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would you run these clearances?
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clay
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PostPosted: Fri Mar 18, 2011 9:06 pm    Post subject: Reply with quote

Quote:
I run all my race engines under .002 on the mains with no problems.

True, and I think that is the trend with every form of racing. However I believe it can happen because all of those parts are getting better - race blocks that are stiffer and keep the main bearing bore straighter, crankshafts that are stiffer and generally machined to tighter tolerances and with more attention paid to surface finish and another plus is all of it is balanced. It sounds a little snug to me and if the tolerance is 0.002 - 0.0017 (don't see how it could be 0.00017 as listed) then your 0.0015 is actually tighter than the factory tolerances. Another way I look at it - it's going to be making more power than the factory engine and could use the oil flow for cooling. If they were going to stick to running a lighter weight oil and not put 50w in it it would probalby be fine. I don't see why he couldn't polish and extra 0.0005 or so clearance - things shouldn't get out of round of tapered with that little bit of material removal. I too vote for the 0.0025 - 0.003 number but sometimes you have to deal with what is dealt to you. Clay

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disturbthepeace1
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PostPosted: Fri Mar 18, 2011 9:37 pm    Post subject: Reply with quote

Ya, polishing the crank seems to be he most pratical solution to me.


I guess my main concern is that according the the MS #2 was the trouble maker and the reason for the line bore and hone. So if #2 has history of distortion then then tight clearance only is asking for a problem. Maybe not soon, but most likely later.

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disturbthepeace1
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1965 Volkswagen Beetle

PostPosted: Fri Mar 18, 2011 10:05 pm    Post subject: Reply with quote

Quote:
It sounds a little snug to me and if the tolerance is 0.002 - 0.0017 (don't see how it could be 0.00017 as listed) then your 0.0015 is actually tighter than the factory tolerances.


I posted that spec from memory Embarassed

It's .0002-.0017
I don't know who would run it at .0002 but tha IS the spec Confused

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10sec.et
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PostPosted: Sat Mar 19, 2011 1:03 am    Post subject: Reply with quote

disturbthepeace1 wrote:
Ya, polishing the crank seems to be he most pratical solution to me.


I guess my main concern is that according the the MS #2 was the trouble maker and the reason for the line bore and hone. So if #2 has history of distortion then then tight clearance only is asking for a problem. Maybe not soon, but most likely later.


the #4 main on my block was .0005 tighter than the rest. i stuck the crank in the lathe at work and BY HAND polished out the .0005. it took nearly an hour but its straight and has the same clearance as the rest.

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It seems we can look at our magical Balls and come up with a fix?

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Knarley Darley
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PostPosted: Sat Mar 19, 2011 4:58 am    Post subject: Reply with quote

I usually run stock volume pumps with the stiffer spring supplied so at high rpm it has at least 50 psi. You mentioned this is not going to see any more than mild street performance. Another yet not as favorable method would be to use steel wool lightly, and I stress lightly on the bearing to add a bit more clearance. I usually only do that to the upper half of the bearing since the oil feeds there, and the crank rides on the lower untouched half of the bearing. Just curious, Is the thrust bearing the center, or rear main?
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disturbthepeace1
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PostPosted: Sun Mar 20, 2011 11:33 pm    Post subject: Reply with quote

I think another line bore is gonna be the only thing that can fix this one. Check out my measurements and let me know if I'm being to pickey.



If you can't see, #2 left side of main has a .004-.005 clearance and the right side maxes out at .0025 and is at .0015 straight up.

Confused

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squeeezer
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PostPosted: Mon Mar 21, 2011 9:47 am    Post subject: Reply with quote

i agree, unless your measuring devise is inaccurate

im sure you measured twice

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