How do you have your Holley Double Pumper tuned?
#1516132
10/12/13 02:45 PM
10/12/13 02:45 PM
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Joined: Feb 2006
Posts: 551 Great Lakes State
ONEBADBIRD
OP
mopar
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OP
mopar
Joined: Feb 2006
Posts: 551
Great Lakes State
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I have the car on the road and running good all summer. My question is is how do you have your Holley set up for good performance and the best mileage possible. I know every engine setup is different, just want to know what is working best for you? In my 69 Road Runner, I have a rebuilt 440 (30 over) with 9.5 compression,flat top zero decked forged pistons, rebuilt iron 906 heads, and a comp cam 268 xe cam, stock iron intake, and a Holley 4150 750 cfm double pumper with mechanical secondaries. I am hooked up to a 727 trans, and rear with 3:55 gears. My carb is set up like this: jet primary side 74 jet secondary side 80, pump nozzle primary side 35, secondary side 31, power valve on primary side 5.5 secondary side blocked off. Running a new fuel tank and 3/8 fuel line. Thanks
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Re: How do you have your Holley Double Pumper tuned?
[Re: ONEBADBIRD]
#1516133
10/12/13 07:49 PM
10/12/13 07:49 PM
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Joined: Jan 2003
Posts: 12,025 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
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Posts: 12,025
Benton, IL.
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The DPs are essentially race carbs. And as such are rather rich in the transitions. The wide open is typically okay, but on a street car, the off idle and cruise are very rich.
On a milder engine, jetting down the slots will clean that up. And then going a few steps smaller on the mains, opening up the PVCRs to compensate and then getting a little quicker opening power valve will help clean the cruise up without sacrificing performance.
An O2 sensor makes this more accurate, but can be done without it. You will have to guess and then experiment on the main jets, but you can do the math to get the PVCRs to the right balance.
Master, again and still
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Re: How do you have your Holley Double Pumper tuned?
[Re: Mr.Yuck]
#1516136
10/13/13 01:17 PM
10/13/13 01:17 PM
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Joined: Jan 2003
Posts: 6,224 JERSEY
RJS
master
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master
Joined: Jan 2003
Posts: 6,224
JERSEY
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Guys are giving you vague suggestions. You need to have the timing set first, about 35 degrees total to possibly 38 degrees. That is a total all in by 2500 without vacuum advance. With vacuum around 45 to 50.
The 750 double pumper is a bit much for an automatic with your cam and gearing. A 650 DP would be better but don't throw out what you have. Set floats correctly first, front just under hole where you have to shake car slightly to drip out. Rear a tad (and I mean a tad) higher. Power Valve is determined by the engine vacuum. Car fully warm IN GEAR (brakes set and tires blocked)with a vacuum gauge hooked up adjust idle screws to highest vacuum reading. let's just say the highest steadiest is 18". Half that # and add .5 to it so in that case 9.5 is the optimum PV for the set up. In this case a PV with say 11 tamped on it would be too rich and a PV with a 4.5 on it would be too lean. The # stamped on them is the vacuum opening value. Jetting is determined by power test runs or dyno. I'd look up what Holley lists your 4779-? as stock jetting and go up or down two sizes with much testing. Squirter and accelerator cam/position is determined by throttle response.
Also many people don't know how to properly set the accelerator pump arm clearance which can either produce and off idle stumble or tear the diaphragm. With engine off holding throttle fully open you need to measure with a feeler gauge the clearance between the pump arm and the pump lever.
3 hands make this easier to do, OK so throttle is held at WOT and use something like a small open end to push pump arm down fully, now measure the clearance between that pump arm and pump lever. I like using 8 thousands but any thing between 1 th to 15 th is good. You just want to make sure there is a small clearance to not tear accelerator pump gasket. I've seen carbs. with 1/8" clearance and guy's wonder why does my car POP or stumble when I rev it.
Hope this helps Ron
Last edited by RJS; 10/13/13 01:20 PM.
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Re: How do you have your Holley Double Pumper tuned?
[Re: RobX4406]
#1516139
10/13/13 11:39 PM
10/13/13 11:39 PM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
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top fuel
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Philadelphia
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I have mine tuned with thicker and thicker wires stuck in the IFRs until the idle mix screws came out to 1.5 turns from seated to best vacuum. Then slightly bigger IABs finished cleaning up the low throttle cruise which formerly fouled the plugs quickly unless I blew it out on the highway. The Power Valve and PVCRs are tuned to give sharp low throttle manners and economy until passing power is needed- then at the point where the conservative primary jets become too lean and vac drops with throttle opening the PV opens and richens the mix back up to max power. My secondary is opened along with the primaries at idle to reveal square sections of transition slot. I run a plugged 2nd PV and big jets for best times at WOT. I watch my vac on the big end to make sure my primary PV doesn't close at high rpm creating a lean condition. Good luck with yours
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Re: How do you have your Holley Double Pumper tuned?
[Re: ONEBADBIRD]
#1516142
10/14/13 09:30 AM
10/14/13 09:30 AM
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Joined: Jan 2003
Posts: 12,025 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
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Posts: 12,025
Benton, IL.
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Since it is apart, now is the time to wire down the IFRs. That way you can get the idle screws out to the 1 1/2 range and clean up the off idle transition a little.
Master, again and still
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Re: How do you have your Holley Double Pumper tuned?
[Re: ONEBADBIRD]
#1516144
10/14/13 06:04 PM
10/14/13 06:04 PM
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Joined: Aug 2003
Posts: 43,126 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,126
Bend,OR USA
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Quote:
School me on what IFR's are? ,and why should I wire them down? In your earlier post, you mentioned PVCR's also? Power Valve Circuit something? Still learning these acronyms. Thanks, Jay
IFR can mean either the idle fuel feed or the intermediate fuel feed, they are part of the main body and to change them you need to drill and tap and use a blank brass set screw and drill it smaller than the stock passage was to lean them out, make them bigger to enrichen them, confused yet PVRC means the power valve restiction channels in the metering blocks behind the power valves, same process on them to change them. Holley has normally made the idle fuel feed, transition fuel feed and PVRC larger than needed to run clean and lean like most Mopars like it The transition slot is the rectangular slot in the throttle body that is centered where the throttle blades ride in the primarys, the four corner idle circuit carbs. have them on all four corners. Not all Holley carbs. have a intermediate circuit in them, some of the bigger race carbs do IHTHs BTW, if you look on the front of the choke tower you will see some numbers stamped into it like List 4779 or List 4779-4 or some other number after the dash if it is not one of the original 4779 before Holley started making modifications to the original design Let us know your carb and dash number
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: How do you have your Holley Double Pumper tuned?
[Re: ONEBADBIRD]
#1516147
10/14/13 09:40 PM
10/14/13 09:40 PM
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Joined: Jan 2003
Posts: 12,025 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
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Benton, IL.
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IFRs are the Idle Fuel Restrictors. One for each barrel. They meter the fuel to the idle screws. The Idle Air Bleeds in the throat of the carb meter the air. Together, they provide the ratio for the idle mixture. The adjustment screws are simply a volumn adjustment. If your adjustment screws are only 3/4 turns or so out, then the mix is usually too rich. If so, then you can either size the IFRs down or you can open up the IABs. I like to size the IFRs down first, that way I don't mess with the timing of the main circuit. The proper way to adjust the jetting on the IFRs is to drill and tap them for jets. But what I do is to mike a bunch of strands from some 12 to 16 guage electrical wire and use pieces of that inserted in the IFRs to see what the engine likes. Quick, easy, cheap and effective. I leave them in when I get them about right, but a guy could go back and drill and tap them for the jets. PVCRs are the Power Valve Channel Restrictors. They are the holes under the power valve and are essentially jets. The main jets plus the PVCRs add up to the total amount of fuel being fed. Which is why you step the mains up when you block off the power valve. The mains must be larger to compensate for the PVCRs no longer flowing any fuel. The PVCRs can be drilled larger if the main jets are stepped down or can be wired down if they are too larger and providing too much fuel. Either way, the mix overall (mains + PVCRs) usually needs to remain about the same. Holleys, in my experience, are usually close at Wide Open Throttle. But need a lot of help in the low speeds, transitions and cruise. Which is where a street car spends most of it's time. There are many, many combinations in these circuits on any given size carb. Which is why all carb manufacturers make street and track versions of the same size carb. It is not just about mechanical or vacuum secondaries. Track oriented carbs like the DPs, are much richer in these areas than a street carb needs to be. For one thing, a track carb isn't too concerned about cruise. Do you have Emanuel's Holley book? You will need it. And if you are going to experiment with the IFRs, IABs, and PVCRs, you will need to get familiar with Pi x r2. That gives you the area of the holes you will be modifying. So you know how much bigger or smaller you have made the flow. This may be the longest post I have ever made. It had better help!
Master, again and still
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Re: How do you have your Holley Double Pumper tuned?
[Re: radar]
#1516152
10/15/13 10:26 AM
10/15/13 10:26 AM
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Joined: Jan 2003
Posts: 12,025 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
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Posts: 12,025
Benton, IL.
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Just to be safe, I usually use a single wire that runs from one opening to the other. That works for me for all the metering orifices,the IFRs IABS, PVCRs, etc. The longer wire is much easier to handle and has little or no chance to disappear.
Master, again and still
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Re: How do you have your Holley Double Pumper tuned?
[Re: DaveRS23]
#1516154
10/15/13 05:45 PM
10/15/13 05:45 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
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Balt. Md
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Quote:
IFRs are the Idle Fuel Restrictors. One for each barrel. They meter the fuel to the idle screws. The Idle Air Bleeds in the throat of the carb meter the air. Together, they provide the ratio for the idle mixture. The adjustment screws are simply a volumn adjustment.
If your adjustment screws are only 3/4 turns or so out, then the mix is usually too rich. If so, then you can either size the IFRs down or you can open up the IABs. I like to size the IFRs down first, that way I don't mess with the timing of the main circuit.
The proper way to adjust the jetting on the IFRs is to drill and tap them for jets. But what I do is to mike a bunch of strands from some 12 to 16 guage electrical wire and use pieces of that inserted in the IFRs to see what the engine likes. Quick, easy, cheap and effective.
I leave them in when I get them about right, but a guy could go back and drill and tap them for the jets.
PVCRs are the Power Valve Channel Restrictors. They are the holes under the power valve and are essentially jets. The main jets plus the PVCRs add up to the total amount of fuel being fed. Which is why you step the mains up when you block off the power valve. The mains must be larger to compensate for the PVCRs no longer flowing any fuel.
The PVCRs can be drilled larger if the main jets are stepped down or can be wired down if they are too larger and providing too much fuel. Either way, the mix overall (mains + PVCRs) usually needs to remain about the same.
Holleys, in my experience, are usually close at Wide Open Throttle. But need a lot of help in the low speeds, transitions and cruise. Which is where a street car spends most of it's time. There are many, many combinations in these circuits on any given size carb. Which is why all carb manufacturers make street and track versions of the same size carb. It is not just about mechanical or vacuum secondaries.
Track oriented carbs like the DPs, are much richer in these areas than a street carb needs to be. For one thing, a track carb isn't too concerned about cruise.
Do you have Emanuel's Holley book? You will need it. And if you are going to experiment with the IFRs, IABs, and PVCRs, you will need to get familiar with Pi x r2. That gives you the area of the holes you will be modifying. So you know how much bigger or smaller you have made the flow.
This may be the longest post I have ever made. It had better help!
This is good info. Ron
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Re: How do you have your Holley Double Pumper tuned?
[Re: 68LAR]
#1516157
10/16/13 01:14 AM
10/16/13 01:14 AM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
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Balt. Md
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Quote:
Quote:
IFRs are the Idle Fuel Restrictors. One for each barrel. They meter the fuel to the idle screws.
Not quite, They meter fuel to the transission slots. The transission slots are the discharge ports for the intermediate circuit.
Some Holley four barrel carbs have seperate idle and transfer circuits and they have seperate air bleeds. Its not the same as the intermediate circuit on the Dominators. Funny how Holley will run seperate circuits on some models. Ron
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Re: How do you have your Holley Double Pumper tuned?
[Re: 68LAR]
#1516158
10/16/13 02:59 AM
10/16/13 02:59 AM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
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Quote:
Quote:
IFRs are the Idle Fuel Restrictors. One for each barrel. They meter the fuel to the idle screws.
Not quite, They meter fuel to the transission slots. The transission slots are the discharge ports for the intermediate circuit.
Well...
The slow air bleeds also called the Idle Air Bleeds combined with the Idle Fuel Restrictions work together to create an emulsion or fuel/air milkshake. The richness or lean-ness of this mixture is determined by the ratio of these air and gas jets.
This emulsion is delivered in whatever quantity your motor can suck from the transfer slots at low throttle openings before the mains come on. The same emulsion comes from the idle discharge holes (sorry don't know the fancy acronym for that one). The corner idle screws, often called idle mixture screws by some, cannot change the a/f ratio of the emulsion. They do not mix anything they just act like a valve on a garden hose- you should be able to turn them off and kill the motor.
Looking at your carb from below the butterflies at idle you'll see the idle discharge holes and if the curb idle is set correctly you'll see around .030 or a square section on the transfer slot. If you show too much slot below the butterfly at idle it will overwhelm your idle discharge fuel and render the corner 'mixture' screws useless because the motor will suck on the t-slot for idle. Thats why sometimes you need to open the secondaries a hair at idle too.
To a certain extent the circuits all stack up- idle, transfer slot, main jet, and on low vacuum the power valve. Thats why you should get your timing right, then your idle 'mix' screws for max vacuum, then tune the T-slot for clean low throttle cruise, then go back and reset the idle screws, see how low you can get the main jets and drive like an old lady, then get the power valve to help out when you need a little more power, then tune the squirters and secondary mains for tire shredding.
This is a rare thread when I was looking for this info I got kinda vague responses and had to spend a lot of nights pouring over holley books and internet misinformation. Once I figured a few things out folks seemed to act like it was common knowledge! "Of course you have to restrict the IFRs on a street car with a holley DP"
You seem to be asking good questions and getting great answers. Please use this info as a jumping off point for your tuning- get in there and try some stuff and come back and let us know how it worked for you. Then later other folks can search and find this stuff out too
Radar
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Re: How do you have your Holley Double Pumper tuned?
[Re: radar]
#1516161
10/16/13 10:39 AM
10/16/13 10:39 AM
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Joined: Jan 2003
Posts: 12,025 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
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Posts: 12,025
Benton, IL.
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The reason I did not mention the slots in my earlier response was 2 fold. One reason was that I was trying to keep from writing a book on the subject and keep it simple enough for a beginner. Secondly, the question was about IFRs. And I wanted to explain why they were called Idle Fuel Restrictors. I always try to explain that one of the biggest challenges with tuning carbs (in my opinion) is that all the part throttle circuits overlap. So when you do any one thing, it has multiple consequences. Just look at another thread here on Moparts where changing his idle circuit balanced his wide open ratio bank to bank. I am still trying to wrap my head around that one. I know that the idle circuit still feeds fuel throughout the range, but I never suspected there was enough to affect the WOT ratio that much. I still stand by my recommendation (based on experience) that if he gets his idle screws close to the 1 1/2 out area, his off idle will be much closer, too. As with so many other things Mopar, tuning a race carb for the street is a collection of compromises. A good example of that is my own carb. I converted a 3 circuit Dominator to 2 circuits for my 500" street Wedge. It cruises on the idle circuit, not the mains. And the cruise RPM likes a very different ratio than the idle does. So, I can have a solid idle or a clean cruise. But not both, apparently. Other than that issue, it is a rockin' carb. Anyway, I know that I left out some details on my earlier post. But it was in the interest of simplicity and brevity. And I figured that if the OP got past this intro, we could get into the next part of tuning his DP. AFTER he bought and read a book or two on Holleys.
Master, again and still
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