Ok, now I need some carb tuning advice (Holley 4160 600CFM)

[Rembrant]

Having said that, I don't worry about AFR at idle. I get the best idle I can get, so I adjust the idle mix screws to max RPM, which is also max vacuum - which should be up around 20" with your mild cam.

Out of curiosity, why don't you worry about AFR at idle?

Oh, and another question...

Is there a reason the gauge was showing me an AFR reading while the engine was warming up and then would not once it warmed up? Does that sound more like a sensor issue or did the AFR actually change between cold start and warmed up? I have the choke adjusted so that it doesn't work, so I was using only the throttle to keep it running until it warmed up. I'm just curious why that changed?

 

[Rembrant]

Ok, I've playing with the carb settings this morning.

I tried the idle mix screws out 1.5 turns first, and then just now turned them out 2.0 full turns. I have the idle speed screw adjusted out all the way and the engine is idling at 750 RPM. I can't get it any lower than this. Vacuum is still only 16-17".

My AFR gauge is still reading full pegged lean. According to the Holley book, I should have a rich mixture right now. Not sure, but maybe there's something up with the gauge? It goes through a little start-up procedure, then sits at 14.5 for a couple seconds, and then rapidly ramps up until it hits 18:1 and then pegs all the way. I took the truck for a quick drive, and it stayed pegged lean. Maybe the sensor/gauge kit is not working properly. So either I'm stupid lean or the gauge isn't working properly. Bugger.

The base timing is still set at 16btdc, and is sitting pretty steady there at idle. Weird thing I see now is if I start to increase the RPM's, the timing starts to retard...sometimes smoothly, sometimes jumping a little bit, but still retarding.

I'll try some more idle mix adjustments and see what happens. Any comments welcome.

[85lebaront2]

Ok, I've playing with the carb settings this morning.

I tried the idle mix screws out 1.5 turns first, and then just now turned them out 2.0 full turns. I have the idle speed screw adjusted out all the way and the engine is idling at 750 RPM. I can't get it any lower than this. Vacuum is still only 16-17".

My AFR gauge is still reading full pegged lean. According to the Holley book, I should have a rich mixture right now. Not sure, but maybe there's something up with the gauge? It goes through a little start-up procedure, then sits at 14.5 for a couple seconds, and then rapidly ramps up until it hits 18:1 and then pegs all the way. I took the truck for a quick drive, and it stayed pegged lean. Maybe the sensor/gauge kit is not working properly. So either I'm stupid lean or the gauge isn't working properly. Bugger.

The base timing is still set at 16btdc, and is sitting pretty steady there at idle. Weird thing I see now is if I start to increase the RPM's, the timing starts to retard...sometimes smoothly, sometimes jumping a little bit, but still retarding.

I'll try some more idle mix adjustments and see what happens. Any comments welcome.

Where is your vacuum advance connected? Ford for years used a ported spark advance, which on most all Holley carbs was the port on the primary metering block.

On your AFR sensor, what make is it? Sanity check, try closing the choke by hand until the engine starts to load up from being too rich, don't keep it there too long as you can foul your plugs. If the AFR doesn't peg rich, then something isn't working correctly. My unit is an Innovate LC-1 with their LM-1 meter, it takes it a little to warm up, then works quite well. There should be instructions on doing a free air calibration on the system. Here is the step on mine:

5.1. Free air calibration

To achieve maximum precision, the LM-1 and its sensor needs to be recalibrated frequently.

When the measured lambda is greater than 6, the display will show the oxygen content in %. For

free air it should show 20.9%. If the display value is different by more than 0.6%, recalibrate. You

can test the oxygen sensor by breathing on it. The oxygen content of your breath will show.

If you can pull a couple of plugs and get pictures and post them, there are several of us who are pretty good at "reading plugs".

[LARIAT 85]

Ok, I've playing with the carb settings this morning.

I tried the idle mix screws out 1.5 turns first, and then just now turned them out 2.0 full turns. I have the idle speed screw adjusted out all the way and the engine is idling at 750 RPM. I can't get it any lower than this. Vacuum is still only 16-17".

My AFR gauge is still reading full pegged lean. According to the Holley book, I should have a rich mixture right now. Not sure, but maybe there's something up with the gauge? It goes through a little start-up procedure, then sits at 14.5 for a couple seconds, and then rapidly ramps up until it hits 18:1 and then pegs all the way. I took the truck for a quick drive, and it stayed pegged lean. Maybe the sensor/gauge kit is not working properly. So either I'm stupid lean or the gauge isn't working properly. Bugger.

The base timing is still set at 16btdc, and is sitting pretty steady there at idle. Weird thing I see now is if I start to increase the RPM's, the timing starts to retard...sometimes smoothly, sometimes jumping a little bit, but still retarding.

I'll try some more idle mix adjustments and see what happens. Any comments welcome.

This is how I tuned my carburetor a few years ago. Perhaps something here can help you:

With the engine off, turn each idle mixture screw in until it lightly seats. Then, open each screw back out to whatever Holley recommends for the initial bench setting. (Ford specifies 1.5 turns out for each screw on the Autolite 4100.) This will probably be a bit on the rich side, but you should be able to start the vehicle up and it should idle without any problems.

Start your engine and let it get to full operating temperature. Make sure the choke is OFF. Adjust the curb idle speed screw to 500 RPM in PARK. This will ensure the throttle blades aren't opened up too far.

Using your ear and/or a vacuum gauge, slowly turn each screw *in* to lean the air/fuel mixture. (I adjusted mine in quarter-turn increments.) As the engine idle speed increases, re-adjust your curb idle speed screw back to 500 RPM. Go back and forth between the two idle mixture screws until you get the highest idle or reach your highest vacuum reading. (My screws ended up at 1 turn out on one side and 0.75 turns out on the other side from fully seated.)

Then, go back and re-adjust your curb idle speed screw. (In order to achieve a 500 RPM idle speed in gear, I set my idle speed to 750 RPM in PARK.) Vacuum should go up with the higher idle speed. (I ended up at 21" of vacuum at idle. )

[Rembrant]

Where is your vacuum advance connected? Ford for years used a ported spark advance, which on most all Holley carbs was the port on the primary metering block.

On your AFR sensor, what make is it? Sanity check, try closing the choke by hand until the engine starts to load up from being too rich, don't keep it there too long as you can foul your plugs.

Vacuum advance is currently disconnected and plugged, but it was on the passenger side of the metering block on the carb. There is a barb there that Holley says to use for vac advance. I'll play with that some more once I have everything else dialed in. I've checked it before, and it is zero vacuum at idle, but the moment you touch the throttle it jumps up to 20" pretty quickly.

The O2 sensor gauge kit is an AEM 30-4110. I'll try the test with covering the choke horn. Thanks. At this point and time, I don't think it's working properly.

This is how I tuned my carburetor a few years ago. Perhaps something here can help you:

With the engine off, turn each idle mixture screw in until it lightly seats. Then, open each screw back out to whatever Holley recommends for the initial bench setting. (Ford specifies 1.5 turns out for each screw on the Autolite 4100.) This will probably be a bit on the rich side, but you should be able to start the vehicle up and it should idle without any problems.

Start your engine and let it get to full operating temperature. Make sure the choke is OFF. Adjust the curb idle speed screw to 500 RPM in PARK. This will ensure the throttle blades aren't opened up too far.

Using your ear and/or a vacuum gauge, slowly turn each screw *in* to lean the air/fuel mixture. (I adjusted mine in quarter-turn increments.) As the engine idle speed increases, re-adjust your curb idle speed screw back to 500 RPM. Go back and forth between the two idle mixture screws until you get the highest idle or reach your highest vacuum reading. (My screws ended up at 1 turn out on one side and 0.75 turns out on the other side from fully seated.)

Then, go back and re-adjust your curb idle speed screw. (In order to achieve a 500 RPM idle speed in gear, I set my idle speed to 750 RPM in PARK.) Vacuum should go up with the higher idle speed. (I ended up at 21" of vacuum at idle. )

Thanks for all the tips Rick. Appreciated. Truck is manual trans though, so I don't have Park.

I pretty much tried all of your suggestions, but I can't get the idle below 750 RPM. The throttle closes and the idle speed screw will start to back out. Also, I can't get the vacuum to go below 17". Right now, I have the mixture screws out 1 turn, idle is set around 850 and vacuum was 17". If I put just a tiny bit of pressure on the throttle the vacuum shoots down to 20" almost instantly. That is confusing me a little bit because I thought it would be higher with the throttle 100% closed, but anyway.

There are some notes in the Holley book about this situation (because of the bigger cam I believe) where they suggest drilling small holes in the throttle plates to increase the vacuum.

Right now it's not running bad. I was out driving around for a while. The engine pulls hard, and it idles fine other than being a little high right now.

Maybe the cam and the carb are too big. It feels to me like it should run a little better than it does at the lower RPM's, but it's possible I'm chasing a ghost here and there's nothing to improve...lol.

 

[Gary Lewis]

Where is your vacuum advance connected? Ford for years used a ported spark advance, which on most all Holley carbs was the port on the primary metering block.

On your AFR sensor, what make is it? Sanity check, try closing the choke by hand until the engine starts to load up from being too rich, don't keep it there too long as you can foul your plugs.

Vacuum advance is currently disconnected and plugged, but it was on the passenger side of the metering block on the carb. There is a barb there that Holley says to use for vac advance. I'll play with that some more once I have everything else dialed in. I've checked it before, and it is zero vacuum at idle, but the moment you touch the throttle it jumps up to 20" pretty quickly.

The O2 sensor gauge kit is an AEM 30-4110. I'll try the test with covering the choke horn. Thanks. At this point and time, I don't think it's working properly.

This is how I tuned my carburetor a few years ago. Perhaps something here can help you:

With the engine off, turn each idle mixture screw in until it lightly seats. Then, open each screw back out to whatever Holley recommends for the initial bench setting. (Ford specifies 1.5 turns out for each screw on the Autolite 4100.) This will probably be a bit on the rich side, but you should be able to start the vehicle up and it should idle without any problems.

Start your engine and let it get to full operating temperature. Make sure the choke is OFF. Adjust the curb idle speed screw to 500 RPM in PARK. This will ensure the throttle blades aren't opened up too far.

Using your ear and/or a vacuum gauge, slowly turn each screw *in* to lean the air/fuel mixture. (I adjusted mine in quarter-turn increments.) As the engine idle speed increases, re-adjust your curb idle speed screw back to 500 RPM. Go back and forth between the two idle mixture screws until you get the highest idle or reach your highest vacuum reading. (My screws ended up at 1 turn out on one side and 0.75 turns out on the other side from fully seated.)

Then, go back and re-adjust your curb idle speed screw. (In order to achieve a 500 RPM idle speed in gear, I set my idle speed to 750 RPM in PARK.) Vacuum should go up with the higher idle speed. (I ended up at 21" of vacuum at idle. )

Thanks for all the tips Rick. Appreciated. Truck is manual trans though, so I don't have Park.

I pretty much tried all of your suggestions, but I can't get the idle below 750 RPM. The throttle closes and the idle speed screw will start to back out. Also, I can't get the vacuum to go below 17". Right now, I have the mixture screws out 1 turn, idle is set around 850 and vacuum was 17". If I put just a tiny bit of pressure on the throttle the vacuum shoots down to 20" almost instantly. That is confusing me a little bit because I thought it would be higher with the throttle 100% closed, but anyway.

There are some notes in the Holley book about this situation (because of the bigger cam I believe) where they suggest drilling small holes in the throttle plates to increase the vacuum.

Right now it's not running bad. I was out driving around for a while. The engine pulls hard, and it idles fine other than being a little high right now.

Maybe the cam and the carb are too big. It feels to me like it should run a little better than it does at the lower RPM's, but it's possible I'm chasing a ghost here and there's nothing to improve...lol.

I think you have a vacuum leak. Here's my theory: You are having to close the throttle completely to get the idle speed down, and even then can't get it below 750 RPM. If the throttle blades are completely closed and it is still running at 750 R's then air is getting in some other way.

You said the brake booster is solid, but what about plugging everything off? Somewhere, something is leaking air into the intake. Have you tried shooting carb or brake cleaner around the base of the carb and where the intake hits the heads?

[85lebaront2]

I think you have a vacuum leak. Here's my theory: You are having to close the throttle completely to get the idle speed down, and even then can't get it below 750 RPM. If the throttle blades are completely closed and it is still running at 750 R's then air is getting in some other way.

You said the brake booster is solid, but what about plugging everything off? Somewhere, something is leaking air into the intake. Have you tried shooting carb or brake cleaner around the base of the carb and where the intake hits the heads?

I will add to that, make sure the secondary throttle plates are closed and not sticking.

[Rembrant]

I will add to that, make sure the secondary throttle plates are closed and not sticking.

Thanks for the comments guys. I'll do a little investigating. I assume the only way to check the secondary plates is to pull the carb and flip it over and have a look?

I'll try the spray test tomorrow and check for vacuum leaks.

Otherwise every single gasket and hose and tube and fitting is new. Brake booster is confirmed to be holding vacuum, and I plugged the PCV hose this morning for a test.

Manifold to head leak....now I hadn't thought of that.

[Gary Lewis]

Thanks for the comments guys. I'll do a little investigating. I assume the only way to check the secondary plates is to pull the carb and flip it over and have a look?

I'll try the spray test tomorrow and check for vacuum leaks.

Otherwise every single gasket and hose and tube and fitting is new. Brake booster is confirmed to be holding vacuum, and I plugged the PCV hose this morning for a test.

Manifold to head leak....now I hadn't thought of that.

You can pry open the secondary air valve, or whatever Holley calls the vacuum-operated blades, and see the secondary throttle plates from the top, w/o taking the carb off.

I don't think there's an adjustment on your carb for how far those throttle plates are open, but I could easily be wrong on that. However there is an adjustment on some Holleys, so maybe yours. If so, that might be a source for the air as I don't think your carb has an idle fuel circuit in the secondaries.

As for the manifold/head interface, Brandon and I had fits getting his manifold on correctly, so I know it is possible to get the think on "crooked". I would have thought that would show up as a lean problem at WOT, but maybe the leak isn't enough to cause problems at WOT but is at idle.

[85lebaront2]

You can pry open the secondary air valve, or whatever Holley calls the vacuum-operated blades, and see the secondary throttle plates from the top, w/o taking the carb off.

I don't think there's an adjustment on your carb for how far those throttle plates are open, but I could easily be wrong on that. However there is an adjustment on some Holleys, so maybe yours. If so, that might be a source for the air as I don't think your carb has an idle fuel circuit in the secondaries.

As for the manifold/head interface, Brandon and I had fits getting his manifold on correctly, so I know it is possible to get the think on "crooked". I would have thought that would show up as a lean problem at WOT, but maybe the leak isn't enough to cause problems at WOT but is at idle.

Gary, Holleys do not have a secondary air valve, Carter AVS and Thermoquads , Rochester Quadrajets, Motorcraft 4300 and 4300D use them. You can look down the secondaries and see if it looks like there is fuel from the idle circuits showing at the rear of the throttle plates. Take the shaft on the driver's side and try to rotate in clockwise, if it moves and the idle drops that is your problem. You can also slide a piece of thin hose in and listen for a load hiss with the engine running.