I am about to tackle taking the plenum off my 1989 Corvette L98 and am wondering if there are any good write-ups out there? Any advice?

Thanks

 

its not a big deal. I swapped mine out yesterday and had it off in 5 minutes.

4 bolts each side for runners. 4 bolts throttle body to plenum. 2- 10mm bolts holding the cable bracket to plenum.

Pull air intake duct, remove cable bracket and set aside, pull TB and pull forward. Pull the 8 runner bolts, lift plenum to d/c the brake booster vac hose. Remove 2 small vac hoses opposite corner. Unplug MAP sensor underside. Lift out. Spray runners clean with Carb cleaner. They will need it. Hose out the TB too. Clean the plenum. This is your chance, it gets dirty in there. When done douching things, cover runners with rags so things do not fall into the open runner tube..you'll never know it until you hear the valve bend.

When reassembling, smear a thin coat of anti-seize on both sides of runner gaskets and TB gasket. This prevents sticking and tearing later and allows re-use.

When torquing runner bolts do the 2 center 1st, then to the outside 2.
With plenum off replace the EGR vac line, clean as needed. Check any intake bolts that are accessable for tightness.

If you are going to the EGR, that requires a couple different wrenches to get to the 2 bolts..the rear hard to get a tool on. A socket is useless...

 

The usual applies, no metal hammers, do not use screwdrivers as pry bars, etc.
it is ok to tap (lightly) with a rubber hammer a little to unstick the gaskets on the plenum. tap on each end, do not tap side to side.
be sure to change the o rings in the fuel railas well as injector o rings. fill the head ports with rags, to keep small parts and dirt from entering them, and leave a "telltale" bit of the rags ouside the ports so you can see that you didn't leave them in there.
Now would be a good time to add an adjustable fuel pressure regulator.
Move the manifold air temp sender on the under side of the plenum to a cooler spot so the computer can accurately measure the incoming charge, not the heat soaked manifold that it is screwed into.
Other than that, have fun. use towels to cover the front tires, and you can use the tires as your chair on each side.
THe injector wires pull back from the front and splay out at the back of the engine if you undo all the connectors.
Be careful that the clips on the connectors do not get bent too much, as they have a tendency to snap off, making you buy new ones.

 

Not always that easy if plenum hasn't been removed for a while.
Gaskets stick everything together solid,
runners clamp the plenum tight requiring loosening / removal of the runner to intake base bolts
Even then on some, with all the bolts out , I have had to crack the plenum loose, levering with a length of water pipe
through the TB holes while tapping on the plenum with a rubber hammer

 

So if the gaskets look good, I can reuse them by applying some anti-seize?

Is it harder than I think to use new gaskets? I imagine since the runners are still hooked up, just disconnected from the the plenum, is it tough to get the gaskets to stick against the runners when putting the plenum back in? (if that's even the correct process, I'm just trying to speculate to figure everything out)

 

Unless the runner gaskets were installed with grease originally you won't be getting them off in one piece
and you will be having fun with a scraper cleaning up the gasket surfaces
TB gasket is often reusable

 

The anti-seize is for next time...if these are virgin they're toast! The new gaskets will have alignment tabs that hold them in place so you dont have to...the "fit" of the plenum in the runners is pretty exact..not a lot of extra room.

Vetteoz is right...I'm making it sound easy 'cause it IS...on MY engine ! and I've done it a hundred times..

Mines been prepped with every means to pull it apart quickly and painlessly..yours will be a wrestling match the first time. And as oz says...no pry bars in the seams, no screw drivers...use the TB ports as a place to stick a cheater pipe but BE gentle ! Remember, its aluminum and its much softer than steel parts or iron.

You WILL be scraping the gaskets off...plan on that. I often make the mistake of thinking that everyone is working on my engine thats got many things "built-in" for ease of maint and disassembly next time. Like EGR bolts...I never-seize those. They come out with fingers after breaking them loose. Why? 'cause those get very hot, they are damn difficult to get a wrench on and if I had to use a wrench to turn that rear bolt the whole way out, I'd sell the car. I plan ahead and use the headaches of today to avoid another one tomorrow...

So be prepared..the first time the plenum comes off is the worst by far. It'll act like its glued on, so be patient and use the tips the other guys mentioned.
I kept looking for another bolt I figered I missed...

 

If removing the runner to base bolts don't forget the" hidden" bolt that goes through from the other side of the intake
Pass side runner from drv side front , drv side runner has bolt from pass side rear as shown in red
Many have only undone the 5 bolts visible on the outside and then destroyed their runners trying to remove
them with the "hidden " bolt still in place thinking it was only the gasket holding the runner

 

Also, make sure you mark the location where the bolts come out. Ther are different length bolts used on the plenum.

 

Good advices,i had my plenum off,i don't know how much time the previous owner did it ,but mine came off easy,just a tap on the end side and i have it on my hands.Now it is a chanche for porting the aluminum boss in front of plenum ports.

look at this ,step by step take off for injectors swap,first part of video shows you how to remove the plenum
http://www.youtube.com/watch?v=49WXmzfOy4k

 

I didn't take the runners off. I just slipped the plenum straight up from between the runners.
I highly recommend replacing the the o-rings on the fuel rails and tubes, the EGR valve, the diaphragm in the Fuel Pressure Regulator, the Manifold Air Temperature sensor, and anything else, while you have it off.
I also recommend that you jack the car up and remove the front wheels to give better access to the top of the engine. Use jackstands. Your back will thank you for it.

 

some of the torx bolts are a pain in the butt to access. here's something i put together that makes things a lot easier -



1/4" drive, 1/4" swivel socket with a T40 torx insert. a little dab of RTV keeps the insert in place.