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Old 05-29-2011, 08:38 AM   #1
Wagga A'er
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Default Engine rebore

I want to rebuild my current engine as its number matches the firewall date. It has been previously bored out to .060 oversized. However it has two cylinders that are sloppy. I have bored it out to .080 and it still has marks in the bore. Would you bore it out more or put cylinder sleeves in the cylinder and go back to standard? I am worried about overheating problems. Your thoughts would be greatly appreciated.
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Old 05-29-2011, 09:21 AM   #2
John Stone
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Default Re: Engine rebore

Not sure why an engine would overheat. Engines are bored to .125 over without any problems.

Last edited by John Stone; 05-29-2011 at 09:22 AM. Reason: corrected english
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Old 05-29-2011, 09:24 AM   #3
tuneman
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Default Re: Engine rebore

I have one at 125 over no problem. Run it abt 5,000 miles a year on average.
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Old 05-31-2011, 01:22 PM   #4
Jim Brierley
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Default Re: Engine rebore

I am running one at +.100" and one at +.125", neither have heating problems. I also race on the Bonneville salt flats with one that is 4" (+.125") and have no problems with it either. I've seen them raced at 4.060" without heating problems too. .100" over would be no problem. Where and how bad (deep) are the marks at .080"? It may be OK to run it like that? I would rather run a large bore than put sleeves in. If it has no sleeves, they will not ever cause a problem!
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Old 05-31-2011, 01:39 PM   #5
James Rogers
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Default Re: Engine rebore

Bore it to .100 and let her rip. I have customers that want their motors bored to .125 no matter what the starting bore is.
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Old 05-31-2011, 01:40 PM   #6
James Rogers
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Default Re: Engine rebore

There is your coast to coast answer! Bore it, right Jim.
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Old 05-31-2011, 07:58 PM   #7
Peter J
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Default Re: Engine rebore

While we're on the subject of scored cylinders, I have one that has one score mark almost the length of the bore but not to the top. I put new rings in. With the rings, will the score smooth out to some extent? Do any of you guys forsee any problems in the future?
Thanks,
Pete
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Old 05-31-2011, 09:47 PM   #8
J and M Machine
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Default Re: Engine rebore

I would recommend that you sleeve them back to standard. The reason being that we have seen the core shift in the model A blocks from boring them oversize"for sleeves"
Where I have seen the blocks being thin is in the center cylinders.

The other thing that no one has mentioned is the erosion from rust in the water jacket. That reduces the original thickness of metal.
We don't go over .080"
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