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

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Rembrant

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

Gary Lewis wrote

Regardless, I think getting the AFR correct will have the engine running smoothly in all situations. And a carb can do that - but you have to be the feedback loop. Run the test and modify. Run the test again and modify. Etc.

I'll be doing more testing Gary, and I could tell even from the little bit I did this evening that the AFR gauge is going to be a HUGE help with this.

My engine is really nothing special, and it will run better than this. For all intents and purposes, it's basically a 1996 Explorer engine with a carb on it instead of EFI.

Anyway, I just spent a little bit of time looking at the carb, and I'm going to pull it this weekend for a more thorough look. I put my 1.5x drugstore specs on and looked down the primary barrels with a flashlight, and it looks like something isn't quite right in there. If I push the throttle harder towards the closed position, I can see the left plate moving more than the right plate. It might be due to the location of the internal stop(s) in the carb, and be completely normal, but I'll check it out. I think fully closed, I should still be able to slip a 0.010" feeler gauge between the plate and the barrel, so that is a spec I can check and confirm.

Anyway, no big deal. I'll get there. Stay tuned for more later.

Thanks folks.

Rem

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

ArdWrknTrk

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

Administrator

This post was updated on .

Seems to me, Cory, that you'd be in the transition slots if you were that light on the throttle.
IDK if your 4160 has annular boosters, but the 4180's did, and if the Summit carb is a Motorcraft clone it should too.

Annular boosters are supposed to help with signal at small openings and they definitely atomize better.

Keep at it.

I think if you monitor vacuum and mixture you will have more data (or clues) to work with.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

85lebaront2

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

Administrator

In reply to this post by Rembrant

There are no internal stops in the carb, but if the fast idle is set too high to where it is touching with the choke off, then the throttle shaft can and will twist slightly.

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

Rembrant

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

In reply to this post by ArdWrknTrk

ArdWrknTrk wrote

Seems to me, Cory, that you'd be in the transition slots if you were that light on the throttle.
IDK if your 4160 has annular boosters, but the 4160's did, and if the Summit carb is a Motorcraft clone it should too.

Annular boosters are supposed to help with signal at small openings and they definitely atomize better.

Keep at it.

I think if you monitor vacuum and mixture you will have more data (or clues) to work with.

Jim,

As you can tell I'm no carb expert, but according to my handy Holley book, my 4160 has "Straight Leg" Boosters.

The 500CFM Summit carb I have my eye on (the M2008 series, I believe) has the Annular Boosters. As I understand it the Summit M2008 is a refreshed Holley 4010 or something like that which was a refresh of the old Autolite? 4100.

I'm going to pull the carb and have a closer look at it, see if I can narrow things down a bit. I've been absolutely swamped with a couple projects at work, so I don't get as much time as I'd like to focus on this stuff.

I'll be back as I learn more.

Rembrant

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

Gentlemen,

I'm back with an update, but first I wanted to thank you all in advance for your help (You were all right) and thank you for your patience with me. I have not been a very good mechanic...the problem was more or less right under my nose the whole time. I do have, as you all suggested, a bad vacuum leak.

I took the Holley off again to go over it and check for any issues with the throttle plates or leaks, etc. All of the surfaces are clean, smooth, and flat.

I go back over to look at the engine again, and I notice that there is some discoloration on the intake on the passenger side bank, next to cylinders 3 and 4.

Upon closer inspection, the intake manifold gasket is pushed out...and it is REALLY obvious...I don't know how I missed this before.

And not only is the gasket pushed out, there's a hole in it...or a crack, and it's big enough that I can slide in a small zip tie right into the dead center of the intake for cylinder #3. Zip tie is 0.097" wide and 0.040" thick for reference.

In hindsight, the reason I missed this previously is that this area is covered over by the electric choke and vacuum secondary assemby on my carb, and in front of both of them, my coil...so I clearly did not get in there good enough with the nozzle when I was spraying map gas around trying to find a leak. Since I did not find a leak there, I didn't even look at the area last time I had my carb off. I have to hang my head in shame here...because now that I see it, it is really obvious...lol.

Oh well, onward and upward. Time to order up some new intake gaskets.

Thanks again gents for all your help. It will be a little bit before I get some new gaskets installed, but I'll report on the results when I do.

Cory

grumpin

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

Good find!

Don’t hang your head in shame. You found it, not everything jumps out at us. It happens to the best of people, and if it doesn’t, they’re lying or haven’t been at it very long!

The bright side to me is since you have checked everything throughly, it’s going to run like a dream!

Edit, I like the zip tie demonstration!

Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona

Gary Lewis

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

Administrator

grumpin wrote

Good find!

Don’t hang your head in shame. You found it, not everything jumps out at us. It happens to the best of people, and if it doesn’t, they’re lying or haven’t been at it very long!

The bright side to me is since you have checked everything throughly, it’s going to run like a dream!

Edit, I like the zip tie demonstration!

I agree. We all have those kinds of problems, so don't hang your head. You stayed with it until you found it.

And while you are waiting on the gaskets, check the throttle plates out on that carb. I think one side is closing before the other. They really should both hit at the same time so that the two sides of the engine are both running the same amount.

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

Rembrant

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

Thanks gents. I'm just a little frustrated that I didn't find this earlier.

I will also investigate the carb further Gary. I think I may have been just twisting the throttle shaft because I was twisting it on one side, and the stop is on the other side, so I might have been flexing things a bit. In looking at it today, from the bottom, the throttle plates actually look pretty good.

I'm not sure thought that the closed position is correct, but I'll look into it more. I see that if I have the idle speed screw backed all the way out, the bottom step on the high idle cam becomes the final "closed" stop. That IS adjustable, but I don't know if I should touch it or not...probably not.

I've just seen several mentions in my Holley books about how much of the transition slot needs to be visible below the closed plate(s). I think it says between 0.040" and 0.060"...but how on earth do you measure it? I seem to recall reading that the amount of slot showing should be "square"...which might be easier to eyeball than to actually get a measuring tool in there.

Anyway...it will probably run fine as it is, and the longer term plan is to install that Summit 500CFM carb with the annular boosters anyway, so I won't beat myself up on the Holley too much.

The old truck won't be moving much now until spring 2020 unfortunately.

85lebaront2

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

Administrator

You should back it off so it is no longer stopping the throttle from fully closing, basically with the main stop screw backed out, loosen the fast idle until the cam will move with no drag, then make sure the main idle stop is still not touching.

Don't feel to bad, years ago, one of our local Ford dealers bought Autolite replacement carbs from us, one of their "mechanics" would set the idle so rich that the engines would lope with the choke on. At this point they would bring the car to Preston saying the carburetor wasn't right. I finally put the limiter caps on the mixture screws, 2 weeks later they wanted a new carburetor because that one "wouldn't adjust".

I have seen intake gasket leaks on the old FE engines that were inside the valve covers, pulling oil in, dead miss on #3 & 4 and if you sealed the PCV and inlet, after the vacuum stabilized it idled pretty nicely.

When you get ready to fix the gasket, get some long 5/16-18 bolts (4) cut the heads off and taper the cut end slightly and cut a slot for a screwdriver. Install the side gaskets being sure to hook the tabs on the ends to the head gasket tabs, put the 4 long studs in the corners as guides. I personally do not use the end seals, just a good bead of RTV on each end. Lower the manifold over the corner guides and start the other bolts, begin tightening them in sequence till you get to the corner ones, remove the guides and install and tighten them in sequence.

Bill AKA "LOBO" Profile

Rembrant

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

85lebaront2 wrote

You should back it off so it is no longer stopping the throttle from fully closing, basically with the main stop screw backed out, loosen the fast idle until the cam will move with no drag, then make sure the main idle stop is still not touching.

OK, this is good to know! Thank you sir! So the throttle plates stop just by closing in the barrels then? The reason I started looking so closely at the fast idle cam is that it is nice and loose and moving freely until I back the idle speed screw all the way out. With the idle speed screw all the way out, there is a little drag on the fast idle cam stop screw. It looks like it could be loosened just a little bit.

And, on the intake gaskets. Do you guys put a little RTV around the coolant ports or install them dry?

85lebaront2

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

Administrator

I put a very thin film, you do not want to block the weep channel around the water passage, this lets any leakage go out rather than down inside the engine.

Bill AKA "LOBO" Profile

Gary Lewis

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

Administrator

In reply to this post by Rembrant

I put RTV around the coolant ports.

I agree with Bill's approach of using studs to position the intake. And the RTV on the end walls. But, I'll add that it is possible to put the intake on at an angle, and it won't always line itself up just by torquing the bolts. So do your best to get it on level.

Gary, AKA "Gary fellow": Profile

85lebaront2

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

Administrator

That's part of the reason for the RTV, if you let it cure partially, it will stay in place as you snug the manifold. I usually take all the bolts down finger tight, then slowly alternately work on the center and checking the ends to be sure it is even as it seats. Once it is evenly seated, then start torquing in sequence.

Bill AKA "LOBO" Profile

Gary Lewis

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

Administrator

If I'm using RTV on the end walls, and I always do any more, I religiously clean the block and the intake, apply the RTV, and then set the intake down level and run all of the bolts in finger tight. Then I snug them up in the torque pattern, but don't torque them down, and let it sit over night so the RTV cures. The next day I torque it down. Otherwise I'm afraid I'll squish the RTV out.

Gary, AKA "Gary fellow": Profile

Rembrant

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

Thanks for all the tips gentlemen! I have never been so happy to find a bad gasket!!

I was beginning to feel like I had a more serious mechanical problem.

Hoping to get the intake pulled today and have a look inside.

Do you think that the gasket has been out of place since it was installed? The leak either started later on, or started out small and got worse over time?

Gary Lewis

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

Administrator

I can't see the gasket moving once the intake is torqued down against it. And if it were exhaust I'd say it got worse over time. But I can't see how an intake gasket got worse. The air going in wouldn't have been all that hot nor corrosive, so I think it had to have been there from Day 1.

It is such a small leak in the overall scheme of things that it wouldn't make much difference in dyno runs at WOT. But it sure will at idle.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

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

Administrator

In reply to this post by Rembrant

Cory, so glad to hear you've come to the root of the problem!

With your new carb tuning prowess I'm sure that you'll have it running like a top once that gasket is replaced. 👍

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Rembrant

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

In reply to this post by Gary Lewis

Gary Lewis wrote

I can't see the gasket moving once the intake is torqued down against it.

Gary,

Again you are correct sir. Upon closer inspection after disassembly, the intake gasket was out of place (and probably broken) from the day it was installed. See pics below. I'm not sure if this had anything to do with the issue, the but the gaskets were installed backwards...the side of the gaskets that said "Head Side" were facing the intake. I can't see what that matters though, except the gasket stuck like glue to the cylinder head, and not at all to the intake.

The other interesting thing is that the gasket is actually broken...and they're actually both broken. The gaskets have a metal core, and I can't even see how that happened...it's broken at the top of cylinder #3, and also on top of cylinder #6. You can't tear them...I tried. They're thin sheet metal in the middle(core).

The only thing I can see is that maybe the gaskets were not sitting correctly when the intake was set into place, and as it was torqued down, it bent the gaskets and broke them? I don't know.

Is this what I get for having a shop that builds a lot of BBC's work on my SBF?>..lol.

ArdWrknTrk

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

Administrator

It'd be interesting to throw a precision straight edge across the head and manifold faces and see if they are truly flat.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

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

Administrator

In reply to this post by Rembrant

Hard to believe they did such a poor job of the intake install. Breaking the gaskets is hard to do, but I'd guess that they put studs through in the center to hold the gasket and align the manifold, and then they had to press hard to get it down on the ends. And since it was sandwiched between the head and the intake the gasket couldn't fold over so tore.

And then to put them on backwards as well. Even lowly Chevys should be treated better than that!

Gary, AKA "Gary fellow": Profile

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