Carter Thermoquads ~ 'More General Information'

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Just had a look in an old CT magazine. Aug 95. The C & S carb is advertised in it, so that is at least 27 yrs it has been around.
A few reasons I can think of as to why there are not more in use: no better than a std Holley, it costs too much, it costs a lot for little gain.
 
4bbl,
Thanks for the links.
Further comments.
- some good info in those links but a lot of nonsense as well.
- I have been tuning TQs for decades. Have never had a problem getting good & adjustable idle quality with the mixture screws. I have never touched the idle or pri ABs, no need to. Since Grant brought out his adj AB Holleys, now everybody is a carby engineer! I noticed on the Ford TQs that they had tiny sec jets. So I investigated. Reason was small sec AB 029, not the normal 040. All TQs that leave here have 040 sec ABs & perform great. No other ABs are touched.
- the idle cct is separate from the main cct, but of course the idle cct has to 'hold the fort' until the main cct starts. This function is controlled by the ABs carefully sized by Carter to get the overlap correct. Rich/lean can be controlled by the fuel jet size.
- some of the idle setting info in those links showed some folks didn't follow [ or didn't know ] the basic rule for setting up the idle cct. A small amount of T slot must be showing at idle, in gear, if auto. Most common problem is too much T slot, from low vac, which then upsets the delicate idle to main transition. The fix is to add bypass air, one method is drilling the t/blades. I do not drill pri blades on TQs or QJs because of the risk of nozzle drip. I drill the sec blades for bypass air; if the carb has a hot idle compensator over the secs, I remove that & use the orifice for bypass air. The engine doesn't care where the air comes from, as long as it gets it.
- a popular misconception is that the IFR in the above scenario needs to be increased for idle purposes. It does NOT. There is always enough fuel available for idling; some very late QJs have small idle port discharge holes, actually become the restriction, & give the perception that the idle jet needs to be bigger, when all that is needed is the holes enlarged.
- increasing the IFR is done for transition, not idle. Low vac cams need more fuel in the mix to prevent lean surge etc.
- I mentioned earlier in this thread soldering closed the holes in the sec discharge tubes & cutting off the the tube ends at angle like the CSTQ. I do that on every TQ that I build for a performance engine. Always perform great, no bogs. We dynoed an 850 on a Pontiac LeMans with a 455. A/F ratio was spot on. Alum heads, 3900 lb without driver, T400, 3.31 axle street driven & registered, street radials, driven by an inexperienced driver. No tuning was done on the carb or ign timing at the track; best time was 11.47; best mph was 118.
 
Bewy said:
4bbl.

I have two 850 CS TQs, bought one new in the 1970s, push in jets. Mate recently bought an 850 & 1000.
The C&S aerosol carbs have been around for years, probably 20 or more. I used to see them advertised in CT magazine. The theory looks good, but if they really
work well, why are not more in use? Especially Nascar type racing.
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Bewy, the 72-up TQ carbs use the Aerosol design on the secondaries until 1984. if you're using that carb, you're already using that design. millions of Chrysler cars used it during that time period, and any surviving running 4 bbl. cars from that era, are still using it, on the secondaries.

if you already have 2 CS type carbs, why are you asking me where the air bleed circuits are ? take one apart, and trace them out, and pin them out.

if you're going to run a CS, may as well run the 1000. go for the gusto. lol. lately, it's not like these cars get driven much anyway, with $6/gallon premium. gas price shocks take all the hot rods off the streets, I've seen it before in 1970's. they collect dust in the garage, and it drives the price of average V8 cars down as well. my kid has a nice 95 Bronco w/302. 32 gallon tank. even if he gets the "cheap" regular 87 octane, it's $160 to fill it up. driven daily, that's $650/month. the party is over. that's a payment on a brand new car or truck, with full coverage insurance. the mortgage on my house was less than that in 1994. the gas is worth more than the vehicles now. the fun is over.

NASCAR doesn't use carburetors anymore, period. they're all fuel injection. NASCAR stuff doesn't belong on a street car anyway, most of that high end pro racing equipment on a street car either doesn't work, is total overkill, or a major pita to use. it was a wide open all day carb pegged to the boards, on the superspeedways, when they did use carbs. on our streets we're limited to 65-75mph highway, and only 35-55mph on secondary roads. with cops and speed traps everywhere. what's the need for anything that NASCAR would use ? there's nowhere to open it up without getting fined, arrested, or worse. they'd have poor part throttle drive-ability, and terrible mileage. if you drive consistently 80mph here you're gonna get so many fines, you'll point out on your license, and it'll be suspended. if you drive 100mph or over, when you get pulled over, the police will be approaching your car with guns drawn, you'll be on the ground, getting handcuffed. driving over 85mph in some states is a felony, with mandatory court appearance, and a $300/hour attorney. 100mph in my state, is automatic suspension of license.

a spreadbore Qjet, TQ, Holley, etc. is really all you need, for the street. or a 750-850 square bore Holley if you want to step it up a bit. even an 850 Holley is too much carb for most street cars on pump gas, it's too rich, and loss of idle signal due to the large 1-9/16" primaries.
if you're getting 10mpg now with a big block/Holley 850, you need to be retired, and a wealthy millionaire to enjoy it, on a daily basis today.
 
Bewy, if you sent your carb to a pro carb builder, believe me,
he'd be changing the air bleeds. that's why modern Holley, QF, etc. carbs,
all have tunable air bleeds, threaded in.
it's become the standard of the industry. tunable threaded emulsion bleeds in the metering blocks on a Holley design as well.
if you ran the early CS racing carbs, of course you didn't have to change air bleeds,
they were already downsized to the minimum size, richer metered, and not emission carbs.
the early CS carbs were in a different league,
then the later 72-up oem emission carbs.
1970's USA emissions carbs were white plug lean right from the factory, for the most part.
that's where the thermobog/quadrabog names came from.
they bogged right from the factory, cuz they were so lean, to pass emissions standards.
bogged and backfired out the carb actually. all the time.
 
4bbl,
Must be some sort of mis-communication here. I never asked, or mentioned, ABs in the CS carbs. You did. My two CS carbs are packed away with my carb collection & have been for about 18 yrs. I used them on various engines & never had any problems such as flat spots, tuning etc, by using the parts in the Strip Kit. Had Carter deemed it necessary to change air bleeds, then they would have made them adjustable. I have no intention of checking the ABs in them, will not be using them any time soon, as my current ride has Weber carbs, four of them.
Well aware than Nascar has gone to FI; but not in the 90s when the C & S carbs were around, so my earlier comments still hold.
Do not agree that TQs bogged from the factory 'all the time'. Only have to read comments on TQ users on this forum who have fitted factory TQs to stock engines & have no problems. This assumes of course that the carb has been properly rebuilt & adjusted to specs.
Once the engine is modified, carb mods are likely to be needed.
 
I’ve never had a TQ bog on me when properly set up
(and used with reasonable drive train combinations.)
 
Bewy said:
Just had a look in an old CT magazine. Aug 95. The C & S carb is advertised in it, so that is at least 27 yrs it has been around.
A few reasons I can think of as to why there are not more in use: no better than a std Holley, it costs too much, it costs a lot for little gain.
Click to expand...

that's not the original 1969-71 CS carb if advertised that late, they stopped making those in the 1970s. they made AFB/AVS copies and also called those CS throughout the years. the 9800 series was called a CS around 1980-onward. or it was new old stock NOS early CS carbs that were sitting on a shelf somewhere for decades.

the Buick dyno test tells the story, you will always make more HP with a 4bbl using 4 equal size bores, for racing. the Holley DP as designed in the 1960's, was first cobbled up at Smokey Yunick's shop in Daytona Beach, Florida specifically for NASCAR racing. He told the story about how the original prototype they made, was lent to Bunkie Knudsen at GM and later Ford, then never seen again. He asked for it back numerous times but never got it.

The small primaries and tiny secondaries on a spreadbore create a velocity difference that is somewhat detrimental to making maximum HP at high rpm. The primary flow bounces up off the plenum floor creating turbulence. It was designed to use with a factory dual plane intake manifold. Edelbrock made the early Torker 1 open plenum intake with a volu-step in the bottom of the plenum, to counteract that effect. The floor was lowered in the front half of the plenum. To this day that is still a good SS class racing intake for a spreadbore carb, if you can find one.

for daily driving on the street using a cam up to around 230 duration @ .050", a spreadbore will give better part throttle response, mileage. A big Holley i.e. 850 with its big 1.56" primary bores will slow down idle/off idle velocity, the mixture falls out of suspension at idle/off idle, and the plugs will look black and rich. It takes custom air bleeds, bypass air holes in throttle plates, etc. to get a big Holley to work on a stock motor on the street, if at all. If you just bolt it on, the plugs will be black or wet, and the motor runs rich. A 750 is a better choice for a mild motor, the smaller 1.375" bores bring the velocity back at idle. Idle quality is a lot better with a 750. A Holley 850 is a LOT bigger than a Holley 750.

in NHRA Stock and SuperStock, if you can sneak an early CS top/middle section onto the car, and use the oem 72-up numbers baseplate to pass inspection, it would pay dividends with the extra cfm. but if you get caught, you could be DQ'd. This is why the class racers seek out the 1971 Mopar 340 carb. It's got the same basic design as the early CS.

the CS aren't used because the jet/rod kits and rebuild kits are exceedingly expensive, in some cases more than the cost of the carb itself- and carb technology has come a long way since 1970 when the CS was first in use. It's a 53 year old design. the Qjet is a 57 year old design. technology moves onward and forward.
 
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rumblefish360 said:
I’ve never had a TQ bog on me when properly set up
(and used with reasonable drive train combinations.)
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agreed. that means tightening up the secondaries spring, and richening it up, and removing all the emissions controls- usually. you may take the bog out of it, but with the stock jetting, air bleeds, it's still lean a/f ratio. all the carbs were set up and designed lean for each specific application, it was the law.
from the factory, everything bogged from 1975 on. they stopped making the good Cuda, Challenger, Charger cars altogether. same with GM, Ford. it was the gas crisis. rear gears got taller in all the cars for mileage, and they dropped 2 points in compression across the board. believe me, they all bogged. they sounded like big vacuum cleaners that went nowhere when you punched it. the fix was, convert it back to the old system. change the heads, intake, cam, put gears in it. we removed tons of that early emissions equipment from the cars.
 
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Bewy said:
4bbl,
Must be some sort of mis-communication here. I never asked, or mentioned, ABs in the CS carbs. You did. .
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I'd suggest taking one of the CS carbs out of your collection, measuring everything, and comparing it to the 72-up carbs. Epiphany still strike. There's a good reason those later carbs are $50-$100 each on Ebay.
 
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this guy hit the nail. truth is, what he did with the air bleeds/idle feed restriction was illegal for car manufactures to do from 1972-onward, the cars could not be sold legally in USA. however, prior to 1972, this is how all the carbs were set up as the industry standard. that's just how lean everything got after '72. an early CS carb has the richer metering already. the later CS 9800 series would also be somewhat richer than the OEM carbs. 12.6 at idle, 14.1 at cruise is dead nuts on. it doesn't get much better than that. I added the highlighting:

ThermoQuad tuning at Cruise

ThermoQuad tuning at Cruise [Re: RayR] #2358872 08/24/17 12:36 AM
chargerjoert
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Joined: Sep 2015

Michigan
What list number thermoquad are you running and what is the top casting 4 digit number (near the fuel inlet, like 2124 etc...)?? Thermoquads were tuned very lean for each application and they got worse (leaner) as the years went by. Changing IAB's, IFR's, Idle air bypass passages, and adding bleeds to lean the circuits. Not to mention all the emissions junk that was added. Also, how many turns out are your idle mixture screws (from lightly seated closed)?

I do not have, or ever used, a lambda sensor for AFR. But I have used a vintage Heathkit Co meter. My experience has been the AFR will (and should) get leaner as rpm goes up (say in Park, and idle to about 3,200 rpm). I have not actually driven on the road with it to get data.
For the gasoline here in the states (E10) I find more idle timing helps a lot. Reduces coolant temp and reduces the exhaust smell. And that big blocks do not like to idle or cruise on lean mixtures. But I also have a single plane intake manifold. My cam (xe268) generates about 16 in-Hg at idle in park.

My thermoquad is a modified earlier 6500 series with a 2124 top casting. This casting in stock form has IAB @ 0.038" and 0.034" IFR. I typically run 18 to 21 degrees at idle and 32 total. The modifications to the thermoquad cruise circuit (currently) is IFR's @ 0.040" and IAB's have 0.011" guitar wire in the holes. And idle air by pass holes drilled to 1/8". Idle mixture screws are about 2.25 turns out. Modify at you own risk (and I would go in small steps to see what works for you). My car runs nice and cool and does not stink. My Co meter reads approximately at idle 12.6 and goes leaner to about 14.1 at 3,000 rpm (in Park). Meter could be off, as I suspect the real readings might be slightly leaner.
 
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what's this all mean ?
bottom line- if you have a 72-up carb, it's a lean carb right from the factory.
75-up was even worse.
be prepared to mill, fill, and drill.
 
4bblfreak said:
agreed. that means tightening up the secondaries spring, and richening it up, and removing all the emissions controls- usually. you may take the bog out of it, but with the stock jetting, air bleeds, it's still lean a/f ratio. all the carbs were set up and designed lean for each specific application, it was the law.
from the factory, everything bogged from 1975 on. they stopped making the good Cuda, Challenger, Charger cars altogether. same with GM, Ford. it was the gas crisis. rear gears got taller in all the cars for mileage, and they dropped 2 points in compression across the board. believe me, they all bogged. they sounded like big vacuum cleaners that went nowhere when you punched it. the fix was, convert it back to the old system. change the heads, intake, cam, put gears in it. we removed tons of that early emissions equipment from the cars.
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I Capped all un needed ports, jet and rod change is a tune up process, what ever the factory did doesn’t mean squat, never needed to tighten up the secondary air door to rid myself of a bog, besides it is not the go to thing to rid yourself of a bog.

All TQ’s I have used other than on stock cars have been on high performance engines. Not factory high performance.

I don’t believe you on all TQ’s bogged. I’ve had post ‘75 carbs and cars that ran just fine. Those late ‘70’s super Hwy. gears were terrible with a TQ. Just as you said. Very lean, tons of hoses, not fun!
 
Couple of comments, then probably no more from me because we are going round in circles.
- $50/$100 TQs. QJs the same. They are cheap because they were [a] not Holleys got a bad rap when folks left out the O rings out, then ran rich, or misadjusted them [c] are 40+ yrs old [d] 000s were made, so plenty still floating around, hence cheap price. There is a guy here, Pro Carbs is the name I think, refurbishing 9000 series 800 CFM Ford carbs for $975....& that is Aussie dollars! [ $US1390 ]
- there is more than one way to skin a cat. The RayR post was very interesting & informative but a LOT of important info missing. He 'thought' it had a purple cam....but purple cams do not make 18" at idle? No mention was made of T slot position, which is the foundation of tuning the idle cct. I do not believe the pri ABs need touching at all to dial in these carbs. What I believe would have fixed Ray's cruise mixture was enlarging the economizer by about 0.004". The idle jet controls fuel only; the Ec controls the volume of mixed air & fuel that gets delivered to the T slot. This would have changed the T slot/idle cct balance & re-aligned things, As I alluded to earlier in this thread, the Ec is hard to get access to, & requires long drill bits; most people wouldn't know where it is. I cut open an air horn to find it. T slot length has a bearing on mixture ratio; a short T slot is rich, long slot lean.
 
Bewy- IMHO, with diligent custom work to jetting, metering rods, idle/high speed air bleeds, the 72-up TQ carbs should be able to come close or equal the early CS carbs. The Mopar BB dyno test proved that. It was a list #6922 ? TQ carb if memory serves. It's not difficult to drill/tap for removable air bleeds. When all is said and done, it may just be easier/quicker to just purchase a CS carb to begin with. That's if someone wants to pursue a spreadbore QJet/TQ/etc. type of carb to that extent in the first place. They were cutting edge 1965 carb technology. Great for their time, but let's face it, they've been surpassed. Spreadbores seem to be slowly losing market share, as everyone with an vintage musclecar migrates to a standard square bore Holley style carb. Valuable numbers matching cars are another story. If I had an original late model 1970's 400 or 440 Charger, Cuda, Challenger, it would have the TQ on it, definitely.
 
Pretty sure there was a 950 Holley 3 bbl that had conventional boosters in the secondaries.
 
He actually listed the 6090S in post #16, with jetting details, may have left it off the list unintentionally. Thx for bumping this thread tho', gave Me a chance to tag it in My favorites. We lost this member soon after I joined FABO, :( , always looked forward to His threads & posts.
 
Bewy said:
Pretty sure there was a 950 Holley 3 bbl that had conventional boosters in the secondaries.
Click to expand...

yes, the 950 3-barrel had booster venturis. I just picked one up for $65
the 1050 3-barrel had secondary discharge tubes, without booster venturis. that's how they picked up an additional 100cfm, making it a 1050 cfm.
the trap door carbs were a 1960's Holley racing carb and short lived fad. they were surpassed by the late-1960's DOMINATOR Holley carbs first used on the NASCAR BOSS 429 engine. truth be told, the early 850cfm vacuum secondary L88 Chevy carbs were better than the trap door 950/1050. Which is why Chevy put them on the 427 Vette motor, instead of a 950/1050.
a trap door Holley was nothing more than a prototype 4150/4160 850 vacuum secondary carb, with bigger secondaries- the primaries are the same size as a modern Holley 850- the single big oval secondary throttle plate gets a little more cfm by eliminating/opening up the wall area between the rear throttles, for 100cfm more airflow.
the problem with a trap door is, timing the secondaries. they either open too fast and bog, or open too slow to the point a standard 750/850 double pumper or vaccum secondary carb is better. the big trap door vacuum diaphragm is a nonstocked discontinued part, and to my knowledge tuning parts for it are not available new. you have to use the cut and try farmer method to tune them. the trap door also uses a special secondary throttle actuating lever, that bolts onto the secondary throttle shaft, and connects to the vacuum diaphragm rod. lose that little part and you're screwed, you have to make a new one from scratch using a standard Holley vacuum secondary lever, and weld a horizontal extension on it.
the one I have was converted to mechanical secondary linkage. that takes a bad situation and makes it worse. no doubt it will bog badly, as the secondary side has no accelerator pump. now the secondaries will open very quickly and it's a sustained high-rpm only carb, which is exactly what it was designed to be in the first place. The trap door was a stopgap design, until Holley developed the modern DP and vac. sec. carbs with 4 equal sized bores. The modern Holley 750/850DP was cobbled up and designed in Smokey Yunick's shop at Daytona Beach, Fl. during the 1960's for NASCAR. He wrote about it in his autobiography. He had the original epoxy/aluminum/tin plate prototype, lent it to Bunkie Knudsen at Ford, and never got it back. John DeLorean also looked at it, and said it was a good idea while he was General Manager at Pontiac, and later at Chevrolet. This was during the pre-Quadrajet era when the biggest 4GC Rochester was only 700cfm. They were at 421/428/455 Pontiac engines, and headed for 472/500 Cadillac engines, and needed more carb capacity. That's what led to the 800cfm Qjet, 800/850/1000 cfm Thermoquads during late-1960's, early 1970's.
 
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Killer6 said:
He actually listed the 6090S in post #16, with jetting details, may have left it off the list unintentionally. Thx for bumping this thread tho', gave Me a chance to tag it in My favorites. We lost this member soon after I joined FABO, :( , always looked forward to His threads & posts.
Click to expand...

I picked up a #6090 for $75 stripped. all it had was 3 castings, and primary jets- nothing else. I'm going to build it using others for parts.
 
here is a model 3916 Holley, 950cfm, 3-barrel carb, with 4 booster venturis,
compared to 4064 Holley, 1050cfm, 3-barrel with 2 boosters on primary, and 2 discharge tubes on secondary- comparison
they just removed the booster venturis from secondary side altogether, less obstruction, more flow, less low end response, more top end/high rpm power

3916 950.jpg


nozzle-jpg.jpg
 
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Nick's Garage from Canada, put a 1050cfm Holley list 4604 three-barrel carb w/vacuum secondaries/discharge nozzles on a 427 Chevy, and dynoed it.

 
Bewy said:
Few things to cover:
- the orifice size in post 134 looks a little bigger than the one I encountered in the 9333, but similar design. This might explain the smaller sec jets in the CS TQ because that would slow down the dashpot release, make the AV function like a choke blade & richen the mixture.
- the CS TQ has the IFR being fed from the fuel bowl, not from he main well AFTER passing through the m/jet like most other carbs. Only other carbs I am aware of that have this are DCOE & IDA Weber carbs.
- 4500 Hs have 2" sec bores from memory; plus a venturi. TQ/QJ have 2.25" bores & no venturi to cause a restriction. This explains the larger the larger TQ jets, & possibly the small holes in the sec discharge tubes might have an influence on the jet size.
- the top section of the AV on 6000 & 9000 TQs is bent forward. This section was straight on the CS series. Do not know why, but suspect AV/fuel flow action started earlier on the CS.
- QJ/TQ have the booster ring in the primaries, Hs don't. I guess that changes a lot of things in regard to jet & AB size & position.
- the 9333 carb had 101 pri jets. That carb had a horrendous 3/4/1" exh thick heated spacer under it, I think EGR related.
- have seen the C&S carb, it is not new. There is a company that specialises in VW engines that converts Dellorto carbs to a spray bar system with claims of more HP.
- in the TQ/QJ/H dyno test quoted above, it would be interesting to know if all of the TQ tuning tricks were used to maximise output. Only 5 hp difference between the H & the TQ. Could the TQ have done better? On the TQ, these tuning changes could have been tried, but were they: WOT position of the sec blades; being so large they can influence distribution & air flow. WOT position of the AV, which is adjustable. There are a few different AV dashpots available, different spring rates.
Click to expand...
I was not allowed to make permanent changes to the TQ, i.e. could only do sec air door opening, jets, rods etc. The sec butterflies were left at 86 deg opening. I completely ignored all advice on the sec air door; in fact I removed the stop so it would open all the way at .960". That was a disaster. Best power was found around .800" sec air door opening. Played around a lot with jets and rods. The pri needed a .109 due to single booster and no plastic venturi. Sec high speed air bleed was left stock, .036" IIRC.

The Qjet was hardly a junkyard deal. It was a well prepped custom piece, custom cal'd to my engine specs and was the Stage 2 recipe from Cliff's book, with an adjustable stop on the sec air door.

Part 2 of dyno testing will resume in a couple weeks (spun a rod bearing back then).
 
I see a lot less TQs here than you do in your country. I have only seen 3 sizes of sec high speed bleeds: 0.027", 0.029", 0.039". Local Ford TQs, there are only 5 models, all 9000 series. These are 029. Majority of early Mopar TQs I have seen are 039. I convert all of them to 039.
 
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