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MG MGB Technical - Tappet chest gasket

I need fit a new tappet gasket on my bgt 1978 model, it looks straight forward ie one bolt to remove to release the ccver. fit the rubber gasket and replace. Are there likely to be any snags I need to look out for. Thanks for your help
si robathan

That about covers it, they can leak (which you may well know hence replacement), the original cork gaskets are best sealed with something like Hermetite red, rubber gaskets are supposed to be better. Make sure the gasket is properly seated, it may be beneficial to stick the gasket to the cover before fitting, especially if your carb or exhaust are in place.
Paul Hunt 2010

Another ideal application for the simple contact adhesive. Glue the cork gasket to the cover using contact adhesive. The assembly becomes reusable and user friendly. Remember to let the contact adhesive dry before bonding – that’s why it called “contact adhesive”.
Richard.
RH Davidson

Si-
An oil separator that works on the turbulence principle is incorporated into the design of the front cover of the tappet chest. The mesh inside of the oil separator is designed to catch the oil mist in the air that travels from the crankcase to the carburetors. If it is in good condition, then the oil returns to the sump in liquid form and only air & fumes go into the carbs. On the other hand, if the oil separator is choked with carbon deposits, then the oil travels up the mesh because of the reduced availability of air passages as well as at a faster air speed. Consequently, gravity does not get a chance to return the condensed oil to the sump. Due to the fact that the effectiveness of the system is dependent upon vacuum, all connections between the fuel tank, the vapor separator, the adsorption canister, the rocker arm cover and its oil filler cap, the dipstick, the distributor, as well as between the oil separator and the fuel induction system, must be well sealed in order to maintain the optimum state of vacuum. Soak it in solvent and get it clean so that it can do its job properly. When installing the gaskets onto the covers of the tappet chest, remember that the rubber O-rings on the bolts tend to take a set when left in place, so always replace them with new ones in order to obtain an effective seal.

If you use cork gaskets, coat them with a thin skim coat of Permatex Ultra Black RTV Gasket Maker. This is possibly the best silicone sealant on the market, able to withstand temperatures of up to 500 degrees Fahrenheit (260 degrees Celsius). Be sure to let the gasket cure for several hours before attempting to trim away any excess material using either an Exacto knife or a single edge razor blade or before installing it. This will result in a rubberized gasket that will not become saturated with oil and consequently ooze drippings onto your garage floor.

Use either Permatex Ultra Black RTV Gasket Maker, Permatex Aviation Form-A-Gasket sealant, or Loctite Hi-Tac to glue the gaskets to the covers and then allow it to harden overnight so that they will not move during installation. The 5/16”-24 UNF nut for the shallow rear cover of the tappet chest should be torqued to 2 Ft-lbs, while the 5/16”-24 UNF nut for the deeper front cover of the tappet chest should be torqued to 5 Ft-lbs. Exceeding these torque values may result in distortion of the tappet chest covers, as well as crushing of the gaskets, leakage being the result.

For those who seek a more advanced gasket material than antiquated cork, there are two choices: Nitrile and Silicone Rubber. Nitrile Rubber has excellent oil and chemical resistance, but its various compounds have upper temperature limits of only 200 degrees Fahrenheit (93.3 degrees Celsius). This is just too close to the operating temperatures of most engines, plus it tends to harden and crack with age. The gaskets of the tappet chest covers are constantly exposed to the radiant hear of the exhaust manifold, which gets them hotter still. Silicone rubber offers a better choice. Silicone rubber has a temperature limit of 450 degrees Fahrenheit (232.2 degrees Celsius), and rebounds to nearly its original shape even after years of installation. Such gaskets resist hardening and cracking from hot engine operation, as well as from cold winter storage. Best of all, silicone rubber is highly resistant to becoming saturated with oil and moisture, or drying out. These are available from Roadster Gaskets (Roadster Gaskets Part # BMC B-VC-PRC). They have a website at http://www.roadstergaskets.com/index.html .
Stephen Strange

I think I'd avoid using contact adhesive anywhere in the engine bay - the manufacturer's specs show that most standard contact adhesives are only good for up to 60 deg C. There are some more expensive contact adhesives available in the UK which are specifically described as 'High Temperature' or 'Very High Temperature' available (usually sold in 1 litre tins) - manufacturers of these quote temperatures up to 160 deg C.
As Paul mentions, Hermetite is good for gasket sealing.
Brian Shaw

Those silicone gaskets look nice, Steve! I'm getting tired of cork rocker cover gaskets getting saturated and leaking. I'm going to get a quote from the local gasket shop tomorrow for a silicone rocker cover gasket of the same dimensions as the cork one - hopefully it'll work out a bit cheaper than importing from the link above (although if it doesn't, that's a great service from those guys).

As I have the aluminium rocker cover, what might you recommend using to stick the silicone gasket to the cover (or the engine block) to keep it in place prior to lowering the rocker cover?
Curtis Walker

With reference to my question above: obviously something that will allow the gasket to be cleaned and reused!
Curtis Walker

Thanks for all the help so far. It was a struggle to say the least to release the tappet cover, I tried with carbs intact but with lack of any clear vision of the holding bolt I removed the carbs to gain access which was still very limited as the exhaust manifold interferred with the withdrawal of the centre securing boltbut I managed to withdraw the bolt by working round the exhaust down-pipes.
Having removed the cover I found that the rubber gasket does not fit as well as I would like, in fact it does not even appear to be the right size! I phoned the supplier who is despatching me two cork gaskets(FOC) and am awaiting these. I will keep you posted.
si robathan

Si, I had the same problem with the rubber gasket and could no get a good seal, in the end I gave up and went for a cork gasket. I tried gasket cement and heating the gasket in hot water to make it more pliable, but had no luck. Cork gaskets are not easy to get a good seal, but they are easier!
Mike

Having just ordered two sets of the silicone gaskets from Steve's link above, I hope they fit properly!!
Curtis Walker

I don't think the 60 degree limit of contact adhesive is an issue as it isn't holding anything in place long-term, just until the cover is bolted up, then it is under compression. It may be more of a pain to remove (the old adhesive that is) next time, though.
Paul Hunt 2010

With contact adhesive the 60 degree is not an issue under compression. After having reached engine temp and cooled down a couple of times, country to belief, the gasket can be removed and surfaces cleaned easier then if silicone or hermitite where used. Naturally it doesn’t stick to an oil contaminated surface. You don’t have to be brave to try it.

Richard.
RH Davidson

Referring back to my note of 8th, the two gaskets arrived, both cork, one thicker and the same dimensions as the rubber gasket, and a slightly larger but thinner one which did actually fit perfectly. With the help of a Hermatite euqivalent the cover re-fitted, no sign of any oil leak so far.
So job well done, thanks for all your help
si robathan

Good to hear you got it sorted Si, thanks for the update.
Mike

I've got the silicone gaskets from 'Roadster Gaskets' (great, fast, cheap service to NZ, by the way).

They look great - here's hoping they work as good as they look. In particular, I'm hoping the side cover gasket fits, since I have an 18V...if not, no big deal.

To answer my own question above, Roadster Gaskets recommends sticking the gasket to either the valve cover or cylinder head surface by coating one surface with Permatex Ultra 'Copper' RTV and curing for 24 hours.

The Ultra Copper which is the same as their Ultra Black, except it has a slightly higher temperature rating at the expense of oil resistance. I'm sure the black will do, since the valve cover won't get to 260 degrees celsius (let alone 371).
Curtis Walker

Are Roadster Gaskets still trading? connected to site when first posted but can't connect now!

Pat
P M Gregory

I bought gaskets from them just last week, so I suspect their website's just gone down.

Here's their email address to try: roadstergaskets@yahoo.com

And some other contact details:
30 McDonald Road,
Wilmington, MA. 01887
(978) 658-9798
Curtis Walker

Just a quick one on this, I replaced my gasket with a new cork type from a UK MGB specialist. It was a bit tight around the lip of the cover, but I thought it had sealed ok! After a long run (yes the same one, see elsewhere) the oil pressure was dropping badly, on checking there was little oil left, most of it having come out from the bottom of the seal. When I removed the cover, the gasket hadn't sealed along the base. I bought another from another UK MGB specialist, and this fitted the cover perfectly, and looks to have sealed around the whole edge. I assume that there are two sizes of these, so beware when purchasing, also don't fit and hope, get the correct one first off!
P M Gregory

I've had the same size mismatch on cork gaskets for rocker covers, both 4-cylinder and V8, so it's more likely a case of crap quality than two sizes.
Paul Hunt 2010

This thread was discussed between 03/06/2010 and 28/06/2010

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