Modifying risers for future ease of removal.

[pgall]

If you have ever tried to replace aged risers than have been operating in a salt water environment, you probably have run into heavy internal corrosion that makes removal extremely difficult. I had a modification made to my new 454 Crusader risers that, I hope, will solve the problem when I next have to replace them.

Currently the long 3/8 inch stainless steel mounting studs pass through the risers and are threaded into the exhaust manifolds. The riser slides over these four studs and is secured with brass nuts and copper sealing washers. This design exposes the studs to the exhaust and salt water and causes the cast iron to corrode around the studs making removal of the risers a chore.

My fix was to have a machine shop line bore the stud holes and press in long, thinwall 316 stainless steel tubing. The tubing is nominal 1/2 inch OD with .049 inch wall such that the OD of the tubing is exposed to the salt water/exhaust, but the studs are comfortably contained entirely within the tubing.

This not only eliminates the need for the copper washers to seal the studs from leaking, but when the riser is removed, it should slide right off. It will be a few years before I find out though.
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[757guy]

Good Idea!!!!!!!!! let us know how it works

 

[diver_dave]

This reminds me of what Chrysler did with their elbows. Only the gas passage ran thru a stainless, large bore tube with O ring seals. This was some 30 years ago + on the 440's. It's certainly worth a try; not much down side, since the salt water parts get tossed every 4 years or so.

 

[RicardoMarine]

Pgall, this sounds interesting. I'd like to see photos of this so that I can better understand what you've done.

Dave, for several years now, Mercruiser has been using what they call their "dry joint" system.

Here is Osco's replacement riser

Here's the required gasket

 

[makomark]

Curious how much the machining costs.....