Thermoquad float questions

[Dino]

I was at 71SE's place a few days ago and he noticed that at idle the passenger side venturi is dripping fuel while the driver's side does not.  I just removed the carb, pulled the top off and looked in the bowl and both sides have an even level of fuel.  I have the brass floats which have that step down at the tip.  Measuring from the gasket to the top of that first step I have 29/32".  I think that's the setting for the nitrile floats and the brass ones should be at 1" but I don't know if that is found measuring the way I did or not.  I initially had the floats set lower but had issues at wot.  At this setting it runs great but how do I get rid of that dribble?  Should I readjust the floats?

The good news is that it still looks clean inside, meaning nothing plugged or blackened.  

Also, I found some debris in the carb, like very fine sand and shiny particles.  In other words, the vapor separator alone is not filtering as it should.  Where along the line is the best place to add a filter?  I have a hard line running from separator to carb.  I also have an open air filter, would my dual snorkel do a better job of filtering air or is that unlikely?

[BSB67]

1) Probably go back to recommended float level setting, at least for now.

2) Remove and clean the needle and seat, or just replace,

3) I think a conventional fuel filter would be okay anywhere between the pump and carb.  I would probably put it closer to the pump.

[Dino]

1) Probably go back to recommended float level setting, at least for now.

2) Remove and clean the needle and seat, or just replace,

3) I think a conventional fuel filter would be okay anywhere between the pump and carb.  I would probably put it closer to the pump.

1)  Will do, I'll set it to 1" and give it a shot.

2) I replaced both not long ago.  The old ones seemed fine but I didn't want to take a chance.  I tested the needles by spraying carb cleaner down the inlet while holding the floats up with minimal pressure and neither leaked.

3) Would it be the best then to have it between pump and separator?  I think that's a hard line as well.  I'll go check and see where a filter would fit and post back.

[Dino]

Ok I don't know what I did before but I measured the floats again and the top of that step down tip is 1 1/4" away from the gasket.  If I move it to the 1" mark that means the bowls fill even more.  I'm going to try and find a pic online to see where to measure from.  This is confusing.  I think if anything I should lower the floats in the bowl so the needles close sooner no?

[ODZKing]

I know little about float adjustment.  I always leave that stuff to folks who are better than me. Hell, I can barely adjust the thing.
However I have a reference book on my site that may be of help to you.
http://www.retrorarities.com/images/Thermo-QuadReferenceBook.pdf

[BSB67]

Ok I don't know what I did before but I measured the floats again and the top of that step down tip is 1 1/4" away from the gasket.  If I move it to the 1" mark that means the bowls fill even more.  I'm going to try and find a pic online to see where to measure from.  This is confusing.  I think if anything I should lower the floats in the bowl so the needles close sooner no?

If it leaks with the float set to the correct level, something else is wrong.  If you set the float to a lower setting to stop the leak, you are treating the symptom, not fixing the problem.  You should verify what the correct float levels are suppose to be, and the correct method for measuring.

Inspect, clean, and adjust everything and put it back together and run it and see what you have.  

Check to make sure that you don't have gas inside the float.

[Dino]

I found that the brass floats should be set to 1/16" but it doesn't say where to measure to.  If it's the very bottom of the floats then the bowls are going to fill all the way up to the rim and that does not seem right.  Measured to the bottom of the float mine are almost at 1 1/2".  Apparently there are two kinds of brass floats but I have not been able to find much more information on this making everything a big guess.  Since I don't have any driving issues or bogs or anything, I think I'm leaving the floats alone for now.  Maybe that rubber seal below the venturi is leaking.  I'll also double check the needles and seats.  I'll buy a new set as well if I can find one.

Heck maybe I should just find another rebuild kit and redo this whole thing... 

[BSB67]

Sometimes it amazes me the info that I have laying around here.

1971 TQ  (4972S and 4973S) float setting is 1".  It is measured from the top (when inverted) of the float at the highest point and gasket in-place.

[Dino]

Sometimes it amazes me the info that I have laying around here.

1971 TQ  (4972S and 4973S) float setting is 1".  It is measured from the top (when inverted) of the float at the highest point and gasket in-place.

Awesome!   

Mine's a different model but it shouldn't matter.  I'll set them at 1".  If the carb floods then I'll reset them, no harm done.  I also found the seal under the venture may have been the culprit as it looked a bit stretched compared to the other side.  I had spares so there's new ones in there now.  Hopefully that'll do it, if not I'll just rebuild the whole thing.

[BSB67]

What is the model number.  I might have the specs on that one too.  Most are actually 1 1/16"

[Dino]

What is the model number.  I might have the specs on that one too.  Most are actually 1 1/16"

6545S.  I looked it up and it says 1 1/16".      At that point I assumed that was measured from gasket to bottom of float (now on top) so that's what I set them at.  I also replaced the venturi seals and reassembled everything.  I just finished putting hooking the carb back up.

I also did my valve cover gaskets so I won't be able to start the car until tomorrow, and since I will be gone most of the day it'll have to wait a bit longer.

I'm curious to see how the carb will perform with the floats so high.  It was almost parallel to the gasket surface.

[Dino]

Alright, I have some more info.

I set the floats to 1 1/16", replaced the venturi seals, installed the new valve cover gaskets yesterday and retightened them this afternoon.  I took the car out and it ran absolutely fine without any bog or hesitation, but the fuel smell was pretty strong.  I drove it for about 15 minutes until it was hot (never got over 190 on a low 70's day).  I hooked up the vacuum gauge and only got around 11.  The highest I ever got was 15 but I think timing was way too advanced at that point.  Base timing is now around 20.  I leaned the idle mixture screws from 2.5 to 1.5 turns on each side and got around 14 mmhg on the scale.  I took it out again and it still ran great but same smell.  In essence, very little difference between the two settings.  I checked the venturis at idle and they now both dribble fuel instead of passenger side only.  I am not sure how it's supposed to look but I don't think it should be this wet.  Since I raised the floats by about 50%, I will lower them 25% to get half way between the old and current setting.  That is unless there is something else I need to do.

Standing behind the car will make my eyes burn immediately, just to give you an idea of how rich it is.   

Why does the car run so well even when it is obviously way too rich?  Does the unburnt fuel just go out the pipes without hindering performance?  The idle is a bit rougher maybe but once running it is fine.  Could it be running leaner at cruising speed maybe?  I should get an AF gauge for this.

Oh, another thing.  My car always is a pain to start when it sits overnight and I have to keep the throttle high enough to keep it from stalling.  Today was different.  It did take a while for the car to fire, but I think that's normal when the carb was off and I have to refill the bowls, but once it fired I could hold it around 1200 rpm real easy and it kept steady.  I held the pedal there for a minute and let off a bit, then a bit more and for the first time it didn't die and settled into a nice idle.

Now how does that happen?  Were my floats set so low that I couldn't have it run well when cold?  Did resetting the floats fix this or is something else going on?

I'm curious to see how it starts in the morning.   

[Nacho-RT74]

I have around a FULL ADJUSTMENT guide ( from an old HigGrade kit ) for TQs whith every measure specification available.

However, per Demonsizzler advice, I set my brass floats at 29/32"

[Dino]

I have around a FULL ADJUSTMENT guide ( from an old HigGrade kit ) for TQs whith every measure specification available.

However, per Demonsizzler advice, I set my brass floats at 29/32"

Interesting.  So with the air horn inverted and the floats sticking up you measure from the top of the gasket to where?  I measured to the base of the float which is now on top.  I set it at 1 1/16" and it's running real rich.  I am actually thinking of setting it much lower, ie higher measurement in this case, just to see where it starves for fuel.  From there I'll just bring the floats back up until it runs right. 

[BSB67]

At the risk of repeating myself:

If it leaks with the float set to the correct level, something else is wrong.  If you set the float to a lower setting to stop the leak, you are treating the symptom, not fixing the problem.  You should verify what the correct float levels are suppose to be, and the correct method for measuring.

Inspect, clean, and adjust everything and put it back together and run it and see what you have. 

Check to make sure that you don't have gas inside the float.


FWIW, Demonsizzler's advice would have somewhere between little to no impact on my TQ tuning decisions, especially if it was contrary to the more than one other information source.

[Nacho-RT74]

I measured to the base of the float which is now on top.

which is the right way

FWIW, Demonsizzler's advice would have somewhere between little to no impact on my TQ tuning decisions, especially if it was contrary to the more than one other information source.

kinda agreed on this specific topic, but my carb originally should get 1", so getting 29/32" won't hurt really

[Dino]

I understand I need to fix the problem and not the symptom.  However, I feel this setting cannot be right.  I suspect the passenger side venturi seal was causing the initial leak so hopefully that is now fixed.  At this point it seems to be running fine but it's too rich.  I found some pictures online where the brass floats were measured not to the very top but to the top of the step up.  That would make sense as it would set the floats at a lower setting.  I wish I still had the plastic floats as I'm fairly certain the brass floats are much bigger so the bottoms of either would not match up.  Unfortunately there does not seem to be a way to confirm all this.  I could buy new foam floats and set them like in Nacho's picture, but I hear the quality on these is anything but stellar.  Still it may be a good idea to do so if for testing purposes only.

I tested the floats for leaks when I bought them but have not done so recently so I'll do that first, thanks for reminding me.

[71 SE3834V]

Dino,
Try backing off the idle a bit just to make sure the throttle plates are closed. If they are cracked open the vacuum above the throttle plate will start pulling fuel from the venturies. I don't remember what the car was idling at when we timed it (my bad). Seems like it was somewhere around 850 rpm's. Just one more thing to eliminate.

[Dino]

I forget what the idle is.  850 sounds about right.  It's pretty low in drive so I don't know if I can lower it more but I'll give it a shot!

[flyinlow]

Dino , I have extra TQ's sitting around if you need floats.

[Dino]

Dino , I have extra TQ's sitting around if you need floats.

Thank you, that's very kind of you!    

I dunked my brass floats in gas last night and just went out to check them, they're good.  

All I need is the spot to measure to.  I know where to measure on the foam ones but not these.

I found this on cuda-challenger.  I'm not sure what the measurement is here but it's not measured to the bottom of the float as I did.  Still, I think my floats are probably close in position to that so maybe I do have them set correctly.

http://i262.photobucket.com/albums/ii100/wbullitt99/tqrebuild/P102BUILD52.jpg

I will reassemble it and lower the idle, see if that changes anything.  Now, if I close my idle mixture screws completely the car should stall, but if it does not then what am I looking for?  I haven't tried this but just in case it happens.  The idle did go down when I turned the screws in so I set them to  1.5 turns out.  That's a complete turn less than before I reset the floats.

If all this fails then I'll have to do a rebuild.  The venturi seals should be good and the epoxy on the bottom of the bowl is also good but I'll change the seals and re-epoxy the wells anyway.

I really love this carb so I want it to work but on the other hand I've been dying to try one of those Demon 1901 carbs as it's supposedly a TQ upgrade.  Too bad I can't afford one right now or the TQ might be shelved.  

[flyinlow]

IMHO... a TQ's should run with the floats at 29/32, 30/32, 31/32, 1inch, or 1 1/16 .  If  1/32 made that much difference we could never drive these things. The fuel is always sloshing around in the carb from engine and vehicle movement. I can drive my Chargers up and down 20 * hills , run down the drag strip , autocross and brake hard and the TQ kept working thru all of that.

Addiquite fuel delivery at no more than 6-6 1/2 PSI .
I set my TQ floats at  29/32
Those square crosssection primary O-rings must be good or the carb will not run right.

I have found that while a TQ is a good driving carb with its small triple boost primaries and the fact that you can adjust the primary cruise mixture slightly with the stirrup screw ,it does have a few down falls. Lack of support and tuning. Its been out of production for 30+ years. The accelerator pump circuit is not adequate for a large, unheated aluminum intaked engine. I have changed nozzles and enlarged every passage I could in mine and it will still gasp for a second if I snap it to WOT. I was using a SD single plane intake,you have a Performer dual plane ,it should be more forgiving.

I stopped by the Demon booth at the Goodguys show and was told that their "TQ" used Holley jets and had a much better accelerator pump system then the original Carter....

[BSB67]

IMHO... a TQ's should run with the floats at 29/32, 30/32, 31/32, 1inch, or 1 1/16 .  If  1/32 made that much difference we could never drive these things.

[flyinlow]

Dino ,

If you close the idle mixture screws (GENTLY)  and the engine does not die or run very rough it means the carb is delivering fuel from somewhere besides the idle ports. Which can be the throttle plates are open far enough that the main jet system is trying to work or the secondaries are not closing fully.

There is a slot in the side the primary bore next to the throttle plates. Ideally if you take your properly adjusted carb off the engine and turn it over dumping the fuel into a pan the throttles should uncover about 50% or less of this slot from the intake manifolds perspective. If you can see most or all of the slot it can be difficult to adjust the idle mixture and off idle drivabilaty can suffer.

So what can you do?  Make sure you are running the correct amount of timing to help the idle speed. Idle mixture set for best idle/highest vacuum. In drastic cases some people have drilled small holes in the throttle plates to let air pass with the throttle plates still in the correct area. (last resort)

Craig

[Dino]

Alright I'll dump the fuel and check the slot.   

I recall messing with the secondaries so I may have it not set properly there.  I don't think I want to drill the plates, at least not until I'm sure nothing else can be done.

Thanks!