Jowett 10 heavy oil consumption

[nigel jarrett]

I am looking into the heavy oil consumption on the 10 .So far the heads and barrels are off .Pistons are std and the bores look good with no lips ,I have 60 thou gap on the compression rings in the barrel and 100 thou gap on the oil control ring ,I have 2pistons with the split skirt on the top the other 2 are on the bottom .The valves have 30thou sideways play in the guides ,what are people's thoughts on this please .Also does anyone know what the head nut torque is .
Thank you in advance.My thoughts are new rings ,possibly new valves and maybe guides depending on what is available

[k. rogers]

Hi Nigel. Good news that you have standard bores as it should be a bit easier to get pistons and rings, and plenty of scope for rebore in the future. As far as I remember, I believe the recommended ring gap should be 3-4 thou per inch of diameter of piston, so you can see yours must be very worn. Also, I think allowable wear on valve guides is up to 2 thou (certainly on the 7hp). It may be worth looking for adverse wear in the bores, ie the measurement across the diameter of the middle section of the bore, as if it is too much it may need to be bored out to a convenient oversize, depending on pistons available.

[Tony Fearn]

Hello Nigel.
I may be 'teaching my grandmother how to suck eggs', but there are a couple of 10-4 items lower down JowettTalk in the Technical Library - Technical Library Index - bottom two items in blue.

Perhaps you could try to speak to Mike Kavanagh at Jowett Car Spares on a Monday night. I'm sure he could discuss things with you.

Tony.

[nigel jarrett]

New rings have now closed the gap to 5 thou and new valves have taken out most of the play once the heads have been refaced due to the extreme difficulty in removing them I shall start to reassemble after Christmas ,then to have new lower coolant pipes made

[Srenner]

IF I am reading your post correctly, a ring gap of .005" would only be correct for a 1" bore or piston. As posted before,most piston ring manufacturers recommend a minimum end gap of .004" per inch of bore diameter. That's for the top ring. The second ring should be calculated at .005". These are modern, general guidelines and can vary slightly. Too tight on the gap and you will break the rings or gall the bores, leading to a seized motor.

It sounds like you have a very worn engine. New rings will not fix oil burning if the bores are worn. Bores wear out in the middle. The home mechanic check is to get a piston with no rings and a new ring. Put the ring in a bore and use the piston to push it down. Using the one of the ring lands and the liner top as a guide, make sure the ring is sitting true in the bore. Measure the gap. Then, use the piston the to push the ring to the middle of the liner. There should be no difference in the gap if the bores are not bellowed out. Any change means new rings will change little.

Also, putting new valves in old guides just means everything wears out quickly and will still allow oil into the cylinder. The valves will not hold proper clearances as the side movement will skew any measurement.

[nigel jarrett]

Both blocks and bores were checked and measured by a local machine shop and given a good bill of health ,the ring gap will be properly set on reassembly after Christmas.