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  • November 26, 2022, 06:50:56 AM

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Author Topic: Coolant/Intake manifold  (Read 5254 times)

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Offline vangremlin

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Coolant/Intake manifold
« on: February 16, 2014, 06:49:42 PM »
Our Eagles have coolant that runs through the intake manifold.  Someone suggested that was meant to help the cars run better when they are cold.  However, its also know that you can get more HP out of a car when the air flowing into the engine is colder.  These two things seem at odds with each other.  Has anybody ever disconnected the coolant from the intake manifold and noticed any changes, good or bad?  Thanks.
1981 Kammback 258 - "Pepe"
1980 Coupe 258 - "Ginger
1972 Gremlin X 304
1978 Gremlin 4 cyl 121 - sold
1964 TBird 390 - sold

Offline Draekon

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Re: Coolant/Intake manifold
« Reply #1 on: February 16, 2014, 08:58:41 PM »
From what I understand, the reason colder air provides more HP is because it is denser and therefore allows more gas to enter the engine while still maintaining the proper ratio.  But for this to happen, the cold air would have to be present prior to the carb.

With the coolant in the intake, the fuel has already met with the air, so the ratio has already been made.  The warmer intake should theoretically help atomize the fuel, however, which would allow for better combustion.

I see no reason to disconnect the intake coolant hoses.

Offline Amc1320

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Re: Coolant/Intake manifold
« Reply #2 on: February 16, 2014, 09:39:42 PM »
I dissconnected all of mine and plugged all the holes after I rebuilt  my engine, I have not noticed any difference even at -2 F or 98 F either

I was on a kick at the time to eliminate as many hoses as possible

It might help it run better when cold I would think, but since I eliminated all the computer stuff and the feedback carb it runs great cold
Rob c
84 Eagle Limited Wagon (driven everyday)
81 Eagle Kammback
81 Spirit (undergoing surgery)
83 Spirit (parts car giving it all to keep the rest going)
Manchester, TN

Offline carnuck

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Re: Coolant/Intake manifold
« Reply #3 on: February 17, 2014, 02:16:58 AM »
It was for emissions and lower fuel consumption. Same with the electric heated plate in the bottom of the intake after '81.
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline eaglebeek

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Re: Coolant/Intake manifold
« Reply #4 on: February 17, 2014, 05:20:23 PM »
Dave, take a look  at this link: http://www.cdxetextbook.com/fuelSys/intakeExhaust/inComp/intakemanifold.html

As I thought about this one I remembered that older straight-sixes, like Chevrolet stovebolt sixes and International Red Diamonds, that I've worked on have all had their exhaust manifolds bolted up to the bottom of the intake manifolds. The purpose was the same as for our water-heated manifolds, to help vaporize the incoming air-fuel charge.

However, its also know that you can get more HP out of a car when the air flowing into the engine is colder.  These two things seem at odds with each other. 
From what I read your thought is valid. It's particularly true for turbocharged diesel engines, almost all of which have some sort of cooling device for the incoming air charge. The article I found above explains it better than I can.

Captspillane, your thoughts? :eagle:
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"The society which scorns excellence in plumbing as a humble activity and tolerates shoddiness in philosophy because it is an exalted activity will have neither good plumbing nor good philosophy: neither its pipes nor its theories will hold water."--John W. Gardner, in "Excellence: Can We Be Equal and Excellent Too?" (1961)
 
Air-conditioning is so cool!

Offline carnuck

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Re: Coolant/Intake manifold
« Reply #5 on: February 18, 2014, 02:54:01 PM »
1980 and older AMCs used combined intake and exhaust
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

 

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