MG B eating manifold gaskets
Discussion
Hi folks,
I've got a tuned up MG B which seems to have a fondness for blowing the exhaust / inlet manifold gaske - that's the fourth time in just over a year. I've even started using a mix of instant gasket and brand new gaskets as they're so cheap, but it's only lasting a 100 miles tops before it starts blowing again.
It's got a peter burgess stage 2 head on it and a peco LCB exhaust manifold with standard SUs, pushing out 122bhp on the rolling road. As the works Bs must have been pushing out more than this, I'm assuming it's not a common issue.
Anyone got any advice? Is there a performance gasket kit? Does a weber sit on the same manifold, or would it be worthwhile looking at that as an option?
I've got a tuned up MG B which seems to have a fondness for blowing the exhaust / inlet manifold gaske - that's the fourth time in just over a year. I've even started using a mix of instant gasket and brand new gaskets as they're so cheap, but it's only lasting a 100 miles tops before it starts blowing again.
It's got a peter burgess stage 2 head on it and a peco LCB exhaust manifold with standard SUs, pushing out 122bhp on the rolling road. As the works Bs must have been pushing out more than this, I'm assuming it's not a common issue.
Anyone got any advice? Is there a performance gasket kit? Does a weber sit on the same manifold, or would it be worthwhile looking at that as an option?
Sounds very strange. I have an LCB manifold and SUs on a ported head, and I have not ever had a problem. Where are you getting your gaskets? I would not use "instant gasket" on the exhaust though. Have you removed the manifold and run a file over the joining surface to make sure it's flat?
Edited by dryden on Thursday 6th October 21:29
Just got the gaskets through normal suppliers - haven't used club / b hive / moss ones in particular. Will have a look at the manifold again - it's an old one and it's possible it's just corroded enough to make it difficult to get a proper seal. Just really annoying having the two manifolds on one gasket - as soon as you get the exhaust one torqued up properly, you have to put the inlet one on the same gasket.
dryden said:
I think it is one of those jobs you have to not just fix, but remove the manifold, and the carbs, clean up both surfaces, get a quality gasket from the sources you mentioned and stick it all back together, should be worth it!
This. I've never had a problem with B's gaskets. However, the trick is to always use high quality gaskets. Have used these many times, they've never failed. Also, check your studs and brass nuts too. If in doubt replace with new as they're peanuts to buy.https://www.ukmgparts.com/product/mgb-midcat-11-mg...
do they blow in the same place each time? (I'm guessing its around the the rear exhaust port?)
Apart from checking the mating faces I would also loosen the exhaust clamp at the bell housing (if fitted). This will allow the manifold to find its best natural position as you tighten the nuts. If the clamp is not there you should fit one as it helps keep the manifold "tied" to the engine movements and thereby transfer any movement in to the exhaust further under the car. If the engine is moving a lot you might want to look at the mountings to see if they have gone a bit soft.
A bit radical this one.... disconnect the exhaust from the manifold before fitting and check if there is any misalignment between the two in the rest position. Anything more than 10mm or so should be investigated as pulling them to fit just adds stress somewhere which will cause problems later (although to be fair a standard cast manifold would be able to handle much more misalignment).
Apart from checking the mating faces I would also loosen the exhaust clamp at the bell housing (if fitted). This will allow the manifold to find its best natural position as you tighten the nuts. If the clamp is not there you should fit one as it helps keep the manifold "tied" to the engine movements and thereby transfer any movement in to the exhaust further under the car. If the engine is moving a lot you might want to look at the mountings to see if they have gone a bit soft.
A bit radical this one.... disconnect the exhaust from the manifold before fitting and check if there is any misalignment between the two in the rest position. Anything more than 10mm or so should be investigated as pulling them to fit just adds stress somewhere which will cause problems later (although to be fair a standard cast manifold would be able to handle much more misalignment).
Edited by Geordie MGmike on Sunday 9th October 20:00
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