TUNING A SIX PACK

[biomedtechguy]

the throttle blade position on the end carbs with them closed, is also adjustable on the OEM baseplates by little screws under the baseplate.

Thanks for the clarification, and I still have the stock front carb nameplate, but I'm not familiar with the "little screws under the baseplate"...I'll have to check that out.

 

[Frustration]

Bio, The covering of the holes in the top of the carb....I understand that it will tell you if it's rich or lean, but is that an indication of the air/fuel mixture, or the jetting, or does it include both? I think mine is really close right now. Tom

 

[biomedtechguy]

Bio, The covering of the holes in the top of the carb....I understand that it will tell you if it's rich or lean, but is that an indication of the air/fuel mixture, or the jetting, or does it include both? I think mine is really close right now. Tom

It only indicates the setting of the outboard carbs idle mixture screws setting, for the carb you are working with, and which direction to turn them.
Only cover ONE of the bleeds at a time.
NOTICE: the idle mixture screws on the outboard carbs require minute adjustments compared to the center carb metering block screws! The outboard screws are way more responsive to slight adjustments.
My suggestion is with the engine off, GENTLY bottom both screws, counting the number of turns (clockwise) to bottom, then turn them both back out an equal amount, start the engine, then make the final adjustment using the blocking the bleed method.
I knew that I had problems with the 3 carbs idle mixture when I turned both of the mixture screws in all the way on the center carb, and the idle improved. WAY too much fuel was being contributed by the outboard carbs.
That discovery and learning how to figure out the adjustment of the outboard carbs was THE defining moment in making my 6bbl change from a nightmare to my favorite performance carb setup.

 

[Frustration]

Thank you. I'll work on it again tonight. It's running pretty good now, but there is room for improvement.

 

[66Satellite47]

Seems to me that the factory settings on the outboard carbs(to meet emission standards) was the downfall for many original owners. They were not that street friendly for many. There was not much tuning information available in the early '70's for these setups. As a result they were quite inexpensive on the used part market. I took advantage & gathered tuning info. The end carb idle setting & idle mixture srtting made an amazing difference. Bio hit the nail on the head, those end carb adjustments are very smaller with big results.

 

[biomedtechguy]

The end carb idle setting & idle mixture setting made an amazing difference.

I will explore the idle (speed) setting that you told me about when I test fit my Weiand 6bbl intake. I know the first alert I got that something was worng was like I mentioned, turning the center carb idle mixture screws all the way in (no fuel) and the idle speed increased, and smoothed out. That is where my introduction to what it's like having THREE carburetors involved in setting the idle on an engine began.
To be clear though, once I embraced the 6bbl and all that it entails, other than the FiTech 3x2 system, which would limit my horsepower with the stroker motor I have planned, otherwise it's very nice, or the
F&B direct port injection 3x2 throttle body setup, which is a lot more expensive than the FiTech, but a lot more flexible with HUGE power potential, I decided to make a big investment in the 3 Holley 2bbl carbs and had Promax "do their thing".
The feeling of the outboard carbs opening at WOT whether stomping it or rolling into it is amazing!

 

[Frustration]

So I've been chasing some issues with float level in my outboard carbs. I would either have fuel pouring out of the vent tube, or the bowl would be empty. It just would not cooperate with an accurate setting. I have the Pro Max jet plates in the secondary carbs. Talking with a friend about it over the weekend opened my eyes to an issue that I've had for years...I never ground the float to clear the jet extension that protrudes into the float bowl. Took the grinder out and fixed the problem and now all is good. I wonder who else may have this problem? I do not recall any information from Pro Max when I purchased the jet plates stating that the float modification was needed, but with a quick measurement, it was clear that there was interference that would not allow the float to travel correctly.

 

[biomedtechguy]

So I've been chasing some issues with float level in my outboard carbs. I would either have fuel pouring out of the vent tube, or the bowl would be empty. It just would not cooperate with an accurate setting. I have the Pro Max jet plates in the secondary carbs. Talking with a friend about it over the weekend opened my eyes to an issue that I've had for years...I never ground the float to clear the jet extension that protrudes into the float bowl. Took the grinder out and fixed the problem and now all is good. I wonder who else may have this problem? I do not recall any information from Pro Max when I purchased the jet plates stating that the float modification was needed, but with a quick measurement, it was clear that there was interference that would not allow the float to travel correctly.

I have heard of this issue with the Promax jetable metering plates. I had the rear carb do that when I got my carbs back from Promax, but I cleaned out the float valve and that fixed it.
Try using the clear fuel bowl plugs to set the float levels, but DO NOT leave them in.
I knew better but thought a couple of days wouldn't hurt. I had to disassemble the fuel bowls from the carbs to get the plastic plugs out that were chemically glued into the threaded holes, AND to clean out the debris that came off of the melted plugs. They're great for setting the level, but replace them with the brass plugs immediately.

 

[62MAX]

I have heard of this issue with the Promax jetable metering plates. I had the rear carb do that when I got my carbs back from Promax, but I cleaned out the float valve and that fixed it.
Try using the clear fuel bowl plugs to set the float levels, but DO NOT leave them in.
I knew better but thought a couple of days wouldn't hurt. I had to disassemble the fuel bowls from the carbs to get the plastic plugs out that were chemically glued into the threaded holes, AND to clean out the debris that came off of the melted plugs. They're great for setting the level, but replace them with the brass plugs immediately.

You don't need to pay Promax's price for plates when you can get these for $20 each,same as O.E.M. no fitting problems.



On another note as to float level if you do not already know.I get a lot of carbs to restore that have center bowls on the end carbs,keep in mind that the center bowl has a 1/4" higher sight plug therefore you front and rear float level would be that much higher that it should be if you used the recommend way to set float level.See below




And to Frustration. If you ground the resin floats you removed the outer coating and will eventually have a problem with fuel saturation.

 

[biomedtechguy]

You don't need to pay Promax's price for plates when you can get these for $20 each,same as O.E.M. no fitting problems.

Quick Fuel is another provider of those plates.
The ones that you have in the picture are available where? I'm asking for archival purposes, since I already have mine.
I had to make a choice when I decided that for the greatest flexibility in tuning NOW, on my current 440, and future plans for utilizing the 6bbl on a stroker motor, and to incorporate the Weiand P3690982 6bbl intake, AND to have someone who could go through all 3 carburetors, repair a screw hole, use the correct rebuild kits, use the reusable non stick gaskets (which have been great) and pretune them on a dyno mule, Promax was the only choice that could accommodate all of those parameters.
If I had the time and experience I may have done something different.

 

[62MAX]

Quick Fuel is another provider of those plates.
The ones that you have in the picture are available where? I'm asking for archival purposes, since I already have mine.
I had to make a choice when I decided that for the greatest flexibility in tuning NOW, on my current 440, and future plans for utilizing the 6bbl on a stroker motor, and to incorporate the Weiand P3690982 6bbl intake, AND to have someone who could go through all 3 carburetors, repair a screw hole, use the correct rebuild kits, use the reusable non stick gaskets (which have been great) and pretune them on a dyno mule, Promax was the only choice that could accommodate all of those parameters.
If I had the time and experience I may have done something different.

Those are Quick Fuel plates,still available if you know where.As for the other things you mentioned,it's easy if you have the means and patience.Larger sight plug for stripped threads,insert for stripped needle/seat and insert for base messed up mixture screw passage.

 

[Frustration]

You don't need to pay Promax's price for plates when you can get these for $20 each,same as O.E.M. no fitting problems.

View attachment 946847

On another note as to float level if you do not already know.I get a lot of carbs to restore that have center bowls on the end carbs,keep in mind that the center bowl has a 1/4" higher sight plug therefore you front and rear float level would be that much higher that it should be if you used the recommend way to set float level.See below

View attachment 946864


And to Frustration. If you ground the resin floats you removed the outer coating and will eventually have a problem with fuel saturation.

This is really good information. Not sure how to get the floats to clear without grinding, but I certainly understand your point. How could I tell if my outboard floats are center-carb floats, or outboard ones.

 

[66Satellite47]

My understanding is that if you grind the foam floats, re-seal the area with a light coat of epoxy. Brass floats - dent for clearance??

 

[biomedtechguy]

Those are Quick Fuel plates,still available if you know where.As for the other things you mentioned,it's easy if you have the means and patience.Larger sight plug for stripped threads,insert for stripped needle/seat and insert for base messed up mixture screw passage.

View attachment 946924 View attachment 946925 View attachment 946926

The screw threads that were a problem was one of the 4 accelerator pump diaphragm "clamshell" screw holes. I had temporarily managed the problem by having a feel for the max tightness just before the point where it would "jump" threads and loosen. I put a dab of epoxy as a thread locker, and tightened it to just before that point where it would loosen again. Promax put in an insert I believe.
There was so much they did, and I had so much to do, including work, that going through them was my best bet.

 

[62MAX]

This is really good information. Not sure how to get the floats to clear without grinding, but I certainly understand your point. How could I tell if my outboard floats are center-carb floats, or outboard ones.

Center brass,outboard resin,no other way.

 

[biomedtechguy]

Center brass,outboard resin,no other way.

That's what mine are, and the center fuel bowl site hole is at a different level than the outboard carbs, so that is "correct", right?

 

[62MAX]

That's what mine are, and the center fuel bowl site hole is at a different level than the outboard carbs, so that is "correct", right?

Correct,center is higher,if you look closely at the set I posted,you can see the difference.

 

[66Satellite47]

Max, just curious, are yours OEM A-12 carbs, the mid '70's "replacements" or??

 

[62MAX]

Max, just curious, are yours OEM A-12 carbs, the mid '70's "replacements" or??

I have to check dates but they are not replacements.I think the two ends are Feb/March 69 and the center April 69,I have a few sets.

 

[66Satellite47]

So the '69 end carbs have the plastic floats?