New riser pressure leak (hiss)

[dpagini]

I have a 2000 Four Winns with a 5.7 GL-C engine in it. I just put new manifolds and risers on this season, Barr brand.
When I start up my engine, and then kill it, I can hear a hiss noise for 2-3 seconds after I kill the engine. I traced it down to my port side riser, and a hold on the inside of the riser is letting out air, making the hissing noise. I notice the riser on the starboard side does not do the same thing. You can see this hole in the picture I have uploaded.
What is this hole for? Is there anything wrong that there is a hiss? What does the hiss mean? Is this exhaust coming out?

 

[dpagini]

Bump. It was suggested to me that this could be some kind of hole for an oxygen sensor or something along those lines, and it just needs a plug. Does that sound like it could be the case to anyone? There is already a plug on the top and sides that is in place. I've emailed the manufacturer as well, hoping they can give me some advice.

 

[Lou C]

I would email or call Barr tech support, that may be a warrantee issue. I spoke with them concerning the proper sealant for the gaskets between the manifold and riser and they were helpful.

 

[USA_boater]

what sealant Lou? will copper spray work?

My risers are OEM and they have some sort of hole that looks like that but not on the side...I see rust inside it so I just assumed it was an un-used tap hole since I do not hear any hiss...are you sure it goes all the way through and isn't just a threaded hole?

 

[Lou C]

Well it depends on which gaskets you used. If you used the Volvo OEM ones, then yes the copper spray is what they recommend. I used the Barr gaskets and the tech guy told me to use Permatex Aviation so that’s what I did....
Mine seems to have the same hole there, but its not open...