Topic: case opening clearance for big bore sleeves.

[gschuld]

So what is the consensus for the ideal diameter of the sleeve bores on the upper engine case for 3.00" OD 970/1060 sleeves.  I have an old big bore upper case here with quite a gap around the perimter. This would appear to allow significant oil drain back from the head/cylinder through the case to sleeve gap and pour onto the top of the crank rather than go back through the two forward factory drain back slots that intentionally funnel excessive oil away from the crank.  Intentional extra crank oiling going on here?

Is something close to a friction fit ideal?  Or is a modest amount of clearance beneficial?  The two alignment tubes make sure the alignment it correct, I'm just thinking about excessive oil drain back on the crank and not taking any more material away from the case than necessary.

George

[MRieck]

I'd leave as much material on the case deck as possible. I think clearance on my FJ and 1000cc CB is about .040...a millimeter.

[Bill/BentON Racing]

And mine is even a little less on 915cc. engine. But it needs to not TOUCH anywhere but mating surface!

[gschuld]

I've got sleeves at 3.0" and case bore at 3.10"   

At 0.10" total, 0.05" around the circumference seems unnecessary loose.

George

[MRieck]

Just to be clear...bore opened up .040 so .020 per side. I have seen cases opened by hand....some very very crudely done with big chunks ground out all over the place. I recommend indexing off the individual cylinders ( on a milling machine) to get it right. Like I said....you want as much material as possible on that case deck.

[Medyo Bastos]

i saw one that must have been done with a bench grinder. talk about crudely done


...Save a tree, eat a beaver...

[gschuld]

Good deal.  That's about what I expected to be the case.  Now time to make it happen....

Just for entertainment, the factory case measures 2.81" as the factory sleeves are 2.66"

George

[Big Jay]

We have a jig, and would go about .040" over. You would be surprised how many big bore blocks we get that the new sleeves are not exactly in the correct location.

[gschuld]

Thanks Jay, great info by all.

George1