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How to test my cmi header

Old 02-23-2016, 03:38 PM
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Sorry I don't have any pics but here's how I test them and why I test them the way I do.

I hook up the garden hose on one end and a valve on the other end to bleed all the air out. I run the garden hose full pressure. Then check for leaks. If no leaks, I take a propane torch and heat the areas around each port and the welds inside each tube. (not too hot, you just want the metal to expand) Then I also heat inside the collector and check for leaks.

The reason I use that method is I've seen numerous times where the header did not leak until I applied some heat. Which when it's in the boat, it's seeing heat and could be leaking. About 15 years ago I wasn't a believer in adding the heat and then an old salt marine welder I used to work with many years ago insisted we put heat into my headers and sure enough they were leaking.
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Old 02-24-2016, 02:59 AM
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That is correct about the heat - applying it to the header. Been doing that since Mercruiser came out with the complete one piece exhaust manifold for the V-6 back in 1997. Those cracked internally all the time and had to be checked out.

If you are setting your header in a huge tube of water - you boil some water to throw in the tub on top of and use your hand held temp gun to see what the temp is. Again you are trying to simulate engine running temps and heat soak temps of the header - like true conditions it will see from a running engine and heat soaked after shut down.

If you are not using a big tub of water to set the header in but using a garden hose / water pressure or I like to use air pressure with gauge attach to monitor it. You take a hair dryer or paint stripper gun and heat up the header that way. Again use your hand held temp gun to monitor the heat at the header. I have always check headers / even cast iron manifolds that way. It is true sometimes they wont leak at all until they heat soak.

Last edited by BUP; 02-24-2016 at 03:05 AM.
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