Replace or Rebuild Thermoquad Carb?

[Weavebago]

Sent: 4/19/2005 9:12 AM

is it worth it to get a kit and re-build my Carter carb(thermoquad) or should I just buy a new one? right now I'm not sure its all that bad but it has a plastic body and I was told that they get saturated from sitting(it sat like 2yrs at p/o's house)also if I do buy a new one should I get the same one(plastic body) or should I go with and all metal one(Holley or Carter)and if I do re-build it what are the chances that it wont be just right? all I've heard about re-building have been horror stories! lol

[DaveVA78Chieftain]

Sent: 4/19/2005 9:27 AM

Some go with an Edlebrock replacement, others rebuild their thermoquad.  In many ways it will come down to your experience/comfort with rebuilding carbs, condition of your current carb, just plain ole personal perference, or financial position.  The plastic body does not absorb gas.  That issue is related to plastic floats used on many, many different carbs.  There are copper floats available via the internet.  The plastic body can get cracked.  Rebuilding them is actually not that hard.   Take your time and research the web for the several how-to articles available.

Dave

[greasemonkied]

Sent: 4/19/2005 1:29 PM

I would go with the Carter performance series or the Edelbrock, I had a problem with the resin body of my thermoquad having a crack in it and when ever you would turn the motor off it it would just drain all that gas that was in the bowl into the manifold, thus flooding it every time and also lousy gas milage. They are very expensive to replace. Buy metal, it will last a long time under the all the heat these motors put out. Dean

[Daved27c]

Sent: 4/19/2005 4:40 PM

Bob;

When we bought the Titanic It wouldn't run. It had sat for so long that the floats were stuck to the bottom of the bowl. I took the carb off, brought it home, took it apart,  cleaned everything, and reassembled it. The kit was not available that day, and I had to get her out of the PO's yard. I drove it 1500 miles this way without a driveability problem. The only thing I had to do was that if sat overnight I had to pour some gas down the carb to get it to start. After that I went and got the rebuild kit and did it right. I still had to pour some gas into it to get it started. A new fuel pump(mechanical) fixed that problem. For me the $ 35.00 and a few hours labor was much better than $$$$ for a new carb. If you take it apart carefully ( i.e. count how many turns of the screwdriver it takes to remove each screw), reassembly should be fairly easy. You may want to take digital pictures as you remove each piece. Having a compressor to blow air through the passages is a must. Hope this helps.

Dave

[Weavebago]

Sent: 4/20/2005 8:45 AM

found out today that the choke thermostst is not working and ordered it from NAPA(like $22)I have to take the carb off to replace it so I'll take a good look at the plastic body to see if there are any cracks but my friend told me that the choke thermostst being bad could be the cause of my horrible gas mileage(something like 4.5 mpg!)could that ALONE cause that big of a loss in MPG? if so,maybe I'll just wait on the carb till we take it for another test run next week.

[DaveVA78Chieftain]

Sent: 4/20/2005 3:00 PM

The choke is used to enrich the mixture during engine warmup so you bet it can create bad MPG if it does not open up.

Dave

[Daved27c]

Sent: 4/20/2005 9:51 PM

Bob;

I have a manual choke on mine, so I may not have the issues you have. We get about 6 MPG out of the Titanic. I don't think that this is too bad as the PO said we would only get 5 MPG. As far as mileage.. we pack REALLY heavy. We have been known to pack 2 Tv's for a weekend trip. I know that this sounds crazy, but this is what we do. 4.5 Mpg is low. The "stuck choke" could easily explain that. If you can fix the "stuck choke" for $22.00...Do It... If you think the carb still needs to be rebuilt, Do It....the Winne will be happier if you do.

Dave

[The_Handier_Man1]

Sent: 10/30/2007 6:57 PM

After reading many reports on carbs, I decided to rebuild my Carter thermoquad.  Since I am cheap and hate to spend more than what I paid for Wilbur in the first place just for a new carb I bought a used TQ for $20.00 in case I needed any extra parts and a rebuild kit for $30.00.  There is much info out there to read like http://tocmp.com/manuals/Carbs/Carter/Thermoquad/1972/index.htm  and http://www.offroadexchange.com/tquad.htm .  As it turns out I needed to use an impact driver to remove three of the bowl screws and then the inlet fitting was stripped on my carb so I used the top of the spare carb.  The model number of the carb is on the left rear bolt flange. My old one is a 6518S and the one I bought is 6545S.  The main difference is the lack of a bowl vent on the 6545S.  Having driven it around town it seems to run better than before.  Could be the 10 years it sat before I bought it.  I think denison said a rebuild every 10 years or so is a good thing.  My carb had brass floats that were good so I reused them.  This was something I wanted to do and now I can cross the carb rebuild off the list.  On to the cold air intake next,  Les

[firehart2]

Sent: 10/31/2007 7:56 PM

I am wrestling with that same issue. My Brave has a 413-3 and it runs like crap. I am not a mechanic, I'm a parts switcher.

[normstow]

Sent: 11/1/2007 9:50 AM

Hi,

I few years ago purchased a 76 Vogue motorhome on a Dodge M500 chassis that had a number of issues easily attributed to a bad carb.  I bought a re-built carb. from Schucks that leaked terribly and ran poorly.

After some research I was referred to www.carbsonly.com in California.  This company has access to brand new phenolic resin bodies, which is a major plus for these carb's.  They identified the exact carb. I needed for this motorhome, (some have different vacuum attachment requirements), and supplied it fully tuned ready to go.  I installed the carb. and it ran beautifully with absolutely no adjustments.

I recently purchased a 76 Apollo 3000 on the identical chassis, and it also had carb. problems.  It was hard to start, and running so rich that it would leave black sooty deposits on the pavement under the exhaust pipes, even when only run for a short time. 

I switched out the carb. from the vogue, and the improvement was amazing.  It nows purrs, and after a trip last weekend, the inside of the exhaust pipes are a nice grey color, rather than pitch black.  On the same trip, the Apollo returned 7 mpg.

I highly recommend this company, but wish you luck whatever route you take.

Norm in Seattle

[Cooneytoones]

Sent: 11/4/2007 8:08 AM

I rebuilt my TQ last year...the process wasn't too hard/...The hardest and trickiest parts were both the linkage, and tree adjustment....Be careful on the tree adjustment, just a little too high or a little too low makes a world of difference......and the linkage you need to adjust by bending a little here and a little there....the rest is just getting the right gaskets, needdles, and rubber ferrells in the right place, and making sure that the plastic body isn't warped...I think that was a great learning experience, (not to mention a very satisfying one too) to rebuilt the TQ.

It was by far (in my opinion) one of the best classic carbs made.....some people knock em' or call em' dogs because they are not the simple. But when you have one that's adjusted correctly and running good.

They will stack up to anything out there.
Let us know how you make out and good luck.

Here's a good link for some info:
http://thermoquads.com/page204.html

Most knowledgable TQ site, and replacement parts I've found.

http://thermoquads.com/index.html


Timmy

[melyash]

Sent: 11/5/2007 9:30 AM

Not a Thermo, but a Rodchester... I had problems with this thing for like 4 years, my mechanic loved those carbs and really wanted to make it work for me. It did not instill confidence and my wife was getting more than leery about any trips in my Chevy powered winne. Finally tole him he could keep the carb, put it on a pedistal in his living room for all I cared, just make the winne run without issue. Dropped on a 650 Edelbrock and have been absolutely trouble free with fuel delivery issues every since. 

My wife trusts it again, and life in that 70's bago is doing great. Ran it 350 miles on freeway and she ran like a dream. Turned around and ran her to 6,000 in the mountains and ran her thru some serious up an down terain, and she ran like a top.

Sometimes, we get caught up in the "gotta save money" trap, and bring ourselves grief instead of enjoyment. We enjoy working on these rigs, but we do not enjoy doing so on the side of the road. Sometimes you just gotta bite the bullet and get what you really probably need.

[bluebird]

Sent: 11/6/2007 7:43 PM

I agree . Sometimes these old carbs aren't worth messing with. I like the quadrajet carb, but they can be a pain in the you know what. Same with the thermoquad. I tried to go through one years ago on a dodge ramcharger. I then tried a carter avs quad, ended up putting a rochester quadrajet on it off of a chevy car. It ran like a top. Unless you are pretty good at carbs, I'd either have a carb guy do it or buy a new one for the aplication. Nothing worse than melting the pistons of of your mh many miles from home. Edelbrock makes a pretty nice carb, and the prices aren't that bad.

Charlie

[ZR91]

Sent: 11/6/2007 8:46 PM

I am a competent mechanic and I rebuilt (2) different carbs for our motorhome.

After less than stellar results I simply replaced my intake manifold and carb-Weiand aluminum intake and Edelbrock carb.

I only wish I had done this sooner. The fuel savings alone are worth it-never mind the fact that it starts now as soon as you touch the key in any weather.

Technology has improved 10 fold in carbs since our motorhomes were built.

You can spend hours and lots of money on these old carbs ( I know-because initially I tried) but you are just trying to polish a turd compared to what a new carb can do -right out of the box.
Trust me, the fuel savings alone will pay for a new carb very quickly.

Jay Masterson

[Slantsixness]

Sent: 11/7/2007 5:28 AM

"Technology has improved 10 fold in carbs since our motorhomes were built."
HUH?

The only improvement in technology delivering fuel to your engine is fuel injection systems, not carburators.

The "Edelbrock" carb is a Carter AFB, pretty much right off a 70's mopar 340 or 360 V8... so it's basically 35 year old technology, with a couple extra ported vacuum lines in the body to accomodate todays cars... not a redesign... just a modification for smog equipments.

Any carb, when properly refurbished and adjusted (note I didn't say rebuilt), will perform just as well as a new carb, for just as long. "rebuilding" a carb is not just cleaning and installing the items you get in a kit, although it might solve 90% of the problems, usually the average backyard rebuilder doesn't even check the condition of the throttle plate and the passages within it (most of the time, they don't even replace the throttle plate gasket, or they use the wrong gasket, or even install it upside down (yes you can on several carb models)....I hear things like "if you take that off, you'll never get it back together again" and "it's not leaking..leave it"... and the last real pain in the arse is..."was that rod always bent like that?...I think so...aw hell...just leave it that way, what does it do anyway..."
Anyway.... a can of gumout, a rebuild kit....and in a few hours you could have a really clean carb that still won't work....

Imagine that.... after swearing by the AFB, AVS and Thermoquad (with the phenolic body, not the fiberglass...) all the Quadrabog and Holley people finally discovered the awesomeness of the simple, economical and uncomplicated AFB....

Was it because they stuck the name Edelbrock on it?
Back in the day, we used to consider the edelbrock performer manifold the cheapest POS you could buy, with the Weiand being the favored, more expensive option...

Funny: after all my dealings with hi-performance mopars, my little 318 runs great with the original itty bitty 2 barrel carb (yes I "rebuilt" it)  and cast iron manifold... and gets 15-16mpg....in a fully loaded 21 foot Brave.
 
I'm not pointing fingers here at any person or member... but even if it's not you, you know at least a freind or two who resembes these comments.

All in fun,

Tom

[Elandan2]

Sent: 11/8/2007 7:04 AM

Good stuff Tom.  Funny how a carb will work fine until someone decides that they can make it "work" better!

Anyways, go to www.carburetor.ca for a ton of info on all makes of carbs. 

This place has links to original service guides and other info.  I bought a kit from them to "rebuild" my thermoquad last year and it came with everything needed, a detailed rebuilding guide, and excellent instructions on set-up and adjusting.  They also have brass floats for these carbs.

Rick

[ZR91]

Sent: 11/15/2007 9:36 PM

Tom,

You are wrong.

You are either posting "wishfull thinking", embellishments from some one else, or you need to re calculate your mileage estimates.

How do I know this?

Well,

1) The Edelbrock carb is a MODIFIED Weber design.-Yes, it is actually stamped into the side of the carb.

2) These carbs have fully replaceabel parts and adjustments ABOVE the fuel level.

Perhaps you should try one before you offer an opinion on something you obviously do not understand or comprehend.

These carbs are very adjustable/tuneable .

[Slantsixness]

Sent: 11/16/2007 1:55 PM

Uh...

MY mileage... (mpg) is not an estimate... I have a 2 barrel carter carb (original) and get reliably 15 to 16 mpg with it in a 318-3 D20 (also original). Not a surprise to me either. I've been running small block chrysler V8's  for many years, and if they're tuned right, that's what anybody can get in a 1 ton truck. I am also, by far, not the only one getting this MPG in a Winnie either.

If I'm mistaken about a specific model number Edelbrock 4 barrel carb, I agree. but a little research done after I wrote the response, about the AFB, and it was first used on Ford vehicles as early as 1958, and pretty much remains unchanged, except for smog and choke adaptations.

Weber now manufactures this carb for edelbrock (carter is long out of business). Weber did not design the AFB, AVS or TQ. There may be some improvements they have made to carb, but nothing I've noticed as far as performance tuning.

[Oz]

Sent: 11/16/2007 6:14 PM

A general overview of opinions:

I am not a mechanic by any stretch of the imagination so, I rely on the advice of other members to make educated decisions involving my RV issues.  The great thing is, you can get all sides of the story from the wealth of knowledge and experience of our membership on a vast majority of topics.  This is why our membership is always growing, active, and we are consitently either number one... or in the top three ranked MSN groups!

From having read every one of the thousands upon thousands of posts here on CW, I get a good, broad perspective of the similar and differentiating opinions on every topic and this is important for the vast majority of members, like me, who are shoestring, learn-as-you-go, RV enthusiasts.

So, here's my broad perspective, proven by the knowledge and experience shared by our respected, knowledgeable members:

The old carbs can and do run efficiently and have a good service life if they are properly maintained and adjusted by capable hands (but, isn't that really true of just about anything?). 

The new carbs do have modifications which can greatly simplify the amount of knowledge and time needed to keep the carb properly tuned and serviced compared to the older models.

All additional input is welcomed!

And, thanks for the incredibly valuable links!  I added them to the Resouces Section.

- Sob

[killme10]

Sent: 11/22/2007 8:46 AM

Tom is right. The edelbrock carb is a carter afb/avs design. It is manufactured by weber for edelbrock. A very good, very adjustable carb. I use them myself and have had no problems with them. Easy to rebuild and adjust. Get a strip kit for the afb and away you go. I get 12 mpg at 7000 ft in my 413-3 21 ft indian. Marty

[ClydesdaleKevin]

Sent: 11/28/2007 6:53 AM

To add to Tom's post, the carb on our 77 Itasca is a thermoquad...I have never cleaned it or touched it because the last time I played with a thermoquad I couldn't believe you had to adjust it by bending rods...no adjustment screws?  Ye gads! 

Anyhow, we have been accused of wishful thinking as well on our gas mileage "estimates."  We are currently getting an average MPG of 11+ mpg in Excalibur, our 77 Itasca, which is 27+feet long with a Chevy chassis and a 454 big block V-8...and we get this incredible gas mileage towing a fullsize 1985 Dodge van, which has a 318 and a torqueflite tranny, and the VAN is fully loaded down like a trailer when we travel:  It is loaded inside and out (on the roof rack) with our entire woodworking workshop (tent, powertools, tables, etc), our RenFaire tent and tables, and all of our stock and plastic totes!  We get less in the mountains (like when we drove through the Ozarks), and if I drive faster than 60mph my mileage drops considerably...but if I keep her at 55-60 in most terrains, I get over 11 mpg!

If she sits a long time (more than 2 weeks) I have to drop gas in the carb for an easier start...she probably needs rebuilt, and I won't TOUCH a thermoquad....but she still gets the mileage!   Sometimes it just works out that way.

Kev

[13503gds]

Sent: 11/28/2007 5:22 PM

Tom, the only thing you missed were the ported heads that went with the fuel injection.

[DaveVA78Chieftain]

 Sent: 12/3/2007 1:34 PM

A Carter Thermoquad on a 454 Chevy?
You sure your not thinking Rochester Quadrajet?

[ClydesdaleKevin]

Sent: 12/3/2007 5:19 PM

You are right, Dave...its a Quadrajet....stupid bendy rods...lmao! 

Kev

[bluebird]

Sent: 12/4/2007 9:11 PM

If that quadrajet is getting you that kind of milage. Don't touch it, and don't let anyone else look at it. Although thru the years I've found them to give the best milage. Late 70s and early 80s carbs were pretty good.