Promax 6-pack End Carb Plates Sealing?

[PurpleBeeper]

I’m finally getting my engine to the tuning phase. 440 six pack, mild cam, Promax outer carb plates. The engine runs great on the middle carb and idles well at 800rpm. However, when I open up the secondaries I’m putting out a lot of black smoke. I’ve got the jets & idle air restrictions set at stock 1970 settings settings. Im wondering if my outer Promax plates aren’t sealing (don’t have the separator plates/extra gasket…just the Promax plates).
1. Is the only reason to leave out the separator (thin) plates because of end carb float bowl clearance? Or other reason?
2. Has anyone figured out how to clearance the end plates/floats to clear?
3. Has anyone tried filling the void behind the plates with epoxy? Comments?
THANKS!

 

[Bird 426]

There is a float available that has a recess in it, to clear the Holley main jets. No, I don't think that you can use that steel plate that the stock metering plate uses.
The Promax plates seal against the bowl gasket. Do you also have the Promax base plates? Did you deal with the interference problem they have with the main body? Main jet size, diaphragm spring color, power valve, manifold vacuum ? Are you winging it in the driveway, or driving it? Is there a bog?
Fuel bowl levels. Finally, degree thermostat.
There is a guy close to you from Crete, in the Chicago land area, 440 Beep. He's pretty good at this too. He has a '69 Bee, stroker Sixpack. Look down in the A12 site.

 

[dan juhasz]

I’m finally getting my engine to the tuning phase. 440 six pack, mild cam, Promax outer carb plates. The engine runs great on the middle carb and idles well at 800rpm. However, when I open up the secondaries I’m putting out a lot of black smoke. I’ve got the jets & idle air restrictions set at stock 1970 settings settings. Im wondering if my outer Promax plates aren’t sealing (don’t have the separator plates/extra gasket…just the Promax plates).
1. Is the only reason to leave out the separator (thin) plates because of end carb float bowl clearance? Or other reason?
2. Has anyone figured out how to clearance the end plates/floats to clear?
3. Has anyone tried filling the void behind the plates with epoxy? Comments?
THANKS!

How did you size the jets for the promax plates? Did you use a drill index to determine the sizes of the holes in the fixed plates, and convert that to jet sizes?
Did you modify anything on the new plates?

 

[PurpleBeeper]

There is a float available that has a recess in it, to clear the Holley main jets. No, I don't think that you can use that steel plate that the stock metering plate uses.
The Promax plates seal against the bowl gasket. Do you also have the Promax base plates? Did you deal with the interference problem they have with the main body? Main jet size, diaphragm spring color, power valve, manifold vacuum ? Are you winging it in the driveway, or driving it? Is there a bog?
Fuel bowl levels. Finally, degree thermostat.
There is a guy close to you from Crete, in the Chicago land area, 440 Beep. He's pretty good at this too. He has a '69 Bee, stroker Sixpack. Look down in the A12 site.

1. I

There is a float available that has a recess in it, to clear the Holley main jets. No, I don't think that you can use that steel plate that the stock metering plate uses.
The Promax plates seal against the bowl gasket. Do you also have the Promax base plates? Did you deal with the interference problem they have with the main body? Main jet size, diaphragm spring color, power valve, manifold vacuum ? Are you winging it in the driveway, or driving it? Is there a bog?
Fuel bowl levels. Finally, degree thermostat.
There is a guy close to you from Crete, in the Chicago land area, 440 Beep. He's pretty good at this too. He has a '69 Bee, stroker Sixpack. Look down in

There is a float available that has a recess in it, to clear the Holley main jets. No, I don't think that you can use that steel plate that the stock metering plate uses.
The Promax plates seal against the bowl gasket. Do you also have the Promax base plates? Did you deal with the interference problem they have with the main body? Main jet size, diaphragm spring color, power valve, manifold vacuum ? Are you winging it in the driveway, or driving it? Is there a bog?
Fuel bowl levels. Finally, degree thermostat.
There is a guy close to you from Crete, in the Chicago land area, 440 Beep. He's pretty good at this too. He has a '69 Bee, stroker Sixpack. Look down in the A12 site.

1. Promax base plate in rear carb only
2. Why can’t I use the separator plate with the Promax metering plate? Is it strictly a metering plate to float clearance problem?
3. What interference problem with main body? Please explain.
4. Jets - 80/80 front carb & 83 passenger/77 driver in the rear carb
5. Main jets #64/#64
6. 6.5 power valve
7. 16” vacuum at idle & 18” vacuum at cruising speed
8. Driving full throttle maybe 80-100mph (allegedly )
9. No bog at all, just black smoke after the secondaries open up
10. Fuel bowls all at bottom lip of sight hole (if I remember right)
11. 180 degree high flow thermostat
12. Short yellow springs (no bog at all)

 

[PurpleBeeper]

How did you size the jets for the promax plates? Did you use a drill index to determine the sizes of the holes in the fixed plates, and convert that to jet sizes?
Did you modify anything on the new plates?

I researched the factory OEM plate holes & converted that hole size into Holley jet size. I also changed the Promax idle fuel bleed hole to .029” same as OEM plates. I think Promax plates came with .038” holes (?). My goal was to start with OEM sizes and work from there

 

[Bird 426]

#2 I just remember trying it and it didn't work, so no steel plates in mine.
#3 It's been 4 years ago that I did this. There was an interference issue between the base plate and main body. I just remember filing it till it cleared. May have been something in the installation instructions, or maybe they have modified it. You would have noticed it.

What do your plugs look like. 2 barrel vs wot? I have never er looked in the rear view mirror to see if I have any black smoke when going to wot.
How did you adj the air/fuel screws on the end carbs? Check by blocking outside air bleeds?
My center carb on SB stroker at 418 cu in is 63/65, 7.5 pv. Manifold is about 15. End carbs are 72/71, a little rich at wot, afr's are 13.5 ish.
If your plugs look good and it runs fine, don't worry about the black puff of smoke. Your there.

 

[dan juhasz]

I researched the factory OEM plate holes & converted that hole size into Holley jet size. I also changed the Promax idle fuel bleed hole to .029” same as OEM plates. I think Promax plates came with .038” holes (?). My goal was to start with OEM sizes and work from there

Do remember the jet sizes and stagger you used

 

[dan juhasz]

I researched the factory OEM plate holes & converted that hole size into Holley jet size. I also changed the Promax idle fuel bleed hole to .029” same as OEM plates. I think Promax plates came with .038” holes (?). My goal was to start with OEM sizes and work from there

Here was my findings on the 69 1/2 fixed plates.

 

[PurpleBeeper]

#2 I just remember trying it and it didn't work, so no steel plates in mine.
#3 It's been 4 years ago that I did this. There was an interference issue between the base plate and main body. I just remember filing it till it cleared. May have been something in the installation instructions, or maybe they have modified it. You would have noticed it.

What do your plugs look like. 2 barrel vs wot? I have never er looked in the rear view mirror to see if I have any black smoke when going to wot.
How did you adj the air/fuel screws on the end carbs? Check by blocking outside air bleeds?
My center carb on SB stroker at 418 cu in is 63/65, 7.5 pv. Manifold is about 15. End carbs are 72/71, a little rich at wot, afr's are 13.5 ish.
If your plugs look good and it runs fine, don't worry about the black puff of smoke. Your there.

I haven’t check the plugs yet. I just went from 4.5 power valve (used to have a bigger cam) to a 6.5 because I had a 1/2-second “ping” going from cruise speed to 1/2-throttle (no more ping). I went from 62/62 to 64/64 main jets to eliminate a “slight surge” at low speed cruise. The surge is gone and throttle response is a little crisper. All of this was last weekend. I noticed the black smoke during a 30 second full throttle run. It wasn’t a “puff” of black smoke, it was a cloud
I read that Promax says “no separator plate needed”. The reason is because of some type of float clearance issue that floats notched for jet extensions don’t help. Supposedly, without that separator plate, the main gasket distorts where it covers the big void in the carb main body behind the plate. The gasket alone isn’t stiff enough to seal & extra fuel bypasses the Holley jets in the Promax plates. So, I’m “guessing” maybe the whole Promax plate + separator plate (& gasket?) sticking further forward hits the float. I’m “guessing” maybe I could grind down part of the plates or modify the floats to fix that clearance problem (?). Is that possible? Second question is would the separator plate work with the Promax plates? (once I got float clearance) OR is the factory separator plate incompatible with the holes on the Promax plates? I’m just hoping someone here knows these answers

 

[dan juhasz]

I haven’t check the plugs yet. I just went from 4.5 power valve (used to have a bigger cam) to a 6.5 because I had a 1/2-second “ping” going from cruise speed to 1/2-throttle (no more ping). I went from 62/62 to 64/64 main jets to eliminate a “slight surge” at low speed cruise. The surge is gone and throttle response is a little crisper. All of this was last weekend. I noticed the black smoke during a 30 second full throttle run. It wasn’t a “puff” of black smoke, it was a cloud
I read that Promax says “no separator plate needed”. The reason is because of some type of float clearance issue that floats notched for jet extensions don’t help. Supposedly, without that separator plate, the main gasket distorts where it covers the big void in the carb main body behind the plate. The gasket alone isn’t stiff enough to seal & extra fuel bypasses the Holley jets in the Promax plates. So, I’m “guessing” maybe the whole Promax plate + separator plate (& gasket?) sticking further forward hits the float. I’m “guessing” maybe I could grind down part of the plates or modify the floats to fix that clearance problem (?). Is that possible? Second question is would the separator plate work with the Promax plates? (once I got float clearance) OR is the factory separator plate incompatible with the holes on the Promax plates? I’m just hoping someone here knows these answers

Perhaps your main bodies on the outboards are warped. Check with a straight edge.

 

[PurpleBeeper]

Do remember the jet sizes and stagger you used

See #4 and #5 above. 70 440 4spd carbs

 

[Bird 426]

I would have to pull a carb to refresh my memory as to why it doesn't like the plate. I also have the recessed floats. Sometime back someone here said that they had the steel plates in, not sure what he did to get that to work. One of the guys from Canada, I think. There are alot of us with Promax plates, I do not believe that not having the plate in has been a problem.
You didn't mention your fuel pressure. Is it at say 6psi?