MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - 1275 Blowing Oil Head?

'72 midget with 1275cc. about 50k orig miles.
Car is smoking quite a bit, blue smoke. The tailpipe deposit is actually almost wet with oil
I took a comprerssion test a couple of months back and found pretty good and close compression on all 4 cyls, around the 150psi mark.
I am suspecting the head, thinking that if the valve guides are really worn that would cause the kind of blowing oil I am getting.?
I removed the valve cover after draining oil and see a good puddle of oil sitting on top especially at the valve side.
If my guides were the problem would this oil not have drained down off the top of the head?
My breather system is in good order, can at timing cover to both carbs with vented valve cover.
I was hoping to do a sort of quick fix to try to stem the amount of smoking and replace the head with another one.
Am I on the right track? any thoughts?
Thanks
MK Mike K

Is this happening constantly, even once fully warmed up?
Lawrence Slater

Normally if its worn valve guilds seals it will only smoke at start up for about 30 sec

You said the breather is working fine... How did you test ??

Have tried a leak down test yet...

im not sure but i think a vac gauge test could indicate a broken piston ring or not

1st thing your going to need is a logical diagnostic plan to track it down cause this can be alot of things...and the spaggatie thrown agianst the wall approach would be daunting at best

Prop
Prop and the Blackhole Midget

If it is caused via the breather (which I doubt) then a quick and obvious test is to temporarily disconnect the breather pipe, pluging the 2 open end of the pipe where it connects to the carbs.

More likely, is that the rocker shaft/ valve rockers are worn so that oil is flooding out onto the cylinder head too fast, and then in turn being drawn down the valve stems.
Guy Weller

History?
And use?
At 50,000 on a 40 year old car, it has sat an awful lot. Usually this means decent miles in the first few years and little to none since.
Last oil change?
How much oil put in? Dipsticks get changed, lost, damaged. Very high oil levels might explain.
Oil used?
Last hard hundred miles?

Not valve guides at that level of oil consumption, and no it will not drain oil down the guides from the head surface.
Not head.

FRM
FR Millmore

Ok thanks guys
Not stem seals as it happens when fully warm

I have y pipe to carbs, snorkel vent on valve cover to atmosphere. Have a vacuum when I remove oil filler cap and idle changes when you remove y hoses from carbs.

No real history that I know, but it has sat a lot for sure.
came with a receipt for a $350 carb rebuild that was nothing but new gaskets so I did a proper rebuild of the carbs.

So a lot of time tuning so I am finally dropping the oil as we speak, last change less than 2k ago but about 3 yrs ago. as per receipt.

Oil level may have dropped a half quart but can't be sure as I know I went both ways with the mixture a couple times so that could have dumped gas, but oil does not smell like fuel too much.

Dipstick is correct type

No idea when this car last did 100 mi.

I have taken it out two times got it some good revs in 3rd gear and it was not billowing smoke but I did not have an assistant with me to watch that closely.

Seems like more smoke when revving it not under load.

Mixtures are close but like I said the inside of the tail pipe is black, almost wet, oily.




MK Mike K

"""Normally if its worn valve guilds seals it will only smoke at start up for about 30 sec"""

Not sure where you learnt that from Prop, When I have witnessed valve guides worn I have seen high oil consumption and smoke after the car has been off the throttle (especially after going down a hill)


Mike do as Guy suggests and undo the braether pipe that I assume you have fitted to the inlet manifold, If it is the one way valve type these generally pass and Suck oil straight into the intet manifold.

After that I would be keen to ensure my valve stem seals were in good nick.
Robert (Bob) Midget Turbo

After the oil change I will try removing the pipes from the carbs. I believe that I have done this at some point already with no difference in the smoking, but I will do it again to be sure.
MK Mike K

less than 700 miles a year and not seen a 100 mile run in memory

whether it's the cause or not that's done no favours

I'd suggest onece a year oil and filter change at that mileage

I have an idea, you can try before or after an oil change or do both

work out a circular route of say 25 miles that will give you the chance to open it up a bit for a good few miles do that route 4 times without stopping - that way you're never more than say 13 miles from home in case you need to limp back

it'l also exercise the gears, brakes, tyres suspension, possibly horn, indicators, wiper motor, heater blower ect.
Nigel Atkins

The valve stem seals may have dried out and hardened if the car was used very little. This would be considerably aggravated if a worn rocker shaft is leaking oil too fast. Its not then that oil pools on the top of the head when running, but that it sprays too much oil around within the rocker cover, saturating the valve stems and increasing any tendency for oil to run down past any suspect valve stem seals.

The shaft can be visually checked in situ by pushing the rockers against the spacer springs and feeling the underside of the shaft for wear steps. If it is worn it can be easily replaced without removing the head. But if this guess (that is all it is until checked) is correct, then to do the job properly the seals will need renewing which is generally a head off job.

But in reality, more information and more checking is needed first, to get a proper diagnosis. But from the nature and info in Mike's posts so far, he is well aware of that! ;-)
Guy Weller

Yeah, wish I could give you more history on the car but I have owned it for less than a year and the guy who had it before me was not much for being able to supply much technical info about it.

It was a 2 owner car before me and one of the two PO either abused it pretty well or just totally neglected it.

I purchased this car to basically fix up and sell.
I am to the point now where I have made it road worthy and safe but to sell it with this smoking issue just bothers me too much.

One note, when I picked the car up I did start it and ran it a bit, reved it up and that sort of thing and there was no sign of any "real" smoke, but it had a noisy w/pump and I did not run it all that long.

Found the dizzy drive gear was a notch off and the dizzy was in a very advanced position, still started right up and ran ok, but I have since remedied that issue

I will get out there and look at the rocker shaft.

I have a few mg's hanging around and I am dedicated to starting them up and running them up to temp and operating brake and clutch pedal at least 10 times, operating all switches, ect even throughout the winter.

I know these cars need exercise or you are asking for trouble.
MK Mike K

Do not run them up to temp on the drive and then put them away again!!!!!!

At low revs you put more strain on the cam and you have less oil circulating (or circulating more slowley)

Driving is the only real way to preserve them
Onno K

Put the specified amount of oil in to be certain level is right.
Rocker wear could do it, but is not typical at this mileage, unless oil/filter changes were never done. If the rockers are worn, you can bet the cam & tappets are toast.
Get in running and drive it hard and long. It is very common for oil rings to hang up after sitting, and it will not show in a compression or leakdown test.

I bought a Rover 2000TC with 43,000, poor maintenance (original plugs and filters still!), sitting for a year or more with a busted gearbox. Fixed the gearbox, tuned, lube/filter etc., and set out on a test drive 350 out and 350 back, mountain roads and hard driving. Used 3 qts going, and 1 on return, Changed again and left for the west coast - after 6000 miles at 75-100 mph, it had used zero oil, and it never used any between changes for the next 100,000. And the fuel consumption kept dropping the whole west coast 10,000 mile trip, finally at 36mpg US gallons at 75mph minimum with two people and full of camping gear.

Same with a VW pickup normally used for parts chasing in Pittsburgh - about 250 each way to Watkins Glen before interstates. Used a qt/100mi going, and none return, mileage went from 22 to 33, and you would be one gear higher at the top of the mountains. Can only drive 36hp VW with foot flat on the deck!

If it still smokes after use, check cam timing. Late cam will cause oil burning, poor economy, and low power. Chain wear is sometimes significant, especially if oil changes were neglected. I have one clapped out customer car (74 Midget) I've changed the chain in twice in 20 years, as a "get by" while the guy decides if/when he wants to rebuild the engine - when I change the chain it works so well he puts the rebuild off!

FRM
FR Millmore

This is true

We do drive them, probably more than most.

I think it's better to run them even if not driving than not run them at all, it's always worked for me

MK Mike K

FRM. Thanks. Sounds like very good advise.
Running it long and hard should tell me something.
Guess it's time to switch insurance from one of the other cars over to this one..
Wanted to avoid even having to re register it but if I want to find out I am going to have to invest more time in it.
Hey?? maybe by then the prices for cars will rise out of the toilet
MK Mike K

Don't know where or when I will have the time to drive that many hours/miles.
Hopw I can get it done in like 25 or so......
MK Mike K

starting them up and running to temp does very little for the engine let alone the car, certainly does nothing for the brakes, tyres, steering, transmision, drive, electrics

if you really are struggling for time let someone else take the car or pick at bar 50 miles away drive there quick drink drive back - if you haven't got time for that then I don't know what to say
Nigel Atkins

Mike-
Where in NY?
Donate to me!
As you can see, the VW took about 250 miles, but it had been in regular around town low speed use.
Rover took more than 350, and the best part of 700.

I usually find good but not complete results starting at 100, = < 2 hours.

Maybe you need the same treatment!

FRMK
FR Millmore

Hi, had the same problem with a genuine 60K 72 Midget.
Oil smoke & very high oil consumption - 100-200 miles per pint.
Compression test good and even on all four.
It was the oil control rings had worn, they reach a wear point where they "pump oil" rather than scrape it back to the sump.
The compression test was good, because all the oil flying about in the cylinders makes a better seal.
Once the rings were changed, problem solved.
Tony
Tony G

new rings i reckon.
p bentley

You guys are probably on the right track like FRM about the rings.

Maybe I will price out the cost of new rings and con rod bearings??

I guess I am going to have to make a decision on what to do.

Really needed to have this car sold, need the money and the space.
I have a '77 MGB waiting to have a rear main seal replaced and transmission sealed..

Decisions, decisions, it's hard with the market in the dumps right now.. oh well

FRM: I would love to give it the treatment but just don't know how to work it.

I do the mechanical and restoration and up keep but I am unable to drive them myself, I have a severe Visual Impairment

Im on the Queens/Nassau border of Long Island

Regards
Mike
MK Mike K

Mike,
as it will only cost a bit of oil rather than money and time why not see if a freind or club member fancies giving the car a blow out drive and see if things improve if not it's cost a little oil extra
Nigel Atkins

Plus Insurance, plus registration
New York State will pin your ass to the wall if they catch you doing that

If i was keeping the car, yes absolutely but I am already
in it for too much.

I live on the edge of a commercial zoned area where I have a little 1/4mi test track.
I may just take a few days and run it up and down that, but can't stay in high gear for but a few seconds doing that.
MK Mike K

sorry I assumed (making an ass out of me) that it was a road legal car

you'll want to warm the car fully first but a good few runs might improve things or at least be able to measure consumption and see if it decreases next time
Nigel Atkins

Hey Nigel,no problem
Yes, I think I'm going to try tearing around the industrial park a bit, I usually have to wait for Sat or Sun for that.
I appreciate the suggestions I am getting.
MK Mike K

We used to remove the plugs and pour diesel into the cylinders and leave overnight to free up stuck or gummed up rings. And being short of cash I would drain the sump of oil first. And then let the diesel run out before putting the same engine oil back in again!

Nowadays, there are additives that are sold specifically for unsticking gummed up oil control rings, if that is the problem. Might be worth a try.
Guy Weller

Guy-
Good point. I was thinking last night, might use a carb cleaner substance sprayed in the bores and let soak.

Thing here is, running it will do no harm and cost nothing, unless the rings and pistons are toast already. Then you do the rebuild, but my extensive experience gives much hope of success with the cheap & quick.
If you have a spare car you can transfer plates-ins etc from, just use the Midget for a driver for the summer. Or do you have to meet emissions on this car/location?

Prolonged high speed is not necessary. You need heavy load, on and off, just as in engine break in. This lubricates the rings and bounces them around in the grooves as pressures reverse. So, second/third accel runs are in order, full off throttle to slow down. Combined with the soaking, might work pretty quickly.

Mike- Sorry to hear about the vision, bummer. Might have some suggestions, depending. E mail me if you want.
What is the car like and what is the sales situation?

FRM
FR Millmore

Good idea, I actually put a little Sea Foam in each plug hole while waiting for the oil to drain.
I think you are on the right track with it, hopefully

Yes, sometimes it's frustrating especially in situations like this.
When I am a passenger in one of our cars sometimes I feel lucky not having to deal with the poor quality drivers and utter madness that goes on these days, especially here where I live.

But I do miss driving my cars

I am blessed that I still have enough sight and the ambition to work on them.
I need to use some visual aids and it take me longer but it keeps me going.

Frank, I will mail you some details about the car later.

MK Mike K

Update on the smoking issue
Wow!! What a difference a oil change can make...
New filter, 20/50 oil and a touch of Sea Foam in the cyls and now there is MUCH less smoke and even seems to be leaking a little less. LOL until it starts to thin.
like I said earlier the crankcase was not full of gas but I had not changed the oil since aquireing the car last Sept. So no idea what was in there
I wanted to get all the tuning out of the way first.
Now I'm working on putting some load on the engine.
One of the most drastic changes I've seen after changing oil.
Thanks
MK Mike K

Mike-
Great!!
And a good indicator that the flog it approach will have good consequences.

I once was commissioned to rebuild an MGB engine, on a car stolen/wrecked/recovered. Had to do it in a body shop - horrible. Engine was already out of car and drained. Took it apart to find the cleanest engine insides I ever saw, in perfect condition! Seems that when they ran it off the road, and got stuck in the bushes nose down at a 45, they stalled it and ran, leaving the key ON. Pumped a whole tank of gas into the sump! Dragged out of the weeds, For some reason it then knocked severely on startup, so they shut it off immediately - GOOD IDEA. And the dummies who pulled and drained the engine did not figure out that MGB does not normally hold 8 gallons of extremely thin oil that smells like gas!!!

Will be emailing in a couple days re other matters, got involved in another wild toy chase!

FRM
FR Millmore

Mike,
I always recommend potential and new owners get a copy of the Driver's Handbook and carry out a staged full 36k-mile service and check up

normally an oil change every now and then is what a lot of owners consider as a service so if yours has even had that for a while then possibly a lot of other service items have been neglected and if you complete the full 36k-mile service it might seem like you have got a different and better car
Nigel Atkins

Oh yes. I have been through the 36K service and then some on this one.
As oil is not cheap and I did a complete carb and ignition rebuild and poured some more money into it I was waiting till the end to do the change. Glad I did.
I guess you never know what you are going to get.
My '63 Sprite has a early 1275 I transplanted into it back in 1976, The engine came out of a car I watched rot into the ground for at least 10 yrs before the guy let it go to me. Probably did not run for longer than that.
I removed the head and sump to make sure all was ok, re gasket'd
the engine and fired it up. No smoke at all, in fact still no smoke as of today, i have never done a thing to it besides regular oil changes, tune up and maintenance
Sounds like a little jet engine when I rev it up.
Must be that EN40...
MK Mike K

Mike,
you've got me confused then but that not hard to do

if you do regular oil (and filter) changes then this change shouldn't have made the big difference it does unless your not doing very many miles in the car which would want much more frequent oil and filter changes under severe use (stealing from FRM there)

whilst oil isn't cheap it's not expensive and I'd have thought costs less in USA as a consumer purchase

just realised we've been all through this before

you need to look at time intervals rather than mileage so every 3 years instead of 36k-miles and I'm guessing it's this thread FRM has put 1,000 mile oil changes
Nigel Atkins

ATTN Nigel:
"like I said earlier the crankcase was not full of gas but I had not changed the oil since aquireing the car last Sept."

FRM
FR Millmore

Sorry Mike, FRM, I got this thread confused with another elsewhere

I only clicked back into which thread this was by FRM's last post - apologies to Mike

now I wonder what I posted on the other thread(!?!)
Nigel Atkins

by way of explanation I have computer problems my end and on top of those the cumputer is getting stuck on or loosing the internet every now and then, when it feels like it
Nigel Atkins

Not a problem
MK Mike K

cheers
Nigel Atkins

This thread was discussed between 03/07/2012 and 16/07/2012

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.