31 replies to this topic

[germini30]

Some of you may of seen my post the other week about my mini that will puff smoke if I accelerate hard after cruising. Basically I have been through everything I can think of. It's a 1275cc mg metro engine. Runs fine and will pull with plenty of power. However, if I cruise along and accelerate hard I get a puff of smoke out the exhaust pipe. If I accelerate slowly then I get no smoke. All the plugs are a good colour and the car isn't running rich. Dashpot oil is topped up, oil and filter been changed and timing all set, but its still doing it. Any ideas please.

[nicklouse]

valve stem seals

[cal844]

Valve stem oil seals, you'll need 8. While you have the head stripped check for wear and if unleaded valve seats are fitted.

[germini30]

The valve stem seals are only a few months old and off a mpi mini so the better quality type

[unburntfuelinthemorning]

Worn valve guides that have worn out the new valve stem oil seals quickly.

[germini30]

No blue smoke puffing out of the oil filler cap and I have 155psi compression across the four cylinders. Is it a big job to change valve guides??

[germini30]

Is there a way I can test to see if its definitely the guides without stripping????

[unburntfuelinthemorning]

How come the valve seals are only a few months old?  Was any other work done on the head?

 

If the guides are worn you'll need to have the valve seats recut.  Basically you'll need to overhaul the head.  It'll be worth it though if it needs it.

[unburntfuelinthemorning]

Is there a way I can test to see if its definitely the guides without stripping????

If you fancy taking the manifolds off you may with torch and mirrors be able to see the valves in the ports.  Mine were noticeably covered in oil when the guides were worn although I removed the head to look.

[germini30]

May sell this engine and stick the 998 back in the way I feel

[unburntfuelinthemorning]

I've been looking through some of your previous posts.  Tell me if I'm wrong but it looks like last September you were concerned about oily valves on the MG head and you ended up replacing the head with an unleaded SPi head.  It appears you may still have the same problem with this head but there has been a question too over rich running under certain conditions.  You also did a compression test on the engine and found that the wet and dry compressions were very close - this would indicate that the condition of the rings and cylinders are good.  If this is the case why not have the MG head reconditioned and add hardened valve seats as this should make for a nice engine.  Finally get the fuelling sorted on a rolling road to take care of that side of things.

[russo]

Is it actually using oil on the dipstick?  Do you know if pistons have the standard oil control ring below compression rings as well as the scraper oil ring at the bottom of the piston?  It could even be the oil rings lost their tension.

[unburntfuelinthemorning]

May sell this engine and stick the 998 back in the way I feel

Or, if the 998's a good engine, you could stick that back in and then take your time and rebuild the 1275. 

 

Tha's a nightmare when you just want it sorted and working but don't give up, you often end up with something better than you thought if you work through the difficulties.

[germini30]

Yes that's true. You are correct with the previous posts. Once I fitted the spi head the smoke stopped for a while. I had the spi head skimmed and the guy in the machine shop said that the valve guides had a little play but nothing to worry about. I just want to know for certain that it's the head that is the problem

[germini30]

The thing is that the car also has megajolt fitted. Unfortunately no one down our area can tune it up. Its a very reliable system but I could sell the megajolt system and the mg engine and two heads, the big valve head and spi head as well as a hif 44. I got the chance of a 998 that has only done 33k and drives lovely. The 998 has a hif 38 and stage one kit too. I don't really need the extra power as I don't race the car about. Also I would love to go to a 3.1 diffs as the 3.44 is too low geared for me as when I use the mini it's usually for long distances with the family.