SQ4 - Decrease Crankshaft End Float

[DaveH]

Hello all,

I measured the crankshaft end float on my 1952 Square Four Mk1: .016" rear and .033" front. According to Drags, correct float is .003” to .004” on the front crank and .005” to .006” on the rear.

But also according to Drags, "Ariels only ever listed shims to increase the end float, not to decrease it"; I believe these would be K115-48, fitting beneath the "oil seal" steel washers.

Which leaves the question - what's the approved way to reduce excessive crankshaft end float?

Thanks,

Dave

[DaveH]

OK, a followup after more research. It seems I measured the rear crankshaft float incorrectly, and the front was artificially high because the bush itself was loose in the case, free to move back and forth. It looks as though the float is actually zero to slightly negative without shims, and thus adjustable with the normal shims beneath the thrust washer. So, never mind...

But another question does come up - what do do about the loose bush? It's an easy sliding fit at room temperature, with no real wobble visible. I see Drags sells a bush with an oversize OD of .010", which should work. I assume it could be machined down for a proper interference fit - would it be necessary to clean up the recess as well? Or, has anyone used one of the Loctite products made for this purpose (620 or 638)?

[simon.holyfield]

OK, a followup after more research. It seems I measured the rear crankshaft float incorrectly, and the front was artificially high because the bush itself was loose in the case, free to move back and forth. It looks as though the float is actually zero to slightly negative without shims, and thus adjustable with the normal shims beneath the thrust washer. So, never mind...

But another question does come up - what do do about the loose bush? It's an easy sliding fit at room temperature, with no real wobble visible. I see Drags sells a bush with an oversize OD of .010", which should work. I assume it could be machined down for a proper interference fit - would it be necessary to clean up the recess as well? Or, has anyone used one of the Loctite products made for this purpose (620 or 638)?

Personally, I'd get the machine shop to fit the oversize bush - since they are going to have to line-bore it anyway, they will have the timing side case set up to be co-axial with the drive side bearing housings.