looks like my riser gaskets are leaking

JPass:

What you are doing is close to what I did recently. While skiing at Lake Powell in October, my muffler blew out. 1994 boat (351W) so I figured that the muffler didn't owe me much. While installing the exhaust gear, I noticed the tell-tale leaks on the risers. So I decided to replace the gaskets. I was concerned with bolt extraction, so I applied PB Blaster 2X per day for 3 days. To my surprise, the bolts came right out.

Then the fun started. Upon further inspection of the manifolds, I could see where the exhaust manifold bolts were badly corroded and rusted - directly under the riser leak. Can't have that now, can we? So I decided to pull the manifolds and re-work the exhaust system. My problem came with the exhaust manifold bolts. I did the same PB Blaster technique of 2X per day for 3 days. Of the 16 bolts, 12 came out fairly easily. The bolts are 5/16" hex cap bolts. On the 4 stubborn bolts, the corrosion was so bad that the allen key just spun. I used a big Easy-Out and they also came out relatively easy.

As for your question regarding air tools, I've had too many bad experiences with bolts breaking due to over-use/misuse of air tools, so I try to exhaust the "hand" method first.

The biggest challenge I had was cleaning up the surface on the risers and on the manifolds where the gasket mates-up. I also used Permatex on both sides.

I have a question for all you motor-heads: I bought the replacement exhaust manifold bolts from skidim. They appear to be stainless steel. The original bolts were carbon steel. I used a liberal amount of anti-gall / anti-seize during installation, but I'm a little concerned with stainless bolts in a carbon steel block...particularly in a high heat environment. Any thoughts?

Good luck.

JQ

J - You might have to clean up the cast iron gasket surfaces.   Mine very very pitted, about 1/2 of the wall was gone.     I used some emory cloth stapled to an oak board to cut it flat. You can use a file too, but it won't cut very easy.

I would tap out the threads while you have it apart. Anti-sieze compound is always a plus for reassembly.

Make sure & position the new gasket so that the lower riser port is blocked.

Happy New Year!

Thanks Pete.

So permatex each side of the gasket prior to installation?

I wasn't planning on messing with the manifold. Should I?

Back when I posted pics of my ignition swap someone questioned all the rust streaks coming from the riser gaskets.

The recommendation was to repaint the manifolds and look for fresh signs of leakage.

When I was messing with the boat yesterday I noticed some dried water streaks coming from the same area. I'm thinking I need to replace my riser gaskets.

Couldn't find any good How-To's.

I'm going to drop some 50/50 acetone/trans fluid on the bolts today and attempt to remove them New Year's Day.

I have hand, air, and power tools at my disposal. Should I start with hand tools (box wrench or socket)or should I hit the bolts with an impact first (air or electric)?

I know I may wind up having to heat the manifolds up.

Any tips or suggestions would be great. See below pics for new signs of leakage.