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Anonymous
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Maximum over bore on a 200? .060? Assuming a sound block.
-Chris
-Chris
mraley
Well-known member
Chris....I've got mine bored .60 over without any problems. In talking with others I've been told that .60 over is too much and I'll have overheating problems, however my mechanic says no. The first engine I had in my mustang was also .60 over. The only reason I had to start over was due to a transmission shop putting a bolt in my flywheel that was too long....Anyway....Just my 2 cents.....Michael
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Anonymous
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mraley":3lhhuh8m said:
This just happened to me. A bolt too long in my flywheel. Cut my starter up. I ground it down and now am troubleshooting a vibration.
What problems did it cause you?
My case...
http://fordsix.com/forum/viewtopic.php?t=22134
why do you want to know what the max is?
to me, overboring for that last cubic inch is a bit silly, i'd rather have a block that i'd be able to clean up several times if need be than having to go out and find one that was clean enough to use
not too mention the fact that it would be more fragile when in a high horsepower application
but i don't really even know what's going on with your situation, so i'll just agree that the max overbore is .060, then point out that boring it out to .60 over would give you lots of problems and then i'm gonna get off the soapbox
to me, overboring for that last cubic inch is a bit silly, i'd rather have a block that i'd be able to clean up several times if need be than having to go out and find one that was clean enough to use
not too mention the fact that it would be more fragile when in a high horsepower application
but i don't really even know what's going on with your situation, so i'll just agree that the max overbore is .060, then point out that boring it out to .60 over would give you lots of problems and then i'm gonna get off the soapbox
A
Anonymous
Guest
Just curious is all. 
I was at a machine shop yesterday and one of the technicians had a 200 block and head that he was will to part for 50 bucks. Good shape. But during our conversation we started talking about stroker kits for my 5.8L and I got to thinking about my straight 6.
Again, just curious.
I know it's probably not worth the effort but knowledge of the facts still doesn't hurt.
-Chris
I was at a machine shop yesterday and one of the technicians had a 200 block and head that he was will to part for 50 bucks. Good shape. But during our conversation we started talking about stroker kits for my 5.8L and I got to thinking about my straight 6.
Again, just curious.
I know it's probably not worth the effort but knowledge of the facts still doesn't hurt.
-Chris
When dad and I built these 200's back in the '60's we would always bore .060 over because that's what Ak Miller did. My present 200 is .030 over. .060 over in a 200 will not cause overheating problems. I do know from experience that to much overbore in a small block chevy will cause overheating problems.
Howdy Chris and All:
The max OB on a small block Ford Six is .060" because that's the largest size aftermarket piston easily available. More is possible, and I've heard of .080". Cylinder wall thickness should be checked with a sonic tester prior to OB this much, IMHO.
When boring, it is best to bore only enough to establish a clean, straight cylinder wall. The increase in cubic inches going from .020" to .030", or even .060" is miniscule. The loss in cylinder wall rigidity and integrity can be significant. The thicker the cylinder walls the more rigid the bores can be. In dealing with FoMoCo thin wall casting process less OB is better. As an engine is assembled and torqued into place parts and surfaces can and do distort. That is not good and frequently causes heat.
That's why is is a good idea to bore and hone with the main caps torqued in to place and a torque plate on top (if you can find one).
Another issue is the trueness of the casting. This is not much of a problem with our engines, but it is with Chevy sixes. When checking a block for core shift during the casting process, inspect the seam where the water pump is inserted. The seam should be almost invisable. If this seam is misaligned it may indicate a difference in wall thiknesses from side-to-side.
Adios, David
The max OB on a small block Ford Six is .060" because that's the largest size aftermarket piston easily available. More is possible, and I've heard of .080". Cylinder wall thickness should be checked with a sonic tester prior to OB this much, IMHO.
When boring, it is best to bore only enough to establish a clean, straight cylinder wall. The increase in cubic inches going from .020" to .030", or even .060" is miniscule. The loss in cylinder wall rigidity and integrity can be significant. The thicker the cylinder walls the more rigid the bores can be. In dealing with FoMoCo thin wall casting process less OB is better. As an engine is assembled and torqued into place parts and surfaces can and do distort. That is not good and frequently causes heat.
That's why is is a good idea to bore and hone with the main caps torqued in to place and a torque plate on top (if you can find one).
Another issue is the trueness of the casting. This is not much of a problem with our engines, but it is with Chevy sixes. When checking a block for core shift during the casting process, inspect the seam where the water pump is inserted. The seam should be almost invisable. If this seam is misaligned it may indicate a difference in wall thiknesses from side-to-side.
Adios, David
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