OldIHC

Looking on EBay for parts and found an intake manifold that came with a sheet metal tube that went down inside the intake manifold underneath the carburetor. I have never seen this before and of course it's missing on my truck. The parts manual I have also does not show or list it.

If this tube is missing maybe this is why these engines have such terrible uneven mixtures between different cylinders front to back?

The tube would force all the fuel/air mixture to the floor of the intake.
This does 2 things.
1. Forces the mixture against the hot metal base of the intake which is bolted to the exhaust manifold. So this would help vaporize the fuel for better combustion.

2. It would also keep the center intake port from thieving the majority of the fuel since it's straight across from the carburetor. Give the 2 end ports a bit more even mixture?

Here it is installed;



Here it is with the tube removed;



I do see that manifold has 2 squares cast into the top that my intake does not have. This was supposed to come off a 1947 KB5?

Is anyone running these?
Anyone have a part number?
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To be honest, I have never seen anything like that before. These engine don't have a heat riser valve to direct the exhaust around the intake when cold, and then shield it when warm like later engines do. It is possible, that was to direct cold mixtures to the hot spot, but it is the 1st I've seen.
One thing comes to mind. Some of these engines were fitted with up-draft carbs (carbs mounted below the manifold) and I wonder if you intake came from that set-up, and the tube was there to direct the heavier gasoline in liquid form, to the hot spot to vaporize. On a down draft carb set-up, the liquid gasoline would tend to fall onto the hot spot without such a tube.
Up draft carbs were favored by the military, ag and industrial engines because they are less likely to flood than down draft set ups do.

Would the same intake manifold be used for up and down draft carburetors?
It appears they are the same.

Looking in the parts book it does show a number of different carbs used and some are labeled up draft.
But I would have thought the intake/exhaust diagrams would show the tube but so far I can't find it shown on any diagrams.

I was hoping some of you experienced guys could explain it?
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I'm sorry but I have no answers. If you have a parts book, are the part number the same for up and down draft? I would expect not, but could be wrong, it depends on how the manifolding sits on the block or head.

Another possibility is it isn't OEM. There have always been add on's sold to "double you mileage" with a simple device that the OEM's were too "stupid" to think of! The "tornado" or fuel line magnets come to mind, may be this was another.
One concern, if it starts to rust out, do you really want your engine to ingest the pieces?

never seen one in a K, or KB, and I've seen a lot since 1975 on, not saying it isn't factory, but I'd guess since it isn't listed in parts book, it's some sort of after market like CB suggested,

ask him for the part number embossed on the manifold, that would help, I'll prowl my parts book later,

I don't remember about the tube but I had some manifolds off a D series Green Diamond motor that were a little different looking but would still fit. I've been looking at manifolds on eBay too and saw that one. I pulled the motor out of my KB-5 and scrap metal thieves got my manifolds, bellhousing, flywheel, oil pan and radiator. I can probably find a parts truck cheaper than buying all that separately off eBay.

My 47 K-1 has that as well. Found it on engine tear down too.

I have a Green Diamond intake /exhaust manifold I would consider selling. Stickman 207

Thanks for the help!

Here is the auction if you want to look at it;

http://www.ebay.com/itm/131795422040?ul_noapp=true

It seems to have the standard number cast into the manifold?
95069-HA

That's a good point about it rusting and going into the engine piece by piece!
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