1998 Vortec 5.7 Intake Gasket... Help!

[300sflyer]

Please have a look at the pictures below. The Felpro intake gasket in the picture fits perfectly on the heads. When you lay it on the intake, [2 barrel carb] you can see it does not seal on cylinders 3, 5, 4, and 6 on the bottom inner corners. The engine burns about 1/2 quart of oil in 4 hours, and now I know why...

How can I fix this? Does an OEM Merc gasket have different port opening sizes than a Felpro or Sierra?

Thanks for your help!

 

[Scott Danforth]

welcome to the world of the small block chevrolet.

FYI - oil does not flow into your intake. there is NOTHING in the intake or its gasket that can cause an oil leak. coolant leak or air leak - yes, oil leak - no.

gasket is fine, the port mis-match is common for intake manifolds and heads. hence the reason you can get 30hp by simply port-matching the heads and intake.

 

[Grub54891]

Thats strange. Aftermarket gaskets should work but I'm not an absolute expert either. Them slots look as if the gasket could be moved up/down to the proper place. But how do you keep it there when installing?

 

[300sflyer]

The engine is burning oil. There is an internal vaccum leak, and it is sucking up oil from the lifter valley. The 4 spark plugs in those cylinders are caked in oil. The intake manifold is OEM Merc 2 barrel .

 

[300sflyer]

Thats strange. Aftermarket gaskets should work but I'm not an absolute expert either. Them slots look as if the gasket could be moved up/down to the proper place. But how do you keep it there when installing?

There are two pins in the gaskets that go into the heads that hold them in place. They cannot be moved.

 

[Scott Danforth]

even if there is a vacuum leak, the crank case is under pressure, hence the breather lines to the spark arrestor. in an automotive application, it would be a PVC valve.

do a compression check and a leak-down and you will find your oil leak if it is truely being burned. many times, the oil cooler springs a leak and it is pushed into the Fresh Water stream.

also, Felpro makes more SBC gaskets in a year than Mercruiser makes motors.

 

[300sflyer]

even if there is a vacuum leak, the crank case is under pressure, hence the breather lines to the spark arrestor. in an automotive application, it would be a PVC valve.

do a compression check and a leak-down and you will find your oil leak if it is truely being burned. many times, the oil cooler springs a leak and it is pushed into the Fresh Water stream.

also, Felpro makes more SBC gaskets in a year than Mercruiser makes motors.

The engine does have a PCV valve. There is no external oil leak, it is being burned. Compression is 175-185 in all 8 cylinders. There is NO DOUBT it is being burned in the those 4 cylinders, because the intake is not sealing properly on the intake ports on the heads.

 

[Bt Doctur]

You cannot just match it to the manifold, how does the seal look when the gasket is placed on the heads?

 

[300sflyer]

You cannot just match it to the manifold, how does the seal look when the gasket is placed on the heads?

As stated in my first post, it lines up with the heads just fine. The issue is how it sits on the intake. Look at the bottom inner corners of the two inner intake ports in the second picture. You can see the gasket does not even make contact with the intake in the corners.

 

[Bt Doctur]

The first pic shows a perfectly good gasket seal, don't see where you mean in the bottom pic.

 

[300sflyer]

This picture provides a better view. The other inner corner is the same. You can see where the gasket does not touch the intake casting.

 

[Watermann]

I've done a couple of intake jobs on my auto 5.7's and have by good advice only used OEM gaskets not the Felpro. I also tossed out the rubber end rail seals with the same advice and used the black RTV. Also the 5.7's are notorious for oil creeping up the bolts and pooling in the valleys, all except the corner bolts which are blind and aren't open to the lifter valley so I've used thread sealer on them to stop the oil leaks.

 

[Bt Doctur]

post a clear pic of just the manifold, I don't see that missing chunk in the first pic

 

[Bt Doctur]

there are 3 different manifold gaskets by fel-pro with different port sizes.
fp 1205S3 2.090H, 1.280 W
fel1267 2.280 H, 1.380 W
fel 1255 2.110 H, 1.080 W

 

[dan t.]

First of all throw out that crappy plastic based gasket and get the Fel Pro aluminum based gasket. The rubber sealing beads are 3 times wider and will seal perfectly. As for oem gaskets junk is the only word to describe them, they are plastic based and are garrenteed to fail.

 

[300sflyer]

post a clear pic of just the manifold, I don't see that missing chunk in the first pic

The picture you requested is below. You can clearly see the gasket does not seal in the lower right hand corner.

 

[300sflyer]

there are 3 different manifold gaskets by fel-pro with different port sizes.
fp 1205S3 2.090H, 1.280 W
fel1267 2.280 H, 1.380 W
fel 1255 2.110 H, 1.080 W

The gaskets used were Felpro 90131, pictured below. Not sure what size ports they have.

 

[300sflyer]

The original OEM Merc intake gasket part # is 27-807473A1. Does anyone know what size the ports are on this gasket? [h=2][/h]

 

[Watermann]

No doubt about it, 100% that gasket doesn't fit your intake and that would surely cause the intake port to suck in oil just like you say. No other option but to find a gasket that does fit unless you want to go to a 4 BBL intake and carb. Just out of curiosity what was the original gaskets failure symptoms?

 

[300sflyer]

No doubt about it, 100% that gasket doesn't fit your intake and that would surely cause the intake port to suck in oil just like you say. No other option but to find a gasket that does fit unless you want to go to a 4 BBL intake and carb. Just out of curiosity what was the original gaskets failure symptoms?

The OEM intake gaskets were tossed, when the original engine was replaced with a long block. The intake is the Merc original, and was reused.