Thermoquad rebuild question

[zombezoo]

I'm watching the rocky road show series that goes through rebuilding a thermoquad. I noticed my float bowl has some damage. Looking for experts to weigh in, seems like areas that won't cause a problem but since I have no experience with these i would prefer to hear from someone who knows better.

Note the missing piece in the center and the small missing bits on each of the primary wells.

None of these appear to line up with gasket sections so I'm thinking it's ok to run this. Please let me know your thoughts.

 

[70bigblockdodge]

That primary side chunk that's missing is where the square o-ring seals to booster transfer tube, probably no good

 

[zombezoo]

It's no where near the seats for those seals.

 

[Geoff 2]

You can certainly re-use the bowl. The area on the top of the bowl where it is chipped is recessed. Nothing there to seal. The secondary air baffle fits into the slot where the chip is, but is secured in slots in the body on both ends. Good to go. Congrats on using the TQ.

 

[493 Mike]

If it really bothers you, the center could be repaired with JB Weld but as the others have stated, function will not be impaired.
Mike

 

[GTX JOHN]

I would use it and not ever worry as the areas are
not critical.

 

[zombezoo]

These were the answers I was looking for. Thanks. I'm not worried about the aesthetic just the function. Going to work on finishing the cleaning and start reassembly today. Hopefully it works when in done.

 

[zombezoo]

Got it reassembled and installed. It starts and idles. Previously any throttle would immediately kill the engine, now it revs (albeit with a slight bog). It doesn't appear to be leaking fuel into or onto the engine.
It's a 9097s unit that I bought from someone who had it in a parts pile for who knows how long. Was plugged up with sand and other debris.

Going to call this a success for now till I can get my wideband installed and start looking at where things are at. Thanks for the replies.

 

[Geoff 2]

Tell us more about the combo, maybe able to offer some tips.

When/where is the bog occurring?

 

[zombezoo]

Right as I hit the throttle. If I roll on carefully it will come up smoothly but a short part throttle snap result in a quick bog. The rebuild kit I bought did not come with a new accelerator pump plunger so I cleaned up the original leather one. I planned to order a new one along with new floats.

I see it squirting gas from the small nozzles at the top of the primaries so I think that means it's working but not sure how to tell if it's working "right"

Based on the number on the carb it looks like a 1.5in primary model from a 440. I'm currently running a 318/automatic with a factory 340 intake. I have a wideband sensor that I thought would help me figure out what's going on, but it's not installed yet.

I have not even driven it yet as the throttle brackets are no where close to being usable. The car was originally a 2barrel and I'm pretty sure the bracket is from that (it's been 25 years since I put an Edelbrock 600 on it)
It looks like there are two different style brackets that say they are for the 340 but I'm not sure which one to get.
Anyone have a clue on which is right for my 340 intake with a 904 automatic and a thermoquad?

UPDATE:
NOT THIS ONE

THIS WAS THE RIGHT ONE FOR 318/904 WITH 340 INTAKE. (I had to make an extension for my 904 single piece kickdown rod to get it to reach the proper pivot location. Short piece of 1in aluminum bar with a bolt and nylon lock nut.

 

[Geoff 2]

What cam is in it?
Is the idle smooth/lumpy?
What is the minimum idle rpm before the engine becomes 'unhappy'?

 

[Geoff 2]

Unless you can find another leather acc pump, I would leave it alone. Pump is working & the leather ones are the best.
.

 

[zombezoo]

Ok on the pump plunger. My only concern was it was really dirty. Filled with sand looking crap. I cleaned it pretty good. Seems to seal ok.

Stock 73 318. Only mods are full length headers and the 340 intake.

Idle is a bit lumpy.

 

[Geoff 2]

Headers would not make the engine lumpy. So this lumpy engine could have a myriad of causes for the lumpy idle:
- burned valves
- valve adjustment
- worn cam
- air leak
- ign timing
- etc.

What is the minimum idle speed the engine is comfortable with?
This has a big impact on carb set up/flat spots.

 

[zombezoo]

I will report back in the coming days. I need to get some tools to do this effectively. It was part of the reason I called idling a success.
I have a compression tester, a timing light with a tach, a vacuum gauge, and what I hope are the proper throttle linkage brackets coming by next weekend so I can work on this further.

 

[zombezoo]

Finally got some cooler weather and made some progress.

Got the proper throttle cable bracket. Throttle cable now attaches normally. I had to make an extension to connect my 904 single rod linkage to the stock kickdown pivot location on my 340 manifold. Kickdown now works like it should

Set timing to 12 degrees before TDC which improved idle somewhat but still really rough. Turned out I had connected the vacuum advance to a port that had full vacuum at idle, moved the connection to a ported vacuum port and idle went back to normal.

Installed my dual wideband O2 sensor setup. Turned out the 1.5 turns on the idle mixture screws netted an almost 20afr. Connected a vacuum gauge and proceeded to adjust the screws for max vacuum. Afr now just under 15 at idle. My idle rpm is about as high as I would like 900ish but idle stop screw is as far out as it can be.

Went on to the metering rods. Adjusted the screw all the way out (low as they will go at idle, turned the screw back in until they started lifting and then added another 1.5 turns. This netted slightly lean wot (15-16) so I added another full turn (now 2.5 from bottom) and wot is between 13 and 14.
There is no bog slamming the throttle from cruise, it pulls pretty cleanly so I apparently got the secondary door about right during the rebuild. (I had removed everything and had to reset the spring tension)

I still have a lights out near stall from a stop. I just barely crack the throttle and Afr goes lean into the 20s. Cruise afr is also lean (about 17-18), not sure if that's related.

I messed with the accelerator pump link by moving it from the inner hole to the outer hole on the arm (this linkage only has 2 spots). But I'm hard pressed to notice much difference.

Any tips from here? How do I get my cruise afr a bit richer and why does it want to die from a stop and why does it go lean at the smallest throttle input from fully closed throttle blades.

 

[zombezoo]

Made more progress. Counterintuitively (to me) by taking bend out of the accelerator pump linkage, the throttle tip in is much better. Does it make sense that by reducing the bend in that linkage I would even out that lean spot at tip in?

Cruise is still 16-18 afr but with the accelerator linkage adjustment the cruise throttle inputs are better too.

Looking to understand better what's happening. I chose this carb largely because it was an interesting project.
I would say at this point I'm 90% there.

 

[zombezoo]

Did some more reading. Seems like I need to adjust the metering rods to get the cruise afr richer. Will get that dialed in a little more and see how everything responds.

 

[zombezoo]

Closer. The stall as soon as you hit the pedal is almost gone. Now an occasional stumble.
I seem to have maxed out the adjustment screw on the metering rod hanger. Cruise afr still a bit lean but less so. Now solidly in the 16s
Part throttle afrs look good in the mid to upper 13s
Wot maybe a little lean in the 14s

We have E10 fuel in IL so that may be part of the issue.

It runs much better than it did on the Edelbrock 650 it had on it previously. Will continue to tinker, was going to pull the metering rod assembly out and see how much adjustment is left. The slotted rod is now level with the top of the hanger. I might be able to get a little more out of it. Otherwise I may need to find different metering rods?
Not exactly sure will do more reading, but all in all this carb is pretty awesome. Car has never run so well.

 

[Geoff 2]

The met rod hanger screw is a tool, not meant to be permanent. Sounds like the primaries need to be richer on the power step. Bigger pump shot might help, really depends on the type of stumble. Options are drill pump nozzle 3 thou bigger, drill pri jet 2-3 thou bigger, get some met rods that have thinner power steps or file the power step on the met rod with a modeller's file.