I recently purchased an '89 coupe that's in poor condition. It leaked oil like a BP Gulf oil well. I am replacing the intake manifold gaskets in hopes of stopping the leak. Fel-Pro gaskets are marked with the coolant passages to the rear. The Chilton manual says the same. I have a factory service manual that clearly states to block the front coolant passages. What is the correct passage to block?

Also, before I reassemble this thing, is it very likely that the leak could be from the head gasket? Before I started this project, the entire rear of the engine was drenched in oil. The source of the leak did appear to be behind the rear of the intake. But there was so much oil it was impossible to tell for sure.

Any and all information would be greatly appreciated.

 

there are several threads on here under the search option on intake gasket replacment for your year vette, i belive there is a really good one with pics. check it out,,,,, i just changed my intake gasket as well and cant seem to remember which passage was the blocked one, front or rear, i want to say rear but not 100% positive. your gasket from felpro should have one of the holes blocked off already. not to sure about your oil leak, sounds like alot of oil to be comming from the intake, could be valve cover gasket

 

These head gaskets cannot leak oil. It is physically impossible. For one the only oil passing through the head gasket is though drain holes leading back down to the oil pan via gravity. This oil is unpressurized anyway. The other factor is the location of these drain holes in relation to the cylinder bores. The oil would end up in the bores before it would end up on the outside edge of the block/head past the head gasket even if it could. Bottom line your head gasket is not leaking oil because it can't.

Any oil that you are seeing in the crevise between the head and block is coming from the back of the motor and seeping down along that parting line making it look like the head gasket. The same can happen for the front.

It's either your distributor gasket which sits sandwitched between the intake and base of distributor shaft, the intake manifold, or the oil pressure sending unit that's back there or a combination. Since your intake is off make sure you don't have any leaks form the pressure switch because once the motor is assembled it's a pain in the azz to access it.

When you install new intake gaskets you have to lay a good bead of sealant along the front and back walls of the block. You also have to overlap the intake gaskets by about 1" both on top and bottom sides in this area. Do not use the supplied cork strips that come with some intake gaskets. They are garbage and unrealiable. All surfaces must be immaculate and completely dry in preperation.

Your bead should look like this.



Remember there should be sealant overlaping onto the gaskets on the underside as well as the top side as pictured here on both ends of the engine block. So the bead is layed down first overlapping onto the head by about 1". Then you set the intake gaskets down while tacky. Then you add more sealant only on the uncovered upper edges of the gaskets to complete the overlap.

The intake needs to be set exactly straight down and torqued while the sealant is still tacky. If not start over. If you set then shift the intake around to align it you'll smear around the sealant and disturb the gaskets which compromises your seal.

 

To answer your question, the restricted ports ( port with the small hole) goes to the rear of the motor.. Your 89 GM factory service manual is wrong, just like mine is..This is a misprint and has confused a lot of people..I have found many errors in the Factory Service manual , quite a few of the torque specs are also wrong...WW

 

Thank you for the information.

 

with above posts......except you can suck oil from the block valley if the intake gasket is bad directly into the intake port. Your plugs will foul and be covered with oil. Chevy's have been known for this problem for years. It was one of the problems I fixed when I first got my 85. You should take a center punch and dimple the "china wall" at the front and rear of the block. This gives your sealant as shown in the picture by 86PACER something to bite into. I also dimpled my intake in these sections too. I would also recommend using the RIGHT STUFF instead of silicone.

It is also possible that your oil leak is from the sending unit located at the rear of the block under and to the drivers side of the distributor. These can pour out more oil than you can believe possible in a short time. It will be pouring off the back of the block and have a pool within minutes.

 

What J A M said. I would check the oil pressure senders before I started taking things apart.