Thermoquad help needed

Raul I have 340 with 3310 holley love it Im a mechanic for 30yrs hated to try and rebuilt the TQ never any sucuss 3yrs ago had a bug up my ass for the TQ bought a 72 new one for 300 removed choke flap drilled squirters to 33 changed jets and rods runs just as good if not better than the holley call demon sizzlers he knows the TQ if need help call or email me they do run good when done right

To be honest - that carb setting and those rods don't seem "super rich" for a flat 11 car.

Are you sure its not "flat lining" due to poor fuel supply through the secondary system? -

One tip with a TQ is to drill the sec spray bars to .055th on the end spray holes, as they can "go lean" in a HiPo application and not provide enough fuel at high RPM.

My guess would be that if changing the venturi gap by bending the air door tang didn't change the mixture - it may be too lean, not to rich.

Have you checked using an A/F wide band meter?

Just some thoughts - This list should help you in staged tuning progression-

(dimensions in inches):
- - - - - - - - - - - - - - - - - - - - --
16-XXX is for 71 OEM and CS TQs.

75-XXXX is for 72 OEM and 9000 series.
Step sizes listed, Econ = economy, Mid = midrange, Power = power steps.
Rod # Econ Mid Power
------- ---- ---- -----
16-615 .059 -- .040 For CS only.
16-616 .064 -- .030 For CS only.
16-632 .057 -- .040 For CS only.
16-633 .055 -- .040 For CS only.
16-634 .062 -- .030 For CS only.
16-635 .060 -- .030 For CS only.
16-655 .062 -- .040 For 71 OEM TQ only.
16-683 .060 -- .035 For 71 OEM TQ only.
16-683 .058 -- .035 For 71 OEM TQ only.
75-1937 .070 .046 .040
75-1938 .071 .051 .040
75-1939 .070 .058 .040
75-1940 .072 .060 .045
75-1962 .067 .055 .045
75-1965 .069 .061 .045
75-1966 .067 .052 .045
75-1994 .068 .043 .035
75-1995 .066 .040 .035
75-1996 .069 .048 .035 *
75-1997 .067 .045 .035 *
75-1998 .070 .057 .040
75-1999 .068 .054 .040
75-2000 .066 .054 .035
75-2001 .064 .051 .035
75-2002 .065 .052 .040 *
75-2003 .063 .049 .040 *
75-2004 .067 .058 .040 *
75-2005 .065 .055 .040 *
75-2024 .066 .054 .040
75-2086 .069 .061 .040
75-2103 .069 -- .045
75-2109 .069 .061 .045
75-2110 .069 .053 .040
75-2144 .069 .061 .050
75-2145 .069 .061 .055
75-2153 .067 -- .055
75-2159 .070 .062 .040
75-2179 .074 .066 .042
75-2210 .069 -- .045
75-2211 .0715 .064 .040
75-2385 .069 -- .053

I have had several thermoquads in my history,new yorkers,had a broughm with leather and all options it could have in 76 including electric sun roof and never had a porsche pass me when I would go in mountains in colorado going snow skiing,or anything else for that matter,look at stock class record holders from 70`s on.I like both for some reason,guess carbs of any kind never scared me,I do rotten chesters too,strombergs ball and ball carters,you`d be suprised what you can learn by experimenting,anyone can do what the fad is.Don`t mean I will ever own what they fit,I had a flick with my middle finger on air door trick and when it shut with a certain sound it was go time.My sister bought a new turbo baby mopar at the time,her smile wasn`t so wide when she tried to pass me going up a big hill after she bought it and brought it home to show it off,new yorker 1,turbo shelby 0.I had four people she was alone.You can make anything run if you work at it.Comedy is alright but depends how serious the help was that was needed,some people may have no where else to get the knowledge needed this site provides as long as it is not a keyboard kick fest,I wish I had a stock class car,mopar didn`t all have a holley option,mine did but 2 barrels.Have a nice weekend fellas.....oh yeah and it is sad they have to pm to get the problem solved,I know the class has secrets but I won`t use em to beat ya,just to better my ability`s,it is sad they have to pm,this place has some major attitude problems at times,why the pros don`t hang out with the real help,just a thought

Moparmal Thanks for the chart.

I managed to find some 2144 rods that I installed along with the 136 secondaries. When I ran the car last week I was using a wide band A/F meter to get the readings. I also made a pass with a friends thremoquad and the A/F ratio was 12.7. I tried the air door at different settings with no difference.

I checked the air door yesterday and found out it is set at .825. Tonight I'll try closing it and openning it to see if that effects the richness. I was told by another racer that uses thermouads that it will not affect the richness.

I plan to modify the carb by replacing the carter jets and metering rods with Holley jets in the primaries. Hopefully I can get that done in a week or two.

The secondary spray bars had already been modified when I got the carb.

Raul

I know of one Super stocker that picked up almost 40 HP by shutting the door almost shut. This was a 318 though. Sounded crazy but it ran the best with it almost shut

You didn't say what combination you are running.Putting the Holley jets in the carb will make it very rich at idle. If you have a lean misfire it can make the o2 sensors think it is fat from unburned fuel. I have run 10.80's at 122 in a legal NHRA 72 340 stick car. The quickest carb I have ever run is a 4972 that I have modified. i have tried 6138 modified with and without Holley jets with out was quicker. Your results may vary.

moparmal just the end holes and can u go smaller dont know size of stock holes once drilled cant go back mine runs good now but would shoot frome the hip and hope for the best

did you drill out your seats from the .093 to .110? it does seem that the 4972/4973 air metered carbs run a lot harder with a lot less mods than any other production t-quad.

I had the car out last night. The jetting modifications worked just right. I made 5 passes and the A/F ratio was 12.7. The car picked up .05 in et and .5 mph. The weather was almost the same as last week, but the track was terrible. I spun on two of the runs. I did not get a chance to try openning or closing the air door because I ran out of time.

I'm not worried about the carb being rich at idle, I'm worried about it being right at full throttle. We were running metering rods that were .051 at the end and the primary jets were .091. That made the openning .040. I will start out with #71 Holley jets and go from there.

The carb is a 9077 and was built by a shop in St Louis. I don't know much else about it.

Thanks for the responses and suggestions. I made two passes at 11.87 and since my index is 11.85 I plan to go to the Division 7 race the end of the month. I have a set of radial slicks on order. I tied a set before and they were 1.3 faster then bias tires on my car. I'll probably be the lowest qualifier on the ladder, but at least I'll be able to dial the index or lower so I'll have a bit of a chance. I'll let you know how it runs.

Raul

Anyone ever try making an adjustable stop for the upper limit of the metering rod tree? Couldn't you fab up a small threaded stop so at WOT the tree wouldn't go quite all the way to the top of it's travel? I would think that would allow you to tune the primaries leaner without pulling jets or rods...?

Secondary spray-bar work ?

... my thoughts? .. I was going to add MORE but SMALLER holes(in new tubing) ... for better atomization of the fuel.

A miss-fire will never show rich on an O2 sensor because it measures oxygen not fuel. If it miss-fires it won't use any oxygen so the sensor will actually read lean.

Kevin

Interesting thoughts......