V8 using oil, pistion rings or valve guides ?

DamianZ28

DamianZ28

Active Member
Hi guys,

Sorry this question again, done about 1000 miles since top end rebuild but now its using oil, say about 4~5mm worse case on the dipstick after about 200 miles.

Oil pressure is fine, stays just passed the 30psi on a run, no knocks or rattles on start up cold or hot, still has good accelleration, But it'll puff blue smoke once the engines hot on start up, NOT when its cold.

Am a bit baffled as too where to start, could it be worn valve guides, its a 72 car with no guide seals, or is it worn pistion rings ? or even a broken ring perhaps ?

I will do a compression test to start, does anybody know what it should read, got 70k on the clock I know its hard to pin point until I remove the engine to see what is going on in there, any ideas/thoughts greatly received, big thanks, Damian
 
As a general rule if it smokes from the exhaust on acceleration it's the rings, if it smokes on the overrun it's the valve guides. If it smokes when it starts when hot that's normally guides as well. It could all be leaking away of course.....
Do your compression check and see what you get, then interpret the results, don't waste time trying to predict the outcome before you do it.
 
Are you sure you've got no leaks ?
I'd weigh up the cost of oil against the cost of the problem , if it's otherwise running OK
Also , like Stina's dad's Calibra , did you clean off the pistons when you had the heads off ? If so, it might coke up a bit in time
 
I've found that the (usually Gunson) compression testers are fairly inacurate for actual readings, they do however give repeatable results so are fine for getting an idea of the balance between cylinders, which is usually what you're looking at. So don't get hung up about actual values, it's the variation between readings that's important.
 
just try a bottle of stop smoke or the like, you have nothing to loose except £4.99 and thats cheaper than the oil these days lol
 
Well I've just given the car a good run to get it hot, gave hard accelaration, no blue smoke bellowing out, let of on over run, stil no smoke, it's literally a blue puff on hot start up, it's drop a tiny amount from the rear of the engine, I guessing old rope seal, also I noticed it has oil on the rear of the block both sides under each head, I replaced the head gaskets with the composite versions, could be its leaking from there, but there hardly any oil under the car floor pan from a bad leak,
Both heads were fully decoked & each piston top cleaned, they werent to bad.
Thanks for the input guys! Damian :)
 
For the oil down the block is it the Rocker cover gaskets??? did you reuse the old ones? I know pae let a bit out there when i reused gaskets...
 
I used new ones, I couldnt see any oil on the heads though, odd! i think it really is christine!
 
There are two sorts of engineer. First there's the toolroom engineer, for whom everything must be within a tenth of a thou of new tolerence, able to eat dinner off anything (except that would make it dirty). Then there's my sort of engineer, who is absolutely perfectionist about everything working to maximum potential, but really couldn't give a .... what it looks like (within reason). I'd go so far as to suggest that I regard external oil leaks as a positive boon on the grounds that they protect the underside of the car....

So if it works correctly and the rate of loss both doesn't change and is within affordable limits, then I'd say you have a splendid product of the British motor industry!

Chris
 
I would say that various small leaks could point to some mild crankcase presurisation, have you checked that all the breathers are clear and working ?
 
Good thought Richard! If it's done a lot of miles it's certain to need a new pair of flame traps - the grey steel mushrooms in the pipe runs on the top of the rocker covers - and don't forget the breather under the air filter box at the back of the engine - just use a reasonably clear fuel filter to replace.

Chris
 
Like your thoughts Chris :LOL: , I think I'll check the rocker cover seals which are new, clean off the block either side, get it warm & up on ramps to see if I can spy any leakage, maybe re-check the cylinder head torque settings, flame traps & rear breathers were all replaced when I did the top end rebuild.
Possible I'm fretting to much :oops: , as you say Chris if its running good then leave it, with no knocks or rattles, no constant blue smoke, Good oil pressure then Bobs your Aunty Sue as they say..so I think I'll leave pulling all apart until next winter, enjoy the summer months cruzing... now lets have a look at carpet sets ! cheers again guys Damian
 
Back when I were an impoverished 'pentice lad, my Mini leaked like a sieve for about 6 months while I scrimped to buy the bits I needed to make the changes I wanted to the engine once it was opened up.
It saved me on servicing, though.... just kept topping up fresh oil. The engine was clean as a whistle inside when I opened it up. :D
 
webmaster said:
I call it the "Rover continuous oil change system" :LOL:
Click to expand...

And underbody corrosion inhibitor. Just a shame they didn't channel some of it directly into the inner sills... :LOL:
 
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