Blue Smoke Issue

[mbwoy84]

Just wondering what the most likely cause of blue smoke on a little 3cyl 6v engine would be under the following circumstances.

Engine has been cleaned out with engine flush and then been serviced (oil is exceptionally clean) as it’s a car which I suspect has been neglected and not serviced for some time. It’s also had a new oil pump and timing chain fitted now.

The car drives pretty well perfectly. Slight hesitation on start up and engine seems to move a lot (that may be engine mount related more than anything else). It also doesn’t appear to smoke, or at least not enough to see from the drivers’ seat under heavy acceleration. The only time I’ve noticed any smoke whilst driving is on pressing the accelerator whilst coasting downhill in 4th gear.

But the only time it does really smoke, and I mean James Bond-esque plumes of smoke billowing out of the tiny tailpipe is when holding it for a while at any revs whilst stationary.

I’m going to pull the engine apart anyway, but just wondering if there are any clues in there to pinpoint the issue, as it seems odd that it smokes that badly whilst revving it stationary when there’s no noticeable smoke whilst driving even if you thrash the thing to within an inch of its life.

[gazza285]

Valve stem oil seals.

[Boosted LS1]

^ Certainly when under vacuum.

[mbwoy84]

That’s what I was hoping, but wasn’t sure whether it may be more sinister than that.

I bought a head gasket set, which came with new bolts, valve stem oil seals, valve guides and even new valves, so that was nice a cheap for all that really.

Will get it cracked open tomorrow anyway.

[Little Pete]

How easy is it to take the sump off and take the pistons out? We are finding with certain small cc engines that only do short journeys, the oil control rings on the piston get-for want of a better phrase-gummed up, sticking in the grooves and not doing the job they are designed to do. If we quote for a head gasket repair, we try to make the customer aware of this and quote accordingly.

[mbwoy84]

Took the engine out today and stripped it down. Valve stem oil seals almost certainly a culprit. Top of the pistons were very oily.

The kit I’ve bought also comes with new piston rings, so they should be here tomorrow.

Not sure whether it’s normal or not, but the pistons do move around a little in the bores in every direction. Assume there must be some movement to allow for heat expansion etc, but not sure whether it could be excessive. Bores seem clean and not scored or anything like that.

Hopefully it was just valve stem oil seals, but the kit I’ve bought has most of the bits in it to give it a good freshen up.

[gazza285]

Not teaching you how to suck eggs, but if you change the rings don’t forget to remove the wear ridge in the bore.

[mbwoy84]

Well, I've totally dismantled the engine and a full list of observations:

Valve Stem Oil Seals shot
Very slight wear to cam, presumably from lack of oil up there (oil pump was failing)
Very slight wear to edge of main bearings
Oil control rings partially sticking
No wear to big end bearings at all

Think that's about it, so both the Valve Stem Oil Seals and Oil Control Rings as predicted on here, were the main issues found.

I've got the head fully rebuilt and ready to fit, just the Piston Rings left to do, bit of honing/cleaning then it's ready for reassembly/refitting.