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MG MGB GT V8 Factory Originals Technical - Cylinder Head Overhaul
I am currently overhauling the top end on my V8 and I want to know what thread sealants I should be using. The work shop manual say's to use 3M EC776 on the cylinder head bolts but the product spec. for this compound states that it is a Fuel Resistant Coating and not a Thread Lubricant Sealant - what should I use?
Also, should I use Wellseal gasket compunf on the cylinder head or just assemble it dry, as stated in the workshop manual.
My thanhs to anyone who can provide me with any assistance.
You need to get hold of the latest(?) info by buying the Haynes Manual for the Range Rover-(look in the supplement in the back).
The 3M EC776 has now been superseded by Loctite 572 which is basically an anerobic PTFE paste normally used for pipe threads etc.
Depends what head gaskets you are using?
|Why do you need a thread sealant? Do the head bolts go into the water jacket?|
Thanks for the info on the thread sealant
In answer to your question I am using a standard cylinder head gasket as supplied by Moss Europe who also supplied me with the Wellseal gasket compound. When I stripped the heads off I did notice signs on both the block & heads that a gasket compound had been used previously.
In answer to your question the bolts are Carbon Steel which are bolted into an alloy block and could corrode due to the meatals being different. The Carbon Steel could also cause stress corrosion cracking in the Alloy
Thanks for your help
|I used Fel-Pro Grey Bolt Prep, along with Fel-Pro Permatorque head gaskets. The Grey Bolt Prep is purported to act as both an anaerobic threadlocker and an anti-seize compound. These seem mutually exclusive, but I've seen stranger materials.|
I'll let you know how it holds up in about 10 years, the next time I need to open up the engine!
|Ah, OK now i'm with you. I was a bit comfused when you said sealant. The ARP head studs that I used came with a molybendium based lubricant. The instructions said to use a sealant only when the bolt holes go into the water jacket (hence the previous question) The lubricant was more to ensure accurate bolt torque than for anti-sieze. I also use a FelPro nickel based anti-sieze compound. It is rated for 2000 degrees F. I can get a model # if you want. |
|I have used Wellseal to good effect on the steel shim head gaskets for some time. This taken from direct experience in some 320bhp plus 3.9 race engine experience in the early 1990's.|
Interested to hear about this 'Wellseal'stuff.. I'm currently putting together a 4.6 with skimmed SD1 heads (measures about 33cc) and the tin gaskets ( I've calculated that I'll end up with a CR of about 9.6). The deck of the 4.6 block that I've got could be a little better than it is so any advice on a good sealant and how & where you applied it would be most welcome.
|I have used steel shim gaskets on the later engines which originally came with the composite gaskets. I have used a smear of Wellseal both sides as this seems to help on the higher stressed V8s. Also the lack of the outer row of 4 short head bolts helps keep an even torque load on the head and so you are less likely to suffer the combustion gas leakage into the Vee through lift on the inside edges of the heads.|
The use of the steel gaskets will increase the compression slightly, unless you use the earlier heads which have a slightly different chamber volume. Here I have not calculated the fdifference as it clearly is not an issue for the engines I have worked with.
I have looked at the issue of the inlet manifold fit to the heads as by dropping the ehads slightly because of the thinner gaskets the separation of the heads inlet faces is reduced. This means the inlet manifold will have to sit that little bit higher and so the risk is for the ports not to match up as well which can be detrimental to power and economy. So far I have not found this to be a problem, but it might on some engines.
The issue of improved head efficiency through modifications and slightly increased compression ratios does lead to a very useful improvement in fuel efficiency. This being available more of the time that the extra power.
This thread was discussed between 26/11/2000 and 13/12/2000
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