Main tunnel size 481X

Just measured main tunnels and have moved around after couple meetings. They are around .0012 over top size straight up and down and have closed up around .0005 at the parting lines. Over all, they are probably 3/4 thou bigger than the large size recommended. It gives me around .0065" main clearance but originally had around .0055". Do you see the main tunnel bore size and/or the clearance an issue. Blown injected alcohol 40 lbs boost.

 

I would have it line bored and honed to make the main bores round and within dia. spec to provide proper bearing crush. The bearing crush is what keeps bearing shells from spinning , not the tangs. I usually specify main bores be finish hones to just a couple tenths over minimum especially on Aluminum blocks. That works best for me , your mileage may vary.

 

Gordon, I'm not all that concerned of the bores out of round etc but more so of the size being larger. Some tell me it will be fine on the big size but I'm not all that confident letting it go out that way. Just wondering if anyone has had first hand experience leaving the main bore that large with no issues.

 

I agree with Gordon 100%.
Should you decide to run it without good bearing crush I'd start looking for another block because eventually you're going to turn the mains out of that one.
Just my $0.02.

 

i do a lot of block repair i have seen top fuel blocks that are plus .002 to .004 over on main bore and dont have bearing spinning issues

 

Just because it is done on occasion does not mean it is correct.