Morris Minor Owners Club

De-glazed cylinders, cleaned grooves, installed rings with correct orientation (clearly marked with "top"), and had no ridge at the top of the cylinder (I checked this several times, as I had the ridge reamer to hand). Obviously, I will have to take the engine out this winter and do a complete overhaul; I was just wondering what my chances were that I would stop or significantly lessen, the
truly wondrous blue cloud left in my wake (burning about a quart of oil per 150 miles).

One bone awarded, now things get tough as it isn't something obvious.
Did you measure the ring gaps by putting them in the bores?
Has it been rebored ever?

What is in place for crankcase ventilation?

My re-ringed engine used a little more oil then settled down but it was never so bad that blue smoke came out.

I assume it was doing this before the rebuild?

It was blowing blue before the 'rebuild'. Not this badly, however! I have the breathers in the timing case cover and rocker covers plumbed directly into the carbs.
The engine showed no evidence, (and the previous owner had no knowledge of) any previous internal work, so I took it for granted that the sizes were standard. Now that you mention it, that assumption was probably a foolish one, as the lack of a ridge on the top of the cylinder should have tipped me off that it had possibly been bored out to an oversize...sigh. Oh well, the winters here are long, and I have an engine crane and a large garage...

As there was no ridge you might have been able to see some cross hatching for about a pistons length at the bottom of the bores.

How much effort did it take to get the pistons into the bores?

If they just dropped in you have your answer

Actually, it was the usual struggle. The piston ring gap on the top ring (after I'd got it in) looked normal, and they had good friction when pushing them down the bores. Thanks for all the input, but I guess I'm just postponing the obvious: engine out, proper rebuild. Naturally, I'll jump right on the forum to report any miracle healing before then!

Seems you have good compression, well worth checking the head gasket as an easy fix!

Is a head gasket leak a common cause of blowing enormous clouds of blue smoke? I mean, this is of near biblical proportions!

Yet another thought, did you stagger the ring gaps around the pistons?
I'm sure you did but not doing so might give the smoke trail.

Yes, I did stagger the rings. I also recall looking for any markings on pistons and shells and finding none. Time doesn't permit my stripping the engine down right now, but I'll report back when I do. (I also can't drive it in this condition, as the clouds of smoke are beyond embarrassing!). Thanks for all the advice, but the only cause I can think of is that somehow my inadequate break-in period followed by a high-speed run must have glazed the cylinders walls. Lesson learned!

One other note: when the oil cap is removed, it definitely is "sucking". I.e., there doesn't appear to be any crankcase pressure at all- quite the opposite!

Bazzalucas- Could possibly be that the ring grooves in your pistons are now too wide due to wear(and possibly over-zealous cleaning...) When this occurs, the rings have a clever trick of acting as a very efficient oil pump! On the down stroke,oil gets caught in the gap between the bottom side of the ring and the piston groove lower face. On the up stroke, the ring shifts down in the groove, forcing the oil round the inner circumference and onto the top face of the ring. As the piston goes down again, the ring shifts up in the groove forcing the oil up the piston, and a fresh charge enters the gap at the bottom of the groove.....Lovely!!, but not what you want to hear, along with the dodgy oil pressure (is that any worse than before the rebuild?)

Sudburypaul- (are you in Sudbury??) If the head weep is a minor annoyance, then a little bottle of lucasoil water leak stopper from Jayar will stop it up! This is weird watery looking stuff with coppery particles in it, but for a tenner or so it has done wonders for me on various far more serious leaks! They also do a power steering leak stopper (not relevant here I know!!), which I dubiously tried in order to get a Cavalier through the MOT, and it worked! I was, frankly, amazed, not generally believing in snake oil!

Hiya

Yes I am in Sudbury (0n the Suffolk border near Essex!). Where are you? I thought about this and was a bit unsure about trying it as didn't want to gum things up. I'm going to retorque this weekend. If this doesn't stop it I may try the sealant, as it does seem easier than taking the head of again. Jayar is just up the road too.

Cheers, Paul

The oil pressure is about 10 psi better at any rpm than before the rebuild. The ring grooves appeared unworn to me, but I did not check the ring gap before reinstalling the pistons. Today I tried venting the breathers to the atmosphere and plugging the carb breather ports, just in case the carbs were sucking up crankcase oil. No difference.

Ahh -I was just about to suggest doing that........ Although I firmly believe it's 'never' the valve stem seals - they may be worthy of an inspection since you seem to have done everything by the book on the pistons...... Are the valve guides worn? Is there excessive oil pouring down from worn rockers??

Hmmm, hadn't thought about excessive oil in the rocker area...but did fit new-style viton seals to the intakes, new o-rings to the exhaust valves. Some advice I got on another forum suggested running 30w non-detergent oil until the rings seat. I'll give that a go, as I can't be any worse off!

Finally got round to retorquing the head tonight. Just nipping the head up a tiny fraction seems to have cured the weep. Note to self: In future retorque to 44lbs per sq inch rather than the 40lbs the Haynes manual prescribes (hopefully in the not too distant future).

New alternator and swap to - earth,rewiring with now working indicators: cure of head gasket leak; solved the blowing fuses problem, weakened the rich mixture. I almost feel like a mechanic !

Paul

Okay, let's see if I can sum up: I finally got round to pulling the head off tonight. There was a lot of oil on top of the pistons, and the ring gap on the top ring was about 1/16th of an inch! Don't have the proper measuring tools in hand to check the diameter of the bores to see if they've been bored out to an oversize, but there are no markings anywhere I can find on the pistons- hence my foolish assumption that the bores were standard size). Now, before anyone asks, the car did NOT burn oil in such obscene quantities before I put the new (standard size) rings in, so I'm wondering: is it standard practice to put in oversize pistons when the cylinders have been bored to an oversize, or simply to use oversize rings with the original pistons? (This is what I suspect has happened). Will get proper measurements and report back. Thanks.

Hello Bazzalucas,

when reboring oversize pistons are fitted (and rings match the piston size, e.g. + 10 thou pistons have + 10 thou rings) The piston will have something like 010 stamped on the top to indicate oversize.

1\16" of an inch ring gap is very wide, but when you preplaced the rings did you de-glaze the bores. New rings in worn bores will take a very long time to bed in and seal. Normal practice is to hone the bores or use emery cloth to take the shine away. This lets the new rings bed in and seal.

Alec