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June 24, 2005
G'day Joe
The standard trick Down Under is to turn up the radio. Or fit one. Or take a nagging wife with you. If you don't have a nagging wife, borrow one from a friend - he will be grateful.
My 1380cc race engine is a little worn. It was worn with rust marks in the bores when I first used it 12 years ago, and it hasn't improved by use. I'm not prepared to bore it to 74mm just yet, and so pistons are a little sloppy. Even new pistons aren't much tighter than the old used ones, so we keep re-using the same old set and just stick in new rings. But here's the trick. At every rebuild, we knurl the piston skirts, which effectively enlargens the pistons. I went a bit overboard (not over-bored) the last time, and had to tap the piston skirts into the block with a hammer as we re-fitted them. It doesn't take long for the soft aluminium of the knurling to wear back down to the block size. And a side benefit - the knurling holds oil which cuts down further wear. Seems to work - the engine still puts out 135 bhp.
So pull off the head and sump (again), pop out no.4 pistons, take it off the rod, get it knurled, stick it back in. Many of the older machine shops with a lathe will also have a knurling tool.
Let us all know how it works, and avagoodday
Colin
"Colin Dodds" < colin@... > 37669
Posted on June 24, 2005 06:53 AM
Posted to category(s) Cylinder Head | Engine (external) | Engine (internal) | Gauges | Lubrication System | Racing | Restoration | Technical Info | Transmission | Tuning
