Installing Dual Stromberg 97’s

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Installing Dual Stromberg 97’s On A GMC 305A


By Cort Corino, Astoria, Oregon.

PARTS USED:

2- Stromberg 97 carburetors

1- Vintage Speed Y-manifold P/N FL-CA-4

1- Progressive Linkage P/N CL-2X2-P (Vintagespeed.com)

1- Rochester to Stromberg pattern adapter P/N 5605159 (The Hot Rod Co.)

2- Helmet air cleaners P/N 91011025 (The Hot Rod Co.)

1- Holley Fuel Pressure Regulator P/N 12504 (The Hot Rod Co.)

1- Stromberg banjo fitting P/N 9082K (The Hot Rod Co.)

1- Stromberg banjo fitting P/N 9083K (The Hot Rod Co.)

2- Heim joints P/N 732-1131 (NAPA)

1- 1/4-28 All thread for throttle linkage

3- 5/16 inverted flare fittings

1- 5/16 tubing

1- Custom fuel regulator bracket

1- 5/16 fuel hose

THE INSTALLATION:

After procuring all of the afore mentioned parts, the installation went pretty smooth. It was important

to me not to cut or modify any OEM parts. That way I can restore the truck later on with all the

original components, if so desired.




First I located a later model 2-barrel V-6 intake to work with the adapters. My 305A originally had

the One-Barrel Holley 1907. After installing the new intake, I bolted up all of the adapters & then

the carbs. I made a custom bracket to mount the fuel regulator as close as possible to the carb, while

also keeping asthetic appeal. I used 5/16 brake line bought from NAPA, & made a line from the pump

to the regulator & then from the regulator to the primary carb. I did not hard pipe the second fuel

line to the primary carb, instead I used about 2-3″ of 5/16 fuel hose. Just a preference.




From there I routed the original choke cable to the passenger side & it actually had enough reach

to choke the primary carb fully open & closed. I made another custom bracket for the choke

cable which bolted to the secondary carb.




Finally I installed two Heim Joints to a 1/4-28 all thread to connect my throttle linkage on the carb

to the factory linkage from the accelerator pedal.

Because Stromberg’s have no provision for vacuum advance, I installed a vacuum fitting to the rear

of the manifold & connected it directly to the advance mechanism on the distributor. Having manifold

vacuum full time to the distributor seems to really make the engine happy at idle. After a performace run,

this engine has never been more responsive & smooth at idle. I am extremely happy with the end results.




Lastly, The whole assembly will stick about 2-3″ above the hood. To facilitate this, I have removed the hood &

am in the process of finding another hood I am confortable with cutting to allow the air cleaners to clear.

I couldn’t bear the thought of cutting my original “eye-brow” hood.

That is basically the gist of it. The whole process took about 6 hours, stopping for a snack & a parts run.

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