Tuning a Proform/Holley carb, what parts and tools?

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KnuckleDuster

KnuckleDuster

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Getting ready to start tuning my Proform 750

Proform 67213: Street Series Mechanical Secondary Carburetor 750 cfm with Electric Choke | JEGS

I have couple of books for reference, but what are some other good sources for tuning info?
I am getting ready to order jets, gaskets, power valves, accelerator pump cams, and tools.

What do I really need and what do I not really need?
What gaskets? Holley non-stick, or other?
Is it necessary to buy specialized tools for jets and power valves?
What is your favorite fuel bowl catch can?
Any tips, tricks, or advice is welcome and appreciated!

Just looking to get anything I will need in one shot, and keep from wasting money on stuff I could do without.
Here is what I am planning to buy-

Holley 36-182: Double Pumper Kit | JEGS

Proform 67469: Carburetor Jet Installation Tool | JEGS

Proform 67454: Aluminum Power Valve Remover Tool | JEGS

Holley 20-12: Accelerator Pump Cam Assortment Includes 8 Different Cams | JEGS

JEGS Performance Products 15273: Anodized Float Bowl Catch Can 1-5/8" x 6" | JEGS

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If you want to spend money on that stuff, cool.

PV removal tool. Use a box end wrench
Jet tool - a wide flat blade screwdriver.
Catch can... A really small funnel and a cup.

No way would I spend 110+ on a box of stuff you may never use.
IFR/IAB blanks from BoLaws and a set of 1-60 and 61-80 drill bits and a in vise.

Take the money you saved on that stuff and buy some air bleeds and IFR's
 
Crackedback- exactly the kind of info I was looking to get, but please eloborate on the abbreviations.
 
FWIW I agree with Crackedback. Those things are nice, but not needed. Just be careful and use a big bladed screw driver and a box wrench. For a catch can, I use sardine cans or whatever. Sometimes I place under the bowl screw a triangular plate with two sides bent up.

In one of those Urich books I'm pretty sure he mentions 'killing' the adhesive a bit on the gaskets. Good tip. The brown Holley gaskets are pretty sticky. The blue ones not so much.

Depending on your patience, I'd buy gaskets but hold off on parts until you know what you need. That is, unless you plan on doing lots of this. In that case then it makes sense to have a large stash of parts.

Gaskets: Buy 10 packs for the Bowl and meter block. Much better pricing than 2 packs. If you can't find them from a speed shop, try A..'zon.
One rebuild kit can be useful in case you need bowl screw gasket/washers, accel pump diaphrams and check valves, power valve gaskets, and inlet gaskets.

Lemme add this friendly tip. Do not use nylon or rubber gaskets. Nylon flows when the engine compartment gets real hot. It normally doesn't get that hot, but when it does, let me tell you, its very annoying. Rubber types hopefully aren't even offered anymore but if they are stay away.

To figure out what parts you *might* need to swap, you might need a set of tiny drills to measure the restrictions sizes. The main jets are stamped, the others may or may not be. And any pressed in ones are definately not.

Take the bowls and metering blocks off and 'map out' the carb while its off. It makes life easier to do this first. Those books will help ID the restrictions and jets. Do both Primary and Secondary ides something along the following.
I'll note [common abreviations] with each one which will answer your question to CB.
* Are things to track while tuning. Make a little table of the amount of transfer slot visible below the throttle relative to each 1/4 or half turn in on the idle speed screw.

Float inlet valve size. (not critical but good to know)

*Idle Mix Screws (turns out from seated)
* Turns in of the idle speed/ throttle stop screw
* Transfer slot visible

Idle Feed Restriction [IFR]
Idle Air Bleed [IAB]

Main Jet [MJ]
Main Air Bleed [MAB] also called High Speed Air Bleed [HSAB]
Emulsions Holes [e-holes] quantity, diameter.
Kill Bleed (if present)

Power Valve Channel Restriction [PVCR]
Power Valve [PV] (opening point)

Accelerator Pump (size)
Accelerator Pump Cam (color and/or number)
Pump Cam postion (which hole the screw is in)
Accelerator Pump Shooters (type & size)

Now with the above, you'll have a better idea of what size jets etc you might need to make a change.
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I bought my micro drill set from McMaster and use the shanks as a gage. Of course a real pin gage is better. Here's some more sources http://racingfuelsystems.myfunforum.org/Numbered_drill_bit_sets_about126.html
 
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Knuckleduster, I just noticed in the Ignition forum that you've already tried running the carb and you fouled the plugs. I assume this is idle and off idle, and if it is, controlling factors are:
1. Ignition timing. If the cam has a bunch of overlap, it will need more initial than factory.
2. Throttle position because the transfer slot is both a variable fuel restriction and an airbleed. So the primary side throttle needs to be set in the .020-.040" range as Urich describes in the book (its a sidebar). But don't rush to drill holes or file the throttle blade. Work the initial timing first.
3. Idle feed restrictions and placment. (submerged is more consistant, http://racingfuelsystems.myfunforum.org/viewtopic.php?f=25&t=1425)
4. Idle Air Bleeds. (the combination of IFR and IAB will control when the idle circuit tapers off as the throttle opens)
5. Float level (this is a fine adjustment and also effects the other circuits)

As that Proform is a 4 corner idle, do not be surprised if you end up reducing the IFRs and/or having the idle mix screws only a little bit open. As long as the engine responds to turnng the idle mix screws either way, its fine. By doubling the idle circuits, its potentially doubling the fuel delivered. This can be real helpful dialing in engines that have low idle vacuum. But if the idle vacuum is somewhat decent, they'll need to be a bit more restricted.
 
First of all i woukd start with a vacuum gauge and an Air Fuel Ratio gauge. Without that, all is just best guessing and playing a trial and error game on the carb
 
A/f meter is a invaluable tool if your really trying to dial in a carb for cruise. A lot of time your cruising on the transfer slots and not the primary jets. To dial this in it takes a meter, ifr jets, and sometimes you have to restrict the transfer slot passage. A/f meter also shows what your air bleed changes are doing.

This is what they are talking about with the lower ifr. You can see where I tapped the proform block.

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IMG_2472.JPG
 
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Watching this thread with interest. I'm wondering why a so called STREET series carb is running rich enough to load up plugs. To the OP, what is your motor combo and how long did it take to load the plugs??
 
Start by varifying that what proform says is in the carb actually is in the car. Last proform 750 I bought had a set of air bleeds two sizes smaller then what was supposed to be in it. Once fine tuned that carb was awesome.
 
abodyjoe said:
Start by varifying that what proform says is in the carb actually is in the car. Last proform 750 I bought had a set of air bleeds two sizes smaller then what was supposed to be in it. Once fine tuned that carb was awesome.
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Good point joe, I was also wondering if this was a used carb possibly tuned different than stock.
 
Engine specs here-

What shoud it run? Estimated HP anTQ?


Carb is brand new.

Loaded up sitting at a light, but had idle screws way too far out at 1-1/8 turns. Now at just under 1/2, and may stiil be too much.

Have an AF meter ready to go in as soon as I can get to my exhaust guy to weld in bungs.

Ordered a tuning kit, should be here tomorrow.

It ran great yesterday, today it was breaking up for a minute at cruise after some heavy throttle action. It cleared up after I pulled over to check things out. Thought my positive choke wire had fallen off.
Floats are a little high, level is a little above center in sight glass.
Had a brutal day at work, gonna get after it tomorrow after parts show up.
 
* Good photos of IFR relocated back to submerged position.
I mentioned it because most of us who get deeper into testing and tuning come around to recognizing how helpful it is. But OTH I realize that most people have some trepidation about doing surgery on a new carburetor, and also more tools and things to buy and learn to use.

* I agree AFR gage can be helpful. Logging AFR with RPM and/or Vacuum and/or throttle position is even better. Nowadays you can probably set up a cell phone to video record.. OTH not a magic bullet, especially if the carb has weird characteristics or timing is way off. The AFR gage is really an O2 sensor, so it can give erroneous AFR in some sitations. Anyway, you can tune without it especially at idle and off idle (street use). Spark plugs etc reveal a lot the old fashioned way as you already can see.

*"Street Carb" Probably how they label their carbs that come with a choke.

FWIW. The old (read I can't find it on he website anymore but saved a copy) BarryGrant/Demon selection guide suggests a initial timing for an engine that size between 16-20 BTDC, if the cam has less than 240 degrees at .050; and 18-20 degrees as a starting point if it has 240-260 @ 50. If you're already in range, then go ahead start messing with the carb - one change at a time!

I'd start with one size smaller IFRs on all 4 corners. Or if that's too much work right now, experiment with one step larger IABs on the primary side only. Drive around, note if there's any hesitation while very slowly increasing the throttle from idle to 1/3. You can also do this in neutral as Urich recommends but its much harder (for us mortals) to observe a hesitation without the load on it.

*Floats. Another option and easy to experiment with. Try turning them a hex flat or two lower and see what effect it has, if any that you can observe. Lower should be slightly leaner.

"Should be" Carbs don't always do what we think they should do.
 
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OP, as was mentioned a few posts back...you MUST verify every single bleed size in that carb. ProForm is notorious for not installing blanks in emulsion holes, and sending carbs out with mismatched air bleeds. Check the size of the idle feed restriction as well. This stuff has to be verified. I just opened up a PF 750 and it had 3 emulsion holes open instead of the 2 it should have had. I wouldn't use more than .026-.028 emulsion in the #1 and 3 holes and block 2 and 4.

And verify the Power Valve Channel Restiction.
 
Whats the correct procedure to lower the floats on this carb with the sight widows?
 
I am watching the Holley tuning video, and it was saying if you don't remove some fuel from the bowls first you will bottom out the floats. Does this not apply to this carb because you can lower floats with the engine running?

I have heard conflicting info on where the fuel should be in the window. In the middle or at the very bottom, which is it on a Proform/Quickfuel?
 
KnuckleDuster said:
I am watching the Holley tuning video, and it was saying if you don't remove some fuel from the bowls first you will bottom out the floats. Does this not apply to this carb because you can lower floats with the engine running?
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Not sure what "bottom out the floats" means, but if you lower the level slightly, you shouldn't need to remove fuel. I guess if your fuel level is waaay to high and you lower it to the bottom, it may put strain on the float's arm since the float would then be submerged in fuel. Shouldn't be an issue with minor adjustments though.

KnuckleDuster said:
I have heard conflicting info on where the fuel should be in the window. In the middle or at the very bottom, which is it on a Proform/Quickfuel?
Click to expand...

I'll defer to the 'experts,' but I've always run the level even (or close to even) with the bottom of the window. Keep in mind that float level adjustments may change AFR slightly.
 
mopowers said:
Not sure what "bottom out the floats" means, but if you lower the level slightly, you shouldn't need to remove fuel. I guess if your fuel level is waaay to high and you lower it to the bottom, it may put strain on the float's arm since the float would then be submerged in fuel. Shouldn't be an issue with minor adjustments though.



I'll defer to the 'experts,' but I've always run the level even (or close to even) with the bottom of the window. Keep in mind that float level adjustments may change AFR slightly.
Click to expand...




Just watched a Quickfuel video, and it says that the floats are preset for the fuel level to run at the mark in the center of the window at 6.5 psi.
My secondary float level is way too high, almost at the top, and the primary is a bit high also. My regulator is currently set at 5.5 psi.


So I set the level at the middle and the regulatot for 6.5psi. Going out to test.
 
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Counter clockwise raises fuel level, clockwise lowers. Let the motor idle for a few minutes to leak check and fuel level to stabilize with new setting. After the first test drive take a peek again.
 
mderoy340 said:
Counter clockwise raises fuel level, clockwise lowers. Let the motor idle for a few minutes to leak check and fuel level to stabilize with new setting. After the first test drive take a peek again.
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This is good info.
Some of the information posted before that is wrong.
a. The hex nut controls the float level. The screw is the locking and sealing.
b. You're using a Proform bowl, not an old school Holley. Use Proform's level which I suspect will be the center because IIRC they're using the big clear sight glass, not the little screw in ones.
c. There's no need to make the adjustment with the engine running. Just make a little adjustment (1 or 2 hex flats) and then start it up and take a drive.

PS. Setting your regulator lower will reduce aeration of fuel in the bowl. There should be no need to run at 6.5 psi unless there's a lot of restriction. But what's really important is not the PSI at idle (as long as it doesn't push open the valves) but the PSI on the highway and down the track. As long as it has enough pressure to keep the bowls full all is good.
 
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I did. It ran good at first, then total crap.
I took it to my normal spot, as I hit third at about 90mph I could feel it falling flat.
If I get on it from a dead stop and let off, it dies.
If I get on it starting from 20 and let off, it dies.
Even died on ne twice in a grocery store parking lot at idle, and must be flooding because it would not fire back up without holding the pedal down.
While my amatuer tuning attempts might be contributing, I think I may have a fuel issue and or ignition issue or both. I just replaced plugs and wires. Starting to suspect the coil or voltage regulator, and or fuel pump.
I have had issues with three different carbs now.
I worked all night and I'm so tired and pissed. I might pull the plugs, but getting into the carb will have to wait.
 
Sounds like it's flooding. Float level, fuel pressure, or debris in needles. Fuel filter is the most important element to any type Holley carb. I always run sintered bronze. Saves all the flooding needle and seat issues.. and I only run 5-5.5# of pressure. Volume not pressure is key as stated.
 
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KnuckleDuster said:
I did. It ran good at first, then total crap.
I took it to my normal spot, as I hit third at about 90mph I could feel it falling flat.
If I get on it from a dead stop and let off, it dies.
If I get on it starting from 20 and let off, it dies.
Even died on ne twice in a grocery store parking lot at idle, and must be flooding because it would not fire back up without holding the pedal down.
While my amatuer tuning attempts might be contributing, I think I may have a fuel issue and or ignition issue or both. I just replaced plugs and wires. Starting to suspect the coil or voltage regulator, and or fuel pump.
I have had issues with three different carbs now.
I worked all night and I'm so tired and pissed. I might pull the plugs, but getting into the carb will have to wait.
Click to expand...

I didn't realize you were also trying out high speed WOT. Be patient on that. Get the idle much closer first (which also means steady cruising up to around 40-50 mph).
So first, just get the fuel level about in the middle of the sight glass for both primary and secondary. Then readjust the idle mix screws. Test the how it responds using as little accelerator pump as possible.

As far as the other possibilities for problems.
Since you cleared the carb using the throttle wide open technique, flooding seems to have been the problem at least that time. That's too much pressure for the needle and seat, or just set too high. Check that out first.

Next check out the choke, make sure its opening up quick enough. Also, see if you can observe whether it has an internal 'qualifying'. That is, as soon as the engine fires, manifold vacuum pulls the choke open. Original mopars from 60s and 70s have this as an external vacuum pod on the choke assemble. Most aftermarket carbs have this as an internal passage or some don't bother.

Back to the carb tuning. It will be iterative, but the sequence is also important. The idle circuits draws on the mains. They also can act in reverse at when wide open throttle. This is why the best tuners spend time working the "idle circuit" first. It saves time in the long run. "Idle circuit" includes the "transition" slot and starts with getting the throttle position in the correct range. Refer to that sidebar in Holley Carburetors and Manifolds For street and return road etc, only the primaries transition slots are in play. So don't move the secondary throttle position very much from factory setting at this point. Secondary transfer slots are sometimes higher up than the primary side. So they may or may not have slot showing under the throttle blades at idle. Just note what you find when you take the carb off and map it out.
 
Fuel pressure was close to 8.
Remembered these guages are inaccurate when warm so let it cool with a fan blowing on it and rechecked/reset to 6psi.
Started all over with alll four idle screws.
Now set to about 7/8 of a turn out, and adjusted idle screw from all the way out. Idles about 900 rpm in park and 825 in gear.
Tired tonight but will get a vacuum guage and a helper tomorrow to set in drive.
Tune up kit and accelarator cams showed up today, but might as well wait on the AF meter before trying to do any real tuning. Gonna look into a micro bit kit and check everything as YR suggested. Gonna get this all figured out at some point, be patient with me, and thanks so much for all the help. Been working out bugs on this car for at least two years, and it gets frustrating, but always willing to learn.
 
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