Last October I yanked both my 1988 454's (just over 1,000 hrs-still good compression) and decided to have them remanufactured over the winter by a local engine rebuilder. All part of a larger plan to totally re-finish the engine compartment, but that is another story.
While I was at it, I recalled how difficult it was to replace the risers on both engines about 5 years earlier, and this time, even with the engines out and on engine stands, the risers just did not want to come off! Thankfully, I was replacing the exhaust manifolds too, so it did not really matter—I just wanted to find out.
Examining the design, I recognized that the long stainless studs that thread into the exhaust manifolds are surrounded by seawater. Even though these are FWC engines, five years of exposure to salt water in the risers made them almost impossible to remove despite all my precautions when I last replaced them (copious amount of marine never-seize, etc)..
Solution (I hope): The studs are 3/8 diameter and the bores through the castings are oversized to allow the risers to slide over the studs. So the studs and cast iron bores are directly exposed to the corrosive effect of the seawater and exhaust gas mix.
I purchased some 1/2 inch diameter x .049 wall 316 smooth bore stainless steel seamless tubing from McMaster-Carr. Then I had the bores in the castings opened up to .500 leaving a light press fit. Cutting the tubing to the exact length measured between the mating surfaces, I pressed them into the bores so they were flush at each end.
The risers slide right over the studs as you would normally install them (theoretically the copper washers and nylock nuts are no longer necessary). Now the the studs and bores are isolated from the seawater and I expect that in 5 years or so, I’ll be able to remove the lock nuts and copper washers, and the risers will slide right off with no effort!
Stay tuned for my update in a few years.
While I was at it, I recalled how difficult it was to replace the risers on both engines about 5 years earlier, and this time, even with the engines out and on engine stands, the risers just did not want to come off! Thankfully, I was replacing the exhaust manifolds too, so it did not really matter—I just wanted to find out.
Examining the design, I recognized that the long stainless studs that thread into the exhaust manifolds are surrounded by seawater. Even though these are FWC engines, five years of exposure to salt water in the risers made them almost impossible to remove despite all my precautions when I last replaced them (copious amount of marine never-seize, etc)..
Solution (I hope): The studs are 3/8 diameter and the bores through the castings are oversized to allow the risers to slide over the studs. So the studs and cast iron bores are directly exposed to the corrosive effect of the seawater and exhaust gas mix.
I purchased some 1/2 inch diameter x .049 wall 316 smooth bore stainless steel seamless tubing from McMaster-Carr. Then I had the bores in the castings opened up to .500 leaving a light press fit. Cutting the tubing to the exact length measured between the mating surfaces, I pressed them into the bores so they were flush at each end.
The risers slide right over the studs as you would normally install them (theoretically the copper washers and nylock nuts are no longer necessary). Now the the studs and bores are isolated from the seawater and I expect that in 5 years or so, I’ll be able to remove the lock nuts and copper washers, and the risers will slide right off with no effort!
Stay tuned for my update in a few years.