TUNING A SIX PACK

[biomedtechguy]

I'm wondering if this is due to the size of the cam

Are you using the factory metering block on the center carb? One of the biggest advantages to the PROMAX aftermarket center carb metering block is it works much better with hotter than factory cam profiles.
I'd ask PROMAX about your issue(s) IF you still have the stock metering block.

 

[Frustration]

Are you using the factory metering block on the center carb? One of the biggest advantages to the PROMAX aftermarket center carb metering block is it works much better with hotter than factory cam profiles.
I'd ask PROMAX about your issue(s) IF you still have the stock metering block.

I do have the PROMAX metering block. Good suggestion. I will give them a ring. I actually purchased extra emulsion plugs to be drilled to size later. Never did anything with them.

 

[68 HEMI GTS]

We've talked here before, and I wanted to ask you about how your car performs on the street. I run a .575 solid roller in my 496RB with CNC ported Stealth heads and a 9.5" converter. I have some issues when I come to a stop sign, or red light...the car's idle drops to below satisfactory levels, and requires additional fuel via pushing the gas pedal. I've adjusted the float levels multiple times, thinking that it's starving for fuel, but there was little change. I'm wondering if this is due to the size of the cam and the fact that the 9.5" converter is a bit tight. Any info is appreciated. Tom

What I’ve found on my car is the my six pack 511 is it does the same. The intake distribution sucks on the bigger engine at low speed. Seems ok at WOT. I had to fatten up the outboard idle slightly to help it out. Unfortunately that also fattens up the cruise. So I kind of found a balance but it is a 2 footer most of the time. I’ve ran a few different single planes and different 4 barrels and that problem goes right away. A looser convertor would probably help a bit.

 

[Frustration]

Thank you for the response. I figured this was the case, but you confirmed it. I've been driving it like this for a long time, and just deal with it.

 

[68 HEMI GTS]

I do have the PROMAX metering block. Good suggestion. I will give them a ring. I actually purchased extra emulsion plugs to be drilled to size later. Never did anything with them.

promax metering block is not a magical fix. It’s a BLP block that he has his name engraved into. The emulsion does nothing for the idle. It’s all in the IFR which can be easily changed in that block as well as the idle bleeds which are non adjustable unless you drill and tap them for set screws. It can easily be done but you need an O2 meter to adjust. Hope this helps.

 

[69 GTX]

I found the post where Jim showed and compared intakes if your into that kinda thing it's very interesting.
https://www.forbbodiesonly.com/moparforum/threads/69-gtx.51515/page-26#post-910382121

 

[Frustration]

Thank you for posting the link. I've been following along. Good stuff! Much like you, I had planned all along to run the 6bbl intake, so I haven't messed with others. Never had mine on the dyno, but I would guess it has similar numbers to your's. Good luck with the rest of the build...and then the testing!

 

[Frustration]

OK, here's a little update. Last night I bucked up and took my road runner to the local chassis dyno. I'm trying to get the car ready for a track rental Memorial Day Weekend where lots of my buddies will be fighting for the top of the hill honors. My main goal for this session wasn't necessarily to get optimum HP and TQ, but rather to be sure my air/fuel metering was good and that I wouldn't lean it out up top. I made four full pulls and one half pull due to a lean condition. In the beginning the car was lean through the entire pull and made just 400 HP to the wheels. After a lot of changes to the outboard carbs, the lean condition didn't seem to go away much, if at all. For the final pull, I upped the jets in the center carb to #84's. The front carb had #85's, and the rear #86's. I ran a #28 squirter in the center carb. On the final pull, the lean condition existed between 4200-4800RPM, then went to 12.9 for the rest of the pull to 6500 RPM. What we think we found out is this: The lean condition is likely due to an incorrect power valve in the center carb. I do not see any numbers on the valve, and have no info to tell me what it is. After work, I plan to warm up the car and check the vacuum while in gear. I'll purchase new power valves to test at the track in a little over a week. The final changes netted a peak of 426 HP and 411 TQ. Peak HP is at 5600 RPM, but it's pretty flat up to the 6500 RPM shut off point. At this time the best ET on the car is 11.04, and the best MPH is 122.84, but they were not on the same pass. It hasn't run over 120 MPH in quite a while. Fingers crossed it will hit the magical 10.99, and will hold off the competition next week. If all else fails, I'll probably uncork the headers to hit the mark. More to come in a little over a week!

 

[RJRENTON]

IMO.....
At wide open throttle, the power valve in the center carb will be open. The valve responds to manifold vacuum, which at WOT will be zero. The additional fuel is being metered by the PVCR or Power Valve Channel Restrictions, located beneath the power valve as NON REPLACEABLE orifices. These orifices are parallel to the main metering jets and the primary well emulsion channels where liquid fuel mixes with air to form an emulsion. On the stock Holley carbs, the PVCRs are not replaceable, but on the Promax offerings, these orifices are change-able along with the emulsion channels air bleeds offering adjustability. Perhaps you might consider changing to the Promax designs or pieces. Others will have differing opinions...
BOB RENTON

 

[440+6]

IMO.....
At wide open throttle, the power valve in the center carb will be open. The valve responds to manifold vacuum, which at WOT will be zero. The additional fuel is being metered by the PVCR or Power Valve Channel Restrictions, located beneath the power valve as NON REPLACEABLE orifices. These orifices are parallel to the main metering jets and the primary well emulsion channels where liquid fuel mixes with air to form an emulsion. On the stock Holley carbs, the PVCRs are not replaceable, but on the Promax offerings, these orifices are change-able along with the emulsion channels air bleeds offering adjustability. Perhaps you might consider changing to the Promax designs or pieces. Others will have differing opinions...
BOB RENTON

I have to agree
on this one.......so many thing make will effect performance...as rj mentioned listen to him , it's not as simple as most think.
Racers have been modifing the pvcr channel from day one.
Also on a vacuum secondary the channel to the venturyhas been blocked or restricted results will indeed vary

 

[biomedtechguy]

Perhaps you might consider changing to the Promax designs or pieces.

PROMAX for 6bbl

 

[Frustration]

IMO.....
At wide open throttle, the power valve in the center carb will be open. The valve responds to manifold vacuum, which at WOT will be zero. The additional fuel is being metered by the PVCR or Power Valve Channel Restrictions, located beneath the power valve as NON REPLACEABLE orifices. These orifices are parallel to the main metering jets and the primary well emulsion channels where liquid fuel mixes with air to form an emulsion. On the stock Holley carbs, the PVCRs are not replaceable, but on the Promax offerings, these orifices are change-able along with the emulsion channels air bleeds offering adjustability. Perhaps you might consider changing to the Promax designs or pieces. Others will have differing opinions...
BOB RENTON

Bob, I was talking with one of my good friends about this yesterday. He said the same thing, and does not think the issue is coming from the power valve at all. He thinks it's coming from the delay in my secondaries. I run a purple and brown spring to slow down the hit. It's mostly a street car. Switching to lighter springs would likely help at the dyno/track, but would be problematic on the street. I may switch them out next Sunday at the track to test.

 

[RJRENTON]

Bob, I was talking with one of my good friends about this yesterday. He said the same thing, and does not think the issue is coming from the power valve at all. He thinks it's coming from the delay in my secondaries. I run a purple and brown spring to slow down the hit. It's mostly a street car. Switching to lighter springs would likely help at the dyno/track, but would be problematic on the street. I may switch them out next Sunday at the track to test.

Sounds like a good plan. Consider the following: the end carbs receive their opening signal from the center carbs venturi pressure differential signal and applies it, in unison, to the end carbs. The end carbs respond to this increasing pressure signal, limited to the diaphragm spring tension AND a small bleed orifice and check ball in the diaphragm housing. The purpose was to control the RATE of opening, by allowing the pressure signal to build slowly, with the overall TIME to open determined by the diaphragm spring tension. Since the end carbs had no accelerator pumps to aid in the start of booster venturii fuel flow, the end carbs like a "slightly" rich idle and off idle transition to avoid a momentary lean sag or bog, b4 the main fuel system starts to contribute.....at least this is what my RS23V0A likes. But, like any application, other engine variables (cam, compression, rear gear ratio, rate of ignition advance, etc) will influence how the carbs react.
Perhaps, you should inspect to see if the diaphragm check balls are present and that both diaphragm spring tensions are the same. In addition, there is a small venturi vacuum passage on the end carbs that "help" open these secondary diaphragms (in addition to the primary vacuum signal). Check to see if its not plugged with crud. Anyway....just my thoughts and opinions of course, others may differ.....
BOB RENTON

 

[66 Cornpicker]

Give Dave a call @ Woodruff Carbs, he can help you for sure on the six pack tuning.

 

[69 GTX]

I had always wondered about putting a needle valve in the vacuum signal line and installing the lightest springs. My theory is using the needle to adjust the amount of vacuum to the pods. This would be a easier/quicker way to make adjustments. Let me know your thoughts. Hope this doesn't highjack the thread, thought it might be relevant.

 

[66Satellite47]

I had one setup that used the needle valve in the vacuum line. It was a neat deal. Swapping springs is not tough, but having some added adjustment is nice.

 

[biomedtechguy]

I had always wondered about putting a needle valve in the vacuum signal line and installing the lightest springs. My theory is using the needle to adjust the amount of vacuum to the pods. This would be a easier/quicker way to make adjustments. Let me know your thoughts. Hope this doesn't highjack the thread, thought it might be relevant.

I had one setup that used the needle valve in the vacuum line. It was a neat deal. Swapping springs is not tough, but having some added adjustment is nice.

I wonder if there are pods like this that could replace the factory pods:
https://www.holley.com/products/fue...ponents/vacuum_secondary_parts/parts/63-12QFT

 

[RJRENTON]

I wonder if there are pods like this that could replace the factory pods:
https://www.holley.com/products/fue...ponents/vacuum_secondary_parts/parts/63-12QFT
View attachment 1113283

IMO....Not sure they will fit the Holley 2300 body. It looks as if they were designed to fit a Holley 4160 series (maybe the 4150 series also) 4 barrel body. In addition, I believe the reason for the large diaphragm housings on the Holley 2300 six barrel carbs is to provide the necessary torque to operate the butterfly valves with a low venturi pressure signal against high air flows. Just a thought.....
BOB RENTON

 

[eldubb440]

you can tune a six pack, but you can't tune a fish

 

[66Satellite47]

IMO....Not sure they will fit the Holley 2300 body. It looks as if they were designed to fit a Holley 4160 series (maybe the 4150 series also) 4 barrel body. In addition, I believe the reason for the large diaphragm housings on the Holley 2300 six barrel carbs is to provide the necessary torque to operate the butterfly valves with a low venturi pressure signal against high air flows. Just a thought.....
BOB RENTON

The 2300 Six pak diaphragms are not the same as the 4150/4160. The needle valve deal does work.