1967 Triple Deuce Carb Question

[Bill S.]

Can you determine if the 2 vacuum outermost carbs carbs are working while the engine is running?
If you can't determine at idle or increasing RPM how do you determine if they're operating?
Thanks in Advance
Bill Schroeder

[Duke W.]

Re: 1967 Triple Deuce Carb Question

If you blip the throttle real hard you should be able so see them begin to open or hook up a vacuum pump to the vacuum chambers and check that they open. Also you can use the mechanical closing linkage to see if they open.

Ran across this on a '67 L-71 three years ago practicing for a PV. It didn't pull at WOT like it should. Investigation showed that the end carb throttle plates were jammed shut against the throttle bores. I was able to free them up with the mechanical closing linkage.

Subsequent testing revealed the engine pulled as it should, and there was a whole lot more induction noise.

Duke

[Mark K.]

Re: 1967 Triple Deuce Carb Question

With my 67 L71, the kick from the outside carbs opening up is self evident at WOT when the engine hits roughly 4000 RPM. To feel the difference, plug up the vacuum lines to the outside carbs so the vacuum actuation cannot take place.

[Timothy B.]

Re: 1967 Triple Deuce Carb Question

Get an air chuck and blow air past the center carburetor passenger side venturi vacuum pick up hole. This hole is located in the passenger venturi near the narrowest area. See if the secondary throttle blades open, make sure you open the throttle full so the linkage doesn't keep the blades shut.

The secondary carbs also have an idle circuit that omits fuel through constant feed holes located under the transfer slots which keeps fuel fresh in the outside bowls when non use. Very nice set up when things are working properly.

[Richard M.]

Re: 1967 Triple Deuce Carb Question

Timothy told me that trick years ago iirc. A great test. I also tried it using a Mitt-Vac with the hose end sealed overt the venturi hole. Worked pretty good too.

And yes I always thought the F & R carbs did nothing at idle and mistakingly tried to get them shut at idle by playing with throttle plate snugging in the bores. Wrong! At idle you will get the engine to bog down or stall if you cover the air horns. Again, Timothy smartened me up.

One other issue about the secondaries not functioning at WOT. Replacement base gaskets may be just a tad oversize on their ID's causing the throttle plates to hang up. Had a rebuilt original carb set do this on a body-off '67 L71 at a buddies shop. At first I thought the diaphragm springs were hung up or reversed. Turned out to be those repro gaskets.

Edit... Just thought of maybe another test of the secondaries. Maybe tee in a long hose from the secondary vacuum circuit to your Mity-Vac held in the cabin. In a safe place, go WOT. Listen. Pump up the Mity-Vac and see if the sound changes. Also could run at half throttle or so cruise(to ensure mechanical linkage is off the stop) and pump up the vac and listen if they engage.

Rich

[Timothy B.]

Re: 1967 Triple Deuce Carb Question

Rich, your to nice :-) .. Like most of us here I am just a hobbyist. Your last paragraph got me laughing though, I am trying to imagine wide open throttle, pump the miti-vac and don't forget to shift gears. Hold on!, do you think he would remember to listen for the secondary's.. LOL!!

[Richard M.]

Re: 1967 Triple Deuce Carb Question

Rich, your to nice :-) .. Like most of us here I am just a hobbyist. Your last paragraph got me laughing though, I am trying to imagine wide open throttle, pump the miti-vac and don't forget to shift gears. Hold on!, do you think he would remember to listen for the secondary's.. LOL!!

HaHa Yes that's a good one! I guess a helper on the Mity-Vac might be safer. But not as much fun!

[Tim G.]

Re: 1967 Triple Deuce Carb Question

I pull the vacuum hose of the primary carb with the engine off and open the throttle full. If you inhale on the primary hose, the secondary's open.

I do this after everything is set up and I'm nearly ready to start the car. Amazing how many times there's interference from one thing or another.

[Robert K.]

Re: 1967 Triple Deuce Carb Question

Duke,
I like your words "whole lot more induction noise" in your post reply!

Bob