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I made a thread about carb needles which was very helpful but I feel the issue could be bigger then the carbs.

When on its maiden run back home from the mechanics there was a sudden exhaust leak blowing noise. I kept going thinking it was down low and not a major.

The next day I investigated while the exhaust was cool. The leak is actually coming from a burnt hole in the manifold gasket at the center exhaust pipe location.

You can just make it out in the photo but with the naked eye its been burnt out. Its a new gasket from minispares only 20 miles old so I know its not really a gasket issue.

Could my 'bogging down' until 3k revs and this gasket problem be the same problem? Timing?

Just interested who else has suffered similar and what caused their problem.

Thanks Steve

Before you get too technical about the blown gasket, just replace it and check the manifold to make sure it's clamping the gasket properly! this is a fairly common problem after all. And it's not likely to be a symtom of anything else.

minimans wrote: just replace it and check the manifold to make sure it's clamping the gasket properly

My thoughts exactly.

Quite likely as the other guys have said, however, while it's apart, check that the flanges on the exhaust manifold are the same thickness as those on the inlet. I have come across a few in recent years that seem to be cut from metric plate and are a different thickness. I've also had a few sets that the centre branch were not bent quite to the same angle as the outer branches (ie, the faces of the flanges weren't all looking the same way) as so need some manipulation. These were a poplular and well known brand too.

Spider wrote:Quite likely as the other guys have said, however, while it's apart, check that the flanges on the exhaust manifold are the same thickness as those on the inlet. I have come across a few in recent years that seem to be cut from metric plate and are a different thickness. I've also had a few sets that the centre branch were not bent quite to the same angle as the outer branches (ie, the faces of the flanges weren't all looking the same way) as so need some manipulation. These were a poplular and well known brand too.

Me too. As it always happened/became obvious when I was in a rush, I just milled down half a side of the thick manifold washers so the they were all "flush".
Funnily enough when I had more time to assess the problem, I realised that my quick solution was probably the easiest, cheapest and it did the job. This was in 1991 and it hasn't let me down yet.

Thanks for the constructive comments YMJ and Spider. A friend James also suggested similar.

My mechanical knowledge isn't great but you learn through experience. I have not seen this before so needed some reasons why it was happening.

I took the carbs off tonight. Will investigate further next night or two and report my findings.

OK, some updates.

As far as can tell the manifolds were tight against the head. The problem would appear that where the center exhaust port has been quite largely ported there is not enough 'meat' on the gasket now.

I've put a photo below and added a red circle to show the size of the port against the gasket. As you can see the top edge has bugger all gasket. Its even started to go on the bottom but photo does not show it well.

Are larger gaskets available? I don't see them on minispares website. I'll take it to my local mini parts supplier tomorrow but wondered if anyone else has had this problem.

Cheers
Steve

more photos.

Try using a Metro turbo gasket.

http://www.minispares.com/product/Class ... o%20search

Hi Mark

Thanks for the quick reply. I had looked at these and wondered if my port would still managed to bypass the edge of the ring in that gasket. I certainly think it would work alot better than a std gasket though.

Do you have any idea who modified the head?

It looks like the centre exhaust port is simply to large or too low.

The highest spec Competition heads do get close here, but they do seal using a turbo gasket.

I don't know who did the head. A 'expert' checked it over for me and said its been done well and of coarse its been crack tested.

The head is a 940

I'll get a turbo gasket as see how I go. Worth a try.

Cheers

I've swapped over to the Swifttune gaskets now, thicker and with bigger ports.

went to order one and it comes up 33 pounds postage to new zealand. :/

Ouch!

Looking at the tell tale marks on the gasket, your manifold isn't a very good fit. Could be a case of filling the stud cut outs and doweling the head and manifold, so it can be located correctly.

What about this one?

http://www.minispares.com/product/Class ... o%20search

Try Karcraft (in Sydney), be sure to ask to speak to Tim, they have them under P/N LKJ100580EVA. They are in stock and I think you'll be happy with the price.

Ricardo, how did I not see those?

I got a larger gasket from a local supplier today but not sure about it yet. Its quite flimsy with no metal backing. I also ordered one of those metro turbo ones and also have a couple of the ones you show ricardo coming also.

So I will have 3 types to choose from when they arrive.

I dropped my distributor off to a performance specialist today for overhaul and James is helping to give my Carbs a once over.

I don't think the info in Vizzards book saying the no6 needle was the way to go. Its longer for a start. I got 2 H6 Needles which are std for a 1071 and will start from there.

SteveG wrote:I don't think the info in Vizzards book saying the no6 needle was the way to go.
Its longer for a start. I got 2 H6 Needles which are std for a 1071 and will start from there.

Attached is a sample from the Basic tab of the "Needles" spreadsheet...
It details a few of the likely suspects, here. The total length will not
be relevant as only the first 9 index points will only ever get used.

The carb is 1&1/4", 9 index points is 1&1/8", don't forget that the
"bridge" area is a venturi and will be smaller than the stated size.

The graph shows the index points along the bottom, and the exposed
area along the y axis. Units are square thou. This allows it to validly
compare needles from from different sized jets on a like-for-like basis
on the same graph.

Points 10 onwards will never see the light of day and will not affect
the metering so you can ignore them.

The H6 needle is listed as the "Rich" needle for a bog standard
Morris Minor 1098 with a single HS2... It's quite lean! At index
point 9, H6 is only showing 79% of the exposed area compared
with the No6 needle at the same point.

Ian