4180C rebuild observations and questions

[Saturn V]

I’ve read that the primary throttle transfer slots should be adjusted “square”. That appears to mean that the throttle plates are at the point where the transfer slot (as viewed underneath the carb) is as tall as it is wide. On my carb, this alignment occurs when the throttle plates are completely closed and primary throttle idle screw backed all the way out. I wasn’t sure this would work, since I’ve always had to screw in this adjustment screw to adjust the idle. But it seemed to work for my engine. With the primary transfer slots square and ½ turn on the secondary throttle screw, the engine idles at about 800 RPM when warm.

Last weekend, I adjusted the idle mixture screws. Previously, these were 1.75 turns out. I left them at 2 turns out and achieved AFR of 13.3 (air cleaner on) and vacuum of 19.5 in HG at 840 RPM. Now that I’ve adjusted the primary transfer slot openings and the secondary throttle stop, I should probably take another look at the idle mixture screws, but will leave them alone for now since I hate that adjustment process on a hot engine.

[Saturn V]

I had trouble getting the choke/fast idle adjusted. After the engine was warm, when I goosed the throttle, the medium speed idle would keep engaging. I messed around with adjusting the electric choke body until the engine is off of the fast and medium speed idle cam when warm.



I also adjusted the little set screw accessible above the fast idle cam. However, I don’t really understand what that little screw does and how to properly set the fast/medium idle. The little screw is backed out further now than what is shown in the pic. I just finished this adjustment today, so I need to see how it does when I start it tomorrow.

[JACook]

The setscrew in the fast idle cam is to adjust the positioning of the cam when the choke is on. This
adjustment affects which step of the cam the fast idle screw will contact when the choke is fully closed,
as well as the timing of when it drops down to the next lower step, or off the cam completely as the
choke opens up.

[84GT350CONV]

Thanks for the post. I'll use it for reference shortly.

[84GT350CONV]

During removal to adjust the secondary throttle screw, I noticed that the black throttle base gasket that came in the Holley rebuild kit is getting wet with fuel and separating. I replaced it with a good Motorcraft part and scraped the residue from the carb base (it all came off cleanly with one swipe of a razor blade).

I don't like the look of that gasket. Was wondering where you got the Motorcraft gasket and what the part number is? I want to avoid this during my rebuild.

[JACook]

The original gasket is Motorcraft CG-659-A. They've been discontinued for a while, but can still be found.

What I see on that ^^^ gasket is the rubberized layer stuck to the carb (and I presume the intake too),
and only separated because the carb was removed. I keep a good used Motorcraft gasket around to use
while I'm adjusting the carb, then when I get everything where I want it. Once It's all dialed in, I'll swap
in a new gasket and touch up the idle mix if the propane enrichment test shows me anything changed.

[84GT350CONV]

The original gasket is Motorcraft CG-659-A. They've been discontinued for a while, but can still be found.

What I see on that ^^^ gasket is the rubberized layer stuck to the carb (and I presume the intake too),
and only separated because the carb was removed. I keep a good used Motorcraft gasket around to use
while I'm adjusting the carb, then when I get everything where I want it. Once It's all dialed in, I'll swap
in a new gasket and touch up the idle mix if the propane enrichment test shows me anything changed.

Thanks. If I can't find one of those, would a gasket from Felpro or Mr. Gasket be a good enough quality? Saw another post where the Felpro quality was said to be questionable as well. I'm probably not going to mess with the adjustments other than documenting how many turns it takes to seat a needle valve and put it back to where it was before, as the only issue I have is with a leak and hard starting due to that leak.

[Saturn V]

Below is a link to one of the Motorcraft gaskets, which seems to have a kind of waxy coating. I installed it after pulling the black one above and the Motorcraft gasket didn't separate when I removed the carb later after a little run time. I bought mine from the same seller below.

http://www.ebay.com/itm/CG-659-A-MOT...-/161296583958

The choke and fast idle still aren't set correctly on mine. I'll have to work with the little set screw again when I have some time.

I've read about the propane enrichment method in the Ford Shop Manual. Is it worth getting the equipment, versus adjusting idle mixture for highest vacuum?

https://www.google.com/shopping/prod...ed=0CD4QpiswAA

[84GT350CONV]

Below is a link to one of the Motorcraft gaskets, which seems to have a kind of waxy coating. I installed it after pulling the black one above and the Motorcraft gasket didn't separate when I removed the carb later after a little run time. I bought mine from the same seller below.

http://www.ebay.com/itm/CG-659-A-MOT...-/161296583958

The choke and fast idle still aren't set correctly on mine. I'll have to work with the little set screw again when I have some time.

I've read about the propane enrichment method in the Ford Shop Manual. Is it worth getting the equipment, versus adjusting idle mixture for highest vacuum?

https://www.google.com/shopping/prod...ed=0CD4QpiswAA

Thanks for the link. I'll order one when I get back into E-Bay.
Not familiar with the propane enrichment method. I'm sure someone on here is though.

[Saturn V]

OK, had some time tonight so adjusted the choke and fast idle. I think I've got it right, it idled at about 2200 on startup ... about the same as before the rebuild. The engine has been much harder to start cold since the carb rebuild, and it wasn't easy before. But I've been making lots of little adjustments and I think part of the reason that it was hard to start tonight was that it was flooded after I messed with the throttle several times getting the choke and fast idle adjusted. I took it for a spin to get Sonic shakes (1/2 price after 8pm) for the family. I hope it starts easier in the morning.

JACook mentioned the propane enrichment in his post above.

[JACook]

The propane enrichment can be done without any special tools, but I will say the tool makes things
a little easier. All you need is a way to repeatably supply a low flow of propane. When I first started
using the propane enrichment method, I modified a regular propane torch by removing the torch bit,
and attaching a hose.

I have altered the factory method just a bit though. Rather than inject the propane into the air cleaner,
I prefer to aim the hose down each individual throat, to make sure I'm getting the same reaction from
all of them. Then I work with progressively lower propane flow rates to fine tune the mixture setting,
while watching both engine RPM and manifold vacuum.

It takes a bit of practice to find the balance, but once you know what feels right, it's much quicker and
more accurate than just using the vacuum gauge.

[Saturn V]

The setscrew in the fast idle cam is to adjust the positioning of the cam when the choke is on. This
adjustment affects which step of the cam the fast idle screw will contact when the choke is fully closed,
as well as the timing of when it drops down to the next lower step, or off the cam completely as the
choke opens up.

Thanks, Jeff. After getting some hands-on experience, I understand these adjustments better. And somewhere you recently mentioned in another thread to adjust the choke so that the choke plate is completely closed. I didn't read anything about that in the Holley rebuild instructions, or anywhere else. But I now tend to believe this step is crucial for cold startup. After adjusting the choke accordingly yesterday, the engine started a little easier cold, though I did have to crank for a few seconds since I hadn't started the engine in about a week. Today when I started the engine, I only had to pump the throttle twice with no dry cranking. The engine almost stalled, but picked up and ran on the fast idle just fine. I don't recall it ever starting that easily after sitting overnight. I think that a completely closed choke plate is needed to get the correct rich mixture for startup, right? Otherwise, 5-6 (or more) throttle pumps and lots of cranking are needed (at least previously, in my case). Hopefully, this trend of easier starting will continue.

So below is a summary of my choke and fast idle adjustment observations.

1) Loosen the choke housing screws and adjust the choke housing until the choke plate is completely closed with the throttle held slightly open. You may need to turn the choke housing a little more counter-clockwise than the previous position in order to achieve a fully-closed choke plate. Tighten the choke housing screws. (If turning the choke housing doesn't move the choke plate while the throttle is slightly open, remove the choke housing and ensure that the choke coil is correctly connected to the choke actuator tab.)

2) With the engine not running and the choke cold (sitting for a few hours), and after holding the throttle slightly open and then releasing it, note the position of the fast idle screw on the orange cam. You might need a little mirror to see this while the carb is on the engine. The fast idle screw should be solidly in the fast idle part of the cam (the tallest part). See the first pic in post #27 above. If needed, screw in the little socket head set screw (see second pic in post #27) with the throttle held open slightly to get the fast idle screw up on the fast idle cam. The next step down on the cam is the medium idle step. After step 3) below and with the engine warm (temp gauge in the NORMAL range after 5-10 minutes of running) you should be able to blip the throttle, releasing the fast idle screw from the fast and medium idle cams. If the fast idle screw is still on either the fast or medium cam positions, then you may need to back out the little socket head set screw to get normal idle after blipping the throttle again (~800 RPM, assuming the primary and secondary throttle plates are adjusted correctly per posts above). If the engine and choke coil are not completely warm (engine running for about a minute) and you blip the throttle, the fast idle screw will probably drop down to the medium idle speed, which is OK. If the choke plate doesn't open fully after warmup or if the engine speed stays at the fast idle speed well after warmup after making the adjustments above, ensure that there is about 7 volts at the choke electrical connector with the engine running. If the correct voltage is present, the problem could be a failed choke coil.

3) Start the engine. The choke plate should now be slightly open, due to the action of the choke plate pulldown mechanism. See the Holley rebuild instructions as there appears to be at least two different styles of pulldown mechanisms. My choke plate opens slightly (~.2") with vacuum applied to the specified baseplate port, but I didn't try to get it exactly per the clearance specified (partly because I didn't want to destroy the little plastic cap on the vacuum pulldown diaphragm in order to get a more precise adjustment and my carb model wasn't on the list of opening specifications, anyway).

4) My Holley rebuild instructions don't mention the correct fast idle speed, but I set mine to about 2200 RPM when the engine is first started. As the cooling fan clutch unloads and the engine warms up, the speed will creep up to 2300-2400 RPM. If yours is too high (>3000 RPM, I'd say) and the fast idle screw is on the fast idle part of the cam, then loosen the fast idle screw that touches the cam using a 1/4" box end wrench until you achieve the desired fast idle speed. My medium idle speed is set at about 1500 RPM.

Comments/questions/corrections on the above are welcome.

[JACook]

What I have found is that, if you have the choke plate adjusted correctly, even one full pump is
usually more than the engine wants on a moderate summer morning. Depending on temperature,
I often give the throttle just enough of a stab to set the choke. Having your base idle mixture set
correctly also helps.

The choke unloader adjustment is one of the improvements I really like about the 4180C, because
it separates the unloader function from the choke cover adjustment. There are three styles of choke
housings, that can be roughly classified as '83, '84, and '85 style. Each has the the adjustment in a
different place. The unloader adjustment can be fine tuned if the engine needs more or less choke
right after cold start-up.

Good writeup on the sequence of fast idle adjustments, and what each of them do. I normally set
the fast idle cam position so that the unloader allows the cam to drop to the middle step when I
operate the throttle, and fine tune from there, for the amount of run time before I can kick it down
to the base idle.

On a cold (for us) morning, I will start the car and idle it down to the end of the street without
touching the throttle. On warmer mornings, I let it run on the fastest idle for a few seconds, then
nudge the throttle to drop it down.

[Mgino757]

Awesome write up. I'll definitely be referring to this thread when I rebuild mine in the next coming weeks. One thing I didn't do on my last rebuild, and probably neither did Ford, was soak the main body and other hard parts in solvent. I should have known better...