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 - Turbo question

Hi guys, Ive not been on for a while (what with moving house and a baby on the way, the old midget has taken a bit of a rest),but its good to be back!
Anyway....

You may or may not recall my oil leak woes.... quick recap..
Frontline 5 speed box
Rear oil seal on crank.
All breathers clear and operational
mech fuel pump breather vent,to sealed catch tank then to carb. (as is the front breather)
single 3/4 hif
oil leak.... not a lot but enough to annoy, and a considerable amount more than i used to have when first fitted rear seal.
New seal is on, and fitted as I did before but now with oil leak. Only difference this time round is the single carb rather than the twin.
It may be possible its my sump gasket , but im not 100% convinced until i get a better look, i really really dont want to pull my engine again, especially after pulling it 3 times previous due to clutch, then oil leaks!!
so any ideas? (also got an advisory on the MOT for the leak!! dont they know old cars leak?)
Now we come to the turbo part... I aim to turbo charge my little midget, (have most of the parts ready to go on etc) My question is this...if i cant cure the leak, and its just a case of living with it, will the turbo conversion make matters worse or by some strange fluke is it possible the turbo set up may actually control it?
Yours fingers crossed...
Ian
i coxon

if the breathers go to the carb/inlet manifold then under boost you will be pressurising the sump/front cover etc which is not good. Either plug the carb and route breathers to a ctahc tank racecar-style or fit a non-return valve in the breathers just before they meet the carb.
David Smith

Ian,

I've run a rear crank seal on my 1330 without problem. I would suggest the only way to track the leak is to clean all the old off and watch for the new. We find that the air draft in the engine bay can distribute the oil around the outside of the engine, so don't assume it's coming from where you first suspect.

Ref vent systems we (Ford Powertrain) use a tapping just upstream of the compressor, to pull the gases through the vent system. We typically run some sort of oil/gas separator, and a PCV valve to limit the crank case depression. However for an ultimate power set up (i.e. competition) I would run the vent into a catch tank, as the gases going into the compressor effectively offset power 'producing fresh' air going in.

Regards, J
James Eastwood

Thanks guys for getting back to me so fast.

At the moment I havent set up the turbo yet, but in terms of the breathers when I do fit the turbo, I have the 3 way valve that the metro turbo uses, and the one way non return valve that is tapped into the inlet manifold to stop the turbo pressurising the manifold under boost. If i remember correctly from the haynes manual, the front breather (timing case) goes to 3 way valve, a pipe goes from this valve to the non return valve on the inlet manifold, and the remaining side of the 3 way valve has a breather to the air inlet/ filter pipe to the intake on the turbo. As the manifold pressure rises the non return valve closes and the 3 way valve diverts the crancase vent direct into the air intake pipe. (I think!)

As for where the oil is coming from...well i know for sure it drips out off the bell housing drain, but mainly collects and drips from the endplate/bellhousing joint, and from the sump plug.
Im just hoping i disturbed the sump gasket when i had the engine out last. (and of course if easy to change with the engine in situ)
But with the correct breather set up for the turbo, would it make an already present oil leak worse?

Ian
i coxon

Have you done a leak down test?
Verify the valves and rings are sealing properly.
If not, this WILL cause a significant amount of crancase pressure.

Also, I did a leak test on my Sprite prior to the turbo upgrade, which checked out great. (Hardly any leakage). But I still have an excessive amount of crankcase pressure. I believe this is due to the valve seals. The seals in a stock 1275 head are little more than O-rings (from what Ive been told). Which is why this winter Ill be having the head ported and the seals updated/ upgraded.
David Barrett

This thread was discussed on 27/08/2008

MG Midget and Sprite Technical index

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