Moss Motors, Ltd

After spending five years restoring a 1966 solid axle TR4A which sat for 20 years, it is on the road.  However, it is a short road!  After slowly bringing the motor back to life, it appears to have good compression and oil pressure.  The big problem is oil leaking from the cylinder head.  I have isolated it to where the pushrod tubes go into the lower portion of the head.  

I am looking for some insight on how to make this leak go away.  I know full well it will entail getting the head to a machine shop and I know Moss stocks replacement pushrod tubes.  The problem is that I find no reference in the Bentley Manual on the process for installing, and more importantly sealing, these tubes into the head.

Any insight would be GREATLY appreciated. Thanks in advance. 

Dan

Interesting 

Are all the tube bottoms, where they go back into the head, oily?  Wash and wipe them all and re run the engine to see where it is leaking.

The push rod tubes are aluminium and are 'swaged' into countersinks machined in the head top and bottom faces.

To re-tighten in the top face (where the oil is probably dripping down from)  remove the rocker gear and push rods, ensure all is thoroughly clean and using a conical ended piece of steel that is a bigger diameter than the tube. (about 1 " diam)  Squarely tap it onto each tube with a hammer. This effectively swages the tube outwards and re-makes the contact seal with the cylinder head.

I have had to do this on a TR head recently and used a No 3 morse taper fixed centre from the lathe as the swage tool - This has a 60 degree included angle cone point and fitted just right.

To re-swage the lower end of the push rod tubes the head must be removed. - In honesty I doubt the oil to be running 'up hill'  and out of the head.

However before you do that be sure of the following:-

Check the rocker cover gasket is good before you do anything else.  There was a batch around that 'shrunk' end to end after being fitted for a while.

Take the cover off and offer the gasket up to it. 

I would glue the replacement gasket to the cover before refitting - that makes sure it will not move when the cover is refitted. Do not forget the fibre washers on under the attachment nuts

OR

Is the PCV, mushroom shaped thing connected by rubber tubes to the manifold/rocker cover, working OK. Strip it and clean it and be sure the spring, plunger plate and diaphragm are OK. They do get very gummed up with breathed engine oil over time- spares are available.

You can bypass the PCV.

If you do you must then block up the tube going into the manifold - push a ball bearing or marble in the hose. Then either run a long hose from the rocker cover down into the air stream under the car or into a catch tank over. You could also connect it to the air cleaners like the TR4 had.

REMEMBER - The engine must have some sort of breather tube or oil will P... s out when the crankcase pressure rises.  

This removal may affect smog checks if the tester knows what a TR should have.

Hope this is of use.

Cheers

Peter W

Peter,

You were spot on regarding the linkage to the PCV valve.  Sealed the pushrod tubes externally with a light application of JB Weld.  Checked the PCV and it appears to be incomplete and cannibalized. Internally the valve has a set of four prongs that appear to guide a small pin which rests on the one way valve in the lower portion of the valve.  In the servicable (upper) portion of the assembly I have only the pin, a spring and diaphragm (which I have replaced).  In that configuration, when the engine is running there is no suction to the valve cover as the small pin blocks the valve.  I removed the pin and readjusted the carbs to compensate for the additional airflow into the manifold, and all runs well and the motor no longer leaks. However, I instinctively feel this is still not right as there is a constant vacuum pull on the valve cover outlet now.

Do you have a picture or know of a detailed schematic that shows all servicable parts of the valve?  TIA.

Regards,

Dan 

Sorry for the delay in replying, I have been on holiday.

The PCV (positive crankcase ventilation valve) is supposed to allow air to be sucked from the valve cover and engine crankcase into the inlet manifolds when the engine is running.

Parts for the PCV are limited and there were different 'types' to choose from.

The OE part number supplied now is 13H5191 - this is a help as it points you to the fact it is an Austin/Morris/Mini part number, therefore also an MG/Austin Healey item. (it also was fitted to Land Rover and Freight Rover in the UK) The MG item is interchangeable as an assy. A whole item is devilishly expensive at GB £40.00 !!!

The diaphragm rubber is offered as a spare part but no more than that -   Diaphragm Part No 27H7758. More reasonably priced at under a fiver.

The spring, and plunger are now not serviced as far as I can work out. 

I still favour ditching the valve and plugging the manifold.

Route the breather hose from the valve cover into the atmospheric side of the carb air cleaner. ala TR4

Better still - With a long hose, down into the airstream under the car. - You will not be sucking oily air into the engine combustion chambers then.

Cheers

Peter W

The insight is much appreciated.  I did manage to locate the inner workings of the stock valve.  Replaced part of the stock workings with a somewhat upgraded (higher tension) spring and now all seems well.  The valve now remains open and working under a larger range of vacuum loads and all appears well.  All that remains now is to get the speedo back to working order.

Thanks again,

Dan