'88 plenum
Thread Starter
Racer
Joined: Jul 2006
Posts: 277
Likes: 0
From: TONOPAH AZ.
St. Jude Donor '06
'88 plenum
How much of a job would it be to loosen and "lift up" the plenum so I can get to my thermostat and egr solenoid valve better? I want to replace the vacuum lines while I'm under there.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Just use a #40 torx bit to remove the top runner to plenum bolts. Take all the hoses, cables (don't loose the clips), air duct, and connections off the TB and it can stay on the plenum. The gaskets actually have little plastic fitting that push into the plenum so becarful and you may want to have a extra set of gaskets if the vette is only transportation. The brake booster vacuum has to be removed and the MAT sensor has to be disconnected. If it is too difficult after that you may want to loosen the bottom runner bolts. These are aluminum so becarful when tightening them.
Start the bolts back in by hand as far as you can so you don't strip them.
Start the bolts back in by hand as far as you can so you don't strip them.
Race Director
Joined: Jan 2004
Posts: 18,722
Likes: 708
From: Bergen County, NJ
Originally Posted by RRT vette
Just use a #40 torx bit to remove the top runner to plenum bolts. Take all the hoses, cables (don't loose the clips), air duct, and connections off the TB and it can stay on the plenum. The gaskets actually have little plastic fitting that push into the plenum so becarful and you may want to have a extra set of gaskets if the vette is only transportation. The brake booster vacuum has to be removed and the MAT sensor has to be disconnected. If it is too difficult after that you may want to loosen the bottom runner bolts. These are aluminum so becarful when tightening them.
Start the bolts back in by hand as far as you can so you don't strip them.
Start the bolts back in by hand as far as you can so you don't strip them.
Basically, take off all the bolts that holds it together and put them back the same way. Take your time.
The plenum is soft aluminum, so the advice about starting the bolts by hand is important. Make sure its lined up properly and don't force the bolts.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
All the comments above are very good. A couple of points to add:
1. After you remove the upper runner bolts (note that some of these bolts are different in length) and the throttle body, tap under the plenum with a soft face or rubber hammer. The plenum will just come free.
2. Do not use any gasket sealer on the new runner gaskets. You may want to use gasket adhesive to hold the gaskets to the runners for ease of assembly.
3. Use anit-seize compound on the bolts prior to inserting them into the soft aluminum.
4. Torqe the runner bolts to 25 ft lbs torque. I think the Helms manual gives a higher torque value. GM put out a service bulletin to change the torque value in late 1988.
5. My 89 has a vac fitting under the plenum that is easy to miss when removing vac lines.
Take your time and note what goes where.
1. After you remove the upper runner bolts (note that some of these bolts are different in length) and the throttle body, tap under the plenum with a soft face or rubber hammer. The plenum will just come free.
2. Do not use any gasket sealer on the new runner gaskets. You may want to use gasket adhesive to hold the gaskets to the runners for ease of assembly.
3. Use anit-seize compound on the bolts prior to inserting them into the soft aluminum.
4. Torqe the runner bolts to 25 ft lbs torque. I think the Helms manual gives a higher torque value. GM put out a service bulletin to change the torque value in late 1988.
5. My 89 has a vac fitting under the plenum that is easy to miss when removing vac lines.
Take your time and note what goes where.
Last edited by Sam Lam; Oct 15, 2006 at 07:08 AM.
