Carb power valve height

[MNcarbturbo]

I am in need of the power valve height for a non CCC carb. Really all I need is somebody to stick the shaft end of a caliper into the vent hole right above the primary power valve and push down the spring for the measurement.

I rebuilt my carb and guessed the height and the carb leaned out when I hooked it up due to it being too low.

Thanks!

 

[charlief1]

The height of the power valve isn't adjustable. You have to change the needles and seats to get more fuel along with the power valve spring. Is this NA or C/T?

 

[MNcarbturbo]

There is a threaded plug underneath the primary power piston. Mine is too low. I know for a fact it is adjustable. It either limits the amount of vacuume to the bottom of the power piston or it physically limits the primary rods from bottoming out in the jets.

This is my 80 turbo carb on my turbo motor.

 

[charlief1]

The valve on the throttle plate is for the idle height, don't mess sith it unless you have a way to check idle emissions. That's all it controls. The power valve should be hooked up to the PEVC valve which cuts the suction of the plenum off to the power valve when the engine sees over 3 lbs of boost. If you don't have a PEVC valve (Rich calles it a PEVR) then the power valve is seeing engine vacuum all the time and that's how you end up with a lean condition from the carb.

 

[MNcarbturbo]

Last winter when I rebuilt the carb I put it back on and it started right up. I dint chance the idle air bleed or anything else. I only adjusted the choke stuff and the power valve plug.

So why then does it not run when I hook up the power valve? All I did was hook a line from the power valve port to one of the ports on the plenum just to get it like a NA carb would be. It would idle fine, but as soon as I drove it around it just stumbled and wouldnt run. Ive always assumed that I screwed that brass plug down .050" too far which plugged the primary jets and limited the fuel I needed around 10" of vaccum. It runs like it should when the power valve is disconnected. Doesn't smell ritch, although a wideband is coming sometime soon.

I dont have my PEVR. Ive got all the stuff for my electric one that turns on at 2 inches but didnt put it together last fall.

Theres an old Q-jet and holley guy half an hour from me that I might the carb to just to see if he can see anything obviously wrong. The person that rebuilt it before was just a hack.

 

[charlief1]

If you're running a non CCC carb then you need to have some sort of PEVR to cut the vacuum to the power valve. If you don't the power valve acts like a normal carb and will adjust just like one. The vacuum signal must be eliminated at 3 lbs of boost or the engine will run lean and cause detonation. Here's a link you need to throughly read so you can understand better. Wish Pete was still around but I think he's passed now unfortunatly.

petesbuick.html

 

[MNcarbturbo]

I run around with no power valve hooked up. It doesnt run that ritch judging how it doesnt smell and runs good. The only time ive ever hooked up the power valve is for 5 minutes last spring. Didnt even get a block from the house.

I will have a PEVR this spring.

Really what Id like to do is measure it just to see if its right or not.

 

[charlief1]

Read the link. Pete's tells you how to make what you need. A simple hobbs switch and a two port electrical switch will work. Read the link! Seriosly, it will give you the info you're lacking.

 

[MNcarbturbo]

I have the Hobbs switch and a vaccum switch to build the thing. Just have to wire it up and hook up the hoses.

 

[charlief1]

Then get it done and it should solve the issue.