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Intake manifold hot in middle, both sides

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mmoody435
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Intake manifold hot in middle, both sides

Post by mmoody435 » Mon Jun 06, 2016 8:01 pm

The boat – 1959 CC Continental, 21’ Hard top with original 283-H engine, 235 hours. I bought the boat in July, 2015.

The issue - I recently put the boat in the water for the first time and have put about 5 hours on it. The engine was freshly painted when I bought it. I have noticed the paint burning off near the center of the intake manifold, on both sides (photos attached). I took some temperature readings after the engine had been running at high RPMs for about 30 minutes. On the center part of the manifold, where the paint is gone, the temp was around 150 to 190 F on both sides. Moving outward from there, towards the front and back, the temps were around 120 to 130 F. As far as I know, this is an original intake manifold.

Is this an issue?
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Morris Moody
1960 18' CC Continental
1959 21' CC Continental Hardtop
South Louisiana

charlesquimby
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Re: Intake manifold hot in middle, both sides

Post by charlesquimby » Tue Jun 07, 2016 4:06 am

Most likely an automotive manifold with a feature that picks up exhaust heat to operate the choke. You will have to remove the manifold and block those passages to eliminate the burn. There are s/s blockoff tabs made specifically for that purpose, but you will have to remove the manifold to install them along with new manifold gaskets. With the tabs installed, your choke will not heat up, but you will probably not need a choke in Summer weather anyway. If you need a choke it is simple to adapt a mechanically operated one. CQ

boat_art
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Re: Intake manifold hot in middle, both sides

Post by boat_art » Tue Jun 07, 2016 6:00 am

Charles, is there any problem with leaving these passages open? I have it on an AMC engine and it appears it was always like that.
Tom
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1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

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Bilge Rat
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Re: Intake manifold hot in middle, both sides

Post by Bilge Rat » Tue Jun 07, 2016 7:05 am

My 327 Graymarine with a 2 barrel Rochester has the exhaust passages in the intake manifold to pre-heat the air/fuel mix and provide heat to the climatic choke. When I restored her, I used a high temperature exhaust manifold paint there. Looked good for about 2 seasons and now looks like yours. I was having the usual difficulties with the climatic choke, so I converted it to electric and starting/warm up is much more reliable. I left the exhaust ports in the manifold as-is.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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evansjw44
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Re: Intake manifold hot in middle, both sides

Post by evansjw44 » Tue Jun 07, 2016 3:39 pm

The burned paint is around what I will call the "hot well". There is a "well" (5 sided box) cast into the manifold that exhaust gas heats that is used for the automatic choke sensor. On many GM engines there is a spring inserted in this cavity that changes tension as it warms to control the choke on the carb. If you look, there is a tube extending down into this area which is picking up warm air to warm the choke spring in the choke box (the black cylinderical thing) on the carb. The burned paint is normal for an engine that has been run.

Unless--- Most CC early V8s didn't use the "hot well in the intake manifold. CC intake manifold gaskets blocked it off. Instead CC cast a "hot well" into the exhaust manifold and a heat riser tube (as seen in your pic) to the exhaust manifold "hot well" instead.
Jim Evans

mmoody435
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Re: Intake manifold hot in middle, both sides

Post by mmoody435 » Tue Jun 07, 2016 5:18 pm

Thanks all for the explanation and comments.

I suppose the channel on top of the wedge (see photo) is somewhat in reference to the same thing?
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Morris Moody
1960 18' CC Continental
1959 21' CC Continental Hardtop
South Louisiana

boat_art
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Re: Intake manifold hot in middle, both sides

Post by boat_art » Tue Jun 07, 2016 5:58 pm

Im still wondering if there is any harm in leaving the passages open.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

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mfine
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Re: Intake manifold hot in middle, both sides

Post by mfine » Tue Jun 07, 2016 7:40 pm

The passages were left open on our OMC marine conversion. The biggest downside is the extra heat can make it more prone to vapor lock. I certainly would not pull the manifold just to fix it, but next time the manifold is off I would block them off.

boat_art
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Re: Intake manifold hot in middle, both sides

Post by boat_art » Tue Jun 07, 2016 9:41 pm

Thanks!
Tom
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jim g
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Re: Intake manifold hot in middle, both sides

Post by jim g » Tue Jun 07, 2016 10:34 pm

The passage is suppose to be open. If you block it off your choke will not open up. It operates off the heat that passes through there.

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NOT Firewood
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Re: Intake manifold hot in middle, both sides

Post by NOT Firewood » Mon May 20, 2019 8:24 pm

So I picked up a hand held digital read out thermometer it showed me today that I have the same issues as this post which gives me a bit of comfort this hot spot is to happen. My hot spot is on the choke intake is 308f and on the other side is 205f. This seems real excessive for temp so what is to be normal? Do is have something else going on?

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NOT Firewood
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Re: Intake manifold hot in middle, both sides

Post by NOT Firewood » Thu May 23, 2019 8:06 am

Hey guys any thoughts on this? is there a issue with the high temp of 305 F that I am getting?

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