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1500 Intake/Exhaust Gasket - Siamese Ports?

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dklawson

dklawson

Yoda
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A while back I bought a couple of intake/exhaust manifold gaskets. I didn't get around to using one until today after putting the 1500 in our project Spit.

I had not noticed until now that the gaskets are different than the one I removed. The old gasket had one opening for each port, 8 total. These new gaskets have a Siamesed, large rectangular common opening for the exhaust ports for #2 & #3. Why would they do that? I know that it will be cheaper to do it that way, but, is this going to cause me problems with my header? Will there be any kind of weird scavenging that will leak exhaust between #2 and #3's exhaust ports?

Thanks in advance for your thoughts.
 
Doug,

Have you tried checking with any of the vendors on this like SpitBits? Where did the new gaskets come from?

Scott
 
I'm looking at a question like that on my 76 spit engine rebuild.
One gasket i have is the paper/carbrd type, the other gasket looks like it has aluminum pressed on to it. Both the same size. Is there a preference or issue with using either one?
Thanks Tom
 
Thanks all. I posted this question at the NASS group also and have some additional information.

In answer to the questions and comments above (in no particular order), the gaskets I have came from BP Northwest. I am not saying they sold me anything wrong... but the picture of the gasket on their web site shows all 8 ports, not the type I received with Siamesed exhaust ports.

As mentioned above, the Siamesed port version of the gasket appears to be a Euro spec item. Some exploded diagrams imply that the cast iron exhaust manifold uses a Siamesed exhaust collector for cylinders 2 & 3. So I can see this doesn't matter for a cast iron manifold of that type. However, I have a header and the thought behind tuned headers is that exhaust gasses all travel an equal (relatively close anyway) distance before reaching the collectors. IF this gasket will seal against my header (I have to look, I'm not even sure it will) it seems that this gasket design change could work less effectively.

The gaskets I have are the laminated type with thin metal skins sandwiching the traditional high-temperature fiber material between. I've been told that the laminated construction is "heavy duty" and less likely to blow out between ports. That makes it kind of an ironic choice of materials for the gaskets I have where there is a complete wall missing between cylinders 2 & 3 exhaust ports.
 
Give them a call. I've always found the people at BPNW to be very knowledgeable and helpful when I've talked to them on the phone. I believe the owner used to race Spits.
 
I've got my reply from BP Northwest.

The answer is... don't use gasket JB765 (which I bought) with headers.

They say to use JB765HD with headers.

There is quite a difference in price between the two.
JB765 = $2.71/ea
JB765HD = $15.44/ea
I'm going to assume that the HD version has the material between the exhaust ports for #2 & #3.

EDIT:
I've also called Spitbits. Their recommendation is for gasket AJM648 which is their "heavy duty" exhaust gasket. Googling I found that PDF exploded drawings at Canley Classics show this gasket has the right profile. Color pictures at Rimmer Bros show it has the right profile and is metal clad. I ordered two.
 
The gasket that comes in a Payen set has the gasket between the middle exhaust ports. I put a UK 1500 spec exhaust manifold on my Spitfire this spring and the gasket I was sent did not have this middle gasket material. Given that the exhaust manifold has a common middle exhaust port there is no need for the middle material in the gasket.

The exhaust manifold gasket with no gasket between the middle exhaust ports is GEG581 and was used on UK spec 1500 cars. The gasket between the middle exhaust ports is GEG648 and was used on Canada and US 1500s
 
Mark Jones said:
The gasket between the middle exhaust ports is GEG648 and was used on Canada and US 1500s
Click to expand...

That is one of the two gaskets that Spitbits sells. The other gasket, AJM648, is considered the "heavy-duty" version of that one.
 
Do you by chance have 1500 MGA intakes by mistake(not yours of course)to some parts guys MG ,Triumph,Austin, its all the same if its a 1500......I have seen it before.
MD(mad dog)
 
No, no mistakes. There really are at least four different possible intake/exhaust manifold gaskets for the Triumph 1300/1500. The sources for the information collected above (by me and others) are all reputable, well informed suppliers. Thanks for the suggestion though.
 
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