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MG MGB Technical - Head gasket: jointing compound

It's time to change the head gasket on my MGB. I haven't done this for ten years or so. Last time I added a smear of Hylomar along the edge of the gasket closest to the distributor. It worked well and there was no leak there.

Should I do this this time too? Has there been any change in the gaskets in the last decade that makes this unnecessary?

Mike
Mike Standring

Mike, use a Payen black composite gasket. It already has a sealer built into the head gasket. They're considered the best head gaskets on the market, for a B series engine, and their cost is quite reasonable. Accept no substitutes. I've been running one on my supercharged engine for over ten years with no problems. Chamfering the first thread in the the block will improve how the gasket seals. These often get pulled up, over time, and prevent the head from sealing properly. If you have any doubts about your head studs, replace them with ARP units. These are the strongest ones on the market and are used by every performance engine builder. RAY
rjm RAY

Mike-
I have to agree with Ray's recommendations. Chamfer the threaded holes for the cylinder head studs and use a Payen black composite gasket. I've been using them on every engine I've built for the last fifteen years and never had one leak yet! Since el crapo Chinese items seem to have flooded the market, the ARP cylinder head studs are also a good idea.
Stephen Strange

Mike, why do you want to change the HG?
c cummins

Unless youve got a jet engine ARP are a waste of money. New std studs are perfectly capable of holding down fast road and big block engines. Save the money and put in the gas tank insead, youll have more fun for it :)
JS Ahlund

Ignore scaremongering about age and heat cycles, as long as they are not badly corroded and the threads are not damaged then old standard studs are also more than capable of holding down fast road engine heads and are less likely to break than some of the new ones on offer!

Chris at Octarine Services

I had started getting a coating of mayonnaise on the radiator filler cap. I had been driving in heavy traffic in hot weather so I suspected the head gasket was on its way out.

So now the engine is in pieces, head on the bench and the other parts in a big box. The gasket looks OK with no particular signs of impending doom but it was a small dose of gunge. I have bought a decent gasket from the most trustworthy parts supplier in this neck of the woods. It is the black Payen gasket.

The old studs will be reused. Last time I changed the gasket, I bought special studs, two of which promptly broke. I chucked the lot and used the old ones again. Sorry to say, I can't remember what type they were.

Mike
Mike Standring

I had trouble with ARP studs on the 1275. I tried three different gaskets, including the Payen. There were persistent oil leaks from the high pressure galley to the outside of the engine.

I installed the original studs, torqued them correctly and all is well.
Glenn Mallory

If I were getting mayonnaise at the oil filler cap, I would suspect that the tappet cover wasn't vented properly.

warmly,
dave
Dave Braun

yes or possibly lots of short journeys too

plus (if fitted) the chrome oil filler caps don't vent as well as the black plastic vented and filtered ones, you could clean it or for £4 (from MGOC Spares, £10 from some other places as I found out too late) you could just put a new plastic one on
Nigel Atkins

Sorry, it was the RADIATOR filler cap. I had been driving in baking hot weather with heavy traffic, there was a coating of mayonnaise under the cap. I wanted to catch it before the gasket went in a big way. The oil looks perfectly normal.

If it had been the tappet cover, I too would have considered driving short journeys in cold weather. My usual journey is a 7 mile commute to work or back and the weather has been anything but chilly!
Mike Standring

oh yes, you did put it was the rad cap before, sorry I was distracted, I blame Dave :D

I'd also do a thorough clean of the cooling system, cleaner followed by flush/backflush/flush of the rad, engine and heater matrix with a scrape out of crud with a bit of wire from the engine drain hole on the flushes

I'd try and extend that 7 mile journey especially on the way home as it's (perhaps) a bit short to get everything running and charge back into the battery especially in the winter
Nigel Atkins

Chrome oil filler caps don't vent at all, as they were used with the non-positive crankcase ventilation system, and there was just one tube from the rocker cover going into an air-cleaner and another hanging down the side of the engine from the front tappet chest cover. Which way any ventilation went, if there was any at all, was a matter of conjecture.
Paul Hunt

I also wonder on other engines where owners have adapted the breather systems whether the vents vent or draw air in
Nigel Atkins

Usually because the seal round the filler cap is not that flash and allows the air in there.
Paul Walbran

This thread was discussed between 23/08/2013 and 30/08/2013

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