Stalling at hard acceleration

[Anonymous]

I recently purchased a 66 Mustang with I6 and am new to the world of car work, though I have had such fun with this thing over the past year. I had to put on a new carb and am having a hard time getting the settings correct. Idles great. But when between 30-50 mphs and I accelerate hard, the engines stumbles a bit. I have been fiddling with the choke a bit and still can't get the problem taken care of. Sound mostly like choke needs to be adjusted? Too lean perhaps? Or should I look at the accelerator pump, which I am not absolutely certain how to adjust? Any suggestions would be appreciated.

By the way, I have really enjoyed observing and reading the forum the last few months. Learned a lot so far.

 

[barishiman]

What kind of carb do you have?

Autolite 1100?

Weber/Carter YF?

more info the better, btw welcome to the forums!

 

[Anonymous]

Sorry

Autolite 1100

Thanks for the welcome

 

[barishiman]

First, is the Autolite just a regular rebuild or a Pony carb?

Second, do you have an automatic or manual choke?

I've had problems like yours with my carb. I've had 3 rebuilt 1100s on my 200 from places like Napa and Autozone until I finally purchased a Pony Carb. The ones from Napa etc... are not rebuilt correctly and have many flaws. Its probably your carb. Your fuel to air mixture could be out of wack alittle.

I had a Pony Carb for over three years and it just quit of me couple months back. The float was bad and my choke was about shot.

http://www.ponycarburetors.com/main.asp

If you want to stick with the 1100, I really suggest getting a Pony Carb. They are by far the best 1100s out on the market and they are rebuilt perfectly and all the factory flaws are fixed.


Andrew

 

[Anonymous]

Hi Bailey66,

You have an interesting problem. Could be one of several issues. If it is the accelerator pump, you may want to exchange it for another rebuilt carb. Did you purchase it rebuilt or do it yourself? Do you have an automatic? I assume you have an electric choke? You say the car idles fine. How does it run at a constant 30 - 50mph? Any surging, or a nice steady drone? When you say stumbles under hard acceleration, is this foot to the floor (WOT) from 30? Does it clear up, i.e., is it a short stumble, or a prolonged hesitation? What we need to do is determine if this is a jetting issue (running lean / rich) or an accelerator pump issue. If you rebuilt you old carb, did you change the jets? Assuming the choke opens up completely once the car is warn, you do not have a choke issue. The fact that it idles well would indicate that the choke is operating correctly. Have you checked the timing?

Regarding the Pony 1100, for $180 there are several better options. But let's not go there yet.

Steve

 

[Anonymous]

It's a regular rebuild with an automatic choke. Got it at Napa. This is, by the way, the second such carb I have tried. Gave it a go about a year ago, had similar problem--didn't feel capable of getting it sorted out, so I returned it. This time, though, the old carb was leaking and felt had to go ahead and make the swap.

It is an automatic. At constant speed, it run smoothly, no surging. Only when I put foot down hard, though not to the floor usually, does it stumble--at which point it pauses for a split second then takes the gas fine and I continue on my merry way.

Choke does open completely when at operating temp. As for the timing, no I have not checked it yet. I guessed it was more likely a carb issue, since there were no similar issues at all with the old carb (well, except for the gas it keep leaking onto the exhaust manifold).

As for other options, I would certainly be willing to entertain them it this can't be resolved. To be honest, I wasn't sure how many options existed that I, as a novice, could take care of myself, which is why I went for the Autolite 1100--of course, not necessarily taking care of the 1100 as easily as I hoped either.

Thanks for the questions and suggestions.

Richard

 

[barishiman]

Set the timing without using a timing light. The timing light is useless on these engines. Do it by hand and have the vacuum advance pointing between the 5th and 6th spark plug. Gotta go.....



Andrew

 

[Anonymous]

Yup, I'd guess timing too, based on my VERY recent experience (last night). My car was doing the exact same thing also with a rebuilt carb, but when I set the timing properly (it had been retarded too much), it ran amazing with the rebuilt carb (a YF).

 

[Anonymous]

Hi Baily66,

It certainly sounds like an accelerator pump issue. I think you are on the right track. How does it perform off the line. Any hesitation there. If so, take it back to NAPA and exchange it.

As for timing, changing the carb won't impact timing. If you didn't have this problem B4 the carb change, your issue is fuel related. As for setting timing by ear, I am not a supporter. You will never know where you are so you can't make thoughtful adjustments. Same with doing it with a vac gage. Your car probably has the dual vac advance dizzy, the Load-o-matic. If not set-up correctly they do not perform well. Once set-up they rarely need adjustment.

The 1100 has a history of being troublesome. However, with the 1.5" carb bore head you do not have many "stock" Ford options that can be used without a custom made adapter of some type. This is because the later carbs are all set-up for the 1.75" bore. The upgrade I would recommend is the holley 5200. However, installing same requires an adapter, some minor linkage mods, and a new / modifed air cleaner. Not difficult, but you will need to be comfortable with the process. Also, you will need to change the distributor as the dual vac will not run with any of the carbs normally used as alternate to the 1100. Again, not difficult.

Easiest fix. Exchange you 1100. Better fix, upgrade to Holley-Weber 5200 and mechanical advance dizzy (the dual advance type - not dual vac, dual advance).

If you are going to continue to play with your car (lots of fun to be had), I recommend you purchase the Falcon Performance Handbook. This is a very useful tool re: understanding these cars (Falcons and Mustangs use same drive train). Go to this sight and order the book.

http://falconperformance.sundog.net

Stay with the 1100 until you have had a chance to do some homework. Then plan your upgrades so that they build on each other. If you would like more detail on the 5200 / dizzy conversion send me a PM.

Enjoy the trip - Steve

 

[Anonymous]

Ya, Hi Bailey and Welcome ^_^
Hm, I wish I knew more about carbs and technical stuff bout engines cause I'd really like to help ppl more.

ANyways, I started wondering about the accel pump like some said, then I thought bout timing too. However, u said this dint happen w\ the old carb, that is was jus leaking right ?
Maybe the guys r right, its jus Napa and other locals arent offering quality in those rebuilt carbs., maybe u can take it back and get one of those Pony carbs ?.
I saw an ad about them in NPD, National Parts Depot catalog. I went to their site, the carbs lookt nice but it was teeny bit pricey cause of cores etc. I'd really like to jus get a head w\ the removeable intake and then buy the 4 bbl aluminum intake from PAW and go from there.

Hey barishi, howcome u say that a timing light is useless on these engines ? I mean, the marx r there but if I cant use a timing light, then how am I post to make sure its accurate ? (my engine isnt near running capability, just askin)

 

[barishiman]

Ok, as for timing without the use of a timing light here is why and how:

1st: The main reason to not use a timing light on the 200 is the harmonic balancer. Most of the time the balancer's outer ring is rubber and can bend, warp,etc... and give you false readings.

2nd: Instead of a timing light, you want to use a vacuum gauge. Take a small rubber hose and run it from the intake manifold into the gauge. If the carb is set correctly and the vacuum advance is pointed between the 5th and 6th cylinder, there should be a reading of 20 1/4 inches of vacuum at 7000 rpms in neutral or 5500 rpms in drive with an automatic tranni.

After test driving the car, if you experience spark knock or pinging, retard the distributor 1/8 in. I tried and tried a timing light on mine and I still couldn't get my engine to run correctly. After buying the Pony Carb and watching and reading the materials on installation, timing etc.... I finally got my problem solved.

This is all of from experience and going through 3 carbs until I found out the problem, half-ass rebuilt carbs and timing.


Andrew

 

[Asa]

The timing light is useless on these engines

i couldn't disagree more, the timing light isn't useless on these engines, just make your own mark, the way i do it is i remove the #1 spark plug then turn the engine till it gets to TDC, at that point, use white-out, or some other easily visible substance to mark 0 degrees (using the timing indicator/pointer as a reference), then use the timing light as you normally would
if your balancer has slipped, then from what i know it should be replaced anyways because it is a sign that it is going bad, and once that is done, then a timing light is very helpful
i might be wrong about the balancer, and what it means when it starts slipping, but i know that i've always set my timing using a light, and using the white mark as a reference point, besides, what happens if you have a vacuum leak? it causes the same problem of not being able to get the engine in time as a balancer that has slipped, but, if it works for you, go for it
good luck
evan

 

[Anonymous]

If the choke stays partially closed, it will act exactly as you describe: when you hit high throttle it will stumble and eventually regain itself and run.

Here's another clue: is your gas mileage poor?

Be sure to hook up the hot-air pipe to the choke housing, even if it is an electric choke. The electric part by itself will seldom open the choke all the way. Pre-1976 200 engines used exhaust gasses to heat the choke: 1978 and later had a fresh-air line from the air filter that went into a coil of tubing inside the exhaust manifold, then out and up to the choke. Mostly these little coils got burned away by the MTBE additives in the major cities' fuel (lower emissions, you know). Then only hot gasses would enter the later-style carbs, which were not designed for it. It usually would ruin the carb in about a year that way.

The electric chokes have a "thermostat switch" in them (actually a semiconductor) that prevents current flow until the choke reaches about 50 degrees temp. Then the current begins to flow and heat up the choke element to open it up. Without some hot air from a politician or the exhaust, the electric choke will never fully open.

 

[MustangSix]

Mark, they never used exhaust gases to heat the choke in any year. It looks like the line is plumbed into the exhaust manifold, but it is simply a heated passage that goes all the way thru and to the bottom of the manifold. Air is drawn by vacuum thru this passage and is heated by the exhaust. There is a fitting at the bottom and steel wool in the passage to filter the air. This method is also used on V8 engines.

Your assessment on the effects of MTBE additives are also incorrect.

 

[BIGREDRASA]

I've rebuilt many carbs in the past 40 years, and was having trouble playing with timing and accel pump. Whenever I put in enough timing to take out the bog, I got pinging under load at highway speeds. After installing the Pertronix unit, the problem cleared up.
By the way Andrew, are you sure you get 20 1/4" vacuum at 7000 RPM?

 

[Anonymous]

Mark, they never used exhaust gases to heat the choke in any year. It looks like the line is plumbed into the exhaust manifold, but it is simply a heated passage that goes all the way thru and to the bottom of the manifold. Air is drawn by vacuum thru this passage and is heated by the exhaust. There is a fitting at the bottom and steel wool in the passage to filter the air. This method is also used on V8 engines.

Hey, MustangSix;
Most of the Fords I have (or had) were set up like you've described, except my 390 and the T-Bird's 351W. They both use straight exhaust gases from a tapped hole in the intake crossover. Oddities, I guess, because the choke pistons (vacuum operated) stay clean until about 40k miles, then get sticky. I run a can of Gumout thru the gas and that cleans them up nicely. They don't have any steel wool containers, but I think I might make one on the outside of the manifolds - that's a good idea!

'Later,

MarkP