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MG MGB Technical - Tips for head reinstallation

Just got my head back from the machine shop. The said other than a mildly burnt valve. Head was in good condition. No cracks, surface was flat. While the head was off, I removed the carbon on the pistons and cleaned the block. Water passages are all pretty clean. All head bolts came out easily.

Have a Payen gasket set and head studs/nuts from Chris in the UK.

In previous posts it was recommended to assure the stud holes were cleaned out.

Any other good things I should do?
Bruce-C

Bruce you can check the deck and taper-sink the stud holes to guard against thread pull. Did they do a pressure check? Good time to paint the head.Ric
RIC LLOYD

Bruce-
Prior to lowering the head onto the engine block, follow the aircraft mechanic's practice of wrapping the threads of the head studs with tape in order to protect them from damage.
Steve S.

Studs screwed right in but only finger tight.
Denis4

In order to insure against antifreeze from weeping at the
head-block joint near the heater valve, I smear a very thin film
of Hylomar on the head gasket (both sides) around every water
passage that is on the starboard side of the engine.
Daniel Wong

Thanks all.

Ric. Can you describe the process for taper sinking the stud holes?

Steve. Super Idea. Another I will add to my "what I learned today" List.

Daniel's topic is one that I would appreciate input on. I actually have a bottle of copper head gasket varnish. I know in the past, it was recommended to coat the top of the block and head with varnish. It was a common practice. Using the Payen gasket, is it still recommended? If so, do you do both sides or just one. Have not done that on the TD and I have not had any issues using copper gaskets.
Bruce-C

Don't tape the centre stud on the plug side - it is a very tight fit in the head as it serves to locate the head fore & aft.

In fact, because of the clearance in the other holes you would be hard pressed to damage the threads anyway!
Chris at Octarine Services

With the Payen gasket you really shouldn't need any additional sealant on the gasket as it is already coated with it from the factory. RAY
RAY

Thanks Chris

What are your recommendations on installing the head gasket. Do you use any other sealant? Also, if the block itself was not refaced, do you taper-sink the stud holes?
Bruce-C

No - the threads are counter bored to remove the top couple of threads as standard, it should not be necessary to do anything else if the deck is original.

No other sealant is necessary - a little Wellseal can be used on the water way metal rings if you are really concerned about water leaks.
Chris at Octarine Services

Isn't the Payen composite i.e. very different to the original copper? I've always been led to believe these need a very special and particular installation procedure if they are not to leak again in a short time, like it did on a friend's midget the first time he had it done.
Paul Hunt

When I did my first startup with my Payen gasket, I noticed the slightest weeping at the edge of the gasket until the engine warmed up, and it has been dry ever since (hope I'm not jinxing it by saying that!). My understanding is that the Payen gasket has a coating that melts as the engine warms for the first time, then bonds to the block and the head when it reaches full temperature. I installed it without any added sealant.
That coating plus the extra material around the water holes is supposedly what makes the Payen gasket a higher quality product.
Erick Vesterback

That's why I asked. My understanding is the first run of the engine must be done dry, to quite warm, with the head and block surfaces having been totally degreased, so the coating can bond. Must then be allowed to fully cool, retorque, fill with coolant but not fit radiator cap, run uo to temperature. Allow to cool, retorque, reset valve clearances, fit radiator cap, and away you go.
Paul Hunt

Paul-
The resin softens when it gets hot and makes a better seal. These gaskets seal by heat-bonding to the mating surfaces of the cylinder head and the engine block. If the mating surfaces are not scrupulously clean, or if you allow the coolant to pressurize before the bonding has fully taken place, then the resin-impregnated gasket will not bond properly to the mating surfaces and subsequent leaks will be more likely. Consequently, you should run the engine without any coolant in it until the engine gets hot so that a good bond can be achieved. While doing so, the V-belt that drives the coolant pump should be removed so that the seal of the coolant pump will not be damaged by its shaft running against it without the benefit of the lubricants contained in the coolant.
Steve S.

That's what I said! (apart from removing the drive belt)
Paul Hunt

So what then is advised on an engine rebuild when you are first running in a new cam? Still no coolant?
Frank
Frank

Frank-
Running-in a new camshaft takes longer than it takes to seal the new head gasket. Just let the engine idle until it gets hot. Once the head gasket is properly sealed, let the engine cool off, and retorque the head. Do not completely loosen the nuts during retorquing. Instead, just back them off enough to get them moving, otherwise you will be measuring the torque to break the stiction between the nut and the stud rather than the torque that results in the necessary stretching of the stud. Note that a cast iron cylinder head should be retorqued while the engine is hot, while an aluminum alloy cylinder head should be retorqued when it is cold. At that point you can then start the running-in procedure for the new camshaft and tappets.
Steve S.

FWIW as one experience with the Payen type of gasket.

When I installed a Payen gasket on my 69 I took all the cleanliness precautions mentioned above. However I did the first run with water, not dry, nor with
antifreeze (because of the slip factor), and changed that out for a coolant mix after 500 ks.

I didn't retorque the head but used antiseize as a thread lubricant (stable to 600C) in case I had been required to do so. To date, three years, there have been no signs of any leaking (touching wood and bowing to Mecca as I type that).

I used the Payen after unsuccessfully installing a conventional metal/asbestos gasket, but that failure was in all probability due to a clumsy retorque I did do on that installation.

I would certainly use a Payen again. When all is said and done, the thorough surface cleaning required with them is no less than should be done irrespective of the type of gasket used.

Regards
Roger
Roger T

This is a little concerning since the gasket kit comes with no specific instructions. Head was surfaced and clean, block was cleaned. I did use a small amount of shellac around the water holes as there was small pitted circles at these points. These are not the areas on the gasket that have the rubberize material on it.

So now I need to consider if I take it off or ?. Chris, could you give details on how you fit these gaskets?
Bruce-C

I fit them dry and torque up once. I only recommend retorquing after 500 miles.

I would not advise running the engine without coolant!

The resin of the gasket deforms under pressure and moulds to the block & head surfaces, it does not bond with them.

The ideal surface finish for head & block is clean and rough - flycut or circular ground, not surface ground and smooth.

From the Payen website -

"These gaskets do not require head bolt retightening, are surface-coated for microsealing and provide a clean release. For performance and consistency in a flexible, cost-effective sealing solution, choose Payen."
Chris at Octarine Services

Thanks Chris

You use them and sell them. That works for me.
Bruce-C

Hi Gang- Here is the story-tell, one more time, of the famous west coast MGB Guru Lawrie Alexander. He is credited with the famous quote that ".... 95% of all MG SU carburettor woes are electrical ones".
I'd rate Lawrie, Calif., on the schmarts and dedication level of the venerable John Twist in Mich. He published a "tip" on head gasket install I've used on every changeout since reading it and watching him do it in 1998. He built my 1977 MGB engine then, and it has performed without hickup for 11 years ( this one has the P285, Peter's FRBV head, and showed a 10.3 second 0-60 with the NEW 1 3/4 SU from Burlen)
Lawrie twists together 2@ 8-10 inch long strands from a length of common 18 gauge electrical twisted copper wire. He thinly coats the outside edge of water jacket side of the Payean gasket with blue hitemp silicone, and torques down. He does ( although Payean no longer recommends it I am told) retorgue cold after about 500 miles. The sealant Payean uses around the water holes and the "dam" Lawrie applies has worked so well for me in those 10 years: not one single head gasket failure. No weeping, even in between cyl. 3-4. A free treat just by clicking his Cameron Park, California, website!
Chris/Steve/Cameron/Ray/Paul/Dennis- Any of you have an elegant explain why between 3-4, problems blossom on the MGB 1800? Cheers Vic
vem myers

Vem,

I have never used the copper wire "trick" on any of my MGB engines and none have leaked water on any side. I have had the occasional gasket leak issues on the A series engines but a quick retorque has fixed those without disassembly.

I could see the wire & silicone working for the copper/steel composite gaskets, but I would think the Payen, with its extra orange resin along the troublesome side, would not need the extra help.

I abhor silicone sealants and won't let any in the workshop, let alone an engine!!

Again, I have never noticed any weakness in the area between 3 & 4 for leaks.

However the thin head gasket bridge between 3 & 4 cylinders is the favourite for a head gasket blow - I put this down to the fact that 4 runs hotter than the others and is also favourite for piston failure.

Chris at Octarine Services

My theory as to why the gaskets tend to leak between 3 and 2 is the siamese setup of the exhaust valves, causing a hotter than normal area and early failure. RAY
RAY

"I abhor silicone sealants and won't let any in the workshop, let alone an engine!!"

Ditto. I changed the head gasket on a Midget 1500 and the carbs, spacers, heat shield and so on had all been assembled with silicone. When I dismantled I found the silicone had oozed inside and was reducing the throat by 1/4" or more, let alone what bits had gone through the valves.
Paul Hunt

hI pAUL- LONGTIME AMIG..... Just to be clear, the schmear of the hyplar is near invisible and should be so thin, the torgue squeeze down should not produce any oozing as the film thickness applied should be no thicker than onion skin. Rgerads, Vic

PS_ Paul, how is that big bad EDIS SC Moss screw cranking nowadays? Any updates pard? Vic
vem myers

Paul,

Reminds me of a guy who brought along an overdrive unit and watched me while I rebuilt it for him.

A few weeks later he was back and said the OD didn't work - so I pulled the engine & gearbox and the OD unit - he had fitted it with so much silicone (or should that be silly - cone?) that all the oilways & filters were clogged with it.

Cost him an exchange rebuilt unit and the labour to fit!!
Chris at Octarine Services

"should be so thin, the torgue squeeze down should not produce any oozing"

I only use Hermetite Red and just a smear wiped on with pressure from a finger-tip so it is almost translucent, and that still oozes a little.
Paul Hunt

I still question the use of any sealant on Payen composite gaskets - surely it will compromise the surface coating ( that slightly tacky feeling ) doing its job?

A little Wellseal ( a thinish fluid) round the waterway metal rings is all the extra insurance against leaks I would recommend and I don't use that except on race engines.
Chris at Octarine Services

I've not used anything on composite, Wellseal on steel shim. Couldn't call my Wellseal 'thinnish', more like honey in both colour and texture i.e. sticky.
Paul Hunt

This thread was discussed between 19/02/2009 and 13/03/2009

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