1275cc Oil Leak help!

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super trimbo
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1275cc Oil Leak help!

Post by super trimbo »

My 1275 engine has started p#ssing oil from the back of the engine all of a sudden. It runs strong, compression test was normnal, and the obligatory breather pipe from the front of the engine to carb is in place.

It's using over a litre of oil per 100 miles, and the underside is covered in it. I assume its the oil thrower, can anyone shed any light on how to fix this ?

Cheers

Tris

P.s - It's a midget engine on a 5 speed ford box[frame]Image[/frame]

bmcecosse
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Re: 1275cc Oil Leak help!

Post by bmcecosse »

Crankcase pressure and worn main bearings allowing excessive oil to flood over the scroll are the cause. No easy answer - other than double check that the breather pipe is clear. One pipe is not enough - a rocker cover with breather connection from an earlier engine will help...... To check for pressure - hot engine idling, remove the oil filler cap and rev up. Is there a plume of smoke/fume?? Do you have an oil pressure gauge? If so - what pressure at 50 mph in top gear with hot engine ?
Just to check - are you SURE it's leaking from the scroll - and not just leaking from the rear sump 'half moon' seal ?
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super trimbo
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Re: 1275cc Oil Leak help!

Post by super trimbo »

bmcecosse - Thanks for that.

Going to get her up on the ramps tomorrow and have a proper look where the oil is coming from. Oil pressure reads 40 on tickover (warm) and circa 60 when in 5th gear at 50mph...

More to follow.

bmcecosse
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Re: 1275cc Oil Leak help!

Post by bmcecosse »

Oil pressure sounds ok - it's crankcase pressure from piston ring blow-by that pushes oil out of the scroll. But maybe it's just the sump seal that's leaking?
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ColinChandler
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Re: 1275cc Oil Leak help!

Post by ColinChandler »

Hi all,
Sorry to hijack the original thread but I read with interest the bit that bmc suggested adding a second breather to these engines ie one from the rocker cover too. Is it a simple "teeing" together of the two pipes (rocker cover and timing chain cover) and connecting them to the carb? Also, what about the rocker cover oil filler cap. I think the one on my 1275 midget engine is ventilated(?) so should that be changed too?
Many thanks, Colin.
bmcecosse
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Re: 1275cc Oil Leak help!

Post by bmcecosse »

The ventilated cap was intended for the 'closed circuit' breathing system that BMC had going for a while - it worked very well to eliminate fumes. So - if you can smell fumes/see oily mess around the cap - change it!
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ColinChandler
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Re: 1275cc Oil Leak help!

Post by ColinChandler »

Thanks for the reply.
Cheers, Colin.
minor_hickup
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Re: 1275cc Oil Leak help!

Post by minor_hickup »

If it's a 1275 it should have closed circuit breathing. The canister in the timing cover should be connected to the take off on the carb or to the inlet manifold via a PCV valve. The canisters usually get blocked up, its worth cutting it open, clearing it out and re welding it. If the closed circuit breathing has been left off the engine will need to vent through at least two good breathers.
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