Defective Secondary Port Vacuum Actuators

[Rob]

Someone brought this to my attention and it should probably be mentioned here. The following information comes from the ZR-1 Net and has been edited/corrected by me:


In some of the original LT5 engines it has been found that some of the secondary port vacuum actuators are installed upside down causing the actuators not to open completely. The fix is to just turn them rightside up.

According to Gordon Killebrew: "If the actuator lever, that extends from the center opening of the actuator and is attached to the bladder within the actuator, is sitting at an angle, it is 180 degrees out of correct position (on backwards). The actuator lever end that is attached to the actuator diaphragm should be pointed to the center of the engine. When installed correctly the lever is in a straight line with the port throttle arm."

In order to determine if they are opening correctly: connect a vacuum gauge to the secondary port vacuum hose system as described in this thread in order to measure how much vacuum is needed to open them. Check your Corvette Service Manual for correct specs.

http://corvetteactioncenter.com/forums/showthread.php?s=&threadid=14272

The second problem is that the new actuators from GM (the diaphragm piece is red) are not built correctly. The spring is not centered on the post in the back of the can. The actuators either have the spring on the post or off to the side. The actuator valves equipped with the springs that are off to the side bind as the arm is pulled in. They are either good (spring on the post) or bad (spring off to the side). There's no in-between.

NOTE: The arm must retract into the can all of the way to the taper on the arm for full opening of the secondaries.

 

[90 Corvette ZR-1]

Great info, anyway to check to make sure that they arn't backward on the car without pulling anything

 

[Chris@vettefinders]

I am currently chasing down a hesitation problem and noticed that my actuators were on backwards. I don't think that is my problem, but I'll fix it while I'm there. Here's a picture of what it looks like backwards.

 

[Rob]

I am currently chasing down a hesitation problem and noticed that my actuators were on backwards. I don't think that is my problem, but I'll fix it while I'm there. Here's a picture of what it looks like backwards.

Chris,

I'm not 100% sure, but I believe that if the actuators are installed backwards, their range of motion may be limited so that the secondaries are not opening all the way. I don't think that would cause your hesitation problem.

Let us know what you find and how it turns out.

 

[White 68]

Great info, anyway to check to make sure that they arn't backward on the car without pulling anything

You can see the drivers side actuator using a small flashlight ...its located under the vacuum hose coming out of the plenum in that gap you should see it ...if that ones 180 out the other probably is to..:bang

 

[DDSLT5]

I am currently chasing down a hesitation problem and noticed that my actuators were on backwards. I don't think that is my problem, but I'll fix it while I'm there. Here's a picture of what it looks like backwards.

What's up with the little spring/wire that is coming off the side of the actuator? What is it doing?

 

[Demps]

Good Actuator

Here's a pix of one of the new ones retracted.

 

[Demps]

Bad Actuator

Here's a pix of a bad actuator retracted.

 

[roadster]

Don´t say I´ll have to pull that plenum again...By the pics shown it looks like my left actuator lever arm is sitting at an angle, unfortunately I can´t quite se the right one.

Do I really have to correct them?? Whats the diffrence in HP, anyone dyno tested or can you really feel a difference in performance? Mine seems to open ok and do not bind.

Is it the hole vacuum actuator lever assembly you turn upside down or the cannister or the arm itself? I read somewhere that if the actuator has been mounted incorrect from factory, turning it right could cause the bladder to leak.What do you guys think...

Regards

 

[xsmph]

I've had really bad luck in the past with the New RED (internal) actuators and coil bind. Those red actuators need so much pressure to fully open, or at least the ones I got. I decided to leave the old one I had wich would hold only 4 h.g instead of 7, but the pump was able to take care of it. Pump cycles every 30 sec. or so ,I went through 3 red ones before the parts guy got upset!

 

[95ZR1#418]

Is there any other source of good actuators. I would imagine it won't be long and GM will discontinue them anyhow.

 

[FrankUrbinati]

Just bought 4 new accutator's. To replace the 2 that were installed backward's. ALL 4 new accutator's were bad. The spring's were installed crooked. And they required 11-14+ hg. to open them fully , with severe coil bind. The old stock one's opened at 7 hg.I reinstalled the old one's backward's , in fear that the new position would tear a hole in them. Oh well the manifold was up for other reason's anyway. BTW the old "backward" secondary's opened just fine.

When the heck is GM going to get with the program. And stop getting part's made in Mexico ?? (RANT)

Anyone know where I can get a set of GOOD accutator's ??

TIA !!!

 

[roadster]

Mine was also on backwards, but they operate just fine anyhow..
8Hg to fully open, and no bind. To tell by the post in this forum many owners have them on backwards, and as long as the valves open and closes fully there´s no reason to buy new ones or correct them.
If on the other hand they are bad, leak or bind etc the new ones from GM with red diaphragm seems to be bad, spring of post..

Try Kurt white at whiteracingproducts.com he has new actuators, but I don´t know who he gets them from...