Power Enrichment Control Valve

Buicksandrail

New Member
Joined
May 27, 2001
I really need some help on this. I have been unable to find the PEC valve anywhere. Is there an aftermarket source or some other way to protect the power valve from boost?

Thanks,

Trent
 
I looked into how it works before. I think this is correct, but i don't have a non-CCC car to confirm it.

There are four ports, one at the bottom and three on top. (altough I only see two in the vacuum diagram). One of the top ports is a vacuum source from the carb, the others are trying receive this vacuum, one of which should go back to the power valve's carb port. The PECV is a switch to connect and disconnect these vacuum lines. The bottom port senses the manifold pressure and opens and closes the switch, and is not actually connected to the other ports.

So in the Buick design, the power valve can never actually see boost pressure. But if the PECV fails, the power valve will not function properly. So a vacuum swicth which operates in the same manner must be found, or made. These may be available.

Or the power valve's carb port may be connected in a another manner. The traditional (non-Buick) way is to use the lower intake manifold (post-turbo) as the vacuum source, instead of the carb (pre-turbo). Using an in-line check valve will keep the power valve protected from boost pressures. This is detailed in Hugh MacInnes Turbochargers book.

I need to re-read my website's info on this. I think I based it upon the traditional set up in the Macinnes book and not the Buick design.
 
Originally posted by b4black
Or the power valve's carb port may be connected in a another manner. The traditional (non-Buick) way is to use the lower intake manifold (post-turbo) as the vacuum source, instead of the carb (pre-turbo). Using an in-line check valve will keep the power valve protected from boost pressures


I think Fred Carrado has his Holley carb plumbed this way, right?
 
PECV alternative

Get a three port vac. switch. I got mine from some unidentified japanese car at the wreckers.

Connect one side of the coil to a switched 12 volt source.

Find the boost light switch that operates the yellow boost light. [ Zero P.S.I. on my car. ] Connect the other side of the coil to the boost light switch that does NOT go to ground.

Pipe the common port of the vac. switch to the carb. "power valve" port.

Pipe the normally open port to a "vac./boost" manifold port.

Pipe the normally closed port to the carb "vent" port.

Remove the original PECV and plug the hole left in the manifold. Do not throw the original PECV away , there must be someone on the planet that re-builds these things?:D

What does all this do?

When the manifold pressure is below zero P.S.I. the power valve is connected to the manifold, and will operate according to the vac. signal.

When the manifold pressure goes over zero P.S.I. [boost] the yellow light comes on , and the three port vac switch will connect the power valve to the carb vent. This will prevent boost going to the power valve and give a full rich condition at all boost levels.

I am not sure if this what Buick intended, but it is better than a blowen PECV diaphram and will prevent damage to the carb. :)

If the ports on the three port vac. switch are not identified , check as follows.

Blow through the ports. The two ports that you can blow through are the common and the normally open. Energise the coil and blow again ,you are now blowing through the common and normally closed ports. The common port is the one that you can blow through under both conditions.
 
I found a parts car with the complete moter carb turbo ,I may be able to help .let me know
 
Peter,

I think that is a great solution. When I find time, I will add to the website (incase the board crashes again.) with proper credit. If we can find a specific part number for the switch, it would be great.


Now we just need a simple solution for replacement ESC controllers. ;)


THANKS!!!
 
Rich ,

Checked the switch today, but it has no identification. I found it on the second car I looked at in the yard, so I either got lucky or they are plentifull. It is about an inch cube with three ports and two electrical contacts. Anyone you can find will do. Can not imagine they would be anything other than 12 volts.

I am presently running an electronically controlled PECV and an alternative ESC unit combination in my car. When I am happy with the performance I will publish the results. Hang in there.;) ;) nudge nudge.
 
Hi

Yes I did plum my hiolley this way , I welded up the hole in the base plate , It all ready had a check valve there. And I used the port at the base of the carb an ran it to the manifold. Works good :D
 
That should say "holley"

Hi rich when are we gettting spell check back ? :eek:
 
I wish we had the spell check back too. The new board has polls, ratings, and other stuff, but no spell checker. :(
 
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