It’s confirmed, I’m a dick.
I went back to the engine and stripped the top end. It shouldn’t take that long to strip the top end but the head was a shit to get off and basically I had to fight it all the way up the studs.
The cams are a bit odd, I’d say one’s a genuine S1 and I think the other one is a re-profile because the stamping is different and it’s also got Joy Eng. etched on the side of one lobe. I’m ok with that because Joy always had a good reputation for their camshaft work and if one of the originals was showing wear on the lobes so got replaced then so be it.
First shot is the cams still in position.
Cam buckets and bearing caps. I’ll buy new needle roller bearings because they’ll be cheap enough and while it’s apart it’s stupid not to.
Once I’d got the head and barrel off I had a look at the pistons and to be honest, they don’t look as if they’ve got 25k miles on them. They’re a bit sooty but the outside diameter of the pistons have no burn marks on them so no oil has been getting past and leaving crap on them.
The valves look very black as if it’s either been running super rich or burning oil. When you look in the ports the RH exhaust valves have oil on the stems with more on the outer one plus there’s oil in the port. That’ll be the valve guide seals then.
Another pointer towards the head having been off and the issue being failed seals is that the combustion chamber is cleaner with no soot on the inlet side.
Anyway, it’s all apart, I’ll order seals and think about a rebore. I’d say it’s right at the top limit before needing a rebore because front to back the bores are +0.12mm and left to right they’re +0.05mm
I’m going to struggle sourcing high compression pistons, I can get Alpino ones for about £300 then pay for a rebore. If I put standard compression pistons in then that absolutely rules out racing it but it’d probably make it more reliable. What do I want? I don’t fucking know!
I know it’s purely a guess but I think it’s been put back together with the old valve guide seals because they were unavailable for a long time but now I can get them.
The question is whether to flick a hone through the bores and take out any marks plus cross hatching will make the rings seat better even if there’s excessive clearance or rebore with lower compression pistons and probably get increased reliability.
Either way I’ll fit the new guides and seals then lap the valves in give the ports a bit of a polish.
This is where we’re at right now with the engine and I’m currently necking a pint of Otter Ale
Next job is to strip and service the brake calipers while I wait for seals and a gasket set plus maybe a rebore.