I have a couple of 1bbl manifolds just collecting rust in the garage and I want to try something. Is it fesable to take a 1bbl manifold, plasma torch off a large opening for a 4bbl (or a 2bbl for that matter), and weld a plate in? Would that flow like crap? I dont notice a design change between the 1,2 and 4bbl manifolds other than where the carb goes...well, except for hyper-pak

I have seen some old mags, and that is what they did...
I made a holley flange 2bbl intake one time, and didn´t have any problems with it(except the carb)
I just heated the pieces nice and red, and mig welded it.

I am running a stock 1 bbl manifold, modified to take a 500 holley 2bbl carb. I have been running this setup for over twenty years.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Is that on a stock engine? What did you modify?

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82 D150 Slant6 Shorty
http://www.cardomain.com/ride/658846

No the engine is not stock. There is a picture of this mod, in the Mopar Performance engine book. I copied that, but used a holley 500 cfm 2bbl. Put the manifol in a milling machine, and removed the 1 bbl mounting and machined a large flat area. Cut a piece of 3/8 steel plate, in a band saw, to match the holley gasket. Spray welded the plate to the manifold. Then set the manifold in the milling machine and bored the holes for the barrels, and mounting bolts, right throught the plate and manifold. The carb is mounted with the float bowl toward the valve cover.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I was just wondering. I was thinking of getting a one bbl adapter for a 350cfm Holley 1.08 2bbl. But I'll be putting it on a stock engine. What do you think about that?

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82 D150 Slant6 Shorty
http://www.cardomain.com/ride/658846

I'm not a fan of using adapters to put a large carb on a small manifold. I have never tried it myself, but if you want to stay with the 1 bbl manifold and use an adapter, I think I would consider one of the Webber licensed 2 bbl carbs, like used on Pintos and Vegas, etc. Do a search on theis site, and you will find reference to this style carb.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Charrlie_S, you said you welded a plate on top of the 1bbl manifold then machined the bores for the carb? Does it perform the same as the expensive manifolds? To me it seems like it would. What kind of difference did you feel after your little mod, that sounds like a smart idea I might want to try.

I did the mod back in 1977. At that time I had a "blueprinted" stock eliminator motor, with headers, 8 inch converter, and a 3.91 rear. I did the manifold, 500 cfm holley 2bbl carb, crane cam and .100 milled head, all at the same time. The intake system, cam and head, gave me about a 1 second improvement in 1/4 mile times. This was with a 170 engine.
As far as compareing it to the aftermarket manifolds. I only tried a Clifford, once. I used a 2bbl plate, and the same carb. The car wouldn't fall out of a tree. However, I did not change the jetting. Since I had a slant six race, coming up the following weekend, I just put my homemade 2bbl manifold back on. I intend on trying a 4 bbl this year. I have a Clifford, and a Offie manifold, and a 390 Holley, and 500 Edelbrock.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

did the adapter and 2bbl holley 5200. runs great. and only took a half hour.
as far as i'm concerned nothing but positives

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73 swinger holley 5200, 2 1/4" exhaust .030 over new pistons , cam, .010 under crank. stock everything else. 1/4 mile about a week. 0-60 around 15 sec.

Would it work to braze an adapter plate to the manifold? I have a gas welding rig but no mig welder.

The aftermarket manifolds may have a slightly larger runner cross-section, but IDK, and this (if true) is probably only an advantage with a 170. Most of them do not have the nice curve radius of the original.
Another advantage to DIY is that when you have the top cut open you can reach in there with some 6" stem carbides and put a nice radius on the runner entrances, etc. before attaching the top.

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Yes it will work. Brazing has been used to fix cast iron parts for a long time.

Up here we have to make most performance and I made A 4bb
manfold out of A 1bb, and used it for 3 years on the srteet and raced it.
It worked very good. the car ran 16.5 with A stock 2bb carb. and manfold
and 15.8 with a 390 holly carb.with A madeup 4bb manfold.