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[V6 Performance]
The Holley 500 CFM 2-BBL #4412
The Holley 500 CFM 2-BBL Part #4412 Two-Barrel Carburetor is a great improvement in
power over the stock Carburetor GMC Used. These parts can be found at any good parts
house like NAPA or CarQuest, or from Places suppliers online like
JEG’s High Performance.
You will Also need an Adapter to mount it to your manifold.
Mr. Gasket Adapter #720-1937.
NAPA used to sell a Large Stromberg to Holley Adapter, It was Balkamp part number
735-1228. A check of NAPA’s national parts finder service don’t show any in inventory
anymore. Guys in the small towns that have good NAPA’s that have been around a
long time might want to check, you never know, you mite fnd one.
The Holley 500 Project
as done by Dennis Arseneault
Swap the Stromberg for a Holley to give the big 351E the carburetion it deserves.
The 351E intake manifold has a different bolt pattern than the 305 V6.
To bolt the Holley carburetor to it an adapter is needed.
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| 351E intake & Stromberg WWC carburetor | 1966 GMC 351E Intake Manifold |
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| This is the intake for the 351E V6 after it has been removed. It will be sandblasted. |
351E Intake Manifold After sandblasting The intake is ready for primer & paint. |
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| Conversion Kit, A custom machined adapter was made of aluminum. 2 gaskets, 4 nuts, 4 washers, 4 studs & 4 bolts secure the carburetor. |
Ready for installation, the manifold is Painted with high-heat engine paint & is ready for install. |
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| After placing the gasket on the intake, the custom machined adapter is mounted using the 4 allen head bolts. |
The carburetor gasket that comes with the new Holley carburetor fits nicely atop the custom machined adapter. |
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| Look how nice that Holley carburetor looks atop that 37 year old reborn intake! |
To connect the fuel line you must remove the filter & parts on the left & replace them with a #6 90 degree push-on aluminum hose end, part number 239006 # a 36 Holley 7/8″ -20 dual feed fitting, part number 700106. Both parts are from www.XRP.com. |
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| The fuel fitting & fuel line connected to the carburetor. An in-line fuel filter replaces the filter that was removed. |
To attach the accelerator you need to purchase this return spring & mount it. Mounting it requires using a longer bolt than the one that comes with the return spring kit. |
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| Installed & ready to go! The stock choke cable has been replaced with a Holley aftermarket cable. Everything is attached & ready to go. |
1966 1500 w/351E V6, 4 speed transmission in the Desert at South Mountain Park in Phoenix, AZ. See ~~> Full Size Photos <~~ There |
Here’s how Clay Chilton of Colorado Springs installed one on his 351E:
“I took the old carb off & marked the length of the four blots at the base of the intake manifold
& then unscrewed them with channel locks. then I put them in a vise & cut them off just shorter
than the marks with a sawsall & then used a sawsall to make a flat head notch to screw them in. I
then screwed them in to just below flush & sealed the tops with some high temp silicone. Then I
placed the adapter on the manifold & centered the center hole & marked the the four bolt holes,
There was just enough space, then I drilled four new 1/4 inch holes & tapped them with a 5/16″x18
thread tap & bought four new 5/16×18 thread screws at the hardware store. I left the intake manifold
on & used a magnet, rags & vacuum to catch the metal shards, but I would recommend taking the
manifold off if you can find the gasket kit. This all took maybe two & a half hours & was
defiantly worth it! The only other thing I had to do was replace the jets due to living at 6500 ft.”
GMC V6 Manifold Info & Photos
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| The 305B, 305C, 305D & 702 2-BBL Maniflod can use the Mr. Gasket Adapter #720-1937 to mount the Holley 500 CFM 2-BBL 2300 Model Two-Barrel Carburetor. Other brands of Adapters; CP Automotive ~ #40203. |
The 351E, 351M, all 401, 432 & 478 V6 engines use a trapezoid base, so the #720-1937 adapter won’t work unless you use Clay Chilton’s method above & redrill the holes in a wider position. Trans-Dapt used to make the proper adapter part # 2140, its been discontinued. You can use a 305 or 351C intake manifold, though it has smaller ports it will still work on a Magnum head V6s. |
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| If you have the 1960-61 305A you will need a differenet Manifold from a newer engine, as this engine had a 1-BBL Carburetor with the little single hole mount. |
The GMC Twin-Six manifold is a lot like the 305B, 305C, & 305D manifold, only has has the V12 firing order on it. |
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Performance Upgrades For |
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© 2000-2005 6066 GMC Trucks. Last Updated April 20, 2005.