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 MGA - MGA smokes when idle

Hi, I've recently noticed that if I sit in traffic for a while, I get blue smoke from the exhaust. When I accelerate there is none and also when starting from cold it is also clean.
Is this a breather problem or is it something more serious

regards
D J Joy

DJ - a couple of questions:
1. What is your oil pressure while idling?
2. Any smoke on deceleration?

- Ken
KR Doris

Worn valve guides will suck oil into the combustion chamber while idling, making for a little blue smoke from the tail pipe. It also sucks oil when you take foot of off throttle for shifting, and will produce a puff of blue smoke when you put your foot back on the throttle. Worn piston rings can do the same, but would likely be accompanied by low compression, so do a compression check first.
Barney Gaylord

If the compression is o.k., you can cure the problem using umbrella seals, which will stop the oil from running down into the exhaust valves....Relatively easy to install. (without pulling the head)...This assumes that your guides are either slightly worn, or your old seals are worn out or damaged (which they probably are).
I believe there is a discussion, if you do a search.
Edward
Edward Wesson 52TD

Hi Thanks for the replies, there is no noticeable smoke when I deaccelerate or shift , the oil pressure is pretty constant at 65 lbs / sq in when idling.

The engine was rebuilt 3000 miles ago but I have noticed oil in the venturi of the carb when I stripped it recently.

Would you recommend a compression test ?
D J Joy

A compression test doesn't hurt, but since you rebuilt the engine so recently, it probably won't show anything.
Neither would a leak-down test, as your problem is most likely above the top of the head, not below it...
You can put the new umbrella seals in in a day or so....
A choice of using compressed air , to hold the valves in place, or using the "rope trick", at TDC..(i.e. stuffing a clean soft rope into the cylinder , through the spark plug hole)....I seem to remember a John Twist video , where he does this with an MG.
While the valve is held up by air or rope, you release the valve spring retainers (using a valve-spring compressor), lift off the spring and retainer washers and clips, slide the umbrella seal on down on the lubed valve stem, and press it over the guide, then put the parts back, while re-compressing the spring....
I did this on two "B's"...I don't know if the stems are the same size, but on "B's" the umbrella seals for a small-block Chevrolet were a perfect fit. They have a snap-on clip on the base of the seal, that holds it onto the guide, and a nylon insert that the stem goes through.
After you do one, the others will go much faster.
Edward
Edward Wesson 52TD

DJ
Take 5 minutes and watch this video....This is a Chevy engine, but the principles are exactly the same....
The intake seal he uses, is the type that I am talking about.
Edward

http://www.youtube.com/watch?v=OsGqmOQus6Y
Edward Wesson 52TD

I would still do a compresion test to see if your rings have seated ,which they should of after 3000 miles. If compression is low then a leak down test can determine where your losing compression. Do you know if new valve guides were installed? They weren't on my "rebuilt engine" ended up redoing the head using the umbrella type seals Fel Pro number SS70373, I have read sealed power ST2001 will also work. Chuck
Charles O'Brien

This thread was discussed between 07/05/2013 and 15/05/2013

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.