Modifying intake to clear headers

Tom Ginefra

True Classic
I recently purchased a stock euro manifold with a 34 DMTR, and an Allison header.
Unfortunately, the header was designed to be used with a Fuel Injected motor. I also have a complete custom exhaust to match the header, so I would really like to be able to use them both. The tubes for cylinders 2 & 3 are hitting the bottom of the manifold and I need to pick up at least 1/2" of clearance to make it work. Does anyone know how thick the bottom of the stock cast aluminum intake is? I want to maintain the water jacket in the manifold since it's so close to the header tubes, but I dont want to start grinding on it, only to find out it's an 1/8" thick. I also planned on bashing in my beautiful header slightly, to help take up some of the clearance needed. Won't have photos until I'm in the shop, tomorrow.
 

DanielForest

True Classic
Tom,
If your headers were to start at 1/4" or 3/8" of the head, do you think it would help clear the bottom of the intake? If so, you may take a stock exhaut manifold and, using a grinder, remoded the flanges to used them as spacers. Then you will put a gasket between the head and your new spacers and another gasket between your spacers and the headers. That should move it away from the head an may help clear the bottom of the intake. If, "au contraire" it will make it worst then you could instead do the same thing with your stock intake manifold, moving away the new euro intake.

To do some test fit before doing any major work, you may put nuts or washer on the head to simulate the presence of a spacer. One difficuly you may find is some of the studs share by the intake and the exhaust will not be available for both since one of them will be using spacers. You may have to be creative.

I have no idea of the thickness of the intake, but you could take your old one and drill thru it to measure.
 

Tom Ginefra

True Classic
Daniel,
The problem is that this design has the tubes exiting from the flange at a slight upward angle. No practical amount of spacers would alleviate the interference. I would literally have to cut, pie slice and re weld the center tubes to shorten them and get them to pitch downward immediately after they exit the flange.

Carl, while they look identical on the outside, the internal runners on the Euro manifold are a larger diameter than the US version. It looked as though there wasn't a whole lot of meat between the water jacket and the exterior of the casting, and I didn't want to risk breaching that thin wall. I did grind off the casting seams and a bit more, but was hesitant to take too much material away. I carefully dented the 2 center tubes away from the intake. It took quite a while of repeatedly fitting and bashing. I managed to get the header flange to fit perfectly on the block with the intake manifold.
Except, the final result leaves these center tubes WAY TOO CLOSE to the manifold. There's no room for a planned heat shield, and you can see from the photos that I've essentially destroyed a beautiful header.

I was excited to purchase this header as it's my favorite, designed specifically for the X. Really well made in the USA, and the only company I know of that has dyno numbers to back up it's performance claims. Having said that, I would never have bought it had I know it wasn't designed for carb'd motors.

I spoke with Mark Allison the the other day. He took my photos and said he would modify his design so any new headers sold would work with any X. Doesn't help me now, as I'm out the money I spent and unless I pony up for a new Allison header, I can't use the cool custom dual exhaust I bought to go with the header.

Live and learn.
 

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DanielForest

True Classic
It's too late now, but I was wondering if a set of DCNFs or DCOEs would fit instead.

Now, I think you should cut the #2 and #3 runners, probably at the weld line, and build a new tube that would fit underneath the intake and end-up with the flange you will removed from the wrong angle header. I think some of our members did some exhaust works in the past and you may finally get what you need.
 

GregS

ProjectX
I would not like to run it with pipe flattened that much. You should be able to take it to a custom exhaust shop and get new pipes made for the top part of the centre pipes that come off the flange at a steeper angle, like the more common headers.
 

Tom Ginefra

True Classic
I would not like to run it with pipe flattened that much. You should be able to take it to a custom exhaust shop and get new pipes made for the top part of the centre pipes that come off the flange at a steeper angle, like the more common headers.
I deliberately made sure I widened the tube as much as I could to minimize the reduction of area and any restriction that would accompany this type of modification, but I'm not comfortable running it this way either. Not to mention the fact that both of these tubes now sit so close to the manifold they're going to boil the fuel mixture before it gets to the cylinders. Water jacket or not.
 

Tom Ginefra

True Classic
It's too late now, but I was wondering if a set of DCNFs or DCOEs would fit instead.

Now, I think you should cut the #2 and #3 runners, probably at the weld line, and build a new tube that would fit underneath the intake and end-up with the flange you will removed from the wrong angle header. I think some of our members did some exhaust works in the past and you may finally get what you need.
Since I suck at welding...looks like I have a visit to a custom exhaust shop in my future.
 

carl

True Classic
What it really boils down to is the company that sold you the header did not properly design it. The Euro intake manifold looks just like a US version on the outside. It's pretty silly to design the perfect header only to find out you can't use it.

I know this does not answer your tech question but sometimes you have to recognize what the real problem is. I agree that a dollar no object solution is to have shop redesign it but really the vendor should have done that. You may be better off in the long run just getting a MWB header. I gather this is not a race car and the last 1/4 hp improvement is ultimately not that critical.

Sorry to be the voice of reason but we have all been down this road. I literally threw in the trash a dual IDF manifold as it was so poorly made there was no way to make it fit.
 

Tom Ginefra

True Classic
Carl,
Had I purchased this from a company I would surely have asked if it was compatible with a carb'd car. Since I bought it from another trusted forum member (who sold me the carb and intake "with the header and exhaust") I assumed I was getting the right part. That's why I said "Live and Learn".
 
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