manifold lifespan

[cdavisdb]

I just changed the manifolds and risers on my 5.7 V8. Total time on risers was 4 seasons, almost 5 years total. Manifolds are original, I think, but looked near perfect in 2009. 2014 should be way over time for the manifolds and a little over time for the risers, but look at the pics below. I've done this job on other boats at 3 and 4 years and the risers normally look pretty awful, major rust pile. The manifolds seem to last a little longer, but by 4 years the water passages are rusted near shut in some areas, overall look pretty nasty.

Look at these. Way less rust than I'm used to seeing. They don't look to me like either manifolds or risers are anywhere close to needing to be changed. These are Volvo parts

I wash mine more thoroughly than most folks. After every salt water use. Usually wash twice, a week apart, always do this if the trip is more than a day. I discovered that letting the fresh water sit in the engine for a week picked up a lot of salt, the discharge is noticeably salty when I start flushing the second time. Also, the boat gets in the water far less trips than most people.

Questions:

Am I imagining things and this looks normal for the amount of time? Or does this look exceptionally clean to you guys?

Is the metal in volvo manifolds and risers different, more corrosion resistant?

Would my type of use and/ or washing schedule result in less corrosion?

Even if they look pretty good, will cast iron get pitting that will go through the walls anyway, such that how they look doesn't matter?.

[Bushwacker]

Connor,

There are some high-nickle versions of cast iron that Volvo might be using which are probably more corrosion resistant, depending on what other elements are in the alloy. I know Chrysler Corp. used it in a lot of their V-8 engine blocks, although I think that was mainly because of it's higher strength, so you'd also like to see a lot of chromium in the alloy for good corrosion resistance. Only way to know for sure would be to put one of those manifolds in a SEM (Scanning Electron Microscope), which analyzes the wavelengths of the electron emissions and shows what elements are present in the alloy.

I'm sure your 2-step flushing procedure helps if it gets more of the salt out, but cast iron still rusts pretty quick, so I think going beyond 4 years would still be pretty risky without at least taking a look at them. It only takes 1 thin spot to kill an engine!

If those expensive Volvo parts really are that much better, maybe it's worth investing in a borescope from Harbor Freight http://www.harborfreight.com/catalog...lt?q=borescope, especially if you could also figure out a way to justify also using it in your business like Strick does with his vet business! Don't know what the resolution is on the HF scopes, but the 9mm Olympus and Cole-Morgan aerospace scopes I've used give you 5X magnification that make a 10 mil crack in a turbine blade look like the Grand Canyon! They're very handy tools that we used for some amazing inspections with that saved a lot of engine teardowns. By just pulling the risers, I think you could get a better look inside both the hot and cold side of the manifolds with a borescope than you could by actually pulling the manifolds for a 1X eyeball inspection! That would allow you to switch from "scheduled" to "on condition" maintenance, which is how the military and airlines maintain the hot sections of aircraft engines! Denny