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I took a three-day weekend the last week of April 2006, ostensibly
to clean out the basement, but also to repair an oil leak which had developed in
the rear seal of my intake manifold. I took pictures, so here's how I
fixed it. Not meant to replace the GM Service Manual, but maybe this will
help if you decide to do this the first time. Throughout the article, you
click on any pictures for a larger view.
The Corvette intake manifold is sealed by a composite gasket on
the cylinder heads, but uses a bead of RTV sealing compound at the front and
rear of the valley. Over time, this seal is prone to leaking and must be
replaced, which necessitates removal of the intake manifold. I begin by cleaning
the engine -- no one likes working on a dirty engine.
is really a pretty straight-forward job of unbolting and re-bolting parts --
there's just a lot of parts. Start as you would any project by disconnecting
the battery, then you're all set to begin unbolting. Here's a general
progression, but remember that you'll need a GM Service Manual if you try this
||Start by unbolting the plenum from
the intake runners and the throttle body, then the plenum comes straight up
to remove. The intake runners are held in place with T-40 Torx bolts, and
the throttle body uses 10mm bolts. Throughout this repair you'll
find that you'll use these two sockets a lot.
||There are two connector under the
plenum which give some people trouble: don't forget to unplug the
Intake Air Temperature sensor, and to disconnect the vacuum feed at the
rear of the plenum (5/8" and 3/4" fittings).
||The first time you do this repair,
you'll wonder how in the world you are supposed to get at the plenum bolts
which are hidden inside at the front and the rear. Just use a long extension.
Note added 5 April 2007: A reader on the Corvette Forum successfully
used these instructions to complete this repair on his '88 and recommended
the 6" T40 extension shown here. It is available from
Snap-On. Thanks Jim!
||Here's how it looks with the
||I can never remember the position
of the two connectors on the distributor, so picture helps. Once the
distributor cover was off, I took a picture of the distributor position
prior to removal. You'll see later that by using this picture, I was
able to get the distributor back in correctly the first time.
||Pull the injectors and the fuel
rail as a unit. I use plastic plugs for the fuel lines to keep fuel
from leaking out during this repair.
||The intake is off.
||After thoroughly cleaning the
mating surfaces, install new gaskets (I used FelPro) and run a bead of RTV
along the front and the rear of the intake valley. I used black RTV
in the front, but opted for the stronger copper RTV on the rear.
||Here the intake is back in place.
||And the runners are back on.
||Done. Believe it or not, it
started as soon as the fuel pressure built (10 seconds). I put a timing
light on it to check timing, and it was dead-on. Credit the photo I
had taken earlier showing the distributor position. I was done!