Don't think that the Thermoquad is a bad carb. When properly set up, it
can deliver great performance. It is a spread bore style, with smaller
primary venturies for better throttle response at low rpm & better fuel
economy.
On the secondary side it has a pair of HUGE venturies. 1050 cfm flow rate
at one inch drop across this carb, so it is a desirable unit for engines
which can make use of that kind of flow rate. Generally you need to turn a
large V8 to speeds far beyond RV needs to approach a thousand cubic feet of
air flow into the engine, and improve breathing with longer duration,
higher lift cams.
It also has an air mass actuated horn (or flap) at the top of the
secondaries, so the engine will not bog if you go to wide open throttle in
a sudden stab of the foot.
If you decide to replace that carb, put it up on Ebay, or drop a note on
the Mopar Mailing List & someone will gladly take it off your hands, and
probably give you a lot of the cost of a new Edelbrock.
Some of the good features also lead to problems. It has a plastic fuel
bowl, to keep the fuel from absorbing as much heat. This item can warp or
crack, so check yours for leaks both internal or external if you keep the
Tquad. I have one on a 77 Ramcharger with 440, and will dig out the
factory service manual if you have specific questions - like the initial
mixture settings & float space setting. Probably your 440 is close enough
to the AW100 version to get a good starting point.
So you might be able to get your existing carb to work, and can breathe
easier knowing that it is a high tech (for it's time) unit. On the other
hand, I replaced the Holley carb on my Superior with 413 - using the
Edelbrock 1405.
The 1405 flows 600 cfm at one inch WC pressure drop, which sounds like a
lot less than the Tquad, but is quite enough to do the job. There is a
model 1407 which flows 750 cfm if you feel the need.
Nice polished aluminum with Edelbrock label looks good, and hides a spread
bore design. Also has the air mass damper on the secondaries, just like
the Tquad. Has some transient fuel delivery systems which give a real
smooth operation. Check out the online owners manual for the 1405 at the
Edelbrock web site for a good explanation of the tricks.
One of those is really slick, it uses the high speed air leaking past the
throttle plate as you just begin to open it off idle setting to pull some
additional fuel out tiny holes in the wall. When the throttle is open
farther, those same holes permit air to enter the emulsion tubes, promoting
better fuel atomization.
It also comes with jetting & step rods set for best power mixture, right
out of the box. Set idle speed & idle mixture & just use it as is for best
power. Or change the metering rod for one with a leaner run position, and
the same number power (lower, smaller diameter section) and pick up a bit
better fuel economy when the power valve is pulled down by moderate driving
conditions.
I left the stock rods in the 413 engine's Edelbrock 1405, and it ran great
for us. Changed the rods on a 1405 on a lighter vehicle with 400 engine,
and it did great also.
If you have the money to change the carb, the Edelbrock might provide less
entertainment for you. It will be brand new. If you do go that route, get
the $10 "Mopar bracket" for the throttle cable attachment, and the fiber
heat blocking base gasket, both Edelbrock parts.
And if you enjoy the sound of a hard working RB engine, both carbs let a
great roar out when topped with a low restriction aftermarket air cleaner.
That is the kind with the entire perimeter open. I happen to love that
sound, clearly letting you know that you are dumping a lot of fuel down the
hatch. So you can back off a bit if that is not your desire, or just grin
& enjoy it on a trip up a short "on ramp".
Jack
-----Original Message-----
Date: Tue, 26 Oct 2004 15:46:41 -0700 (PDT)
From: don rutledge <[EMAIL PROTECTED]>
Subject: 440 engine,78 Southwind
I already bungled the first message. The engine IS a 440 Chrysler and the
Carb IS a THERMOQUAD 4 bbl. I do not know all of the history on the RV as
it was stolen and recovered and then I wound up with it. Mistreated is a
gentle word, but it is all I can afford and need to make it run good.
Engine is fine otherwise. I have watched this forum for awhile now, and I
figger you guys have most of the answers out there. thanks for any input!
Regards, don.
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