All Small Six High altitude jet size autolite 1101

[JStatic7]

Hey all,

With my idle screw turned in all the way the engine is still running rich, not entirely sure how much but I am at 15 in Hg of vacuum currently.

At my ~5,000 feet altitude I’m sure the problem is whatever stock jet is in there, and was wondering around what size you folks would recommend for jet for me.

I’ve got a milled large log head with around 9.2:1 CR and everything else is pretty much stock other than a performance exhaust system & iridium plugs.

Going to test out a few different sizes but I’d like to know the general spec before I order.

Thanks!
- J.N. from Longmont, CO

 

[DON]

What carb and engine do you have

 

[JStatic7]

What carb and engine do you have

Autolite 1101, ford 200

 

[DON]

You can try jets, but I’m kinda wondering if you don’t have another problem. 5k isn’t that high. And the turning the screw until seated is what I don’t like.
New car to you? Has it been running good previously? Done recent work on it, has it been sitting?

 

[JStatic7]

You can try jets, but I’m kinda wondering if you don’t have another problem. 5k isn’t that high. And the turning the screw until seated is what I don’t like.
New car to you? Has it been running good previously? Done recent work on it, has it been sitting?

Here’s my reasoning:

- Cars originally from California, so I’m thinking it’s jetted for sea level.
- can smell the extra gasoline in the exhaust
- just changed out the head for the large log, head great compression so no head gasket leak (which it previously had)

And probably the most important, had it way too rich with my initial settings, hooked up the vacuum gauge and as I turned the screw in the vacuum kept rising and engine running better till I seated it -> leads me to think I need to get a leaner jet so that I can lean out the mixture more than currently possible

It’s always been running rich since I bought it here in CO but haven’t had the time to fix it till now

 

[JStatic7]

Oh and the spark plugs were all black… need leaner jet

 

[DON]

What I’m thinking is the other reasons you are getting to much gas. High float level, idle speed screw turned to far in, past manifold vacuum port-making the idle screw non- functioning because it is running on high speed circuit?
5k alt should only be a size or two if at all.
We’ll see what others say….

 

[JStatic7]

What I’m thinking is the other reasons you are getting to much gas. High float level, idle speed screw turned to far in, past manifold vacuum port-making the idle screw non- functioning because it is running on high speed circuit?
5k alt should only be a size or two if at all.
We’ll see what others say….

You make a great point, I’m going to test that out right now

 

[Frank]

Oh and the spark plugs were all black… need leaner jet

Have you changed a fuel pump recently? The new overseas pumps trend to too much pressure. . . Also- the jet, if perfect at sea level, is only 15% rich @ 5000'. That of itself will not cause your symptoms. Sounds like too much fuel pressure/ float level too high.


Required jet change, 50 jet @ sea level= 46.6 jet @ 5000'.

(50x50) divided by 1.15= 2174. Square root of 2174=46.6

 

[JStatic7]

Have you changed a fuel pump recently? The new overseas pumps trend to too much pressure. . . Also- the jet, if perfect at sea level, is only 15% rich @ 5000'. That of itself will not cause your symptoms. Sounds like too much fuel pressure/ float level too high.


Required jet change, 50 jet @ sea level= 46.6 jet @ 5000'.

(50x50) divided by 1.15= 2174. Square root of 2174=46.6

Didn’t know that about the float, I’ll definitely take a look and measure it.

I am definitely not confident in the jet being perfect though, the last guy that worked on this car did not know what he was doing.

Also a 50 jet seems small, I’ve read that 67-65 is the stock jet size for these carbs?

 

[Frank]

Didn’t know that about the float, I’ll definitely take a look and measure it.

I am definitely not confident in the jet being perfect though, the last guy that worked on this car did not know what he was doing.

Also a 50 jet seems small, I’ve read that 67-65 is the stock jet size for these carbs?

I can not say what the "going" jet is, a small6 guy will have to answer that. I recommend setting the float level without any other changes and see if that cures it. Excessive fuel at idle (screw all the way in, still running, etc.) is fuel level too high in the bowl 99% of the time. Another way to verify high float level: look into the carb at idle and see if any fuel is bleeding from the main venturi or anywhere else. (A bright light helps, timing light on the coil-to-distributor wire, even better.) Any visible fuel entering the airistream at idle or very light throttle indicates an issue.

Obvious, but also verify the choke is releasing to vertical.

After verifying the choke and float level, if it's still rich fuel pressure will need to be verified.

Important checks when doing needle/seat/float: verify the float has not gotten saturated with fuel. If it feels heavy replace it. Use care reattaching fuel lines, as the smallest bit of debris can jam the needle and cause richness.

 

[JStatic7]

Ok I took a look at the float, the height between the gasket surface and the bottom of the brass float is right at 1-3/32”, maybe even a little bit closer to 1-1/8”.

For the rich idle, can we cut out the float level? Or should I try raising/lowering the float in the bowl?

Also took a rough measurement of the jet I have, it is at LEAST a 67# (around 1.72mm), couldn’t get much more accurate than that

 

[DON]

I don’t know your specific float height, but normally it is adjusted so it closes when the float is parallel to the bowel body.
Lowering it a little won’t hurt, it helps with hot soak flooding a bit, and a bit leaner.
It’s interesting your jet doesn’t have a number on it, maybe imported?

 

[JStatic7]

I don’t know your specific float height, but normally it is adjusted so it closes when the float is parallel to the bowel body.
Lowering it a little won’t hurt, it helps with hot soak flooding a bit, and a bit leaner.
It’s interesting your jet doesn’t have a number on it, maybe imported?

Something like that, it’s some remanufactured model that I rebuilt, seems to run ok.

I’m thinking my timing is way off and leaving some fuel to be unused, going to experiment with it sometime today/tomorrow. Thanks for all the messages everyone I’ve learned a lot the past two days

 

[TrickSix]

As stated above, often the jet size is stamped into the top or the side of the jet. They are small numbers and easy to miss. When I bought a rebuilt 1101 it came with a #70 jet, and when I tested it on my small log 200 it ran okay but smelled pretty rich.

 

[Frank]

Ok I took a look at the float, the height between the gasket surface and the bottom of the brass float is right at 1-3/32”, maybe even a little bit closer to 1-1/8”.

For the rich idle, can we cut out the float level? Or should I try raising/lowering the float in the bowl?

Also took a rough measurement of the jet I have, it is at LEAST a 67# (around 1.72mm), couldn’t get much more accurate than that

67 might be rich sure enough @ 5K feet. But the main jet is not responsible for the idle issue, regardless of size. What Don said above: make the float sit level with the top when letting gravity hold it in the closed position. Lowering the level to shallower than spec leans everything out slightly. In your situation it may be an effective improvement.

 

[Frank]

Ignition timing is not going to correct excessive rich idle either.

If it's still rich after the float change, going to have to check fuel pressure.

Thanks for the dialog and keeps us posted.

 

[drag-200stang]

I does not take much to make the needle and seat to leak some making it rich. With three carbs I was always chasing issues. What fixed them was putting a screw in filter directly into the carb. driving it some and then taking them apart and cleaning them with out disturbing the filter. junk will shed off the hose/line between the filter and carb if it is not directly on the carb.

 

[DON]

Holley knows the importance of fuel bowel level, on the old v8 tripower, the outboard bowels have a slightly lower sight/plug than the center bowels. I have heard it helps with hot soak but not first hand.
A little trivia

 

[Frank]

Holley knows the importance of fuel bowel level, on the old v8 tripower, the outboard bowels have a slightly lower sight/plug than the center bowels. I have heard it helps with hot soak but not first hand.
A little trivia

The best assist for hot soak is releasing fuel pressure. The old systems with a solid steel line pump-to-carb build pressure way over what the needle can hold back when static and hot. Anyway, hopefully JStatic7 finds the solution.