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davidmij
01-01-2013, 03:49 PM
Hi again gents, wasn't sure if I should start a new thread or stay on my older one "carburetor question" from 11-4-12. BTW, happy new year!

I took your advice and rebuilt the 4100 I bought used. A note that was with it said it was from a 67 T-bird 390. Other than a bent secondary vacuum pickup tube it seems perfect. The rebuild went very smoothly and I feel good knowing that all the little passage ways are clean and flowing great. I put it on yesterday (in the snow) and it fired right up. I could instantly feel a better throttle response, and I hadn't even adjusted it.

Here's my problem though. I can't get it to idle lower than about 8000 rpm. I drove it around and it got good and hot, and the choke was fully opened. I can back off the throttle screw until it isn't seated anymore, then back off the secondary throttle screw too, but unless I push on the secondary throttle screw head it stays idling at about 8000. This carb is a little different from the original in that it has a hex head screw that screws into a plastic piece that seems to tie in with the fast idle cam and bellcrank lever. Here's a few pictures of my setup, and my throttle linkage.

At any rate, can anyone point me at what to look for first when the idle is so high?

Oh wait, I just re-read page 2-30 and noticed that I never set the secondary throttle plate per instructions - that sure looks like it could be my problem. Yes? no?

I'll post this anyways, and go check it now.

thx, Dave J

partsetal
01-01-2013, 04:15 PM
My first thought was that the secondaries were open too much. You're right about the adjustment. It is often missed and best done with the carb upside down.
Carl

davidmij
01-01-2013, 04:51 PM
Yeah, I can get to it with a little bent screwdriver but I can's quite turn it.

Any idea on how to adjust the little hex head screw that goes into the plastic piece and seems to be for the choke?

thx, Dave

scumdog
01-01-2013, 04:57 PM
I can't get my 390 to rev to 8000rpm - let alone 'idle' at that speed!!!

davidmij
01-01-2013, 06:01 PM
Well maybe you should rebuild your carb Tom. Could have something to do with you being on the good side of the equator right now.
;0)

Anyway, after warming up it idles just below 750 rpm now. I think that's good considering it's 27 degrees outside.

I figured out that the little hex head screw allows me to adjust the choke to be fully open after warming up - I think that's all it's for.

The BIG question I have now is how can I tell if the secondary's are working?

I pulled over, removed the air cleaner, and floored it - but I don't see them opening at all. When I was rebuilding the carb I sucked on the the vacuum hole and it pulled the diaphragm as it should. This carb does not have the check ball on the secondary as the manual describes for the 1959 carb so it's not that.

thx for any help, Dave J

scumdog
01-01-2013, 07:10 PM
Well maybe you should rebuild your carb Tom. Could have something to do with you being on the good side of the equator right now.
;0)

Anyway, after warming up it idles just below 750 rpm now. I think that's good considering it's 27 degrees outside.

I figured out that the little hex head screw allows me to adjust the choke to be fully open after warming up - I think that's all it's for.

The BIG question I have now is how can I tell if the secondary's are working?

I pulled over, removed the air cleaner, and floored it - but I don't see them opening at all. When I was rebuilding the carb I sucked on the the vacuum hole and it pulled the diaphragm as it should. This carb does not have the check ball on the secondary as the manual describes for the 1959 carb so it's not that.

thx for any help, Dave J

'Flooring' it is unlikley to cause the secondaries to open, it need a load on the motor to cause that.

The secondaries don't come into play much in daily driving i.e. around town etc.

It's when you floor it to pass another vehicle etc that the carck open.

davidmij
01-03-2013, 12:09 PM
I found a couple of idea's on testing a vacuum secondary. Put a dab of white grease on the actuator arm at the cover and see if it gets smudged. Or, put a paper clip on the actuator rod up against something and see how much it moves - that will tell you how far it's opening. One more, and this one might be best with the autolite, is to loosely put a piece of masking tape across the hinge part of the actuator arm and actuator rod to see if it pulls apart.

I also read that it should be a fairly smooth transition when they kick in, thus it's hard to tell by feel. And having a loud exhaust makes it almost impossible to hear the suction sound.

I'll try these this weekend and see. That is if the weather gets above freezing. I can drive the car for for 15 minutes and the intake barely even gets warm due to my closing off of the exhaust bypass. Tough to get it up to operating temp.

One thing is for sure, rebuilding the carb has given me a lot better throttle response, and plenty of power to spin the wheels. I'd like to find some where nearby where I could check the 1/4 mile time now that it's running smoothly. I know it's far from fast by today's standards, especially weighing 3800 pounds - but I'd still like to know. I'd also like to see how it dyno's.

The base motor was 315hp and 427 ft lbs. I replaced the heads with C4AE 6090G (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CFMQrAIoAjAE&url=http%3A%2F%2Fwww.fordmuscleforums.com%2Fgalaxi e-pages%2F449629-fe-head-question-c4ae-6090g.html&ei=EbXlUI_FN-6n0AGBq4CIDQ&usg=AFQjCNEMzbE3ZAlMAqimhQDyJDSG3lrXAw&bvm=bv.1355534169,d.dmQ&cad=rja)‎. Added FPA headers. I also put in a 1 3/8 shaft - close ratio - 4 speed toploader and changed out the 3.10 rearend for a 3.89.

Dave J

KULTULZ
01-04-2013, 02:58 AM
I found a couple of idea's on testing a vacuum secondary. Put a dab of white grease on the actuator arm at the cover and see if it gets smudged. Or, put a paper clip on the actuator rod up against something and see how much it moves - that will tell you how far it's opening. One more, and this one might be best with the autolite, is to loosely put a piece of masking tape across the hinge part of the actuator arm and actuator rod to see if it pulls apart.

I also read that it should be a fairly smooth transition when they kick in, thus it's hard to tell by feel. And having a loud exhaust makes it almost impossible to hear the suction sound.

I'll try these this weekend and see. That is if the weather gets above freezing. I can drive the car for for 15 minutes and the intake barely even gets warm due to my closing off of the exhaust bypass. Tough to get it up to operating temp.

One thing is for sure, rebuilding the carb has given me a lot better throttle response, and plenty of power to spin the wheels. I'd like to find some where nearby where I could check the 1/4 mile time now that it's running smoothly. I know it's far from fast by today's standards, especially weighing 3800 pounds - but I'd still like to know. I'd also like to see how it dyno's.

The base motor was 315hp and 427 ft lbs. I replaced the heads with C4AE 6090G (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CFMQrAIoAjAE&url=http%3A%2F%2Fwww.fordmuscleforums.com%2Fgalaxi e-pages%2F449629-fe-head-question-c4ae-6090g.html&ei=EbXlUI_FN-6n0AGBq4CIDQ&usg=AFQjCNEMzbE3ZAlMAqimhQDyJDSG3lrXAw&bvm=bv.1355534169,d.dmQ&cad=rja)‎. Added FPA headers. I also put in a 1 3/8 shaft - close ratio - 4 speed toploader and changed out the 3.10 rearend for a 3.89.

Dave J

Dave,

As for that adjusting nut, you need to refer either to the Shop Manual for that year carb or the instruction sheet (FORD) for the MOTORCRAFT carb kit. I thought I scanned and posted it here at one time?

Kinda makes for rough driving in cold weather without the heated crossover doesn't it? You will have to run the choke a little tighter during cold weather and lean it out in the spring.

As for the secondaries, it should be an un-noticeable transition if set properly. If they open too soon, there will be a bog and if late, a lack of performance and the transition being noticeable (delayed).

Uh... A few photos would be nice... ;)

KULTULZ
01-04-2013, 03:03 AM
...forgot...

You said there is no check ball in the secondary circuit?

Camshaft choice?

davidmij
01-04-2013, 04:36 PM
Thx Gary,
there are a few pictures of the choke area, and the hex head screw and plastic piece in the #1 post. The top two pictures are with the carb off before I rebuilt it - they also show the manual choke. The second two pictures are with the carb on the car and with the thermal choke.

This carb is supposedly from a 67 T-bird, and my old one was from a 67 LTD - they are both identical other than this one had a manual choke. I think I'm going to put the manual choke back on it because I have headers on the car and my rigged up heat tube is just open at the hot end. Don't want it to be sucking up dust and dirt.

Yes, this carb does not have the secondary check ball. My manual is for a 59 t-bird which says the 59 did have one.

From what you and others wrote I'm pretty sure the secondaries are working fine. The car has a very good feel power and running wise when I step on the gas. Doing the rebuild and using the manual really helped me get a feel for how everything works and ties together. I just wanted to be sure that the secondaries were working, I'll try the tricks I found as soon as the weather warms a bit. It doesn't stay this cold here for very long. And your are right, it does make for rough driving when it's really cold! When the car is warm and idling it gives the occasional pop sound, almost like it has a non stock cam. I think that's just because the choke is still a little shut. It doesn't stutter or miss at all when I hit the gas.

It's nice to be able to pump the pedal a couple of times and fire it right up without having to ride the pedal when it's cold. Then seeing the choke working correctly, and the fast idle cam go through it's progressions as it should.

If you want some specific photos just let me know and I'll post them. I took tons of pictures as Simplyconnected always advises.

thx a ton, Dave J

KULTULZ
01-05-2013, 03:11 AM
rigged up heat tube is just open at the hot end:eek:

I think with your setup, the manual choke will be better. Does it have an orgional appearing choke cable/handle to look period correct?

I meant to show you detail on how to make a nice looking choke stove but you got the headers in before I could reply.

HOLLEY used to make a cap to go over the vacuum inlet that included a small filter. It just used under hood heated air and not choke stove. That might be another option.

Glad it all worked out for you...

davidmij
01-05-2013, 11:06 AM
I'm not really sure if it's an original appearing manual choke - you can see it in the second picture.

jopizz
01-05-2013, 11:40 AM
I've rebuilt a ton of 4100 carburetors from '58 on up and I've never seen one with a secondary check ball. The picture in my '59 shop manual doesn't show one. Where did you see it.

John

KULTULZ
01-05-2013, 01:43 PM
There is a check ball to prevent diaphragm damage in case of a backfire.

KULTULZ
01-05-2013, 01:47 PM
I'm not really sure if it's an original appearing manual choke - you can see it in the second picture.

I meant the cable housing and knob asm on the interior to make it appear as a factory install.

The choke kit you have is a make-do. It uses the original choke cap. I would show you a photo of an original HI-PO piece, but...

You know, why I am thinking about it, the carb may be too lean (jetting). Usually headers makes one breath a lot deeper and it requires a richer mixture.

jopizz
01-05-2013, 02:05 PM
There's never been a check ball in the secondaries on any 4100 I've ever taken apart. Can you show me a diagram that shows it.

John

davidmij
01-05-2013, 04:57 PM
Hey John, if you look on page 2-25, figure 13 in the 1959 Ford Thunderbird shop manual it shows it. If you don't have the manual I can post a picture of the page, just let me know.

At any rate, my carb does not have the ball check.

So, I used a blob of grease on the body of the carb between the the body and the actuating arm of the secondaries. I left about 1/8 of an inch between the grease and the actuating arm of the secondary. Warmed up the motor and took it for a spin. I have a close ratio 4 speed. I floored it and ran it up to 4000 rpm in first, shifted to second and did the same. I pulled over to check and the grease hadn't been touched. Thus, it seems my secondaries are not opening. Tried it twice.

Any one have ideas on what to start with when the secondaries don't seem to work?

Gary, thx for the info on my manual choke. This car is sort of a "ratrod" kind of project so I will most likely use something like an old valve for the choke pull knob - it doesn't need to look original.

thx, Dave J

davidmij
01-05-2013, 05:15 PM
Wait a minute, hold the press.

I just went through the the troubleshooting on page 2-18. I looked at the secondary vacuum pick up tube and it's not there. It was bent when I put it together so I bent it back. It must have kinked the tube because it's been broken off. I looked around my work table and found the piece on the floor - THANK HEAVENS. If that thing had fallen off when the carb was on it would have sucked right into the motor. It must have been barely hanging on when I bent it back and it kinked.

Luckily I have my old carb for parts, I'll replace the top plate and see if the secondaries start working.

more to come.......

jopizz
01-05-2013, 05:34 PM
I see the check ball on page 2-25 as you indicated but it's not shown on the exploded parts view on page 2-27. Strange. I've taken dozens apart and have never seen one installed. There are quite a few typos in the manuals so I wouldn't take it as gospel.

John

davidmij
01-05-2013, 06:23 PM
There's a great video on www.youtube.com (http://www.youtube.com) done by "Mikes Carburetors" and it's free. I used two of them to do my carb. He shows a primary pump check ball too. He say's some have them, some don't. It's at 23:20 into the video if you want to check it out.
https://www.youtube.com/watch?v=BUrP_kTbMXs
He also has a couple of shorter videos on how to check the 4100 for operation. Be sure to check it out.

So, I changed out the top plate on my carb and YEEHAW, the secondaries open. I floored it in 1st gear and right about 3500 rpm I could feel them kick in. I pulled over and checked the grease blob trick and sure enough there was grease on the actuator arm.

Another thing I notice is it really pops and growls when I down shift - you know the sound, like little backfires. Is that probably caused by running too rich, or could it just be because of the little glass pack mufflers?

Hopefully tomorrow I will get warmer weather and I can go through adjustments and timing for a good hour and get it just right.

thx again, Dave J

KULTULZ
01-05-2013, 06:42 PM
So, I changed out the top plate on my carb and YEEHAW, the secondaries open. I floored it in 1st gear and right about 3500 rpm I could feel them kick in. I pulled over and checked the grease blob trick and sure enough there was grease on the actuator arm.

Another thing I notice is it really pops and growls when I down shift - you know the sound, like little backfires. Is that probably caused by running too rich, or could it just be because of the little glass pack mufflers?

Hopefully tomorrow I will get warmer weather and I can go through adjustments and timing for a good hour and get it just right.

thx again, Dave J

It is normal for it to pop when gearing down (no fuel pressure applied) as the mixture is overly rich and is being fired late and maybe entering the exhaust system. Remember the NASCAR cars when backing out of the throttle and flames being shot?

It may be overly rich and the mufflers don't help much either... ;) Have you done a spark plug reading?

As for the secondary check ball, it may not have been used on all models. You need the CARB I.D. NO and cross it to the MPC under Basic PN 9576. I would imagine most fall out at dis-assembly unnoticed.

YellowRose
01-06-2013, 01:13 AM
Thanks to the posting by David ~ davidmij on the Autolite 4100 video by Mike's Carburetors, there are now 6 of his videos posted in the Technical Resource Library (TRL). Including the one on how to download the Autolite 4100 4 Barrel Carburetor Manual. Check them out in the Carburetor section. The TRL link is always part of my signature element. Just click on the link! Thanks, David!

davidmij
01-06-2013, 10:19 AM
No problem Ray, thx for organizing it, and making it easy to get to. I just saved that manual, it will come in handy.

Gary, it also pops just a little while idling once it's warmed up. Is that normal, or should I work on adjusting the mixture a little more lean?

Dave J

KULTULZ
01-26-2013, 03:08 AM
Gary, it also pops just a little while idling once it's warmed up. Is that normal, or should I work on adjusting the mixture a little more lean?

Dave J

I'm sorry Dave, I did not notice your post.

The occasional misfire may be due to the mechanical choke (your fully opening it too soon). Apply it very lightly during cold idle and see if the idle improves. The choke has to maintain a rich mixture until the heat riser feature takes over. A properly adjusted auto choke does this automatically.

I am also sending Ray a photo (within Shop Manual) showing secondary check valve (ball).

...mmm...

Let me try it this way-

http://www.tocmp.com/manuals/Ford/1958/Service/index.html

Go To Page 2-61

davidmij
01-26-2013, 10:06 AM
Funny that you just posted this Gary. Just yesterday I went through the adjustments again. I didn't have a tachometer before and I realized I hadn't set the timing since installing it. I got the car good and warm, adjusted my idle to just above 600 rpm and reset the timing to about 8 or 9 degrees. (It was around 6 before) I them reconnected the vacuum advance line and adjusted the jets. Took it for a spin and it did much better. Still pops and growls when down shifting, especially when rolling down hill, but not so much while idling.

I'll tweak the jets some more today and see if I can get it even better. The choke seems pretty good now.

My carb is supposedly from a 68, and the old one was from a 67 LTD. I'm guessing the check ball, (and a few other things) changed over the years.

regards, Dave J