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MG Midget and Sprite Technical - wonders of proper crankcase ventilation :-)

Hi chaps
Got to share some happiness.
Finished a 1000 hour rebuild of a speedwell midget before xmas.
Includes a hif44 single carb setup.
Anyhow, all went well with getting it all running until I started driving and everywhere I went seagulls started getting trapped in the oil slick I was leaving behind. Leak was from the jiggle pin under the gearbox. Anyhow lots of thoughts of pulling the engine ( which frankly made me shudder. Lots of fresh paint to chip)
Today I solved it :-) Pipe from vent on timing chain cover to the correct take off on the hif44 and not a single drip.
WOO WOO!

Tim
T Dafforn

Nooooooooo!
Not another 500 post on how to stop the carb sucking oil out the sump.
Fortunately Lawrence is away
Graeme Williams

I consider this thread to be an example of mans inhumanity to man! Ha ha ha! :-)
Steven Devine

TBH I reckon Lawrence runs his car upside down which is why the oil falls out ....
Chris at Octarine Services

I was part of one of those mega threads.
In my case at the time the problem was incorrectly fitted oil rings.
Thought it was worth posting success for Lawrence's benefit. I think the vacuum output of the hif44 was deemed as rather modest but seems to work. I tried the vacuum from the manifold with pcv but didn't work probably because the pcv wasn't behaving.
Tim
T Dafforn

And so it begins.....Mega thread return to claim more poor souls!

http://www.youtube.com/watch?v=0me7iwBqSu8
Steven Devine

well done Tim, I think the >>Pipe from vent on timing chain cover to the correct take off on the hif44<< might be a clue to your success

I'm sure some hints and help to this conclusion were given in some thread(s) on here but whether it was in the mega-thread who can remember :)
Nigel Atkins

Yes.
Hadn't connected the hif44 vacuum vent as the seemed to be some discussion about the level of vacuum. However I reasoned that the important thing may be capacity for flow. Given the newness of the engine I have a reasonable amount of blowby. So I thought that I needed vacuum with reasonable flow and that has to be what you have at the carb before the jet. After the jet eg at the manifold the flow is the same but you can't drag so much flow from the crankcase as you upset the mixture.
So thought it was a good idea but had to wait to get the adapter for the carb vacuum pipe.
Cheers
Tim
T Dafforn

Well done tim, an accomplishment like that sure makes you feel that you grew 3 extra inches of chest hair over night...:-)

Now lets talk about your wheel bearings...

DOH !!!

Prop

Prop and the Blackhole Midget

Wheel bearings? Apparently someone in the Phillipines reported nos in stock.
Graeme Williams

I guess these two subjects will be forever tied together....Wheel bearings and crankcase ventilation!

ROFL...:-)
Steven Devine

Perhaps deny has then inside track on this as well

Rofl

Prop
Prop and the Blackhole Midget

My engine runs upside-down almost all the time and nothing bad happens. It's when I turn it over that everything goes wrong.
Growler

That will be because when it is upside down the oil drains away from the breather in the front of the timing chain cover😊
T Dafforn

Perhaps we need an aircraft engine breather system - after all they run OK whatever way up they are.....
Chris at Octarine Services

I guess the only solution to Lawrence's breather problem may be a dry sump system.
Cheers
Tim
T Dafforn

Well thought all was lovely, but went for a longer run and plumes of oil smoke out the exhaust after about 3 miles...
have transfered to the mega-thread on crankcase breathing..
Think I am going to move the breather from the timing chain case to the fuel pump blanking plate or rocker cover.
Cheers
Tim
T Dafforn

Tim - keep it simple! No need to modify existing breather, just add a 1 litre catch tank with extra breather pipes from both rocker box and fuel pump blanking plate. Almost all race cars run this way with no problems.
David Smith

This thread was discussed between 08/03/2014 and 17/03/2014

MG Midget and Sprite Technical index

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