[Chrysler300] Hi-Temp coatings

["Ray Melton" <rfmelton@xxxxxxxxxxxxx>]

There are several easily available high-temperature coatings available which
are widely used by the hot-rod and circle-racing crowd.  These ceramic-based
thermal barrier coatings are applied to the piston crowns and combustion
chamber surfaces, valves, inside exhaust manifolds, etc., and provide vital
thermal insulation under extreme conditions such as high-boost supercharged
and turbocharged applications.  I have had direct and very favorable
experience with High Performance Coatings, Inc. and Jet-Hot.  Swain
Technologies is another.  Might suggest Googling on ?automotive thermal
coating?  -- I found 1.19 million entries!

 

Ray Melton

1957 300C convert

 

   _____  

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of John J. Hertog
Sent: Tuesday, March 13, 2007 12:59 PM
To: 'Richard Osborne'; chrysler300@xxxxxxxxxxxxxxx
Subject: RE: [Chrysler300] AFB 2903 electric choke conversion

 

Richard, Andy, and all: 

I do believe that the aluminium manifolds burn through due to the heat and
corrosive effect of the exhaust gases passing through them. It's kind of
obvious - the damage is always located in the same area: choke pockets, heat
tube mating surfaces, and under the carb. 

Blocking off the heat passages can be accomplished in a variety of different
ways. I have seen various solutions over the years, from freezeout plugs
inserted in the holes to block the flow, to custom made flat shim plates
fitting between elbows and rams. 

I have spent many, many hours rebuilding the heat riser portions of exhaust
manifolds on various cars, to get them to run right; I do believe that those
are necessary in order for the chokes to operate properly on the carbs.
Rich, was is the purpose of having new chokes, as you state, if there are no
heat riser butterflies? Chokes will "come on" when the car is cold but will
stay on way too long afterwards, since there won't be any heat supplied to
the pulloffs. 

Andy, now your statement confuses me most of all. The purpose of the chokes
are to furnish more fuel / less air when the engine is cold. If one
disconnects the chokes, then the car will be cranky when cold. If one
removes the heat riser butterflies (or jams them) then the car will run
overly rich AFTER it is warmed up and foul plugs. The purpose of electric
choke system is to get the chokes to "come off" after the car has run a few
minutes, not the other way around. I don't see why having electric chokes
would make the car hard to drive when warmed up. It's the other way around!

Another Club member has suggested coating the inside of the rams (heat
passages) with high-temp exhaust paint. My only comment to that is that,
even though it sure won't hurt, it won't help much either as the paint will
surely bake off within a couple hundred miles. Yes, if there WAS a way to
coat the insides of the rams with some product impervious to heat and
exhaust gases, that would be the solution. But, heck, if the red paint
bakes off the outside of the rams when the car is driven, can you imagine
what would happen to paint inside the rams heat passages? 

I've put on about 35,000 miles on my 300G convert since purchasing it a few
years ago; those rams are getting thin. I just removed the rams off my
52,000 mile 300F and those already have holes in the choke pockets, are thin
all over, and need to be replaced. I am running out of manifolds and wish
to preserve what I have. Unless someone can come up with a specific
product to coat the inside of the ram heat passages, that will stay on there
and protect them, I intend to block off the flow of exhaust gases as a way
of keeping my manifolds healthy. If you, like most people, don't drive your
car much - then don't worry about it. 

Warren, thanks for the info. I guess I may have to play with the bimetal
spring inside the elctric choke housing to make it act slower... However,
some choke will be better than no choke, don't you think ?

John H.

-----Original Message-----
From: HYPERLINK
"mailto:Chrysler300%40yahoogroups.com"Chrysler300@xxxxxxxxxxxxxxxxx
[mailto:HYPERLINK
"mailto:Chrysler300%40yahoogroups.com"Chrysler300@xxxxxxxxxxxxxxxxx] On
Behalf Of Richard Osborne
Sent: Tuesday, March 13, 2007 11:36 AM
To: John J. Hertog; HYPERLINK
"mailto:chrysler300%40yahoogroups.com"chrysler300@xxxxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] AFB 2903 electric choke conversion

John,

This sounds like a great solution, but I want to understand a couple of
things: First, do the intake manifolds burn through due to heat riser
failure, or simply due to design? 

Am I understanding that the heat passages into and out of the intake
manifolds are completely blocked off? Does this require machining of the
parts to accept block off plates?

I have not dug into the convertible to see what the intakes look like, but
the hardtop showed a little wear, not too bad. I have new chokes, and broke
off the heat riser butterflies. No real problem other than when it is really
cold out, it can be a pain in the butt to start.

Looking forward to hearing more.

Richard Osborne
>>> "John J. Hertog" <HYPERLINK
"mailto:crossram%40optonline.net"crossram@xxxxxxxxxxxxxx> 03/13/07 3:34 am
>>>
Hi to all, 

Motivated by the sight of yet another set of original 50,000 mile ram
manifolds burned out in the choke pocket area, I asked Jimmy and Bobby at
Allstate Carburetor (www.allcarbs.-com) whether it would be possible to
modifiy the 2903 carbs, and add electric choke units to them without any
permanent alteration / damage to the ca 
rbs. The answer was: "I don't see why not". They are now in the process
of converting a set I gave them. 

The idea, of course, is to block off the heat riser system, by inserting
solid shim plates between the exhaust elbows & heat tubes, and the bottom
of the manifolds; one would also want to jam the heat riser valve in the
open position (assuming it still functions) on each side, and disconnect the
choke pulloffs. 

The benefit would be fully automatic choke operation without any heat
supplied to the bottom of the carbs. No exhaust damage to the rams, no
baked off paint either. 

I will be glad to report on the progress of this carb conversion and take
pictures when I get the carbs back. I can ask Jimmy and Bobby to put
together a "conversion kit" and make it available for sale, if someone else
wishes to do the same to their 2903's ( I understand that they will have to
fabricate one linkage piece) ; or you could just send 'em your carbs for
conversion and/or R&R. All removed parts would of course be returned. 

For whatever it's worth, Allstate Carburetor has rebuilt umpteen sets of
2903 AFB's for various Club members in the past few years. 

Comments, anyone?

John Hertog
Sag Harbor NY





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