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

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

Rembrant
Gentlemen,

I finally got my AEM AFR sensor & gauge installed this evening and set out to check and set my idle mixture, etc.

So I started the engine up (without choke) and just held the pedal while it warmed up.
Idle AFR while cold was more or less bouncing between 15.5 and 16.5 sometimes bouncing to 17.0 or so.
If I revved it a bit while cold, it would go to 13.5:1, right where it was set on the dyno day.
After a few minutes when it started to warm up, the AFR maxed out lean, so it's above 17 or 18:1.

Then I reset the idle mix screws, and decreased the idle stop screw as much as I could, and started adjusting the screws in. I could not get the idle screw adjustments to make any difference until I get in to where they're getting close to being closed and the engine wants to stall.

AFR still pegged lean, and vacuum doesn't go any lower than about 16". If I rev the engine a bit, the vacuum shoots to 20" no problem.

I had the idle stop adjustment down as far as it would go without stalling, so I don't know if I'm too far into the transition slot or not...

Holley book says to try a few different things...

Put toothpicks in the idle air bleeds to see if that richens it up.
Maybe the carb needs a different idle jet?...If it's even changeable...I don't know.

I need to go do some more reading, but thought I'd ask the experts for advice.

Thanks gents.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Gary Lewis
Administrator
I am not one of the experts, but I will comment.

I would have thought you'd open the idle screws up rather than close them down.  (There are some carbs that have the screws adjusting the air instead of the fuel, but I think those are just the emissions carbs, not yours.)  Pretty sure yours are controlling the fuel going in, and you need more of it.  Badly.

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.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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

85lebaront2
Administrator
Gary is correct, starting setting on older Holley carbs is 1.5 turns out from seated, some of the emission ones need 2.5 turns out from seated.

Only time you worry about idle AFR would be with a catalytic converter, and then there is a specific procedure either a lean drop or artificial enrichment.

EFI systems control the mixture at idle, part throttle load and cruise, under WOT, they revert to preset tables.

There are a few emission carbs where the idle mixture screws are actually air bleeds, these are ones where the richest idle mixture is still on the order of 14-16:1.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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

Rembrant
Ok,..all understood gentlemen, thank you. I'm a 4bbl carb tuning rookie here (as if it wasn't obvious...lol).

I haven't touched the carb since the engine came off the dyno. It worked fine.

The Holley book I was reading said to start at 2 turns out, and adjust in from there, ideally ending up at 1 turn, but OK between 0.5 and 1.5 turns out. I have another Holley book here that says to start at 1.5 turns out. In any case, the carb as found was at 0.75 turns out.

I'm done with it for tonight, but I'll be back at it again tomorrow. I'll set them at 1.5 turns and stick the air cleaner back on and go for a drive.

Could be the gauge too I suppose. It was reading while the engine was warming up, but then once warm it went max lean. That was at .75 turns out (I think) so I'll try it again at 1.5 and see what the gauge says.

Thanks for your help guys.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Gary Lewis
Administrator
The # of turns out are a starting point.  I would for sure try turning them out farther to see what happens.  Your goal is to get the best possible idle, regardless how many turns open the screws are.

Having said that, if you have to turn the screws way open to get the best idle then something is wrong.  Maybe not "bad wrong", but wrong.  It might be that you have a small vacuum leak, like a cap off a fitting.  Or it might be that something in the carb is plugged.  But I wouldn't stick with the number of turns open just because that is what the book says it should be.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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

Rembrant
Understood Gary thank you.

One more thing...

The idle mix screws. Do they have internal stops when turning them out? I assume yes...wouldn’t want one falling out..
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Gary Lewis
Administrator
No, they'll come out, but not until well after the spring goes.....  Wait, this is a Holley and the screws are in the metering block.  No springs, just the gasket.  But they'll come out.  However, before they do nothing will be happening as you've already gotten past the "wide open" point.  I think.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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

grumpin
Glad the experts chimed in!

My first thought was a vacuum leak. Something I check quite often on my F250 is vacuum lines and caps.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Ok, now I need some carb tuning advice (Holley 4160 600CFM)

Rembrant
grumpin wrote
Glad the experts chimed in!

My first thought was a vacuum leak. Something I check quite often on my F250 is vacuum lines and caps.
Hey Grumpin!
Well, I've been playing around with this for a couple weeks and searching for vacuum leaks is one of the things I've been doing. I might as well run this by you guys in case I'm missing something.

My Holley has 4 vacuum barbs. There are two 3/8" barbs...one in front which I have piped to PCV, one in the rear which is piped to the brake booster. Then there are two 1/8" barbs, one that is full vacuum up front that I previously had capped but now (normally) have it connected to the air cleaner assembly, but currently it is piped to my vacuum gauge. The other 1/8" barb is the ported vacuum source that I have piped to my vacuum advance, which is also currently plugged.

All tubing is new.
I even disconnected the PCV last night and plugged it for a test.
The brake booster seems to be OK and I pulled the fitting out of it a couple days ago and it was still holding a vacuum after the truck had not been started in 3 days.

Currently running an aluminum 1" spacer under the carb with new gaskets. Everything is still brand new really, but I checked the intake and the base of the carb for flatness, and they both appear to be fine and look like new.

So, for the time being I've kinda given up on looking for any further vacuum leak unless you guys point out something that I'm missing.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Rembrant
In reply to this post by Gary Lewis
Gary Lewis wrote
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?
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Rembrant
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?

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Rembrant
In reply to this post by 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.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

85lebaront2
Administrator
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".
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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

LARIAT 85
In reply to this post by Rembrant
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. )
Lucille:  1985 Ford F150 XLT Lariat

*Colors:  Dark Canyon Red exterior, Canyon Red interior
*Engine: 5.0, CompCams 31-230-3, "Thumper" E7 heads, Edelbrock Performer intake, Autolite 4100 carburetor, DuraSpark II ignition, Thorley Tri-Y headers, Flowmaster dual exhaust, H-pipe.
*Drivetrain:  AOD transmission, 3.55 gears, 2wd.



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

Rembrant
85lebaront2 wrote
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.

LARIAT 85 wrote
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.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Gary Lewis
Administrator
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?
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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

85lebaront2
Administrator
I will add to that, make sure the secondary throttle plates are closed and not sticking.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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

Rembrant
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.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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

Gary Lewis
Administrator
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, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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

85lebaront2
Administrator
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.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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