Head Gasket blown - exhaust to oil.

[Oakwellian]

Hi all,

Just discovered the cause of my oil leak when she is running. Leaking along the distributor side on the head gasket. Also fumes from dipstick pipe. If I'm right, it must be blowing across from exhaust to oil side. No water in the oil or vice versa. She is a 1974 Model with a 312388 head casting number  (Car number CR/6459-O.)

My question is when I've got the head off and replacing the gasket is it worth changing the valves and springs etc, Rimmer's do a head rebuild kit?

Anyone got any experience of it, is it worth the money? Not sure when the head was last off.

 

thanks ,

Ian

 

[Waldi]

Ian,

Small correction: the blow-by is from pistons/rings or valve guides, not the exhaust.

a leaking head gasket on the distributor shaft is not rare. It is related to the low gasket seating stress (“gasket hold down pressure”) on that side of the block.

If you want to know what is causing the casing pressure (IF it is indeed high), you can do a dry and then wet compression test to access engine condition. The wet test (a bit of oil on the pistons that acts as an additional seal) will tell you if the leakage if from the pistons or the valves.

If you have the head off and remove the valves (note their positions), you can check valve guide clearance. Refer to the WSM.

But if compression test provides good and even readings, probably ok.

Plane the head before installing the new gasket. There are 2 types by the way.

I would not install new valves/springs when not needed, and certainly not install “uprated” springs.

Regards,

Waldi

[Nigel Triumph]

In my experience, the valves are unlikely to need replacing unless the engine is very high mileage (well over 100k) or has been thrashed/poorly maintained. With a couple of engines, I've taken the cylinder head to a machine shop who has fitted hardened exhaust valve seats for unleaded, refaced the valves and recut the seats. He also sleeves worn valve guides with bronze inserts rather than replacing the guides. If you have had a head gasket failure, check the head is perfectly flat - it will likely be a few thou out and need a skim.

When you reassemble, make certain you use the correct head gasket, your CR series engine should have a recessed block. I've found Triumph 6 pot motors prone to leaking oil from the distributor side of the head gasket. Using a thin coating of Wellseal along this edge of the gasket and around the rocker oil feed drilling helps, although conventional wisdom is not to use any sealant on a head gasket.

Nigel