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Copper tube needed for Exhaust Manifold????
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75 Express
#1 Posted : Thursday, June 16, 2011 8:43:09 AM(UTC)
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Hello Gentlement, I am in the process of changing the port inboard exhaust manifold. when i went to order it at e-basic power.com there was a copper tube recommended. Does a 1975 225hp chrysler need this tube???
Stan
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pfhlaw
#2 Posted : Thursday, June 16, 2011 9:45:17 AM(UTC)
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Yes (*and no)
Because the cooling water typically enters from the forward (top) of the angled manifold and exits at the rear (bottom), the tube is used to raise the exit point so that the manifold is always full of coolant and any air bubbles are pushed out the tube at the high point. Theoretically, without the tube, if you draw any air through your raw water pump, the air would be trapped in the upper part of the manifold while the water is push out the bottom.

I wonder if you can retrieve and reuse the copper tube from your old manifold?

* Jeff accidently left his out and he reports no cooling problems yet.
Peter
1981 32' sedan bridge
twin Chrysler 360 cu. in. 250 hp engines
Raw water cooled
Nimbus II
Home port: New Buffalo, MI
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75 Express
#3 Posted : Thursday, June 16, 2011 9:46:20 PM(UTC)
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Hmm, that is hard for me to understand. Is there a cut-away drawing somewhere that shows how that works? When I look at the end of the manifold, which has a pipe in it, which is rusted in place, it looks like the water would run straight through the pipe and out the back side and then mixing with the exhaust gas at the elbow. The gasket seems to cover up all of the cavity areas preventing water from getting in there. These are the cavities between the exhaust passage and the outer wall of the manifold. If the pipe wasn't there it seems like the water would me moved around the cavity walls of the manifold before exiting into the elbow, thus providing better cooling of the manifold. I need to stare at it for a while unitl the light bulb goes off.
Thanks for the excellent explanation!
Stan
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pfhlaw
#4 Posted : Friday, June 17, 2011 9:08:46 AM(UTC)
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Here's the diagram from the Chrysler manual:
Note the tube is shown as a dotted line in the manifold.
pfhlaw attached the following image(s):
pfhlaw attached the following image(s): Chrysler raw water cooled.jpg
Peter
1981 32' sedan bridge
twin Chrysler 360 cu. in. 250 hp engines
Raw water cooled
Nimbus II
Home port: New Buffalo, MI
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75 Express
#5 Posted : Friday, June 17, 2011 10:04:28 PM(UTC)
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Thanks Peter, I'll be putting in the copper pipe just to be sure.
Stan
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75 Express
#6 Posted : Monday, June 27, 2011 8:35:48 PM(UTC)
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Now I am confused again, imagine that, but I was looking in my orginal manual and found a raw water schematic system showing the copper tube at the inlet side of the or forward edge of the manifold. Does anyone know which end to insert the tube??? My thoughts are at the rear so the box will fill up until it reaches the tube opening and then flow out. If it goes in the front end then the water will travel all the way toward the back of the box which is tilted in that direction. Any help would be greatly appreciated. I am going to try to install it this weekend and maybe even take a boat ride.Dancing
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fastjeff
#7 Posted : Tuesday, June 28, 2011 7:09:04 AM(UTC)
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My engines were originally FWC. The previous owner converted them to RWC, using the fitting on the FRONT of the manifolds for water entry (instead of the lower rear). Motors cooled okay, and with the copper tubes left in.

Here's where it gets interesting! I accidentally left out a copper tube during a manifold replacement, and that side ran cooler! Since then (couple of years) I have removed ALL of the copper tubes.

Jeff
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell
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vitalidle
#8 Posted : Tuesday, June 28, 2011 12:32:45 PM(UTC)
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I tore my manifolds off this spring because they needed some TLC. I acid washed them and installed them back on the boat without the copper tubes after reading about fastjeff removing them. I only have 2 hours of run time so far, but no issues so far!
Sean Cornish
83 28ft Sportsman twin 318's
Homeport: Munising, MI.
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jralbert
#9 Posted : Tuesday, June 28, 2011 1:23:54 PM(UTC)
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Did that maintenance have any effect on cooling...temp, etc
Joel Albert, Potomac MD
"Charlie B" - 1988 32' FBS
Twin 318's/FWC/16x15 nibral props
docked Deale, MD
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vitalidle
#10 Posted : Tuesday, June 28, 2011 8:58:52 PM(UTC)
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Yes so far it has kept my temps steady. When I drained the manifolds for winterizing I had lots of rusty scaleblockng the passages.
Sean Cornish
83 28ft Sportsman twin 318's
Homeport: Munising, MI.
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