I was wondering if anybody knows what causes corrosion between Gil Exaust Manifolds and the Stainless Steel Risers?

Looks like dissimilar metal corrosion.
When two different metals are joined, like the aluminum manifold and stainless riser, an electrical potential is formed causing electrolysis (corrosion).
Try running a ground wire from the riser to manifold then a wire to the engine block.

Hi Evan, I have seen this happen when a sealer isn't used when installing the gaskets and moisture plate. I usually have to put a small thin bead around the inside flange on the top and bottom of each gasket and then install the risers.

John

gripit - is that a ground cable connected to the tailpipe studs?

Yes, it is a ground cable. Maybe the Ground cable between motors may be causing additional corrosion? What do you guys think? Has anybody else had a simular problem?

I have never ever seen a groundcable on a exhaust !!!!!

Aluminum is ground enuff to the block and the risers are thru the bolts !!!!

What i did in the past is use antiseez on bothe sides befor install or some hightemp gasket sealer and put some onthe studs too.

I believe that ground strap should be running from engine block to engine block