Holley 4160 carb tuning questions

[WisconsinCutlass]

I got my air fuel ratio gauge installed and am working on tuning the carb finally. I have a couple questions about my 4160. What I'm seeing on the afr gauge at heavy to wide open throttle is I get a lean bog reading off the gage, then I'm guessing the secondaries open and it goes rich around 10.0 on the gauge. The Lean bog I think I can fix with a larger pump squirter and adjusting the vacuum secondary spring to open sooner. With my carb not having a metering block with jets on the secondary side what can I do tuning wise to lean it up? Is buying a different metering plate the best option. About $30 a piece. Or is it best to buy the conversion kit to add a metering block on the secondaries side that way I can simply change jets? Am I on the correct track to getting this tuned right? New to carbs so this is all learning for me.

 

[vanrah]

Greetings WiscCutlas & all; If ya got the bucks buy the secondary metering block. It will make lift way easer down the road. $5 to $20 used, new $35 ++ & if ya can make the jump just get a pair of Quick fuel front & rear, I think it comes in a kit for around $80(?). And as you learn more over time you can up grade to their main body # PV 650 or 750 & dial that thing in damn near as good as EFI. How far away from me are you? I'm down by Beloit - Janesville area. And I love working on Holley's, Ole Bob.
Ps: A couple that I worked on last summer including mine.

 

[WisconsinCutlass]

I'm in Fond du Lac so about 1-1/2 to 2hrs from you I believe. I did look at used ones on eBay but don't know enough to buy the correct one. From what I found is the secondary side normally doesn't use a power valve, and they Holley conversion metering block doesn't have an option to run 1 but some of the used ones do. I know they sell plugs for it. The other thing I'm wondering that I cant find is do the idle mixture screws do anything on the secondary side? Does it have mixture screws on that side? The pictures look like it does but I don't understand how it would do anything if the secondaries aren't open. I'm thinking I'm going to go with the Holley part number that way I know it will work.

 

[pontiacgp]

what is the A/F reading at idle?

 

[WisconsinCutlass]

I've adjusted idle already and it bounces between 13.8 at worse to 14.9. I wasn't sure if the bouncing was normal but it does have a cam in it so I figure that was causing that. It cruises at 60mph at 14.5

 

[vanrah]

Greetings WiscCutlas & all; A secondary power valve (PV) is commonly NOT used in performance automobiles. But was common in the old Reo trucks (late 50's & 60's). Hence where the name for the larger acc (50cc?) pump comes from, the "Reo Pump". Anyway why the different uses? I'll ex-plane that when I see ya! But when it's blocked off the secondary jets will have to supply all the fuel to the boosters, no help from the PV "blocked". Requiring 6 to 12 jets sizes larger than the front jets. Keep in mind the front jets will be aided by the PV in the metering block port. Effectively the primary jets are for cruising (off idle to about 1/2 in to it) & when that vacuum drops a bit more the PV will open & help the primary side from going lean. The Quick fuel primary block will also let you tune how much fuel the PV orifices will flow, not just when (PV #). From Holley their are many different PV hole diameters. Buyer be-where! On to 4 corner idle, generally the more cam you have the more ya want (need) 4 corner idle circuits. Most bases can be easily modified for this feather, But only some main body's have the meat (casting shape) to accommodate the modifications. If ya got the QF block kit that has secondary idle adjusters they would do nothing until the main body has the feathers (ports) needed to make them functional. You are welcome to drive down & spend the afternoon with me, I'm retired & home a lot. You buy the beer & pizza and I'll show ya how to assemble & ADJUST it, skim my three Holley books. Maybe I can help give you more confidence & explain with help from said books how these things work. Let me know when ya want to come down, Ole' Bob.

 

[WisconsinCutlass]

Bob, I will have to take you up on your offer if the weather ever gets nicer. 15 dgerees when I took the dog out this morning and it snowed here yesterday. No heater in my car means it doesn't come out of the garage till it's 40 or warmer. I'll see what I can do tuning wise then you can fix it when I come down. I switched to a lighter spring for the secondary, going to order the metering block for the secondary side, and get a 70-80 jets kit. We'll see how things go after that.

 

[pontiacgp]

Your primary side isn't running lean so it has to be the secondary. Have you checked the float level for the secondaries? You could lean out the primaries a bit. At 60 mph if you could tweek it to a low 15 range you'd be surprised in the increase in fuel economy.

 

[WisconsinCutlass]

The float level on the secondary side is just below the sight screw. I read this is where it should be? It's set the same on the primary side. And to lean out the primary side at cruise would just be going down a size or 2 on the primary jets correct? I ordered the secondary metering block, jet kit, and carb fuel line this afternoon so hopefully by next weekend I'll get to start tweaking things again.

 

[Mike T]

I have never run anything but Holleys on my street cars and with enough motor, I have never had one, even new out of the box, that didn't have a low fuel bog when you get into the secondaries. The harder you step into it, the bigger the bog. Any kind of performance setup seems to cause it. While I agree completely with Vanrah that a secondary metering block with all the fixins is the way to go, I don't think you should install them until after you solve the bog issue. If installed before, you just add several more possible carb conditions that may be causing or adding to the problem. The carb you have on the car right now is the fewest number of variables to look at.

If your running rich after the bog, i don't think bringing in the secondaries sooner is going to make things better. Before you do anything else, I think you should make sure your ignition timing is absolutely dialed in. Correct ignition time could also be part of the problem.

I think what is happening is that, when you open the secondaries, you are taking in a big gulp of air through the secondaries before the secondary venturies establish enough negative pressure to pull enough fuel into the fuel stream to keep the fuel ratio right. (The air from the secondaries is going through the motor before the gas can catch up) The accelerator pump was put there to solve this problem. However, the accelerator pump was equipped with a diaphragm, activation cam curve and squirter designed to supply gas for a moderate or incremental increase in secondary activation. You have one or both of two basic issues to look at:

1. Is my accelerator pump giving me a big enough shot of gas for long enough to equalize the vacuum bog?
2. Is my accelerator pump giving me that shot of gas soon enough to match the onset of the increase in vacuum?

You mentioned that your bump stick actually has bumps on it. This makes the questions above even more important. Before installing any of the new stuff you ordered, try the next size up squirter nozzle, if that helps but doesn't solve the problem, get a 50cc accelerator pump kit and if it doesn't come with it, buy an accelerator pump cam kit. While you're waiting for that, go and adjust the rod that leads from you carb linkage to the accelerator pump lever. You should have about .015 ths clearance and no more. Make sure the carb linkage to the accelerator pump lever is tight and reacts instantly. If you have to make any adjustment, try the afr again after you finish

When you do get the secondary metering block and associated doodads, change to the correct power-valve before changing jets, otherwise you are wasting your time.

One last thing, air density at 10*f is about 12% denser than at 70*f your not gonna get the best tune on your carb, no matter what you do, until it warms up a bunch.

Please keep us up on what's happening. Good luck!!