There is a large vacuum port (maybe 1/2 inch) right above the header on 12a manifolds. Located next to the brake vac line and under the split air pipe block off. My problem is that I've had to replace the vacuum cap a few times on this port due to heat from the header rotting the rubber. Has anyone come up with an idea for this or does anyone else have this problem?

Maybe pull the nipple out, thread the hole and stick a bolt or plug in it?

 

Honestly, mush up some jb weld, stuff it in there. Then drink a beer and pretend it was hard work

 

I ended up threading a bolt into it. A bit more permanent. Working great.

 

I put high temp silicone in the cap and then put it on. Otherwise +1 on the JB Weld, bolt, etc... the world is your oyster. Pick your poison lol.