C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Removing Plenum

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Old Jul 22, 2002 | 09:18 PM
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Default Removing Plenum

Can it be done without removing the runners on an L-98? I've had the top apart before to fix the dreaded oil leak on the intake, so I had to remove the runners anyway. But if I remember the Plenum is angled on both sides and maybe will pull straight up. Anyone ever do this? :confused:
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Old Jul 22, 2002 | 09:24 PM
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Default Re: Removing Plenum (cshuman)

Yes, the plenum can be removed by itself without messing with the runners. Be sure to get new plenum gaskets before reinstalling. It comes off pretty easy. You can leave the throttle body on also. I did this project once to replace the egr valve on my '88. Take your time and do it right the first time.....that's my motto! Took my about an hour to r/r the egr.
Good luck,
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Old Jul 22, 2002 | 09:30 PM
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Default Re: Removing Plenum (cshuman)

Just removed the whole top of the engine on my '85 L89 yesterday. The FSM says to loosen the passenger side runner before removing the plenum, and I could see no other way to do it. I couldn't get at the electrical connection under it otherwise. I am a novice with c4's so maybe there is a way. Good Luck
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Old Jul 22, 2002 | 09:38 PM
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Default Re: Removing Plenum (64FITanker)

I think Fixvet is right. Once you get it loose and lift it up a little you can hopefully get to the electrical connections. I am going to try it that way first anyway. Thanks for the input guys! :yesnod:
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Old Jul 22, 2002 | 09:39 PM
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Default

Those gaskets are in there pretty tight, how would you get the new ones in without loosening up one set of runners a smidge?
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Old Jul 22, 2002 | 09:46 PM
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Default Re: (scorp508)

The sides of the plenum are angled a little. I think it is enough to let you set it back down onto the runners when its put back together. I thought it might work, Fixvet says he has performed this magic before
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Old Jul 22, 2002 | 10:12 PM
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Default Re: Removing Plenum (cshuman)

Even with the TB attached you can raise the plenum without removing the runners. You may need to "nudge" it a bit at first though to get it started.

In fact, since two lower runner bolts are inside the lower runner bolts have to be tight before the plenum goes back in.
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Old Jul 23, 2002 | 10:20 AM
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Default Re: Removing Plenum (65Z01)

Fixvet is absolutely right - you can remove the plenum without disturbing the runners at all. I just removed it on my '89 a couple of days ago and was suprised how easy it came off. And the gaskets will go back easy too - the plenum-to-runner mating surface is angled and the gaskets themselves have little plastic tabs that hold them in place. Not a difficult job really.

Just make sure you have a #40 TORX bit ready before you start.

Good luck
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Old Jul 23, 2002 | 10:34 AM
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Default Re: Removing Plenum (TheCorvetteKid)

I wish I was as lucky! When I removed the Plenum last year the runner to plenum gasket on the passenger side got severely wrinkled.


[Modified by War Machine, 8:34 AM 7/23/2002]
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