Boring a V-12 block

Ken/Alabama

Ken/Alabama

Well-known member
Anyone know how far you can bore the later V-12 blocks ? I have a 46-48 V-12 with 2 7/8" bore and want to bore it to 3 1/16 and use Ford pistons. That would be .187 overbore. I have a couple of V-8s that big but not sure about the V-12 .
 
I don't know about your area, Ken, but if you could have a shop sonic test it, and tell you the wall thicknesses, you'd have a pretty good idea of how far you can go. I was always told to have at least .100" wall thickness and would be OK.
Jim
 
You are just asking for overheating problems when boring out cylinders to the max. Much more heat goes into the water with thin cylinder walls.

Jim
 
The 1942 and early 46 blocks had a 2 15/16 bore and had the cylinder walls just as thick as the 2 7/8 bores. However a 1/8 oversize on the larger bore block is still courting problems. You could do a sonic test, but may still run into a thin spot. What do you think ,Dee?
 
If you have a 1946 to 1948 block I would not go any bigger than 0.60 over. I just finished one of them you can view it on you tube.

Frenchy
 
On v12's you should not go over .060. Plus there is no gaskets that will work with a bigger bore. The walls are generally thin and you do not want to junk that block.
 
Don't forget to send the cam to Cam techniques and have an L-100 profile put on it. Man I wonder what that would sound like??
 
Bored a '42 V12 block to 3-1/16" and no heating problems in fact had to install thermostats in order to get it to run 1/2 gauge ( ~170 deg's). The Water pumps are Skip's upgrades so that probably helped. Head gaskets are close and they come right up to the edge of the cylinder so you do need to be selective. You may have to have someone like Olsen's Gaskets make up a set. Running a 77B grind and adjustable tappets. This cam doesn't do alot for a flathead Ford but it really brings this V12 to life. still idles ok with a noticeable lope and gives great throttle response with the autolite 4100 carb. Had to keep this fairly "mild" as it's installed in a '48 club coupe that's intended to be a driver.
 
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