
for a street Flathead, but you are plagued with over heating problems
and cylinder ballooning of the walls. The secret to running a cool
Flathead is; 1. Start with a clean (you can eat off it and in it!)
block. 2. Have the block Magnafluxed. 3. Deck your block and have your
heads lapped, even if there NEW (MCF does a good job on this).
$100 a hole is about average for sleeving. I know drag motors that run
3.5" bore (sleeve) and have heard of 3.4375" (3 7/16) (wet sleeve),
but that's one pass @ 1/4 mile.
I have found that in the average warmed over Flathead, the difference
between a stock block and a 3 5/16" bore X 4" stroke (275 cu.) is 15
hp @ the bottom end (2000 rpm) and 4 hp at the top (5000 rpm).
Remember the Flatmotor is a bottom end engine (Neck snapping, axle
twisting torque) not high rev like small blocks.
Gary
Flatheads Forever
Don Allen
Don
Don Herring
cost $750, 2/3s of that labor. They make cylinders .180 over, but if you go
much past .080 you'll need to sleeve it. Look for a machine shop in your
area that is experienced with flatheads, they can do it.
Juan DelaCruz
walls transfer heat quickly to the water jacket (and that water jacket
already has a lot of exhaust heat to deal with. Sleeving is not only a
possibility, I would suggest that you would be better off sleeving down to
stock bore.
Don Allen wrote in message ...
Wudman69
>From: "Don Allen"
>I was just given a 49-53 Ford flathead that has already been bored .60 over.
>I plan to use it in my highboy (a steel 27' roadster on model A rails) Does
>anyone know how much, if any this can be bored again? Is it possible to
>sleeve a flathead cylinder or is it worth it?
Flathead cylinders are a thick casting. It is possible to bore a flatty to
.1875 over. You stated that you are currently at .060 over. The next standard
size bore is .083 over. You should have no problems going to that. After
that, I think .100 is the next standard size. I would suggest that you
magnaflux the block to be sure there are no problem areas.......they are prone
to cracking. It is possible to sleeve a flathead but I am not knowledgable of
cost. Good luck to you.
Jeff Watts
50 F-1, 239 Flathead
Larry Young
Are you saying that a reasonable maximum bore for a sleeved flathead is
3 5/16, i.e. the same as for no sleeves? I think I've read most of the
books on rebuilding flatheads, but they don't talk much about sleeving.
Ron Ceridono's book has a chapter ("21 Stud Salute") which claims
sleeving is better for cooling. What's the opinion on cooling? What
about weakining of the block?
I've now accumulated several "barn fresh" flatheads and I'm trying to
get 2 or 3 good rebuilt engines out of the lot. Several of these have
bores that are heavily pitted.
Gary
wrote:
:)Gary,
:)Are you saying that a reasonable maximum bore for a sleeved flathead is
:)3 5/16, i.e. the same as for no sleeves? I think I've read most of the
:)books on rebuilding flatheads, but they don't talk much about sleeving.
:)Ron Ceridono's book has a chapter ("21 Stud Salute") which claims
:)sleeving is better for cooling. What's the opinion on cooling? What
:)about weakining of the block?
:)
:)I've now accumulated several "barn fresh" flatheads and I'm trying to
:)get 2 or 3 good rebuilt engines out of the lot. Several of these have
:)bores that are heavily pitted.
No...I'm saying the reasonable over bore for a stock Flathead that you
are going to hop-up is 3 5/16". If you are going to keep it stock you
can go .020, .030, .040 .060 over. One reason you would want to
sleeve a Flathead is to maintain a stock engine (239 cu). Another
reason is if you trying to get the maximum cubic inch displacement for
racing. Your pitted bores might have to .060 or even .100 over.
Gary
Flatheads Forever
Larry Young
I appologize for being such a neophyte. I understand your point that
sleeving can take a flathead back to its stock bore. However, I want to
build a mildly hopped up street engine with 3 5/16 bore. Are sleeves
going to work if I have bores with pits that are too deep or if I have a
problem with cylinder walls that would be too thin? If money were no
object, would sleeving be better in general, i.e. what is the impact on
cooling, block strength, etc.?
Thanks,
Larry (Okie flatheader)