67 Wolseley MkI 18/85

I think it is of more than academic interest to try and identify the reason for the high oil consumption as its root cause could lie in the ancillaries that may find their way onto the replacement engine.

It should be fairly easy to identify where the oil was being burned by observation and taking measurements of wear, but requires further forensic work to determine the underlying cause(s) I think is important given the relatively low mileage. Tommy’s experience proved this can be difficult if nothing is immediately obvious.

My understanding is that high oil consumption may be down to inadequate honing of the cylinder walls, wear in the bores and valve guides, build-up of crankcase pressure, damage to piston rings, oil leaks etc and any combination of these factors that are often inter-related. Poor quality components are also a possibility.

If the bores were properly honed then it should still be evident, if absent then this needs to be considered as a possible root cause.

Assuming that a good quality oil and filter was used and changed regularly which I think goes without saying I think the piston rings could provide an important clue. I assume also that the engines in Chris’ and Tommy’s cars have not overheated as a result of loss of water or head gasket failure that can quickly damage the piston rings.

In the case of Chris’ car he has twin non-standard HIF SU carbs but I believe (but am not sure) the camshaft was not changed to the hotter MGB profile that requires a significantly different (retarded) ignition timing profile. The ignition requirements probably fall between the MGB and Crab. If the distributor and its vacuum advance mechanism was not matched to the twin carb fuelling it could have led to pre-ignition shocks sufficient to damage the piston rings possibly only at certain RPM and load.

The twin carbs on Chris’ car I believe ran needles of similar profile to the MGB if I recall correctly. These could have delivered a weak mixture at certain speed and load even though they were set and balanced correctly at idle. Alternatively and maybe more likely they may have delivered too much fuel and washed the oil from the bores with the milder cam.

One area that can easily be overlooked on engine wear is the crankcase breathing. Premature engine wear can result from something as simple as a blocked filter in the oil filler cap. The crankcase venting and oil mist lubrication system is designed to operate under a low vacuum. This is achieved by drawing the crankcase fumes through a filter in the tappet chest cover and then into the manifold via the PCV (or into the carb constant depression area on Mk111 engines and HIF carbs). The appropriate volume of air is drawn in to purge the crankcase through the restriction and filter in the oil filler cap.

Insufficient air may be drawn through a blocked filter in the oil filler cap, a blocked filter in the tappet chest cover or worse not drawn in at all if a non-vented cap is fitted by mistake. This creates greater negative pressure in the crankcase where the crankcase ventilation is to the carb venturi. The increase in vacuum may draw oil mist into the inlet manifold increasing oil consumption and also interfere with the proper lubrication of the cam and valve gear. Where a PCV is fitted this causes the valve to close, the engine run richer and prevent the extraction of damaging combustion products.

If too much air is drawn in through an oil filler cap where the filter has corroded away, this weakens the air fuel mixture with potential consequential damage. This is more of an issue on cars with the crankcase vented to the carb.  

A PCV diaphragm may deteriorate so that the valve remains open. This leads to too much vacuum in the crankcase, drawing the oil mist into the inlet manifold (consuming oil) and weakening the mixture which can lead to overheating and ring damage.

On cars without a PCV (Mk111 & Chris’ car with HIF carbs) the mixture can also be weakened by leaks in the pipe from the tappet side cover or the cover to block and reduce the crankcase vacuum.

Other areas such as fuel pump pressure should ideally be checked, but they would most likely have shown symptoms.

Clearly, some of these checks are straight forward such as ensuring the filter in the tappet side cover and oil filler cap are clear. However, making sure the mixture and ignition timing are matched to an engine that has twin carbs fitted requires careful analysis of the wear patterns to see whether any of the components indicate a possible issue with mixture or timing - we are into the unknown!

David

As Chris wrote, we are putting it in as is.

Main question, apart from basic design and circlip, is there any difference between the differential gear.
If not then things should just be fine.

I'll check and report back.

I measured where the groove was on a Princess shaft and did a test with a spare 1800 shaft, just marking up and making a groove with a hacksaw and file:-) It was a success. It locked onto the circlip with a light tap.

I believe I've still got the Princess shaft as well as my "prototype". The important thing is not to get the groove too far into the shaft, so it will foul the casing. Indeed, sliding joint driveshafts have to be used. Also, you'll have to change the oil seals.

Tommy

Yes:-) Outer diameter the same, 1800 has smaller inner diameter than Princess. I think the dimension is pretty standard. At least I got them off the shelf from a local seal supplier.

Tommy

Great. Found and ordered new seals. Will put them in the box with the Hobnobs and the tea bags when they turn up.

Chris.

Yes, I can confirm that the original fine has been paid. However, due to the late payment interest and administrative fees need to be applied. 
Also. Item 3 of the original order has not been fulfilled. 
As such, parts may still be available. 


Unfortunately no no progress to report this weekend. Gordon has man flue which has stopped work.