Question , I'm rebuilding my STR motor and there is a ridge around the center hole on this gasket both sides are same . Is this correct ? Is it a compression ridge ? The top photo is on the intake the second is showing the ridge . Any guidance before I install would be great. all other holes are flat.

2003 s type r

Carbon fiber assesories

Engine is back together , fresh

Starting reassemble

 

I read the question many times and still I can only guess what the question is, as you did not circle in the ridge in question.

First of all, I am amazed that this engine block looks like new.
Secondly: It looks unfamiliar to me - maybe this section looks different on an STR (I do not have an STR).
You did not mention your build-year.

So is there only one possibility to position the gasket? Or does a mirror-image positioning of the gasket result in the ridge being located over a different hole instead? If that is the case, there would be only one correct way. I can only guess by looking at your picture: Do I see correctly that you have the ridged section of the gasket positioned over a threaded hole, while the hole in front of it (at the very bottom of your second picture) does NOT that a thread? If that is the case, I'd say you have the gasket positioned incorrectly: Because that non threaded hole is most probably a "channel" in which engine oil or coolant flows, and hence it would require that special ridge to really seal the fluid in the channel, while a threaded hole would be filled with a bolt, not needing a special ridge.]

But all that is just me guessing on the basis, what I think I see on your pictures. I have 3.0L S-Types 2004 and 2005, and no STR, hence, I do not know your setup.

 

I disassembled the car. The engine was rebuilt by a respected speed shop in my area. I'm about a week or so from reinstalling the engine . The ridge I'm talking about is the middle hole in the gasket . It's typical for both sides . I just never seen this before. The picture is of the intake to plenum . Thanks for reponding

 

I still think, I had identified the ridge you were asking about, correctly, but you still have not marked it, which would eliminate misunderstandings.

So did I see things right in your posted picture? Is there one hole without threads?