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Plenum Actuators



I'm brand new to my 91zr1, I bought it about a month ago. A week ago I drove the car in "Full Power" and the secondaries would not "come in". I took the car to have all fluids changed and the radiator flushed and a new thermostat installed. I asked the service people about the secondaries/actuators. After three days they advised me the actuators had been put in "upside down", and they could fix it for $500.00. They also told me a lot of things they should do to the car at a cost of over $7000.00, and none of the required work was covered under the warranty I purchased at the same dealership 1 month ago. I said before I was new to the ZR1, but I'm certainly not new to unique cars. I have built 13 street rods, had two fast Porsches, 1 early Corvette and now have a 550 horsepower Pantera in the body/paint shop.
I was shocked!! They wanted $5884.00 for front and rear shocks and a ride control switch.
Is this a normal occurrence or was I wearing my "Tell me anything, I'm Stupid" t shirt.
If any one of you were to drive my car you might comment on the front shocks being a little soft-nothing else.
So if you try Tom Bell Chevrolet in Redlands, CA bring your $$$$$ and a loan application.



I can't speak for everyone, but I'd say you had that shirt on.

A year ago, I had a high idle problem, and the dealership (who never sold ZR1's), got some software for a laptop with which they diagnosed the car while driving it. Result-Change the entire ECU to a newer version, cost$ 189. I had already replaced the PROM myself, purchasing it at another dealership for $47.

You have enough experience, it seems, you might want to pull the plenum yourself. It's easy, and you can fix vacuum leaks and the actuators. In fact, I don't know how they gave you the "upside down" diagnosis without pulling the plenum. One point some don't agree with. If you do pull the plenum, be SURE to drain the coolant.


Site Administrator
Staff member
Sep 16, 2000
New Hampshire
1990 Corvette ZR-1
Some ZR-1s were known to have come that way from Mercury Marine. If the actuators are installed backwards, the range of motion that the plunger arm has is very limited.

As for the SRC (selective ride actuator), these are very expensive and the teeth that control the internal dampening rod in the adjustable shocks, can wear with age and use.

I pulled the following information out of our Knowledgebase linked above this page under the ZR-1 Category and Chassis and Suspension subcategory:

An alternative to replacing used Bilstein adjustable shock absorbers is to have them re-valved by Bilstein Corporation. Bilstein will rebuid/re-valve your shocks, per your instructions, for $55.00 per shock. (This is much less than purchasing brand new ones) The turnaround time for the rebuild/re-valve service is about 2 weeks. This service is performed at Bilstein in Poway, CA.

They also sell the Bilstein FX3 Controler, Slalom & Road Race chips, and front/rear actuators for selective ride Corvettes.


Krupp Bilstein of America
14102 Stowe Drive
Poway, CA 92064
Email: Bilshox@AOL.COM
Phone: 800 537 1085
Contact: Bill Hindorf
Web Site: http://www.bilstein.com

Hope this helps. Keep us posted!


Great point, I had heard, then forgotten that. Thanks.



Thank you Rob for the Bilstein rebuilding info. When I catch my breath (Pantera restoration) I will contact them and make necessary arrangements. This board has been very informative to me and I appreciate everyone taking their time to respond.

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