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MG Midget and Sprite Technical - Rolling road - leak down test very high!

The car was over advanced by quite a bit so reset and still not right and rich - put back weaker BDL needle for now (was BDK).
Initially quite Smokey less so later.

Down on power from previous runs on Aldon’ r/r some years ago and theirs is not a high reading one either!

Did compression tests and 160- 140ish.

Leak down very very poor !

Engine has only done 4K miles in about 10 years due to many family issues etc.

Options seem to be:-

1. Italian service

2. Remove head and review valve sealing / inspect bores.

3. Pull sump and remove pistons and check if rings stuck etc .
I think you can pull the sump on a 1275 in situ - long time since I’ve been under one.

4. Just drive it as it goes quite well and see if it frees off the rings etc ?

5 Expensive engine refresh.

6. Sell it - had enough !

Any body bought a leak down tester - seem that they are available at both cheap and hugely expensive.
I have a smallish mains compressor which should be big enough. Thought was see if it improves with hard running ?

An old marine Volvo trick for glazed bores on diesels that had been battery charging too long with no hard running was to run hard adding a little vim to the inlet to bust the glaze!!

R.
richard b

Sump comes off easily. Easier still if done in a pit or undet a ramp, rather than on your back under it.

Only 4k miles in 10 years? Yep could be gummed up/stuck rings.

Not **that** big a job to whip the head off for a look at the bores for glaze. How about a scope? You might be able to see without taking the head off.

If it goes well, I'd do your #4 first.

So called Italian service helps keep it clean, but it won't shift existing carbon and glaze.

anamnesis

No recommendations for leak down testers then ?

If I eventually decide to re-ring are rings specific for a make of piston (assume correct overbore) or standard.
I’ve only fitted new pistons in the past.

Assume bores are not scored - glaze busting - 3 leg stone hone in drill with lube or the old loo brush type with abrasive balls or is coarse/ medium wet and dry sufficient? Always had a rebore previously.
I use the 3 leg stone hones on my steam engines with good effect.

R.
richard b

Yep, piston specific rings. Do you know what the pistons are?

Telephone Thorntons. They'll tell you what rings and very likely stock them too.

01952 252892

https://www.fwthornton.co.uk/piston-ring-sets-l

Yep bust glaze. But if bores are nice with no scoring, only light scuffing is all I've ever done, and I have great compression and little blowby. I've re-ringed my current pistons 3 times. That's about 300k miles on the same bores and pistons.

A bit of wet/dry wrapped around a flap wheel in a drill. Move it up and down. I'll take a picture of what I use.

But if money doesn't bother you, take it to a shop and have it done professionally. I never have for just glaze busting though.

Never used a leak down tester, so can't comment.

anamnesis

My glaze buster. Yep crude. But it works. 😁


anamnesis

Thanks Anam,

Have borrowed a camera so will have a look down the bores when I get it working !

I’ll order a leak down tester off evil bay and see what that tells me - it’s fairly quiet around here so any rushing air escaping will wake up the wild life !

Then I’m going to give it some more fairly hard runs and recheck the compression and further leak downs to see if it improves or not.

R.
richard b

Here is a link to the Millers stuff.

https://www.opieoils.co.uk/p-69027-millers-oils-liquid-glaze-bust.aspx
richard b

Sorry managed to loose my previous post !

Had a look down the bores- some cross hatching still visible- some slight vertical scuffing I think- burnt oil on piston tops - not much else to report.

Would another run on running in oil be worth it or past that now - while looking up prices for running in oil came across this stuff from Millers . Anybody use it or snake oil

Will do some leak down tests when it arrives.

Really don’t want drop the sump if I can avoid crawling under it!

R.
richard b

Richard, you said it's been sitting around, but, --

"Initially quite Smokey less so later. "

And,

4. Just drive it as it goes quite well -- "

Seems to me that as it goes quite well and less smokey than it was, you have nothing to lose by running it, and getting some miles on it to see if it improves more, before taking it apart. If it improves, great, if not you've lost nothing.

As for the Millers. I found this about glaze.

" -- The 'glaze' is in fact a lacquer coming from the oil or products of combustion that condense on the cold surface of the cylinder bore and fill in all the ridges and furrows (however invisible to the naked eye) that represent the surface topology. Hard and almost impossible to remove, the ring will pass directly over it, producing excessive exhaust gas blow-by and high oil consumption."

So does the Millers 'disolve' the glaze?

I've read quite a few reviews that say the Millers doesn't work. But maybe those engines simply had too much glaze and stuck rings. If it was cheaper I'd try it. But at that price, without loads of positive reviews/comments, I'd try the above first, and if that doesn't work I'd bite the bullet and get under it to take the sump off.

Doesn't anybody else have a comment?
anamnesis

I had read similar and don’t really like the idea of the Millers stuff as I think the lack of protection to other components is not a good plan.

I had a thought regarding the hard glaze - can it be softened by coating it with a liquid such as Redex injector cleaner/ diesel DPF cleaner etc which I happen to have - put a few cc’s down the bore turn over by hand to coat the bores - leave overnight and give it a run next day or two ? Just a thought.

Hopefully it’s out for a run tomorrow as the SAAB is in for a cam belt change and the drive will be clear for the midget to escape !

R.
richard b

Sometimes ,if you have chrome rings and a finely finished bore, the bore gets smooth before the rings get time to bed into shape, If this happens it can take a long time to bed the rings in--sometimes never.
Best bet, if you know the rings are good and fitted correctly is to take the head off, get the piston at bdc.grease up around the edge of the piston and rehone the length of bore that you can get at with a decent solid hone (3 leg) anything else just follows the shape of the bore whatever shape it is.
CLEAN UP THOROUGHLY.wipe the bores out with a slightly oily rag or poo paper until there's no colour coming off the bore
The Millers stuff maybe works, I've used it but undecided, but it's more or less like running in oil. IF you do use it, don't leave it in there too long and whatever you do don't look in your draintin when you drain it out or you'll have a heart attack, it comes out like a metal slurry--scarey

AND--be carefull if you're thinking of using DPF cleaner--your engine will run on it--DON'T breathe the exhaust with it in there ,not even a little bit, or you'll end up at the doctors like me and you'll be paying the price for years to come----it's bloody dangerous stuff.
William Revit

Thanks Willy for your advice - as always much appreciated.

Will run it a bit more and see but I'll start ordering the bits, Hone, running in oil, valve stem seals etc - I have a turbo composite gasket in stock (ISTR these are still fitted dry) and somewhere a set of ARP headstuds bought years ago !

If I get the head off I may still drop the sump and see 'whats what' Probably enlist a younger relation to assist ! ISTR the big end bolts/nuts are reusable ?
ARP B/E bolt sets are now £150 - just don't trust the replacement stuff that is sold nowadays - especially critical fasteners.

Don't think I'll be using the DPF cleaner after all !

R.

richard b

On my small bore I have used high tensile allen head bolts for the big ends, for the last 18 years. No need for the super-expensive ARP ones. Standard bolts for the mains, and no lock tabs. Nothing has ever come undone. I torque the big ends up to 5 lb ft over the workshop manual's setting, as per Vizard.
Les Rose

This thread was discussed between 26/03/2024 and 14/04/2024

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