Making intake manifold for GMC Big Block V-6

I need to make an intake manifold for my 401 GMC V-6. Right now it's set up for an industrial 1 bbl (came out of "New Idea" harvester) and I'm not sure it can be modified to take a modern carb (big Holly 2 bbl is favorite) so I'm looking at welding up the whole thing.

The beast is definatly a low-speed engine -- like a 3K redline -- so I'm figuring on keeping the runner length short.

What other aspects of the manifold should I minimize/maximize? Small or large plenum, etc.

Should I look at trying to pair up opposed cylinders (fireing order 1-6-5-4-3-2) of at that speed range just make it all smooth?

 

You might go to the 6066 pages I thought there was some info on the manifolds there.

 

id say look threw the tech-o-matic searching for "u-fab" manifolds. that should do the job just fine

 

(6) BVOX Stromberg singles on log manifolds would be cool..... and period to boot.

Maybe (4) in a row down the middle.

 

You might want to jump on over to HotRodders.Com also. There was a fella that was building his own intake for a 305 V-6 in a school shop class. Don't know the outcome however. Butch/56sedandelivery.

 

Hog the top offa it, weld a plate to it, and throw a huffer on top....

 

Correct me if I'm wrong, but isn't the stock manifold a single plane design? If so, it would be a simple matter to mill off the stock carb riser, grind out the opening to size, and braze or weld a 4 bbl. mounting pad on it. Even as a low rpm engine, I'm sure that 401 cubic inches could use a 500 cfm four barrel carb.

 

The V6s rev like a diesel; they're all done at 3600 RPM. In fact, there is a diesel version with more or less the same block and lower end. From what I remember, if you can't just find an existing 2bbl manifold (which should exist), like has been said it shouldn't be a big deal to mill one down and braze on a new top.

 

My daily driver for the longest time was a 60 GMC 1/2 fleetside with a 305 V6..Best damn truck I ever had.Those V6 engines are amazing.

 

I know a little something about carbs on gas truck engines....older V-8's in the 350-400 cube class, Chevy 366,Ford FE 361-391 and IHC 345-392 are governed between 3500-4000 rpm .These engines are rated at around 230-250 at governed RPM.When equipped with a four barrel it's usually a 390 cfm Holley truck carb.Some have a slightly bigger carb,460 cfm.

 

If it is such a low revver, why short runners? Maximize that low rpm torque with some sonoramic tuning (mopar engineering, should work on a GM ) and make the runners as long as practical. These things were torque monsters at about 3000 rpm:

 

The 2bbl intake should be pretty easy to find. There was also the Magnum setup with bigger ports in the manifolds and heads, used on bigger motors in later years, that used a larger 2bbl. I know the magnum intake can be modified to use with a Quadrajet, I've seen it done.

 

If you need any help with the flanges shoot me a PM
Bill