V2Rocket

Does the 1985-1986 "S3" 5.0 DOHC engine have oil check valves in the heads? They are installed in the 944S and the 928S4 heads, but looking at the PET and inspecting my own S3 heads I don't see anything.
Where the check valve would go on an S4, there only appears to be a freeze plug at the top of the drilled passage on the S3 head. No provision for a set screw either.

Below see PET for 87+ S4 (left) vs 85-86 S3 heads, S4 check valve circled in red:

ROG100

I have never seen any on an S3 head. However they did change stuff prior to the end of production late 86 MY.

skpyle

Hello Gentlemen, I recently went through all this.

S3 heads DO have the oil check valves. However, they are not 'easily' serviceable like on S4 and later heads. There are plugs that are pressed into the check valve bores that seal the assemblies. These plugs must be drilled then tapped to receive the end of a slide hammer. Jerk to remove. Inside, the guts are the same as S4 parts. Upon reassembly, the plug must be sealed with green loctite, and a set screw sealed in the drilled hole in the same manner.
Also, from mr merlin, if you disturb the check valve seats, you MUST peen them back into place. Otherwise they pop out and bad things happen...


#$%^&*( For whatever reason, either Windows or IB won't let me post photos today. So...please go here:

See Post #8 for photos of the plugs over the oil check valve bores in the cylinder heads:

https://rennlist.com/forums/928-foru...s-as-well.html


See Post #107 for photos of the drilled and setscrewed plugs over the oil check valve bores in the refurbished cylinder heads. You will have to look closely at the upper right corner of each cylinder head in each photo to see.

https://rennlist.com/forums/928-foru...e-heads-8.html


Sorry, no photos of the actual oil check valve ball, seat, or spring.

Note, my machinist did this work on his work bench. There is no way I would consider removing the check valves with the heads still installed on the engine in the car.

V2Rocket

Seth, thanks for the info.
So when the freeze plug comes out and the "guts are the same as S4"...is there an O-ring needing attention?

skpyle

Hi V2Rocket! Yes, there is an O-ring in there that can be replaced. For what it is worth, the plugs are not freeze plugs, but solid chunks of aluminum.

BC