[Mgb-v8] Exhaust manifold gaskets

[Paul Hunt]

A number of suppliers in the UK at least (try Google), but you need to be 
very careful in what you actually buy.

I've come across four types in my time and used three of them.  Originally 
they were single, thick, metal-faced sandwich gaskets, which have quite a 
good ability to cope with the flanges not being flush with or parallel to 
the head by a small amount.  They do put the manifold closer to the inner 
wing than the others though. The next were thinner, green and black 
composition and were useless. Not only didn't they compress much, but with 
the very small overlaps between flange and head blew a piece out on the 
first decent run. The third type come in pairs i.e. one gasket covers two 
exhaust ports and whilst they are a metal sandwich again they are quite thin 
(Clive Wheatley http://mgv8.homestead.com/gtex.html).  The fourth type I've 
seen but not tried and they have a ripple-effect on the sealing faces which 
is said to give an improved seal, but I think they may only be thin shim 
i.e. very thin.  These are in the MGOC mag but I can't find them on their 
web site.

The problem with the V8 manifold is two-fold - first is that most of the 
tubular types seem to have a mis-match in the alignment of the ports which 
significantly reduces the amount of overlap in some areas, and causes port 
obstruction in others.  The second is that they warp in use, which results 
in the four ports being offset by various amounts, the inner pair touching 
the head but the outer pair not, as well as all the flanges being at an 
angle to the head instead of parallel.  As well as resulting in a very poor 
seal and high failure rate of the gaskets you can't even get the bolts 
through the flanges into the head without overdrilling and filing them out. 
Added to that the holes in the gaskets are quite a bit bigger than the 
manifold pipes and particularly the head ports, which reduces overlap even 
more.

I've had my manifolds on and off because of blown gaskets more times than I 
care to remember, the drivers side of which needs the rack to be removed, 
but so far the way I have it now has lasted the longest.  I welded struts 
between the flanges to hold them apart and stop them turning inwards, which 
keeps the bolt holes aligned as well as the faces parallel.  I tried to find 
an engineering company that could skim the flanges so that all four would 
touch the head but no-one could come up with a way of holding the pipes 
securely enough.  I settled for spending some time on a belt-sander, which 
improved things, but the outer two were still not quite touching.  That I 
resolved by delaminating an old gasket and using a shim from that on each of 
the outer flanges to even things up.  Full story at 
http://www.mgb-stuff.org.uk/wn_engineframe.htm and click on 'V8 Exhaust 
manifolds'.

I think some manifolds now come with the flanges in pairs (RV8 style?) which 
would help, but ideally you need all the flanges in a single strip of steel. 
I did see some blanks like this at Clive Wheatley and he said it wasn't 
until he had those cut to the same dimensions as the original assemblies, 
and offered one up to a head, that he realised just how poor the port 
alignment was.  I'm not sure if he got more recut to the correct alignment 
and made up with pipes or not.

PaulH.

----- Original Message ----- 

> Can anyone tell me the brand and part number for my Rover 3.5L V8 exhaust 
> manifold gaskets.  Looked in archives but could find nothing.