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Topic change - Holley Tuning

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sigtauenus

Active Member
I need an electric choke kit, and don't know if this is a 4150 or a 4160. What are the identifying features?

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I also need any tips you guys have for tuning it. Its running really fast right now at idle. I'd like to have it dyno tuned, but I need to get it into some reasonable range to be able to drive it.
 
SAC69

SAC69

Active Member
Donator
Re: What kind of Holley Carb is this?

The carb does not "know" (or care) how its choke is being opened, either via a electrical operation or manual old-style choke cable. The "method" (electrical or manual) simply bolts to the side of the carb using the same holes and attaches to the throttle shaft in the same manner. You can swap back & forth w/o affecting the carb. FYI, my new Summit came with an elec choke and I converted it to a manual system.
 
tarafied1

tarafied1

Well-Known Member
Re: What kind of Holley Carb is this?

"SAC69" said:
The carb does not "know" (or care) how its choke is being opened, either via a electrical operation or manual old-style choke cable. The "method" (electrical or manual) simply bolts to the side of the carb using the same holes and attaches to the throttle shaft in the same manner. You can swap back & forth w/o affecting the carb. FYI, my new Summit came with an elec choke and I converted it to a manual system.
Click to expand...
that is correct. Actually the black circular thing on the side has a bi-metallic spring in it. That one you have uses heat from a tube that would thread into the fitting just behind the the black thing in your picture. The tube would go to an exhaust manifold for heat source. You could probably just change the black part to one that has the electrical connections rather than the whole assembly.
427_01_08_10_2_11_31_0.jpg

send_binary.asp

As far as adjusting goes, since that choke doesn't have a heat source in the picture, it could be staying on and have the fast idle cam engaged (although the choke is open in the picture). You can loosen the three screws that hold it and turn it until the choke stays open and just leave it. In warm weather it doesn't really need a choke. If that isn't the source of the fast idle, there is also a screw on the throttle plate that sets idle speed. You could back it off. Finally, the idle screws on the metering block will also effect idle speed. Rule of thumb is to turn them in all the way, than back off about 2 to 2.5 turns for a starting point. Then with engine idling, you can fine tune them by going in until it stumbles, then back out until it runs rough. Somewhere in the middle is the setting you want. Ultimately a dyno tune will tell you the air/fuel mixture and you can tune it better that way but it's not really necessary.
That is a vacuum secondary carb so the rear throttle plates should be closed at idle, but if none of the above adjustments help reduce idle speed, you might check that they are fully closed at idle.
 
S

sigtauenus

Active Member
Re: What kind of Holley Carb is this?

thanks Craig, great explanation. I just ordered the electric choke kit and will try adjusting the carb tonight. I have an appointment for a custom alignment on Weds 8 am and will try to get the exhaust done tomorrow or Weds. Assuming that all happens, I could actually have this thing inspected this week and on the road!!! NPD order is in for door panels and stereo, a/c will just have to wait until I pay off some bills.
 
S

sigtauenus

Active Member
Re: What kind of Holley Carb is this?

I tried everything but the fast idle screws on the metering block. Where are those located?

Secondary valves are shut as far as I can tell.

Choke is turned counter clockwise and then clockwise again until the butterfly just opens. According to the label on the cap, that is really rich. The cap was set with the detent/marker right in the center. Should I put that back?

I adjusted the fast idle adjuster on the choke out 1.5 turns with no change. There is very little thread left to turn it out further.

I backed off the timing but it wouldn't run, advanced it until it would at least run with feathering the gas. I know it needs set with a light.

It'll idle with a light feather on the gas pedal, but I think that will smooth out with timing set right.

If I had to guess I'd say the idle is up around 2000-2500 right now.

I may need to tell the shop that they need to push it in to do the alignment and exhaust as I'd be hesitant do drive it like it is, a tad too unpredictable.
 
tarafied1

tarafied1

Well-Known Member
Re: What kind of Holley Carb is this?

"sigtauenus" said:
I tried everything but the fast idle screws on the metering block. Where are those located?
Click to expand...
they are technically not "fast idle" but they control the air/fuel mixture which can effect idle speed. see the pic with the arrow...
index.php

"sigtauenus" said:
Secondary valves are shut as far as I can tell.
Click to expand...
that's good
"sigtauenus" said:
Choke is turned counter clockwise and then clockwise again until the butterfly just opens. According to the label on the cap, that is really rich. The cap was set with the detent/marker right in the center. Should I put that back?
Click to expand...
you don't want it rich, turn it lean so the choke stays open (for now).
"sigtauenus" said:
I adjusted the fast idle adjuster on the choke out 1.5 turns with no change. There is very little thread left to turn it out further.

I backed off the timing but it wouldn't run, advanced it until it would at least run with feathering the gas. I know it needs set with a light.

It'll idle with a light feather on the gas pedal, but I think that will smooth out with timing set right.

If I had to guess I'd say the idle is up around 2000-2500 right now.

I may need to tell the shop that they need to push it in to do the alignment and exhaust as I'd be hesitant do drive it like it is, a tad too unpredictable.
Click to expand...
If the the throttle is fully closed (meaning the idle screw is backed all the way out) and secondaries are not open, then you have a vacuum leak. When it's running, squirt some carb cleaner or starting fluid around the base and where any vacuum lines connect, if it revs even more, you found your leak. It could be the vacuum modulator, pvc valve, carb base plate, etc. It getting air from somewhere...
 
tarafied1

tarafied1

Well-Known Member
Re: What kind of Holley Carb is this?

just for further clarification, the "fast idle" is between the cap you adjusted for the choke and the carb body. There is a stepped cam, as the choke begins to open, the idle screw will be on a progressively lower cam step lowering the idle. The regular idle is on the throttle linkage side. I assume that is the one you backed off. Make sure the one on the choke is not stuck... If the idle screw is not touching the tab on the throttle linkage then the fast idle screw might be holding the throttle open (that's why I recommended opening the choke - lean). If the choke is completely open the fast idle shouldn't be holding the throttle open.
 
S

sigtauenus

Active Member
I'm going to have to spend some time on this or get somebody who knows what they are doing. From what I can tell its not running on the idle circuit. I was adjusting the fast idle last night, I'll try the regular idle tonight, air/fuel mixutre, and check for vacuum leaks.

To clarify what's going on with the choke, if you look at the choke plate in that picture, that is where it is right now with the cap twisted counter clockwise into the rich side. I have to really go CCW to get it closed. From where it is now, I can twist the black cap CW towards the lean side, but the choke plate doesn't move any more as I twist into the lean side.
 
tarafied1

tarafied1

Well-Known Member
okay, as long as the choke is open... we can deal with that later. Just make sure nothing is holding the throttle open other than the idle screw and no vacuum leaks. The air/fuel mixture screws won't have an effect if the engine is not running on the idle circuit.
 
Mach1Rider

Mach1Rider

Active Member
!st thing is to plug the tubing connector for the choke tube or you WILL have a vac leak.
Simple 1/4in compression cap from the hardware dept will work.

The fast idle problem is adjusted on the pass side behind the choke coil. (see the black fast idle cam and adjuster screw)
When the choke opens fully the cam should fall forward releasing the pri plate back to idle setting.
It can be accessed with a small screwdriver with the choke plate closed completely or by removing the carb and turning it over.
Make sure this linkage does not bind or it will not work.

Once you have this choke working correctly, bring the eng up to operating temp.
Set idle speed to a steady 800 rpm and adjust the mixture screws to obtain the smoothest idle possable, then back idle set screw(left side) down to working idle speed.

Now you need to adjust accel pump for off idle responce. A good starting point is .005 gap at adjuster screw and lever.
What your looking for is the squirt from the pump to come out just a fraction before throttle plate opens to avoid flat spot on take offs.

Ps, After you have it good to that point, We can discuss the sec spring change for better get up and go. :ecit
 
S

sigtauenus

Active Member
Going back to basics on idle circuit, what all is involved with that. Right now engine is at temp, and is at a decent speed although I don't have a tach on it. The engine won't stay running unless I feather the gas. Does that mean its still not actually running on the idle circuit and is running off the accelerator pump shot every time I push the gas?

Pretty sure I found the vacuum leak, I had two nipples plugged off on the back of the intake and they were cracking. Its been 2 years since I put them on there.
 
Mach1Rider

Mach1Rider

Active Member
Old School Holley basic set up, You must plug that heat riser tube connection as it draws a vac for old style choke coil operations.
After verifying the choke is releasing the high idle cam and it is not holding the throttle plate open.
Turn the idle speed set screw(lft side) CC till it does NOT touch the stop bump
Turn the idle screw till it touches the stop and 1 1/2 turns inward.
Slowly turn the idle mixture set screws in till it just touches the internal stop, (DO NOT FORCE TIGHTEN THEM INWARD)
Back set screws out 1 1/2 turns.
Set accel pump gap to .005 -,007 clearence from screwhead to pump arm.
Verify float settings are just at bottom of sight holes.

Start engine and bring to operating temp.
Test idle speed set screw up and down to verify eng speed changes with screw movements. (means choke linkage has dropped control of throttle plate)
Turn Idle speed to 800-1000 rpm, turn idle both mixture screws in and out (Equally) to acheive smoothest idle performance.
Once set, return idle speed to 600 (with auto in drive) or 650-700 for manual.

Next step is to fine tune the accel pump squirt with the set screw clearence at the pump lever.
The larger the gap is at the screwhead to the lever the longer it will take to send pump charge into carb throat. ( major cause of off idle bog)
Ideally you want to see the pump spray just as you hit the throttle. Adjust screw as needed to achive this action.
 
tarafied1

tarafied1

Well-Known Member
yeah, what he said...

If you have to give it gas, it my still have a vacuum leak (lean)... it's getting air from somewhere else and that makes it lean out and rev up higher than normal and want to die. The choke tube fitting Mach1Rider pointed out my me a source of vacuum that needs to be plugged, I forgot that they had vacuum. IIRC there is a little cork gasket between the choke assembly and body to seal the port. Once you cap it off make sure that port is also sealed.
 
S

sigtauenus

Active Member
Ran out of time tonight, but did get the 1/4 compression fitting to block off the choke port (this was after my last post). Didn't try it after that because kids already went to bed. Will try in morning to see how it goes.

idle mixture screws are at 1 1/2 turns already.

throttle plate is closed

will set idle speed screw tomorrow, right now it is set up off the stop.

accel pump gap - that is the red spring in the bottom right of the second picture I have above, right? So that gap is measured at the arm at the bottom (accel pump on bottom of carb)?

Help me out on the sight holes, is that the screws on the top of the carb, front and back?
 
tarafied1

tarafied1

Well-Known Member
"sigtauenus" said:
accel pump gap - that is the red spring in the bottom right of the second picture I have above, right? So that gap is measured at the arm at the bottom (accel pump on bottom of carb)?

Help me out on the sight holes, is that the screws on the top of the carb, front and back?
Click to expand...
yes, that red spring is the one. Gap measured between the spring bolt head and lever.

the sight hole are those brass screws on the passenger side of both float bowls, the screws on top are locking screws when you set the float level. The sight screw would be removed to see in the float while setting the level.
 
S

sigtauenus

Active Member
OK, I think I found the real vacuum leak this time. Well, maybe, but this is still a problem.

Passenger side, under the 1" spacer. See how the 1" spacer hangs over the intake in the middle (under the black cap)? That paper gasket is leaking up into the hollow area of the spacer.

I put the 1" spacer on there for the PVC port that feeds all cylinders instead of the port on the back of the intake that feeds just the #4 cylinder. Many stories about #4 running rick or lean or otherwise having problems.

I'm pretty sure the Holley baseplate is solid right there. I can try removing the spacer and get the engine running good then add it back later to fix the PVC problem if there is one or leave it off entirely. I'm not partial one way or the other, I just want it to run smooth right now.
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Suggestions for best course of action?

Thick (.25 or so) composite type gasket under the 1" spacer?
Remove 1" spacer?

If I remove 1" spacer, suggestion for PVC fitting?
 
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