I have the same conditions as this past thread shows where the valves already have carbon/oil build up on them exactly as he shows in his pics. http://forums.corvetteforum.com/show...intake+sealing

My rear intake seal is not working either after two trys with Ultra Black only. I also used a thin finger amount on both sides of Fel-pro 1205 gasket around the intake ports. When I looked at the intake gasket the first time there was no evidence of oil on the gasket near the intake ports. For the rear I had cleaned the block using accetone before applying Ultra Black, letting the sealant sit 15 minutes before intake installation. The leak is seaping right under the sealant bead in 3 tiny areas so the block is not adhereing to the sealant.

I basically have two questions. Is the build up shown in the pics normal and not due to oil consumption?

And, what else can I use to make sure I wont need to try this a 4th time on the rear seal?

 

Use of acetone maybe reacting with the silicone. Try using a brake/electric motor cleaner to sanitize before applying silicone. Even some spray degreasers sold as brake-clean use a propellant in the can that leaves a "greasy" surface; silicone will not bond to this.

Remember, the lifter valley only sees crankcase pressure. When the pressure builds up in crankcase the intake seal is first to go, then old gaskets and seals are the next weak link. The PCV system removes/reburns/scavenges this pressure. Make sure you have a system in place similar to the O.E. with vent on one side and sucking PCV valve on the other. If you have aftermarket v/c, check that they're baffled and not spraying oil right at the PCV valve.

If your intake surfaces match the other post it's not the intake gasket. You could how ever have a miss match in the machining that allows more clamping at the top of port verses the bottom area. This would allow intake vacuum to suck oil from the lifter valley.

Previous post showed a lot of oil, he ended up have a few issues going on at once. But I believe he solved it by checking intake bolt hole clearance around each intake bolt, which prevented proper bolt load. Once he clearanced each hole it seemed to solve the issue.

Hope this helps,
Later.

 

Yeah, I didnt get why he had to open his intake bolt holes. Mine are fine so no issues there. I'll try some brake cleaner this time instead of accetone.

I thought his valve issue may have been from richness and not oil seepage.

 

Use "The Right Stuff" sealant. It is the best but costs much more. You'll see why after using it.