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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.

Clean_first.jpg (167868 bytes)

This 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 yourself.

 
Plen_bolts_lft.jpg (149605 bytes) Plen_bolts_rt.jpg (136227 bytes) 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.
 IAT_location.jpg (43423 bytes) vacuum_fitting.jpg (113071 bytes) 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).
getting_at_rear_of_plenum.jpg (106074 bytes) T40 7 inch trox socket.JPG (24881 bytes) 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!
plenum_off.jpg (145951 bytes) Here's how it looks with the plenum off.  
tach_wire_position.jpg (111653 bytes) dist_position.jpg (161840 bytes) 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.
injectors.jpg (133402 bytes) fuel_line_plug.jpg (119979 bytes) 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.
intake_off.jpg (410081 bytes) The intake is off.

 

 

front_seal.jpg (140480 bytes) rear_seal.jpg (153328 bytes) 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.
intake_back_on.jpg (173279 bytes) Here the intake is back in place.
runners_back.jpg (142228 bytes) And the runners are back on.
done.jpg (335834 bytes) 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!