[Greg Reid]

What's recommended to block the passage off? I'm using a primary bowl for secondary duty.
I'll stop bombarding you guys with questions as soon as I get my DVD..

[Tom Vaught]

When you look at the Power Valve Circuit on a 2G Carb you will see that it is actually a "two circuit system".

The First System is the fuel system side.

There is a "screw in" Power Valve there that is about 1/2" long and has threads on the lower side of the valve and a protruding "stem" in the center of the valve on the upper side. When the stem is all the way up the Power Valve is CLOSED.


The Second System is the Vacuum system that controls when the Power Valve is open or closed.

It is installed in the "lid" of the 2G carb.

There is a very long "stem" (with a spring around the stem) and a machined piston and washer on the opposite end.

The machined piston is installed in the "lid" casting and the washer is peaned over by the lid zinc material.

Vacuum "pulls" the piston upward in normal high vacuum situations (like idle). That compresses the spring slightly on the stem. But the long stem now clears the Power Valve protruding stem and the Power Valve stays closed.

When the engine has a higher "load" condition the control vacuum to the Vacuum Piston drops and the spring forces the actual Power Valve "stem" to OPEN the Power Valve and supply extra fuel to the calibration.

The spring on the long stem is a fixed calibration but you can trim coils off the stem spring to change the Power Valve opening point.

In your case Greg, there are a couple of things that you could do:

The easiest would be to take a small bolt cutter and cut the long stem into 2 parts 1/2 way up its length.
The spring would be removed.
The vacuum piston would still function normally but would never open the Power Valve, because the stem would now never push the Power Valve stem down. This would keep the carb 99% original and with a simple Long Stem PV part change the PV circuit could be used again.
(As a center carb on a 66 set-up if you also changed the nozzle cluster to a proper 66 Tri-power part.)

If you remove the PV Valve and plug the threaded hole with lead shot then the stuff is a pain to remove down the road. Same deal for the control piston cavity in the 'lid".

Just easy to change one removable part on each carb and disable the PV circuits. You do not even need to pull the vacuum PV stem just cut the long stem and remove the spring.

Hope this helps.

Tom V.






There is a "screw in" Power Valve there that is about 1/2" long and has threads on the lower side of the valve and a protruding "stem" in the center of the valve on the upper side.

[Greg Reid]

Yeah, that does help Tom. I like the idea of not making any permanent changes to the casting. Thanks for the 'simplified' solution.

[Tom Vaught]

I prefer to tell people how the systems actually work so that they can understand their operation vs mods that people make to them.

Even if it did take me 17 lines of typing to do it.

Tom V.

[Greg Reid]

Well, I for one appreciate the time you invested in your response...Thank you again.

[Tom Vaught]

Post up some pics when you get it all together and running Greg!

Tom V.

[Greg Reid]

Here's a teaser...The nasty carbs and venturi clusters have cleaned up pretty well so far. Two of them started about like the dirty one in the pic... Lastly, the 389 that awaits them.. Nothing fancy, just like it came from the factory but with rebuilt heads, new rings, seals, bearings and so forth.
This was a running '66 WT engine from 4bbl carb to pan pulled out of a rusty hulk of a '65 GTO that had been rusting in a field for a couple of decades...Even the choke on the original 4bbl Carter was working at the time when my friend started it for me to prove it was running.
Since I've had this '65 tripower sitting in my basement for a while and a '66 GTO sitting in my driveway collectiing dust...I figured, why not?

[Tom Vaught]

The Carb did clean up, really nice.

Glad to help.

Tom V.

[22times]

Originally Posted by Tom Vaught

The Carb did clean up, really nice.

Glad to help.

Tom V.

Tom, Does that vacuum actuated long rod with the spring wear out? I have a new over rich condition I'm unable to figure out. Wondered if that rod could be stuck down allowing the power valve to hang open. I have checked float, and for leaks with no luck.

Sent from my VS987 using Tapatalk

[Tom Vaught]

The Power Piston (Long part with the spring) is SUPPOSED to move freely inside the vacuum Bore machined into the top cover.
If the piston is stuck down then the nailhead will depress the power valve stem and the power valve will add extra fuel when it should not.

You should be able to push down on the flat (nailhead) part of the assy (compress the spring) and have the piston move upward in the cover.

Then when you let go of the part the piston/spring should move the nailhead back to the extended position.

Many times you can remove the staking around the power piston assy retainer by simply tapping the piston into the cover and letting the spring snap it back out. You do this 50 times and the
swedged washer and the casting suddenly come apart.

Now you can clean up the power piston, I use a glass beader machine and get the piston where it moves very easily up and down in the top bore.

Then you restake the washer (pean some casting material over the retainer again and you are good to go.

YES, IT IS VERY POSSIBLE THAT THE CENTER CARB POWER PISTON IS STUCK.

The End Carb power pistons need to be installed or you will have vacuum leaks at those two locations and a higher idle.

Tom V.