Hot Rods Custom intake manifold fabrication

The rear carb on the factory Buick setup sits higher than the front because it's got an air damper valve underneath it, since it was the secondary carb and didn't have an accelerator pump. It's good that Buick made that intake so that 80 years later, people could replace the factory carbs with two normal carbs and run straight linkage, but from the factory, it was a progressive setup with the engine running off of the front carb most of the time. Fuel distribution must have been horrible.

 

I would bet that the air horn height is the same on both carbs when the intake (and thus engine) is installed in the car. Reference this picture:


This is the stock '50 248/264 intake. Note that the runners are different depending on location. When the intake is installed, the carb flange is level.


That is the angle I am looking to compensate for. Wedges under the flanges will most likely be my fix, and anything that I build is probably going to flow better than the factory 2bbl intake.

 

I am in the process of finishing up this custom intake manifold. 6-71 blower to MEL. I got the first examples from the foundry last week, now I just have to do the final machining.

Fabricating a sheetmetal intake would be the cheapest and quickest, especially for an inline where the fabrication is much easier, but below is the process I underwent to create the MEL intake.

I started with an old Weiand LM671 intake, but that intake had a large number of short comings that prevent it from being used on a street engine. The Weiand requires relocation of distributor and thermostat, has a huge plenum that will affect low rpm flow negatively, and interfered with the valley pan / crankcase breather. I wanted to correct all of those shortcomings and build an intake that is much more usable.



I modeled the Weiand in CAD as a starting point, and then started making modifications to the model to include the items I wanted (thermostat and distributor clearance).



Eventually the CAD model progressed far enough that I felt comfortable having a 3D printed model made that I could mock up on the motor to check fit, clearances, and perhaps even use on a flow bench.



Some more changes came about based on what the printed model showed, and I was able to finalize the CAD model. At this point, I started working with FECoffin as he had the foundry contacts to get a couple made. We chose to use a 3D printed mold, and after some tweaks to help improve the mold flow, we had a couple of molds printed up and the samples were poured.





Finally samples arrived and I am now working on building fixtures to do the final machining. Hopefully that will be completed in a few weeks.





6inarow, Depending on your goals for the project, and if you need any help developing the intake, feel free to PM me. I can offer help generating a CAD model, fabrication, or whatever else may be needed.

 

Follow this link, then scroll down to Chevrolet and you will find a top and bottom picture of the intake and 3 Carter YH carbs original to the Corvette 235:

https://www.thecarburetorshop.com/Multicarbsetups.htm

Note that each carb feeds one of the siamezed sets of ports on the cylinder head.

The original Carters are quite scarce (I think I have but a single set left), but the YH was also used on a number of marine engines. The Dearborn Marine YH's, tag numbers 2617s and 2618s are not as "common as dirt", but much more common than the 2366s used on the Corvette, AND they do not carry a "Corvette price tag". The 2617s and 2618s may be used as a "mix or match", as only the external linkage differs.

If you REALLY want to use 3x2 Webers, maybe think outside the box. I know this was an aftermarket option for the Jaguar 3.8 engine; perhaps one of these manifolds could be located / adapted.

Clifford DID make an intake for the 3x2 Webers for the 235/261; part number is C-4851. These were in the 1974 catalog, but not in the 1994 catalog.

If you go with 3 of the YH Carters, I will be happy to assist you in tuning.

If you go with 3 of the Webers, there are others who would be more helpful than I.

One other option on fabricating intakes: aluminum tubing, and various angle bends may be found at a good electrical supply store, they are called "conduit".

Jon

 

There is one of the Cliffords currently on Ebay - 116462160761

Jon

 

There is also one of the Corvette versions on Ebay - 196358765180

Jon

 

A couple of ideas to consider. One I made from three 1V center two cylinders, and the other built from scratch for two SUs.

 

How far along are you as far as cost? I've been tempted many times to design parts (accessory drive brackets keep coming up as one example) for casting using the same basic "3d print then pour" workflow as you but cost uncertainty always drives me to other methods.

 

It definitely isn't cheap. I sent you a PM with a better cost breakdown.

 

Tom, about 7 or 8 years ago I designed and cast 3 different intake manifolds for the Chevy 250/292 engines. One of them was a triple side draft Weber intake. Ironically, I had a GMC guy here on the HAMB tell me he took a side draft intake for the Chevy 250/292 and modified it to fit his Bonneville GMC equipped race car. The port spacing allowed enough wiggle room to make it work and I bet the Stovebolt can as well. Over on Inliners I had a guy want to buy one of the side draft intakes from me unmachined to put on a vintage GMC drag car he was building. So its doable if you can find a used one and may be easier than starting from scratch....

 

I recently sold a Clifford triple Weber side draft manifold to a guy that is adapting it to a Pontiac OHC 6 cylinder. although it's not a bolt on, it is pretty close and some simple adapter plates will make it fit nicely.
Looking at the eBay prices I sold it WAY TOO CHEAP!