Our local club had a shop day yesterday and I had my 89 coupe checked out as I had oil leaks that I wasn't sure where they were from. Looks like the back side of the block is the culprit and the likely problem is the intake. The senior tech said it's a common issue with the aluminum intake and cast block moving at different rates with heat cycles.

So, it looks like I got a new project.

What do's and don'ts can you give me?
How many hours should I expect?
Is there a brand or type of gasket that I should get to be sure on the replacement?
Other things I should consider?

Thanks

 

You can't go wrong with Felpro gaskets. But most of all, use Permatex "THE RIGHT STUFF' for sealant. Past threads have also suggested an additional step which I have used on my truck and the Corvette. Take a center punch and "dimple" the block area between the heads at the front of the block and the rear. This is the area that you will put a 3/8" bead of THE RIGHT STUFF as the sealant rather than a gasket. If you also dimple the same area on the intake this will hold for years.

The logic behind this is that the block and intake in this area are smooth and don't give the sealant anything to bit into. The dimpling of these areas give the gasket material something to grasp. It was worked will on my truck (3 years on that gasket) and on the Corvette (2 years on this one).

The Right Stuff can be used right away, where as silicone should be left to set at least 24 hours.

This is not the most fun mechanical job to perform on the Corvette. Just be sure to take your time and label everything as you take it off. Note that the bolts on the runners are different sizes. Also take a few pictures if you have a camera.

Good Luck,

 

The dimple idea is interesting, it must take some serious force to dimple the block surface if I'm undestanding you correctly.

This area that your suggesting a 3/8" bead of sealant in place of the gasket is this the front and back of the block or just in the corners?

 

Here are a couple more suggestions for you on the 89 intake manifold replacement:
1. The female thread in the head is soft aluminum. Place each intake manifold bolt into a threding die to make sure you have clean threads. If you attempt to install a steel bolt with damaged threads, you will strip out the female threads. Ask me how I know this
2. Take a picture of the position of the intake gasket on the manifold. The Hemls manual is incorrect on the positioning of the "blocked off" water port. Use the original as a guide.
3. Go to NAPA and get some Anit-Sieze compound. Using the brush in the container, place a light coating on the steel bolts prior to screwing into the aluminum heads.
4. If you re-use the Torx bolts, take care to keep the socket and extension on the same center line of the bolt. Apply pressure to the bolt as you remove it. Failure to do this will caues you to strip oun the Torx hole......and this is not good. If you strip out an aluminum thread, use a Heli-Coil device. This is easy.
5. As mentioned earlier, the runner bolts are different lengths. Keep track of what goes where. There are a few runner bolts that are hidden and must be loosened from the opposite side of the engine. Take your time on these bolts.
6. I assume you know to mark the position of the rotor on the dist and mark all spark plug leads. This will save a ton of time when reassembling.
This is all that comes to mind at this time.

 

It really takes no effort to dimple the block. Yes the front and back of block and intake and corners(right stuff).

 

Had to replace my intake gasket on my 89 4 years ago. Not a fun job but not hard either. Good luck!

 

Also, buy an aerosol can of Permatex Gasket Remover. It took me about two and a half hours to remove the old gasket material from all the parts.

 

Any suggestions on cleaning the intake and runner up before re-installation? Mine aren't too bad but I'd like it to look good upon installation, my stock valve covers are bad and I might do these at the same time, that way I will have new seals on the entire top end pretty much.

 

I cleaned the Plenum, Runners and Intake manifold with Simple Green.

If you're going to remove the Valve Covers, mask off and paint them a color you like since simple green won't clean the orange discoloration.