CMI corrosion problems
05-28-2007, 01:03 PM
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CMI corrosion problems
Hi Guys I've had a good look through old posts on CMI header problems, seems like alot of people have cracking problems with their headers but not any with corrosion issues.
I have e-tops and dry tail pipes with water exiting at tips,headers on a supercharged 454 with closed cooling.
My headers have approx 7 hours on them in salt water and have corrosion/pitting on tail pipe flange area and header flange.you can also see pitting holes forming if you look into collector area.(pressure tested ok)
After talking to CMI i ended up sending tail pipes back to them,they said they had never seen that problem before but would weld new flanges on for me.I repaired the pitting on the header flanges my self.They could not say what the problem was but thought it may be electroyis or down to exhaust gases attacking the stainless.
Its seems as if the problem is from the inside(exhaust side) not water jacket side which sudgests to me its not electroyis.
Can any one shed any light on the situation.
I notice some people have put drains on the distribution pipes so headers can be drained,i think i will do this.
Could cooling water from the heat exchanger be to cold and so causing condensation on the inside of the headers mixing with the gases and creating a very acidic enviroment?
Any thougts would be much appreciated.
I have e-tops and dry tail pipes with water exiting at tips,headers on a supercharged 454 with closed cooling.
My headers have approx 7 hours on them in salt water and have corrosion/pitting on tail pipe flange area and header flange.you can also see pitting holes forming if you look into collector area.(pressure tested ok)
After talking to CMI i ended up sending tail pipes back to them,they said they had never seen that problem before but would weld new flanges on for me.I repaired the pitting on the header flanges my self.They could not say what the problem was but thought it may be electroyis or down to exhaust gases attacking the stainless.
Its seems as if the problem is from the inside(exhaust side) not water jacket side which sudgests to me its not electroyis.
Can any one shed any light on the situation.
I notice some people have put drains on the distribution pipes so headers can be drained,i think i will do this.
Could cooling water from the heat exchanger be to cold and so causing condensation on the inside of the headers mixing with the gases and creating a very acidic enviroment?
Any thougts would be much appreciated.
05-28-2007, 02:52 PM
#2
Stainless steel is 80 % Iron. Condensensation can accumulate. If motors don't run warm enough it may not burn off. If motors run too hot , the metalurgy of the header or parts or it can be changed. The chromium and other metals that make it stainless may be burnt off and be dissipated.
Also silicone sealer contributes to corrosion.
I recommend flushing every use too. I have seen the flanges rust and get eaten like you are talking about, but usually only after alot of use.
I like the Cmi's and am going to buy a set soon for my boat.
Also silicone sealer contributes to corrosion.
I recommend flushing every use too. I have seen the flanges rust and get eaten like you are talking about, but usually only after alot of use.
I like the Cmi's and am going to buy a set soon for my boat.
05-29-2007, 01:40 PM
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thanks big block billy i'm going to rig up a drain down/flushing system and hopefully that should hold back any further corrosion,just to let you know this engine is in my 1989 242ls and has only done 7 hours, previously i had a 5.7 and just about managed 50,last season with my new engine clocked 71mph on gps so well pleased.hoping for a bit more with a better prop selection.
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