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Discussion Starter #1
Hello everyone,

This is my first post here. I've been reading and have learned so much from this forum. The amount of information and knowledgable and enthusiastic people here is staggering.
Now on to my question:
I'm working on my '73 Opel GT and have the chance to purchase a Cannon manifold. I've been trying to look all over the net for model numbers and images of Cannon manifolds that will work on the GT but was not able to find anything. The owner sent me a picture of the manifold which I am attaching here. It doesn't seem to be the correct one of the GT to me, but just wanted to get your knowledgable opinion.
Also do any of you know the correct Cannon manifold model number for dual weber dcoe carbs for the GT? Anyone know where I can get one and roughly the price range?
Thank you all for your help.
Igor

 

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Those intakes will NOT work, but, since you're putting them on a GT, you'll have to lose your heater box area. If you wish to retain your heater, then you need to look for the "shorty" versions of these intakes, which are about 1/2 the length.

The ones in this picture are not Cannons, but the length is correct, so it'll give you an idea.

 

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Discussion Starter #3
Hi BQS4,

Thanks for you quick answer. So it doesn't matter that the intake on the GT are square and the ones on the Cannon manifold are round? I plan to remove the heater box so the length is not an issue.
If you confirm these will indeed work I'll get them.
Thanks again,
Igor
 

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Hi BQS4,

Thanks for you quick answer. So it doesn't matter that the intake on the GT are square and the ones on the Cannon manifold are round?
That's actually a good question, now I've never actually seen a Cannon manifold, I ran MISAB intakes back in the day, but those intakes don't look quite right for a CIH engine or maybe it's just the angle.

What I mean is, part from the round intake vs square port, they don't seem to have the surface where the bolts attaching them to the head on a normal CIH would clamp on to (not sure I'm making much sense here, it's times like these I really notice that English isn't my first language as I can't quite seem to find the terms I'm looking for)
 

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Living in the past
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Cannon Manifolds

That's actually a good question, now I've never actually seen a Cannon manifold, I ran MISAB intakes back in the day, but those intakes don't look quite right for a CIH engine or maybe it's just the angle.

What I mean is, part from the round intake vs square port, they don't seem to have the surface where the bolts attaching them to the head on a normal CIH would clamp on to (not sure I'm making much sense here, it's times like these I really notice that English isn't my first language as I can't quite seem to find the terms I'm looking for)
Those manifold that are in the picture are not for a CIH Engine therefore they will not work on your GT. If you are going to get rid of the heater box to make room for manifolds and carburetors then there are several that work much better than Cannon, my questions are (1) are you going to modify the engine (bigger cam, valves, higher compression pistons and so on and (2) if you just want to put dual sidedraft on carburetors because they look good then I guess it doesn't matter what manifolds you use because it is going to run like crap no matter what you got. So I guess what I'm trying to say is find the cheapest ones you can and bolt them on as they will be for display only.
 

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Discussion Starter #6
Hi opelnut10,

Thanks for your answer. Yes I do plan to modify the engine as well. Which manifolds do you recommend? Where can I get them from? Do you have a rough idea of the price range?
Thanks.
Igor
 

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Opelnut
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short manifolds for gt

believe opel gt source still may carry the short manifolds for the gt. call them for current price
 

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Discussion Starter #8 (Edited by Moderator)
Aren't longer manifolds better for low end torque?

I've been reading many posts regarding the manifolds and I seem to understand that short manifolds are good for top speed but longer manifolds are much better for low-end torque, which is what I am most interested in that's why I was looking into the cannon manifolds. Are there other manufacturers that make long manifolds for the GT?
I've been searching for this info for the past few days but am not really able to find much. Any suggestion is much appreciated.
Thank you.
Igor
 

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There aren't many companies making the sidedraft intakes anymore at all. Mostly European companies, since there's no real market for them in the US anymore (these cars are getting old).

The long Cannons work really well when they are welded and ported. They do not fit easily in a GT due to the limited underhood space. Yes, a longer intake runner is better for torque, but you fit what you can fit! To fit the Cannons you generally have to cut out the heater box area.

Probably the best GT-specific intakes were the Irmscher short intakes. Once in a while they show up on ebay, but they haven't been made for some time. They are far shorter, they flow rather well...but they are a PITA to install due to space limitations. Bolt access is really bad.

They also require a special thermostat housing to fit, the OEM one does not clear the Irmscher intakes.
 

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English is just fine . . .

Hi BQS4,

Thanks for you quick answer. So it doesn't matter that the intake on the GT are square and the ones on the Cannon manifold are round? I plan to remove the heater box so the length is not an issue.
If you confirm these will indeed work I'll get them.
Thanks again,
Igor
That's actually a good question, now I've never actually seen a Cannon manifold, I ran MISAB intakes back in the day, but those intakes don't look quite right for a CIH engine or maybe it's just the angle.

What I mean is, part from the round intake vs square port, they don't seem to have the surface where the bolts attaching them to the head on a normal CIH would clamp on to (not sure I'm making much sense here, it's times like these I really notice that English isn't my first language as I can't quite seem to find the terms I'm looking for)
. . . and, yes it does matter and both are correct in what you saw, manifold head flanges are completely wrong and will not bolt up to CIH head. Various 4-cylinder CIH aftermarket intake manifolds were manufactured back in the day, mostly SSD or DSD types, but were always somewhat scarce due to low demand, especially on this side of the pond.

Looking for CIH 'performance' stuff now typically becomes a very long-term endeavor because of that and, more often than not, results in looking 'off-shore' for any hope of results. It took almost eight years to find all the bits and pieces for my 'sprint' Kadett!
 

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Some pics to clarify the differences between the short Irmschers and the longer Cannon intakes.





Here's the special lower thermostat housing for the shorty Irmscher intakes. Note it pushes the upper thermostat housing forward a bit.



 

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Discussion Starter #12 (Edited)
Hi RallyBob,

Thank you for your detailed reply. I am really leaning towards the Cannon manifolds, with the necessary modifications to make them flow and fit correctly. Obviously the one pictured above is not the correct one for the GT. Do you know the model number of the Cannons for the Opel GT? And, maybe, where to get one?
Thanks again.
Igor

*EDIT* OK, I just read the other posts and saw the pictures. Thanks. Above I was answering RallyBobs first answer. I seem to read the Cannon manifolds are 9938. Is that correct?
 

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Hi RallyBob,

Thank you for your detailed reply. I am really leaning towards the Cannon manifolds, with the necessary modifications to make them flow and fit correctly. Obviously the one pictured above is not the correct one for the GT. Do you know the model number of the Cannons for the Opel GT? And, maybe, where to get one?
Thanks again.
Igor

*EDIT* OK, I just read the other posts and saw the pictures. Thanks. Above I was answering RallyBobs first answer. I seem to read the Cannon manifolds are 9938. Is that correct?
It's part #3836. I don't think Cannon manufactures them anymore. It would be an Ebay/Craigslist type of thing. Occasionally they show up for sale in the classifieds here too.

Here's a heavily modified Cannon intake for one of my engines. Welded and ported for 45 DCOE Webers (they are cast to fit 40 mm carbs). It hasn't been matched to the head yet though.







 

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Thank you all.

Thank you all for your great answers and in pointing me in the right direction.
RallyBob thank you for the fantastic photos you posted and detailed information.
I shall begin my search (I have a feeling it will be a long one) for the Cannon #3836 as I think this manifold is exactly the one that would fit my needs.
Igor
 

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This is my first post here.
MODERATOR'S NOTE: Welcome to the site. As an FYI, the GT Forum isn't for posting routine questions, especially of a technical nature. It is reserved for questions relating to the specifics of the model, such as "how many GT's were built in 1968".
Most questions belong in the relevant Technical Forum, which is where i have moved your thread. Whenever possible, please do a search for an answer before you start a new thread, and if you find a thread that is closely related but doesn't QUITE provide your answer, please add to the thread (assuming it keeps it "on topic")

It would seem that you might be spending some time here, so please take a minute and watch




Thanks in advance for your consideration.
 

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Thank you all for your great answers and in pointing me in the right direction.
RallyBob thank you for the fantastic photos you posted and detailed information.
I shall begin my search (I have a feeling it will be a long one) for the Cannon #3836 as I think this manifold is exactly the one that would fit my needs.
Igor
Sorry to throw another wrench into the works, but I just dug up these older pics of a set of modded Cannon intakes. Interestingly, the casting part number is completely different, but they are in fact identical castings for an Opel. I seem to recall these are 20-25 years old, while the ones I showed previously are somewhat newer, maybe 12 -13 years old. The casting number on these is #836.

http://www.opelgt.com/forums/attachment.php?attachmentid=6316&d=1121132343
http://www.opelgt.com/forums/attachment.php?attachmentid=6317&d=1121132343http://www.opelgt.com/forums/attachment.php?attachmentid=6318&d=1121132440
http://www.opelgt.com/forums/attachment.php?attachmentid=6319&d=1121132440

http://www.opelgt.com/forums/attachment.php?attachmentid=6353&d=1121396638
http://www.opelgt.com/forums/attachment.php?attachmentid=6354&d=1121396638
http://www.opelgt.com/forums/attachment.php?attachmentid=6355&d=1121396732
 

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igor the intakes in your photo look like ford pinto ones
 

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I have a used set of intakes with the linkage and a set of Weber 40 DCOE carbs.

Carbs look good and all looks to work.. given the age and dust, I would a assume a rebuild on the carbs would be a necessary evil.

Will post pics soon as I know if they have been sold or not..

Not sure what to ask for them either to be honest.
 

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I have a used set of intakes with the linkage and a set of Weber 40 DCOE carbs.

Carbs look good and all looks to work.. given the age and dust, I would a assume a rebuild on the carbs would be a necessary evil.

Will post pics soon as I know if they have been sold or not..

Not sure what to ask for them either to be honest.
Please do, I'm sorta looking for a set of Weber 40's for my Alfa Spider, I don't care too much for the Solex carbs on there now, and I can always use a set of Opel intakes
 
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