Topic: gAS LEAKING FROM MY 4100

[jcrhodes]

My 65 289 V 4 Mustang has a newly rebuilt 4100, yesterday I started it up and it was running very ruff, I just drove it last week with no problems.  It smelt like gas so I thought it was just flooded, when I took off the air cleaner I saw pools of gas in the manifold, the carb had gas coming out both overflow holes.  Could the float be stuck?

[Soaring]

Absolutely.  Take the top off and check the floats for free movement.  If it is a newly overhauled carb, you shouldn't have any other problem if it was running good last week. 
And, welcome to the site.  Hang around and chat with us. 

[jcrhodes]

Thanks I'll give it a try.

[FASTBACK65GT]

If you can't quite get it fixed, you might consider doing what a lot of people do with their 4100s...get a new aftermarket Holley or other, and keep that 4100 off to the side for when you later sell the car.  4100s are just prone to a lot of problems and the new carbs will make your car enjoyable to drive.

[66GTKFB]

If you can't quite get it fixed, you might consider doing what a lot of people do with their 4100s...get a new aftermarket Holley or other, and keep that 4100 off to the side for when you later sell the car.  4100s are just prone to a lot of problems and the new carbs will make your car enjoyable to drive.

You better stick to your slot cars.
Jim

[jcrhodes]

I think an new aftermarket Holley is the way to go..I'm going to start shopping.

Thanks,  I add some pictures soon of my 641/2

[Soaring]

If you can't quite get it fixed, you might consider doing what a lot of people do with their 4100s...get a new aftermarket Holley or other, and keep that 4100 off to the side for when you later sell the car.  4100s are just prone to a lot of problems and the new carbs will make your car enjoyable to drive.

You don't 'know what you are talking about.  That 4100 is one of the most reliable carbs on the planet.  The first thing I would do would be to give the side of the carb a tap with the handle of a screwdriver to get the float unstuck.  If that didn't work, I'd take the top off and see if the float is maladjusted.  Try doing that with a damn Holley. 

[FASTBACK65GT]

Here's the dreaded "F-O-R-D" What's it stand for? saying (on a Ford group no less!).  Fix Or Repair Daily.  Where did they get that from?  The 4100 was a contributor.  I had a 4100 on my first fastback and it was nothing but trouble.  I've talked to many a Ford person about the 4100 and most all say how they had to constantly tweak or repair their carbs on a REGULAR BASIS - they really hated it.  Look at your own forum columns - two different current 4100 problems on here RIGHT NOW!  Uhhh, correction - three 4100 recent topics.  That should be enough proof for you.  If you want more proof...Go to ebay.  See how many driver 65-66 Mustangs are listed with new Holleys or other.  Do it!

I'm not saying its bad, or was an awful carb - but when its 50 year old technology with 50 year old worn out castings that becomes a nuisance to its owner just replace it with new reliable technology. 

If you want a perfect show car, stick with the 4100.  If you want some fun driving car with little or no headaches, switch it out.

[FASTBACK65GT]

The first thing I would do would be to give the side of the carb a tap with the handle of a screwdriver to get the float unstuck.  If that didn't work, I'd take the top off and see if the float is maladjusted.  Try doing that with a damn Holley.

I don't have to.  I just turn the key and go.   You sound like you have a lot of experience with all the problems on a 4100. 

[66GTKFB]

I had (note past tense) about a half a dozen Holly 4150/4160 carbs that I got rid of. They were not that good for my applications. I will admit that you can get more HP from a Holly than a 4100 Autolite but Hollys are a bitch to dial in, they need constant tweeking, use a lot more gas and leak. Yes they ooze gas. In the three Mustangs I have left, all have 4100 carbs, all are stock, all work fine, all need minimum adjustments, all give me about the same mileage that I got back in the mid 60's with my Fairlane "K" and Mustang "A", and overall are more reliable. To be truthful, I have a 69 VW Baja with a 3110 Holly Bugspray two barrel carb and a pair of 42DCNF Webers set up for a VW 2180cc race engine sitting on the shelf. It's not a bias, it's what is the best for your application.
Jim

[Soaring]

I  been overhauling carbs going on 50 years now, and Jim is right about the dialing in  problems with the Holleys.  Once you tweak a 2100 or a 4100 after you overhaul them, they stay tweaked.  All carburetors will eventually need an overhaul, and the 4100 is not as easy to overhaul as the 2100, but a great deal easier than overhauling a Holley.   If you have never overhauled a Holley, then you will run into a nightmare. 
You have to know what you are doing to overhaul any carburetor, and obviously whoever overhauled this 4100 was lacking in experience.   I'm saying it was human error, not the fault of the reliable 4100. 

[jcrhodes]

Thanks all for the good advice, I got the car running this morning and so far no problems..cross your fingers!!
I took the top off the carb and the front float was stuck, well not the float but the metal piece that connects to the float.   One thing that makes no since, the back float was OK, but when it did leak it came out of both back & front overflow?  Anyway it's a sunny day and going for a ride.  Good day!

[Soaring]

Glad you got it fixed, and that you now know how to unstick a float.  Just a tad of misalignment when overhauling them will cause that.  Now, go drive it like it is stolen.   

[66GTKFB]

Congrats on the carb. I know the feeling. I just spent an hour getting my 66 hardtop "A" code fired up after it sat for four month (I hate rain). All it needed was a bit of a boost from a battery charger, a lot of cranking and it fired up - ran smoothly. While it was on the charger, I repaired an outside 115vac outlet (a real genuine short to ground - blame the installer), pulled the battery from a 66 VW a friend is storing in my back yard and put that battery on a trickle charger in my garage. Yesterday, I fired up my two garage queens, a 65 GT Fastback (it sat for three months) and a 66 GT Fastback "K" car (it sat for two). Ran them about three miles and put them back in the garage. I know a Holley would have given me a bit more problems for cars sitting for that period of time. If you do go with a Holley, consider this - because of the Holley's larger cfm rating, you will need a better breathing manifold, a cam to use that extra fuel/air mixture and headers to get the exploded fuel out. I would spend the money on suspension and bakes.
Jim