MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

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 MGB Technical - Bad valves or rings or both?

On my '79 "B" I'm getting oil blowing out my tappet cover and filler stick as well as no noticeable suction at my oil filler opening when an index card is placed over the hole while running. I did a compression test and got roughly
Cylnder Dry PSI after adding oil PSI
1 110 113
2 100 105
3 95 99
4 45 45

I then adjusted the valves to 0.013" (very little adjustment needed) and verified head torque (found two bolts quite under-torqued) thinking that I wasn't seeing significant change with the oil. Results were about the same with some readings increasing by maybe 2-3 PSI. Cylinder 4 went from 45 to 50. Seems like I need a valve job but not sure why this would increase the base pressure causing the oil to blow out. I'll perform a Leak down test next but would appreciate ideas. Original engine I think, engine # 18V883AEL... Probably never rebuilt and has ~ 105kmiles
Thanks
Tom Gillett

Without a doubt badly worn or broken piston rings, and probably worn bores. valves are also in need of attention. Sorry Tom but I reckon a full engine rebuild is needed.
jim soutar

X2. RAY
rjm RAY

Funny, that's what everyone has been telling me. Guess it's time to move on to finding another engine or rebuilding this one. Thanks all,
Tom
Tom Gillett

Tom. your valve settings at 0.013 seems a little tight. You may have "burned" a valve or two, looking at your compression numbers. Much has been discussed about valve settings. I set mine at 0.18 cold due to a cam change and to not risk a valve burn. Yes a bit "clackety" but that's MG.

Few questions:

How many miles on the engine?

After re-torquing the head, did you test compression again?

How is the oil consumption?

Perhaps you need to re-do the head only. Pull it off then inspect the cylinder walls for wear. You just may be lucky.

Cheers

Gary
79 MGB
gary hansen

Removal of head will tell you a lot. State of valves and seats, state of head gasket, any blow-by, warp of head, state of bores. Rotating the engine will also give any indication of broken rings (scoring) although ~I have never seen one yet!
Allan Reeling

This thread was discussed between 28/12/2015 and 29/12/2015

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now