Joined: Aug 2017 Posts: 138 Threads: 28
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Location: New Forest
Car type: 27 Chummy
Within the last year I have rebuilt my engine, re-bore, new split skirt pistons etc but it continues to smoke and use quite a lot of oil even after 2000 miles. The engine was not idled after the re-build.
The rings were gapped 6 thou and evenly spaced. The rings have no shape to them or markings so I assume have no up direction.
I am still using the oil baffles. The compression is really good compared with other low compression engines that do not smoke.
Is it possible for this amount of smoke to be due to worn valve guides and is there a method to prove definitively that it is the bores or the valve guides at fault.
Your valued input would be appreciated before I strip it all apart again.
Many thanks.
Adrian.
Joined: Aug 2017 Posts: 3,215 Threads: 100
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Location: Darkest Bedfordshire
Adrian, how much oil is a lot? And are you quite sure it's burning not leaking? And are you confident the 'smoke' is burning oil and not 'steam'? I'm sorry, one can't tell these things over the web.
It's not such a big deal to whip the cylinder head off if you want to check the general condition of valve guides i.e. how much can you waggle an open valve?
Joined: Aug 2017 Posts: 2,748 Threads: 31
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Location: Auckland, NZ
03-07-2018, 08:22 AM
(This post was last modified: 03-07-2018, 08:26 AM by Bob Culver.)
Do Sevens ever use significant oil through the guides? If everything that reached them was devoured would it be much? Not like many older ohv which spill a continuous flow over the guide On Sevens, unless going downhill, seldom much vacuum.
Is it a specila with flats on the sides of the followers acting as pumps?
Joined: Aug 2017 Posts: 138 Threads: 28
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Location: New Forest
Car type: 27 Chummy
Hello Guys
I must admit to not measuring the play in the valve guides but sure I would have noticed excessive play when grinding the valves.
The engine is sealed very well and never leaves a single drop when parked.
On a recent run it used about a pint for 100 miles.
Like Bob I was unsure if it was possible for valve guides to account for this much oil usage.
It will not be a problem to whip the head off but I just wanted to know if there were any specific tests to carry out while it was running.
I have guides and new valves ready to put in. Can this be easily done in situ?
I can only assume if the guides are ok that the split skirt pistons or rings are at fault.
I may have to bite the bullet and pull the engine again.
Adrian.
Joined: Aug 2017 Posts: 1,437 Threads: 59
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Do a compression test dry (as is) and repeat it after you've put a squirt of oil in each bore.
The theory is that if it goes up with oil in the bores then you have a ring problem.
Valve guides would need to be utterly shagged to make a big difference in my book
Charles
Joined: Aug 2017 Posts: 3,215 Threads: 100
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Location: Darkest Bedfordshire
Inclined to agree with Charles. Not quite sure how definitive the squirt of oil test is but I can't think of a better one. No more than a teaspoon full mind.
Joined: Oct 2017 Posts: 12 Threads: 0
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How much crankcase back pressure is there?
I thought if it's the valve guides they draw oil in on the over run.
Joined: Dec 2017 Posts: 1,132 Threads: 66
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Location: Nottinghamshire. Robin Hood County
Car type: Austin Ruby Mk1 1935
Adrian, It's not to difficult to do the valves in situe but it does mean removing the manifold to get your spring clamp in. It's also a good idea to make sure you have the brass gauze thimble shaped filters in the valve chest corners (if they are not there cover them with a piece of rag) dropped collets always seem to find them and end up n the sump.
John Mason
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
