Should I replace my Thermo-Quad Carburator?

[The_Handier_Man1]

From: Afubar69 (Original Message)
Sent: 4/24/2006 2:55 PM

I have a 74 D23L Indian with the 440 engine.  This past weekend, I took the Green Winnie out over the weekend, when I went to start her on the second day, found that the batteriers were dead and when jumped, she backfired a few times.  A gentleman that was with our group, got her started, tested the alternator (it was good), them told me that the Thermo-Quad carb was not a good thing to have as they are known for causing fires due to the plastic bowl melting.

So, is this true, should I replace the carb?  I haven't had any problems prior to this trip, some-times, she can be a little slow to start, but she's never backfired before, also noticed that coming home, on the first hill there was a noticable loss of power, I let off and back on with the accelerator and she straightened up.  She didn't appear to want to shift going up hill unless I really put my foot in it.  Also, not a normal reaction for her.

Would a different carb give better mileage?  I'm thinking an Edelbrock (sic), at least that's what this guy recommended (one of his son's has one he thinks will work).  BTW, the gentleman in question owns a feul distributorship and tears down and re-builds vehicles for the fun of it, as do his two sons. 

What's the verdict.  Thanks guys.



From: denisondc
Sent: 4/24/2006 9:40 PM

My opinion is that the thermoquad carb. would work as well as any other make - if it was as new as the other carb - or had been rebuilt within the last few years. I think the Edelbrock will need cleaning/regasketing in less than 10 years; just like any other make

   

From: DaveVa78Chieftain
Sent: 4/25/2006 10:13 AM

The bowls did not melt.  They may crack or the 2 small o-rings inside may dry out and allow it to leak (flood) but not melt.  The purpose for the plastic bowls was to keep the fuel from boiling resulting in vapor lock.   In many ways Thermoquads are a love or hate situation (mine works fine).  Many replace them with an Edelbrock.  They are new and well supported for parts.  Either carb is very adjustable.

Dave



From: Afubar69
Sent: 4/25/2006 4:23 PM

So, basically, you don't feel that it's anymore prone to fires than any other carb?  If not, then is there any advantage to changing it?

Thanks

   

From: DaveVa78Chieftain
Sent: 4/25/2006 4:48 PM

From my prospective, it will be a age and condition decision.  The Thermoquad may have problems you cannot resolve requiring replacement of the carb.  Things like damaged idle adjustment needle valves/seats, flooded floats, cracked body, missing parts, etc.  may not be repairable/replaceable.  The Edlebrock is new and supported  well.  I am just saying that the Thermoquad is not a bad carb, just that it is old and no longer made which is a good case for replacement.  If the one you have is working well then keep it.  If not then a rebuild may be all thats needed or it may require replacement.  You can get a NOS Thermoquad on E-bay but they more expensive than an Edlebrock.

Dave

 

From: Slantsixness
Sent: 4/26/2006 4:57 AM

The thermoquad is NOT as prone to fires as a Holley double pumper or the Rochester Quadrajet.

The bowl is not "plastic". Regular "plastic" would disintegrate over a few months. It's a compound similar to the fiberous resin compound used in Floats, more similar to bakelite or fiberglass than plastic. It's very durable, and just as reliable as aluminum.

I have seen cracked bowl casings on thermoquads, but oddly enough, they did not leak. I have never seen a thermoquad catch fire from the bowl casing. If you treat it well, and keep up with gaskets, seals and general carburator maintenance, it should last forever.

The "Edelbrock" Carb is the old Carter AFB (Aluminum 4 barrel) the only other true "non-Holley" choice is the Carter AVS (air valve secondary) and I assure you that the AVS  is one of the worst carbs Carter ever made, but still better than the Quadrajet (quadrabog)!

The thermoquad is one of the smothest operating spreadbore carbs there is. Just a little simple tuning and you will never have the Quadrajet's "Bogging" disease. The Holley spreadbore is good also, but harder to tune and costly compared to upkeep of a thermoquad.

A lot of mechanics don't understand the Thermoquad. It looks funny, the adjustments are "different" than they're used to on Holley's and even Rochesters. So when you look at most hot rods, a thermoquad is the first thing that gets the axe.

Keep the TQ. When maintaining highway speeds, those tiny primaries will save you on gas.


----off the soap box---

Tom
(die hard Mopar and Carter fan, as you might have already guessed)   

   

From: Afubar69
Sent: 4/26/2006 7:35 AM

Thanks guys, am gonna print out this thread and let them read it. 

What do you think about me running some carb cleaner thru the tank (gas additive), I do this reoutinely in my POV which is a 94 Olds cutlass and it seems to keep her running smoother (about every 5th tank).  Think this might be useful with the Green Winnie?

Thanks again guys, once more you've removed a load from my mind.   

   

From: DaveVa78Chieftain
Sent: 4/26/2006 8:09 AM

Periodic use of a gas additive cleaner is good practice on any vehicle.  The main issue we face with our older rigs is gas tank rust from condensation.  Many have had to pull the tank and clean/reseal the tank using a product called POR-15.  Careful, the tanks are heavy if you drop them.   Doing a message search you will also find many references to having extra fuel filters do to this issue.  Even the metal gas lines build up crud in them.   Then there is the rubber hoses (at carb, tank select switch, or top of tanks) cracking from age.  Results in sucking air not gas and can result in a fuel leak (syphon feed).   Fuel filter on end of pickup tube in tank can clog up (mine acts up occasionally on main tank).  I adapted a spin on fuel filter used on farm supply tanks for mine.  Easy and cheap to replace.  Was having to change the small inline carb filters frequently before.  The spin on filter has lasted over a year so far.  Figure I will change it this year.

Dave



From: poppinjohnnies
Sent: 4/30/2006 6:58 PM

I replaced my T-Quad with a 750 Edelbrock last year because the thing was falling on its face when you were trying to drive up some of those big hills in the Ozarks. The Edelbrock has great performance, but I'm putting the Thermoquad back on. I figured out that the problem was just a bind in the secondary linkage. The Edelbrock gives it a lot of pep, but it also gets 1.5 - 2 mpg worse gas mileage than the trusty T-Quad. At $3 a gallon, I'll take any help I can get!

   

From: Afubar69
Sent: 5/1/2006 11:04 AM

thanks Poppin.  It's nice to hear from someone that went with something else then plans to revert to the original. 

I think mine just needs a few bottles of something or other ran thru it for it to be fine.  (or maybe a few bottle of something run thru the owner, whichever works) 

 

From: cold_spot
Sent: 5/1/2006 10:48 PM

If you after info on Thermoquads, this is a good site. http://thermoquads.com/index.html

I like Thermoquads and will run mine for as long as I can get parts.
Gord

   

From: nitedriver57
Sent: 5/3/2006 6:24 PM

I have a 77 D27RT with a 440-3 with a thermoquad carb. They are a pretty good carbs and living in CA they will pass the smog check with no problems. I consider myself a good mechanic (I make a living at it) but I still ended up taking it to a shop for the final carb adjusting after I rebuilt it. There are about 17 different adjustments to make on these carbs and they must be done in order. the most important thing I found is to make sure the 2 metering rods travel the same distance at the same time. I was told the only real problem with them is the bowls have a tendency to drain after sitting for a few days. Which means a lot of cranking to fill-em back up. I installed an electric fuel pump and regulator and she fires right up now, even after a few weeks of sitting. If you would like them I have the instructions for all the adjustments. E-mail me if you are interested.

nitedriver

   

From: Afubar69 Sent: 5/4/2006 8:55 AM
 
Thanks nitedriver57, private email is on it's way.  Information is always gratefully accepted.

Thanks
Kaye

(if I could spell, geesh!!)

 

From: Cooneytoones
Sent: 5/17/2006 5:54 PM

I deceided to replace my old existing Thermoquad with a shinny new rebuilt thermoquad...I should have it this week-end. I was going to go with an Endlebrock, but as Denison said, you need and adapter, for the manifold, linkage etc. So I'm am staying stock.
One question....If I remember correctly the (but might be confused) The Carter Thermquad had a felt spacer and two gaskets under it....now, correct me if I'm wrong... I think....The gasket that comes with it, is the two gaskets and the felt spacer in one...Am I correct, or did I dream this? 
The reason I am replacing is the one that is on there now is, I do believe it was rebuilt at one time or another by the PO, due to the fact that the tag is MIA. Also, one of the jets is turned off...it runs fine but lacks a little power, when I adjust the jet and give it some throttle, it backfires on the drivers side barral....so I believe there is an internal fuel leak..or the PO damaged the needle valve seat by tightening it too tight. So, off with the old and on with the new...Any advise or suggestions would be appreciated. I think I remember how to tune it with a vaccum gauge...but it's been awhile. 

ThermoquadTunin'Timmy

 

From: poppinjohnnies
Sent: 5/17/2006 9:37 PM

You just need the single insulator gasket. Just curious -- how much did the rebuilt carb set you back?

 

From: Cooneytoones
Sent: 5/18/2006 5:31 PM

A friend of mine works at an auto parts place, I got it for his price of $128 plus a core charge of $33 plus tax and shipping....altogether about $190.....O'Reilly's Autoparts lists it for $179 plus a $30 core......NAPA for $274 plus a $40 core......CarQuest for $294 plus a $50 core...
and a small independant(Economy Auto Parts) lists it for $284 plus a $35 core....Now I got three different stories from the Boneheads @ AutoZone...(three different places too) one quoted $189.00 plus $25 core  the other $289 but it was listed as a Holley Rebuilt Carter Thermoquad ?  and thir web site lists it at $274 plus a 30 core....and the zone bone heads here near me said you can't get one, Not available anymore...He's wrong.....but I wasn't going to argue with him...
So you can see this is the same carb, at a wide spectrum of prices...you gotta shop around....     IT's Carter rebuilt by either TOMCO or CHAMPION.......
Mine is for a '76 440-3

Can't wait to get it....will post how it's doing after I get it installed....

Timmy

   

From: Enigma960080
Sent: 5/18/2006 5:39 PM

If  you need  Autozone  part numbers,  shoot me an  email.   That  way  you can ask them the  price  of  the part  instead of  having  your 'local' boneheads  tell  you lies...
 
   

From: Im-still-Lefty
Sent: 5/18/2006 9:22 PM

When your new carb. arrives, be sure to inspect it before leaving the store to ensure that it has the exact same linkage connections, hose hookups, and etc.... Also, turn the box over, and give it a good hard tap with your hand before you mount it. This will unstick the floats, that have a tendency to hang in the down position due to a carb. being jostled about while empty. This is the No. 1 cause of flooding on a new carb install.
The carb. will arrive pre-adjusted to a general setting that should allow it to run & idle. Follow the instructions provided to adjust it from there.
You are correct that no matter who rebuilds it, it's still a Carter Thermo-quad, but there are differences in rebuilders. I prefer TOMCO over Champion, because of return rates I've seen.

   

From: denisondc
Sent: 5/19/2006 5:36 AM

   I cant recall the site, but I saw a tool for sale, either at www.snapon.com,  jcwhitney.com or summitracing.com whose purpose was to un-warp thermo quad plastic carb bodies.   

   

From: Cooneytunes1
Sent: 5/19/2006 1:52 PM

Thanks Lefty ..good tip on the float sticking...I've had that happen before...

Will call you first Phil if I have to deal with AutoBone....thanks, the most frequent answers I get from them here is, 

Timmy

 

From: ClydesdaleKevin
Sent: 6/24/2006 8:26 PM

I have rebuilt Holley's, Solex's, Edelbrocks, DelOrtos, Carters, and sadly, QuadraJets...and I can tell you truly, the most difficult carbs to rebuild, bar none, have to be the QuadraJets...SO many little parts and springs and rods and jets and etc...and it all has to be JUST right, with NO variance, to work correctly!  Heck, to work at all!  I just rebuilt a Quad in a friend's Suburban, and it took HOURS to get it to run right...Not dissing the quad, I just hate working on them...and adjusting them sucks too!!!  No fancy shmancy screws to adjust things...Heck son!  Just bend this rod, bend that rod...I don't like the Quads...lol.

Kev

 

From: Blaze
Sent: 1/8/2007 12:02 AM

Thermo-Quads have an inherant problem of main body warp.
Which results in internal vac. leak.
I have been rebuilding carbs for years and I have found one of the most important issues to deal with is throttle shaft wear.
If you rebuild be sure to take the base plate in to rebush the throttle shafts.
When they are worn the butterflies dont seat into the bore consistently and therefore will be hard to get to run and idle consistently.

Thats my 2 cents.