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MG Midget and Sprite Technical - Head Off Advice

Took the head off the car today to sort valve stem seals and when I turned it over it looked like this (Image) is this normal or should I be concerned?

I also have a picture of an inlet valve that has a build up of white powder around it and in the port (next post).

What should I be looking for that is causing this or do I need to sort the head with new valves etc?




Shaun

Picture of Valve




Shaun

Hi shaun,
I've seen a lot worse after removing heads in the past, so no real worries, just needs a decoke. I'm guessing it's been burning a bit of oil?

Neil
Neil Williams

Yep it has been burning a bit of oil, thought I would start with the valve stem seals to see if that would be cure it without having to pull the engine and also found a broken valve spring for my trouble.
Shaun

Shaun,

It may be worth your while looking at the state of the valve guides while you're at it. I used to change the guides while I had a head off if it had done over 10k or so. That was maybe 20 years ago and guides were about £10 a set and easy to change as I had the kit. I always used the standard iron guides in the days before lead free, not sure what is recommended these days.
David Billington

Hi Shaun,

We took the head off mine last weekend and found almost identical white deposits and I've been burning a litre of oil every 100 miles.
G Lazarus

For no more then it would cost, combined with alot of benifits, Id take the head in to a good machine shop and have it completely dip soaked and bathed, resurfaced, valve faces and seats reground, and get new springs, guilds and seals,,,,with the oil and water ways all cleaned out,,,,probably not nessacery but even magnifluxed.....and for a few extra dollars maybe even some rim-flow knock off vavles(penny on a stick)....and even get some of the thoose hardened exhauste vavle seats for unleaded gas


just guessing if you did the whole sha-bang I listed...mmm maybe $400...without the new vavles and hardened seats $150...

like I said the benifits in gas milage and performance easily out wiegh the cost

prop
Prop

SO G Lazarus have you pulled your head in an attempt to find where your burning oil from. If so what steps are you taking to find out what's causing it or have you a suspicion of what it is and how to cure it?

Any help would be good, I'm trying hard not to pull the engine out as I now it will lead to modifying.

Shaun
Shaun

Shaun - we knew that Garys engine was drinking far too much oil so a spare engine was built.

Originally it threw a valve seat which buggered up the compression slightly ;-) so a spare head was procured from ebay and fitted. After some miles and a track day and the annual pilgrimage to Le Mans the head looks very similar to yours.

Although I have not striped the engine proper yet the current thinking is that the oil rings were not fitted correctly coupled to the ovaling of the cylinder walls allowing too much oil through. The piston heads are very coked up and the head has similar white trails; I cant open the first photo but from others descriptions it sounds the same.

I'll just pop out and get a photo....
Toby Anscombe

Right - just been out to the garage and here is what No1 looks like.

It only seems to be on cylinders 1,2 and 3 with 4 looking ok.

Only seems to be on the exhaust valves and the white crud goes from the spark plug to the exhaust valve.

To be very contrary I think that valve stem seals are needed on both the in and exhaust valves; most people seem to think that only the inlets require stem seals...

Have you got any measuring tools - you want to see what state the cylinder walls are - my guess is that you will find that they are slightly oval which when coupled to bad or knackered rings will allow oil through.

For the short term new seals an guides may help but start to think about a rebuild in slow time; you can always look to ebay or the classified section of the MASC site for a spare block.....

If Max still has his short engine I would dive in......


Toby Anscombe

Found these on CalverST has anybody used them?

Stem seals - Viton lined type
£1.60
Viton lipped seals bonded to a metal jacket. Supreme longevity compared to the standard A+ sprung seal type. Price is per seal.

Toby, thanks you are confirming my suspicions that the valve stem seals is just a very short term solution.

What measuring tools do I need to check the bors, I have noticed that there is a still scoring in them but not up and down if that makes sense with a black ring at the top of the bore and coked piston tops I will take a picture in a short while to post.


Shaun

I have used those on Cavaliers and Astras

Standard kit for Vauxhall

I would happily use them on my A series

ALL EIGHT VALVES

If the bore has scores you can feel I advise a rebore + new pistons

If you can feel a lip wear mark, again, given the oil burning I would have the full monte this time rather than wait for disaster to strike.
Bill

Hey Shaun,

my engine doesn't burn oil :-), i know this because i can see most of it in a puddle underneth the car.

Take your head to see Alan, he'll sort it out for you, just remember to take a packet of chocolate biscuits.

cheers mate
Brad
B Richards

I guess it depends on your budget, I guess the first option would be to clear off the coke, put stem seals on, and chuck it all back together, I would personally lap the valves in first though, and then the car would be usable through what's left of the summer. From running bangers for many years one tip is not to scrape the coke off the tops of the pistons, or you'll leave a smoke trail behind you.
Cheers
Neil
Neil Williams

Not sure that is contrary is it Toby? Who believes that seals are only required on the inlets? I know with our racing engines a bit of oil down the exhaust guide does no harm but I have never heard of advice that exhaust valve seals are not required on a road going engine. I would expect it to use a gallon every thousand miles without exhaust seals. I would always install them personally.
Bob (robert) Midget Turbo

--Who believes that seals are only required on the inlets?
>>>BLMC that's who! Originally the design intended seals to be on all 8 valve stems; 40 years ago the material was not up to the job, and in use it was found that the exhaust seals went brittle, stopped sealing, and most importantly in a few cases broke up leading to far worse problems of oilway blockage etc so BL put out a Tech Bulletin advising use on inlet valves only. AFAIK this was never rescinded, however I do think todays materials are better and it's probably a good ida to fit on all 8.
David Smith

I found one of these in my tool kit

and then checked the bore of the cylinders it's not oval but ....next imnage please


Shaun

I have read and heard both sides of that arguement... seals on intake only or on both....All I can say is there is no concinsus....I think it comes down to your own belifes and the quality of the seals.

AS to Me...Im using the top hat seals on both exhauste and intake, with no problems, and No oil burning....so thats the way Im going....thats been a 1.5 years scence I did my head.


prop
Prop

and I think it all depends on the exhaust valve seat!

If it is verry racy and small than You should not fit seals because the little bit of extra oil helps to cool the valve down preventing wear

If it on the otherhand it a normal seat with lots of contact area then it won't need more cooling so fit a seal.

o Könemann

well you live and learn David, would love to see that tech bulletin, have you got a copy? At that time all other BMC engines, well the B series anyway had 8 valve stem seals, they were rubbish but they at least did have them.
Bob (robert) Midget Turbo

So this is what the bore looks like (image)

and you can feel the grove in the black area.

So I have resigned myself to an engine rebuild or transplant.

Time to start gathering the parts as I'm just going to get a new set of valve springs, lap the valves and new valve stem seals to ALL of the valves just to see me through to the winter when I should of gathered the parts required.

So please feel free to persuade me A or K

Shaun


Shaun

wow,

I havent seen anything like that before....well except open bores sitting under a tarp by the wood pile anyway

are you sure thats not some kind of rust/glazing like if it had sit for several years unstarted with a small water leak and then fired up one day out of the blue and ran ever scence.


prop
Prop

>>>>>>>>If Max still has his short engine I would dive in......

Alas not :-)

Max T

We have found on occasion that, when driven hard, the exhaust valves in a well tuned midget can nip in the guides if stem seals are fitted to the exhaust valves. No extra oil burning has been reported. The converse is true with FWD A series engines, the oil tends to puddle in the head and go down the guides if the ex seals are not fitted (3-400 miles per pint). We fit stem seals on the ex valve guides for FWD but not for RWD A series. Note there are only 4 top hat seals in most head gasket sets.Worn rocker shaft and bushes tends to exacerbate the oil puddling problem. I think the soft black deposits are the main results of oil burning in the pictures shown.

Peter
peter burgess

I always fit 8 stem seals on both in line and transverse engines, but take on board Peter's findings (very interesting and make good sense). Keith Calver's Viton stem seals make good sense too. With the modern Unleaded fuels, normal rubber based seals tend to break down, Viton doesn't, so that's a good way to go.
Shaun. If I were doing your cylinder head, I WOULD strongly recommend that you overhaul it fully with new guides, seats, valves and springs. As it looks like an 11 stud head with Big valves already fitted, I would guess it's had some attention in the past anyway and as a consiquance, some hard driving. You may find that overhauling the top end with new Rocker Shaft and rockers (or bushes) will give you a new lease of life...
Oh and whilst on the subject Peter May or Swiftune will supply a thick walled rocker shaft, far better than the Std one....

Mark.
Mark T. Boldry

Cheers Mark

I have decided that I may go for a stage 2 or stage 3 head from a reputable supplier that will include a warranty as I have decided that I want new valve guides and new springs so might as well do it all in one. If anyone has a 9 stud 1275cc head going cheap that needs a rebuild....count me in... as I would like to keep the 11 cooper s head and sell it on.

That will then give me time to collect all the parts to do a complete engine rebuild.

I have been reviewing the archive for the best engine solution and am now looking for an ITAL block as I like the solution of where the oil filter lives. Anything easier for that messy job is good.

Thanks Mark for confirming my suspicions about the engine I thought it was not a std one and this is the first time I have had the head off to see what's going on.

I have measured the bore at approx 72mm what does this equate to cc wise?

Any recommendation would be welcome

Shaun
Shaun

Hi Shaun

The 'proper' Midget engine is the best, far superior crank and rods, almost unburstable, but getting a little rare these days.

The 1300 GT also had 11 stud head. One can also drill the extra 2 stud holes, sometimes things are not as they appear.

Peter
peter burgess

Shaun, you might want to talk to Peter in a professional capacity...

Some people think that he is rather good ;-)

http://www.mgcars.org.uk/peterburgess/

Please dont buy a 'stage 2' or stage '3' head; there are no standards and one mans stage 2 is another mans stage 4 etc.

Talk to someone who will match a head to your engine - compression and cam will help inform the various factors that go into putting a good package together. Stages don't mean anything!
Toby Anscombe

Shaun.

I can sell you a complete Ital if you are looking for an engine, I would even take your 11 stud head in Px....

Peter Burgess will machine you a bloody good head, as will keith Calver, and Nick Swift. You must decide what you want.

I agree though with Peter (and shoot myself in the foot again), The Midget engine is a stronger unit (crank and rods wise anyway), I think the Ital block is more ridged so a compomise has to be made. Sadly one can't fit the Midget crank into the Ital block...

However, if you are not racing it (even if you were) the Ital engine is a very suitable unit.

Mark.
Mark T. Boldry

not wishing to turn this into a classifieds list but I happen to be able to offer you a choice of either Ital or Midget engines at the moment. Be aware with the Ital block you still need Midget backplate and flywheel to fit inside the standard bellhousing, and the flywheel needs a bit of machining to fit the Ital crank.
David Smith

And if you go down the Ital route I have a Midget backplate and quite possibly a flywheel.
Max T

Shaun mate,
i have a rather nice anodised ali backplate on my roller skate, but i recommend you fit one of those heavy standard backplates instead, as it'll make your car heavier & i need every advantage :-)
cheers
Brad
B Richards

Thanks all, Now before I go and spec the head what would you say engine wise for a decent spec motor?

Any offers please email me shaun @ richesweb dot co dot uk

Thanks

Shaun
Shaun

Slow road spec please Shaun :-)
Brad
B Richards

This thread was discussed between 16/08/2008 and 21/08/2008

MG Midget and Sprite Technical index

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