oil leak

[ozzies]

well I have finally got the 1275 ital engine in and running.It is performing superbly,except for a rear engine leak,quite severe.Worse when running.

presumably it is the oil seal gone or excessive crankcase pressure.

where's the breather for the crankcase and can you change the seal just dropping the gearbox,removing clutch and flywheel?

Is there a way of checking either or with everything in situ,

thanks

Ian

spridget gearbox
1275
mg 1300 head
fast road cam
hs44 carb
maniflow manifold and exhaust
midget rear diff

[bmcecosse]

There is no rear seal - it'a a simple labyrinth scroll which works to keep the oil within. As you have correctly diagnosed - there will be excessive crankcase pressure - pushing the oil past the scroll. This gets worse if the main bearings are worn - allowing excessive oil to spray out in that area! Check is - hot engine at idle - take the filler cap off and rev up - is there a plume of smoke/fume ? If it's bad - then rings/pistons/rebore etc. However - breathing is vital - and the only breather provided as standard is the one on the timing case cover - this MUST be connected to the carb inlet to allow the engine to draw away (and burn) the fumes. If you can find an older style rocker cover with a breather connection - this too is well worth having - and should also be connected to the carb inlet. Sounds a good engine spec - what 'fast road cam' is fitted ?

[Kevin]

Also make sure you have the correct type of filler cap to suit the engine.

[ozzies]

bmecosse,

thanks yet again for your prompt and excellent advice.

the drip is severe after a run so does a pipe going to carb inlet do all that much as far as suction.

I say this as the breather is left open at the moment no pipe and checking there does not seem to be much airflow coming out,or am I expecting too much?

ihave also checked oil filler cap and nothing out of there.engine sounds really quiet and smooth.A alloy rocker box cover with no breather is fitted with soft plastic cap,should that have a little breather hole in it?

I bought the engine already modified and not sure of cam make.I think it is Piper or is there a firm called Kent . one or t'other

Ian

[mike.perry]

On a 1275 engine to avoid rear oil seal leaks the crankcase must be operated at a negative pressure, in other words the air must be physically sucked out of the crankcase. Just letting it vent to the atmosphere is not sufficient. My carbs are not fitted with breather pipes so I had to use a breather control valve which does the same job but draws the air into the manifold<br><br><br><br>

[bmcecosse]

On ALL engines it is beneficial to keep the crankcase under suction - so YES - connect that breather to the carb inlet. It should help to eliminate the oil leak.

[mike.perry]

The difference between the 1098 and 1275 engines is that there is very little clearance passed the push rods on the 1275. This can be seen when filling with oil, the 1098 rocker box drains a lot faster. Similarly the crankcase pressure cannot escape into the rocker box as quickly on the 1275 and needs to be sucked out by the carb.

[bmcecosse]

As pointed out elsewhere - there is NO difference in the push rod clerance!