Morning all,
I'm at the same stage of rebuilding my crank as Trevor. But I now need to get my the ring in the end of the conrod honed to suit the rollers, can anyone give me the dimensions this needs to me honed to please.
Thanks,
Alwyn
The tolerancing given in the M20 standards book doesn't seem logical...That states a clearance between the pin/roller assy and the I.D of the crankpin eye of .0000"- .0004".....I have never applied such a tight tolerance and at .0000" the whole thing would be very snug...
For road engines I use .0004"-.0006"....
So, measure the actual crankpin diameter...add twice the measured size of the roller (they should be bang on .250")....then add the clearance (.0004"-.0006") to give the finished size for the big end eye...
When assembled the con rod should turn freely without any friction...If it's overly tight the rollers will 'crowd' in the track and make the big end feel 'notchy' when the rod is turned....This can all be checked before assembly of the crank.... Ian
Always supply the the rod, ring, bearings, cage and pin to whom ever is honing the ring pressed into the rod.
I always hone to the tightest fit that allows the pin to spin freely.
Half a thou I would consider excessive for long life.
Nothing wrong with taking that approach to achieve a minimal clearance, though I've done high mileages on cranks with .0004"-.0005" clearances at assembly....Over 80,000 miles in my B33 for example...Ian
