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Hey guys

I have a 850 engine and it seems to be down on compression so I wiped head off and the bores are all sooted up and head gaskets split between 2 & 3

the pistons have movement in them ? is that a allowance for this?

and should there be a small lip near top of the bore where the last piston ring sits?

thanks

Stephen

A small amount of piston play is acceptable but sooted bores aren't. The head gasket split is why it was down on power and compression. The small lip at the top of the bore is indicating cylinder wear, usually associated with "very old engine syndrome". That lip will sometimes break the top piston ring, but you can be sure an overbore and new pistons are needed. For an 850 engine it's usually not worth it. (and I'm here withing I had an 850 and magic wand box for my 64.)

Its an 850 magic wand box got another gear box to put on it to rod change

and its got a lip you can feel it when you rub your nail on it

I have a 1000 cc that just needs new rings in it as i pulled pistons out and broke 5 rings getting it read for the 1275 head convertion then my mate had my head haha why i ended up with the 850

so should i find a head then do the 998 but use 850 for spare bits?

Thanks Stephen

Sounds like a good mate.

The 998 would be better on power, and easier to obtain spares, but use more fuel. A head is cheap, 20 quid should do. It's only the mileage concenious that would use the 850, and since it would be more expensive to put it together, you don't have a lot of choice.

THE 850 was a freebie anyways

and ill try get a cylinder head then if not ill use the 850 head just refurb it

Thanks

a lip doesnt always spell "kiss of death" for an engine
an engine covered 20,000 miles or more will most deffo have a lip opf some form.

if this is less than 6 thou of an inch ,it will even take new rings,contrary to popular belief

i have an 850 engine with a lip thats at least 12 thou ,,doesnt burn oil,and has 160 psi compressions .and has no piston slap from cold.

theres a mega obsession with lips at the top of bores..if the compressions good,and theres no scoring on the pots,,just keep running it

some bmc engines "thrive" on a bit of bore wear..

on these buggers its almost certain the cranks or shell bearings give up the ghost first

ehem,,,most of the time

i have a gold seal 850 thats sweet as a nut,,sounds like new,but it dont half smoke,
it has no bore wear lip at all,,

I can only agree with shaw above:

Years ago I even had a ridge reamer. I've done a lot of engines with this thing. It even helps getting the pistons back in with the new rings.

well I'm going to run the 998 now anyways

its got 45psi on 2 cylinders :/ so thats nothing

Thnaks anyways guys