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#1418345 Tue Jul 27 2021 04:46 PM
Joined: Jan 2020
Posts: 699
Here in the Deep South the spring baffle on the old 216 and 235 engines were removed after the spring rusted off. My old Deep South 235-3100 was long ago taken out and welded over. What is the use of this factory item? Doc

Currently making 1954 3100 better than new and Genetics
Doc.Hall #1418350 Tue Jul 27 2021 05:11 PM
Joined: Mar 2010
Posts: 1,495
Move to Minnesota. It will be hard to start that engine in the winter.
The intake manifold needs heat to help keep the fuel/air vaporized and moving down on down to the head.
The damper directs the heat from exhaust up to the bottom of the intake manifold.
When the spring heats up, it rotates the damper into the open position for normal run.
Here in the humid South, we have frigid days but nothing like the cold North.
Our prize AD trucks usually stay in the garage or carport.
We use the car or truck with air conditioning to defog our windshields so we can see out.

Last edited by buoymaker; Tue Jul 27 2021 05:15 PM.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."
Doc.Hall #1418444 Wed Jul 28 2021 02:04 AM
Joined: Mar 2010
Posts: 10,225
When the intake manifold temperature is below operating temperature, liquid fuel will come out of suspension from the incoming fuel/air mixture when it comes into contact with the cooler manifold. This will then be sucked into the cylinder, but not ignited, then leak down past the rings, washing the oil off of the cylinders causing excess wear, and contaminating the oil with raw fuel.
Unless the ambient temperature in the deep south is above 160 degrees, this will happen upon every startup with a non-functioning intake baffle.
Much of this information was gleaned from the Chevrolet Factory Manual for '47-'51.

Doc.Hall #1418493 Wed Jul 28 2021 01:22 PM
Joined: Mar 2014
Posts: 3,070
Whoever removed it and welded the holes up may have thought this was a good idea, but they didn't do you or your engine any favors, Ed. Sorry to be the bearer of bad news, but it is the truth.

How to fix it?
1...find an exhaust manifold with one still in place and make it work properly again.

2...I've seen people adapt the type used on Chevy small block V8s and some AMC engines. These are different. They fit between the exhaust manifold and the exhaust pipe flange. Like this:

(but there are some used on AMC engines which had 2 the 235...and those have a better chance of fitting). A few years ago I watched a guy make a little 3 hole adapter so he could use the Chevy SBC type on his 235 and then he just used the 3 hole piece on the exhaust pipe.

3...if you had the patience and skill, you could drill your old manifold out (with a drill press) and make a new shaft and flapper and get a new bimetal spring.

Whichever method appeals to you the most, your engine would be happier with that flapper in place.


1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Doc.Hall #1418512 Wed Jul 28 2021 04:11 PM
Joined: Jan 2000
Posts: 2,223
These flappers get so rusty next to impossible to make like new, most get welded in place. Springs may be available, but most are to far gone to rebuild.

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy []
1953 Chevy 3/4-ton Factory Stakebed []
Doc.Hall #1418515 Wed Jul 28 2021 04:34 PM
Joined: Feb 2004
Posts: 25,002
Kettle Custodian (pot stirrer)
I duplicate the shaft and flapper valve in stainless steel, and use a bimetal spring for a Jeep that's available on Ebay for less than half the price of an OEM stovebolt spring. The 3-bolt V8 heat riser isn't a good option, as it blocks off almost all of the exhaust flow instead of re-routing it.

"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

Doc.Hall #1418527 Wed Jul 28 2021 05:38 PM
Joined: Jul 2000
Posts: 1,613
If you install headers, you lose the heat riser. Means poor drive-ability most of the time in the climate I live in. So you get the disadvantages of headers without the advantages.

1954 1/2 ton 235 4 speed
Jon G #1418622 Thu Jul 29 2021 01:45 PM
Joined: Dec 2018
Posts: 1,842
JonG I cut all that sorry trash out of my manifold,with LPG you dont need it ! Summer or winter! Just this morning went out at 5;20 a.m. fired-up with just a bump,went to coffee shot the breeze about an hour went out fired up with just a bump came home.No vapor-lock,no fuel pump,no gasoline fumes in the cab,never cold natured,no sludge,oil like new,one simple filter !! What's not to like ??

Gord&Fran #1418623 Thu Jul 29 2021 01:53 PM
Joined: Dec 2018
Posts: 1,842
Gord&Fran With LPG split will work fine,wont need heat on the intake,no pasky exhaust leaks (at the flapper shaft) Mine have been a win-win ! Can use forklift parts all new,not wore-out antiques !!

Doc.Hall #1418628 Thu Jul 29 2021 02:11 PM
Joined: Dec 2018
Posts: 1,842
As I said earlier I want to cruise my 51 6400 not spend all day in the shop fighting wore-out antiques,and then struggling with vapor-lock in the heat shish no use of butting your head against a gas pump all day !!

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