Crank seals...what's the story?

Post by **youngun** » Tue Sep 18, 2007 8:10 pm

Im rebuilding my 948 at the mo, and im putting in all new big ends and mains, which means i replace the crank seals as well.....whats the story on these and whats the best route to go down as i know little on this subject!

thanks,
YG

Post by **bmcecosse** » Tue Sep 18, 2007 9:27 pm

Crank seals ? Well - there is only the single rubber seal in the timing case, and make sure you refit the oil thrower inside the case - and right way round too. At the rear - there is just a 'scroll' arrangement, where the two halves of the seal (one hlaf is part of the rear main cap - the other half is fixed to the rear of the block with 3 screws) sit close to but not touching the labyrinths on the rear end of the crankshaft. This is why it's important to keep low crankcase pressure in the engine - by connecting one of the breather pipes )usually the one from the rocker cover) to the inlet connection on the carb. This way the engine eats it's own fumes, and oil leaks are minimised.

Post by **youngun** » Wed Sep 19, 2007 1:26 pm

righto, does any of this need to be replaced when re-building the engine?

Post by **bmcecosse** » Wed Sep 19, 2007 8:09 pm

Well -the front rubber one in the timing cover - YES! The sump pan has it's own gaskets and seals - and these of course need to be new.

Post by **youngun** » Wed Sep 19, 2007 9:15 pm

Right, i assume thats the rubber seal like object that comes in the full gasket set from ESM?
And the sump pan stuff, does that come in the gasket set too?

Post by **bmcecosse** » Wed Sep 19, 2007 9:18 pm

Should do - never dealt with 'ESM' - sump should be 2 x thick card shape of sump (!) rim + 2 x rubber strips which press into the lips at each end of the sump. Some older kits supply cork strips - rubber is better. Leave them 3/16" long at each end - so they are compressed when you bolt up the sump.

Post by **youngun** » Wed Sep 19, 2007 9:20 pm

Rightyo.

Post by **IslipMinor** » Fri Sep 21, 2007 9:13 pm

The 948 had a felt timing cover seal, not sure if they all did, but certainly up to the end of 1958. Best bet is to get a timing cover from a 1098 engine, or the equivalent Mini engine with a 'proper' lip seal - and replace that!

Post by **bmcecosse** » Fri Sep 21, 2007 9:51 pm

Ah yes -forgot about the dreadful felt seal - definitely upgrade to the rubber seal!

Post by **youngun** » Sun Sep 23, 2007 7:11 pm

Oh great, how do i do that then?

Oh and do all the seals i need for the engine come in the full engine gasket kit, from the picture there seems to be a couple of seals in there.

Post by **bmcecosse** » Sun Sep 23, 2007 9:58 pm

Well you would need a timing cover from a later engine - or an early Mini - but not the very latest one which has a different shape to allow for the chain tensioner. Actually - you can use the later one - just need a gasket to suit.