100-4 Cylinder Head Leaks

by Norman Nock

Originally published in the Austin-Healey Magazine, Vol. 23-1


Does your Austin-Healey 100-4 leak oil or coolant at the location of the engine number tag between #2 and #3 cylinder?


This is a problem that has been around since the first BN-1 and maybe even before that. Maybe is more studs had been fitted, the problem would not be with us today.


But it is here, and over the years people have developed their own pet fixes for the problem. Here’s how we stop oil and coolant leaks at this location. We have used this technique for many years and it has always worked for us.


First, make sure that the top of the block and cylinder head are very flat and smooth. Next, coat the top of the engine block with Super “300” 83D Permatex where the head gasket makes contact. Install the head gasket.


Coat the cylinder head with Super 300 83D Permatex where the head makes contact with the gasket. Lower cylinder head onto the block, fit NEW head nuts to avoid the older head nuts stripping, and torque as per the diagram in service manual in increments of 20 foot pounds to 80foot pounds.


When repairs have been completed to not start engine for at least 36 hours to give the Super 300time to dry hard.


Do Not Re-Torque


Use a cooling system sealer like Pioneer #T612. We use Irontite T610 ceramic motor seal. Follow instruction on the product.


When you start the engine some bubbles will come from the head gasket but will dry up within a few miles.


If you are still plagued with a leak from the head gasket, you have done all you can do.


Do Not Re-Torque!


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