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

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.

DaveRS23, Thank you for the response. Yes, I believe my car is running on the rich side and that my performance could be better off the line, but really hauls @#$ when I put it to the floor. Thanks, OneBad

Jetting seems a tad low for a 440. I ran 72-80 on a mild 340 and had no "rich" issues. Best way to get the tune is to make sure everything else is right, timing is a good place to start. That's a fairly mild cam, but it might like some stall. You might want to go up on the PV. I'd think it would pull good vaccuum. A few more things, make sure you floats are set right, I like to have them a tad below the sight plugs, and make sure you don't have tooo much fuel pressure. I'd think 31 squared on the squiters would be enough... Have you tuned them for best vacuum at idle?

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

I've run 750 and 800 DPs on two different stockish 440 similar to yours with the factory cast iron intake. They ran very well and got decent gas mileage. The jetting will be either exactly what Holley put in them to begin with, or within a one or two sizes.

So I'm guessing initial timing doesn't matter.

First thing I would do is make sure you have ~14-18 initial timing and then tailor the mechanical to hit your total number. Ignoring initial timing is a recipe for having trouble tuning everywhere else in the band. Inadequate initial usually means a rich and/or high idle and that makes for fun everywhere else.

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

What version of the Holley 750 DP is yours, a 4779-? or is it another one of the later Holley 750 D.P. with four corner idling or what is it exactly? There are probally 9 different versions of the Holley 4779 carbs

I have one of the more recent models with four corner idling (I think it is a 4150 model, I bought about 10 years ago new). I can only adjust the idle screws a 3/4 of a turn out then she starts to shutter and run like crap, even though they suggest starting with them out 1 1/2 turns to start? It idles great the way I have it set up now with the idle mixture screws but just seems odd.!? I have had the carb apart to clean and change the jets and squirters, found some rust debris in it from the old tank, I had hooked up previously now that and the fuel line has all been changed out. I may go with a thermoquad but will have to change my intake to do so, I'm not sure at this point? Thanks for all the information everyone!

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.

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

good read for working on your Holley carb.

http://www.carcraft.com/techarticles/ccrp_0807_holley_carburetors_basics_guide/viewall.html

I will locate the #'s on the carb later this evening and get back with you. Thanks guys, Jay

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!

The # 's on the carb are 4779-9 with 1194 stamped below on the horn. On the primary metering block it is stamped 11180 with a 3 below it, and on the secondary metering block it is stamped 11038 with a 6 below that. Thanks, Jay

Thanks for all the info DaveRS23, Sounds like you have had a lot of experience with Holley carbs! Thank for sharing your knowledge of wealth with a newbie!

Dave you are the man!

When I got here I knew very little and I have several posts about tuning my holleys for the street. I was hoping my brief post above would be a good starting point for you (assuming the initial timing is right first!).

Looks like you are on the right track. Search my posts for some more holley fumbling.

One tip- on the IFRs theres a little hole diagonal to the 'jet'. You can make little v's of wire that kinda clip into the two holes. I ended up with electric guitar B strings fwiw.

PVCR wires just be careful not to drop the straight little pieces out when you unscrew the PV.