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170 rough acceleration, unless choked.

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63RancheroGuy
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170 rough acceleration, unless choked.

Post #1 by 63RancheroGuy » Tue Jan 05, 2010 3:38 pm

Hi folks,

My '63 Ranchero has a stock 170, 1100 L-O-M carb, 4-speed manual trans, pertronix I ignition, new plugs gapped to 0.040", new rotor, new cap, recently replaced accelerator pump diaphragm. I live at about 200 ft elevation if thats pertinent.

The problem is after she warms up, I can open the choke all the way (push the knob all the way in) and it will idle fine at about 850 rpms (is this too high?). But from a stoplight, it will accelerate but roughly - almost stuttery like its missing. However, if I begin to close the choke just a little, say I pull the handle about 1/8-1/4 of the way out which just barely moves the butterfly, it kicks the idle up a tad (to about 1200ish), and then there is smooth acceleration, no sign of trouble. If I push the choke in just a bit, the idle speed decreases a little and the roughness starts to appear but not as bad. The roughness only appears on acceleration, if I just pick a speed and cruise along - no trouble.

The pertonix ignition is fairly new, but the roughness problem was present before the new ignition. After the ignition, the engine does run smoother than before but the roughness on going fromt stand-still up to cruising speed feels about the same.

I don't know if its related but another issue is if I'm cruising along with the choke all the way open, and I take my foot off the gas to decelerate, the exhaust sounds like a motorcycle: "Brap-brap-brap-brap" for lack of a better explanation. But, with the choke-knob in the slightly pulled out position, it makes no such noise on deceleration.

I'm actually fine with driving with the choke out just a tad, but I figure I shouldn't NEED to, y'know?

Any thoughts on diagnoses or diagnosing this problem?

Thanks in advance.

Adam
Last edited by 63RancheroGuy on Tue Jan 05, 2010 4:15 pm, edited 1 time in total.

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Re: 170 rough acceleration, unless choked.

Post #2 by ludwig » Tue Jan 05, 2010 3:40 pm

If you yoke it down with the choke, however slightly it might be, you are leaning it out. There is an A/F mix problem.
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Re: 170 rough acceleration, unless choked.

Post #3 by 63RancheroGuy » Tue Jan 05, 2010 4:24 pm

Hmm... Someone will have to explain that to me. I was thinking that pulling the choke knob out a little would make the mixture richer. Here's my (apparently wrong, and not the first time for sure) reasoning: the butterfly closes a bit, which restricts the space for incoming air. The cylinders still want to draw the same amount of air which has to move through a smaller opening which makes the incoming air have to travel faster. Faster moving air exerts less pressure, less pressure means it would suck more fuel.

If choking it a bit creates a lean(er) condition, can I adjust the float down a little? Would that lean it out a bit?

Now that you say that, it does help explain why the old plugs had some carbon build-up. I was thinking it was because I had been making it too rich with the choke, but that would explain that was running too rich all the time.

Thanks.

Adam

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Re: 170 rough acceleration, unless choked.

Post #4 by ludwig » Tue Jan 05, 2010 4:53 pm

You're right. Busted my over hasty trigger finger. It richens it. What is still true is that it needs adjustment of the A/F mix.
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Re: 170 rough acceleration, unless choked.

Post #5 by rbohm » Tue Jan 05, 2010 7:44 pm

8) try raising the float level a bit, about 1/64", and make sure the accelerator pump is working properly.
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Re: 170 rough acceleration, unless choked.

Post #6 by 63RancheroGuy » Tue Jan 05, 2010 10:15 pm

Accelerator pump is working properly, I get a good stream of gas shooting in when I press the throttle linkage.

I'll adjust the float level and see how that goes.

Adam

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Re: 170 rough acceleration, unless choked.

Post #7 by 63RancheroGuy » Wed Jan 06, 2010 12:48 am

While I'm at it, what is the factory spec float level and how do you measure it? I'm assuming you pull the top of the carb off, and then flip it upside down so the needle (and float) are seated, and then you measure from where the gasket sits to where?

Adam

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Re: 170 rough acceleration, unless choked.

Post #8 by jamyers » Wed Jan 06, 2010 12:59 am

before you take the carb apart, try re-setting the idle mix screw - prolly end up backing it out maybe a half-turn is my guess.
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Re: 170 rough acceleration, unless choked.

Post #9 by CobraSix » Wed Jan 06, 2010 9:54 am

Lud, you were right kinda...he was correcting a lean condition by richening the mixture.

I would check your idle vacuum and spray down the carb base gasket with starter fluid. If you hear the idle pick up, then you have a vacuum leak at the base. You should be getting at least 15inHG.

Also, double check your timing. I wonder if you aren't running a little retarded based on the exhaust note.

Recheck your idle mix.

Try doing some hard acceleration with the choke engaged. If it doesn't have problems, I doubt your fuel float is the issue.

Otherwise, your carb may need a fresh rebuild as one of the ports (probably the power circuit) is clogged.

With the new Ethanol mixed fuels, it is vitally important for these old cars that don't get driven regularly, to have fuel stabilizer. Ethanol has a REALLY BAD habit of falling out of suspension in gas and collecting water which then creates a nice gel in fuel systems and is particularly bad in carbs which don't use a lot of fuel pressure to move fuel. It also causes havoc on 2 stroke outboard marine engines that aren't used often. I had this happen with my Holley. All of a sudden one day, the idle circuit got clogged and I could only keep the car running by keeping the car rev'd above 1600RPM which kept it in the cruise circuit, though a little lean with the lack of the idle circuit adding.

Your idle is a tad high. Should be around 600RPM for a manual transmission (unless the Falcon is different). But that is something I have a hard time rectifying with the other symptoms. Usually high idle is caused by advanced timing and/or high idle mix. That's why I don't think your idle mix is the problem.

Try this test when you get a chance. Get the car over 2000 RPM, warmed up, and disengage the choke. Keep it over 2000 RPM and try accelerating hard. If you are still having problems, my guess is the carb needs to be rebuilt because that would usually indicate a clogged power circuit.

Got a spare 1100? swap it and see if the problem persists.
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Re: 170 rough acceleration, unless choked.

Post #10 by 69.5Mav » Wed Jan 06, 2010 10:17 am

Beofre doing anything else, first check your fuel filters. On such an old car you could have alot of junk in the tank and if it gets stirred up it could plug the tank filter or the carb filter.

Check the carb filter by removing it and blowing through it in both dirrections. You should feel very little restiction.

The tank filter is much harder to check. You can use a compressed air line to blow back into the tank to dislonge any debree on it. Other then that you would most likely have to remove the tank to remove the filter from the tank. Do this last.

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Re: 170 rough acceleration, unless choked.

Post #11 by CobraSix » Wed Jan 06, 2010 11:04 am

Or attach an inline pressure gauge between the carb filter (or pump filter depending on the year), and check the pressure. IIRC, it should be around 7psi.
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Re: 170 rough acceleration, unless choked.

Post #12 by 63RancheroGuy » Wed Jan 06, 2010 11:27 am

Thanks for the good ideas guys -

Where do you measure vacuum on a L-O-M carb? It seems like, at idle, I shouldn't be getting any vacuum to the distributor so where do I "plug" the gauge in?

Timing is spot on, if my balancer is correct, I need to verify TDC - I will do it this weekend.

I have sprayed starter fluid around the carb while she's idling and the only point where I notice any change is near the back of the carb, near the choke shaft - but I think the gases were being sucked up past a bad gasket at the base of my air cleaner. Or is the choke shaft a likely place for an air leak? I need to get a can of starter fluid with a straw so I can be more precise with my aim. I'll do that this weekend too.

Thanks again,

Adam

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Re: 170 rough acceleration, unless choked.

Post #13 by CobraSix » Wed Jan 06, 2010 1:43 pm

Adam,

I think you may have found part of the problem (if not the whole thing).

It will be tough to measure vacuum with LOM 1100 unless you have a base plate with a vacuum port. But the spray down showed a vacuum leak, which is all the vacuum test would have done.

Just gotta do like me...keep a spare carb in the garage to swap out.
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Re: 170 rough acceleration, unless choked.

Post #14 by 63RancheroGuy » Wed Jan 06, 2010 4:34 pm

You got a spare one I can put on my shelf - or bolt on my engine? J/K. :) I'll post something in the wanted section.

I haven't got a vac port on my base plate, so no luck there. I need to pinpoint the exact location of the leak - beacuse my suspicion is that it is just sneaking up into the air cleaner and down into the carb - which shouldn't cause any trouble. I'll let you know.

If there was a leak at the choke shaft - would that cause a lean condition? I didn't think a leak above the venturi would lean it out...but I'm learning something from you guys everyday as I'm lurking.

Regards,

Adam

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Re: 170 rough acceleration, unless choked.

Post #15 by ludwig » Wed Jan 06, 2010 4:59 pm

If there was a leak at the choke shaft - would that cause a lean condition?


The choke shaft is above where the fuel enters the carb throat.

The other thing you can do to check for vac leak is to squirt WD 40 here and there. When it plugs the hole, the idle will level out. Use the straw.

You can also plug the vac port on your base plate and measure the vacuum somewhere else. The vac tube at the distributor is not the place. In my Mustang there is a 3 way nipple off the side of the log with several vac ports for auto tranny modulator, power brakes and something else I don't have. That is where I check my vacuum level. The carb port varies more sharply due to the changing throttle position and the air velocity in the throat.
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Re: 170 rough acceleration, unless choked.

Post #16 by rbohm » Wed Jan 06, 2010 6:41 pm

8) and as i have pointed out in the past, dont forget the gasket between the log and the carb adapter. too many of us forget that gasket when we are looking for problems.
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Re: 170 rough acceleration, unless choked.

Post #17 by Frankenstang » Wed Jan 06, 2010 8:11 pm

ludwig wrote:
If there was a leak at the choke shaft - would that cause a lean condition?


The choke shaft is above where the fuel enters the carb throat.

The other thing you can do to check for vac leak is to squirt WD 40 here and there. When it plugs the hole, the idle will level out. Use the straw.

You can also plug the vac port on your base plate and measure the vacuum somewhere else. The vac tube at the distributor is not the place. In my Mustang there is a 3 way nipple off the side of the log with several vac ports for auto tranny modulator, power brakes and something else I don't have. That is where I check my vacuum level. The carb port varies more sharply due to the changing throttle position and the air velocity in the throat.


Yup, and as you suspect a slight leak around the 'choke' plate shaft (not throttle plate shaft) should not be an issue. The two small pin-shafts that retain the air breather mount are also a loose fit.

This pic has an arrow pointing to the vacuum access on the log Ludwig mentioned, and is usually the best place to measure/set timing by vacuum...mine just has square head plug in that location (manual tranny & no power brakes).
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Re: 170 rough acceleration, unless choked.

Post #18 by james singleton » Thu Jan 07, 2010 2:51 am

Adam, I wrote a reply earlier this afternoon, but evidently it did not go through. Back a year or so ago I installed a 'rebuilt' autolite 1100 carb (that came off of a 63' Fairlane) on my 66' - 200cid engine (with manual trans.). When I first installed it I started with the fuel mixture screw turned out 1 and 1/2 turns (which is a normal starting point for many carbs), and the only way I could keep the engine idling was to do exactly what you are doing. I had to adjust the idle to at least 850-900 rpm, and also keep the choke partly closed for more gas. What I found out, after checking the spec's on my carb (which like I said was off a 63' Fairlane) is that the fuel mixture screw is suppose to be turned out approximately 3 and 1/2 to 4 turns instead of 1 and 1/2 turns. It made all the difference in the world with my carb (and engine) and has been running fine ever since. This may not be your problem, but I thought I would throw this out there since it appears we both have 'stock' Autolite 1100 carbs from 1963; both with manual transmission! Good luck! Jim

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Re: 170 rough acceleration, unless choked.

Post #19 by CobraSix » Thu Jan 07, 2010 8:32 am

I'll see...I have so much stuff sitting on the shelf in my garage, I'll see what's lying around. I know I have a few 2100s, a rare Holley 2V carb (forget the number), and I think an old YF and an RF. Not sure if I got rid of all my 1100s or not. I know I sold the Pony Carb 1100, and got rid of 3 when I sold the Offy set up.
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Re: 170 rough acceleration, unless choked.

Post #20 by 63RancheroGuy » Thu Jan 07, 2010 10:25 am

Jim -

That is interesting. Right now I'm idling right around 850-900, and my idle mixture screw is at about 1 1/2 to 1 3/4 turns out, just like you.

Were you able to get it to idle down to 600 with the mixture screw open to 3 1/2?

Hmmmm....Well, there's something else to try. It would be nice if that was all it took.

Thanks,

Adam

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Re: 170 rough acceleration, unless choked.

Post #21 by CobraSix » Thu Jan 07, 2010 1:46 pm

I can't remember when the LOM starts to activate the vacuum port, but isn't it around this? It can be that once you fix the fuel mix, you may have to adjust your timing.

It is also possible to have the timing too far advanced which would increase idle speed. I remember this happening to me a few years ago. I would adjust the carb, timing would be off, then adjust timing and carb would be off again.

Not saying that's it...but it may be worth dialing the timing back to see, especially if you aren't 100% sure your timing mark is spot on.
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Re: 170 rough acceleration, unless choked.

Post #22 by james singleton » Fri Jan 08, 2010 3:51 am

Adam, to answer your question: 'Yes', I was able to get the idle rpm down around 550 to 600rpm, give or take. If I am not mistaken, you need to back off the idle speed to where it is not even making contact, and adjust the fuel mixture screw first to the approximately 3 to 4 turns out; and then adjust your idle rpm after you have set the fuel mixture screw. It may be necessary to have the idle screw set at very low rpms in order to keep the engine from stalling possibly (?), but I definitely would start by having the idle screw all the way out on your first try. I got this info/specs' from an older Manual that my Dad had given me many years ago. I found on a website (I believe it may have been from 'The Carburetor Doctor'?) that the number on my Autolite 1100 carb (#C3OF-9510-A) was from a 1963 Fairlane with a 170cid engine with a standard transmission. The Manual says for this particular carb, that the "Mixture Screws Turns Open" should be 3-4 turns. If you get a chance to check the # on your carb, I will cross reference the number for you to the numbers that my Manual has listed for 1963; they show about 9 different numbers for a single barrel; some of them for the 144cid engines, one for a 200cid engine, and the rest are for the 170cid engines (not counting the V-8's). Good Luck; let us know what you find out. Jim

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Re: 170 rough acceleration, unless choked.

Post #23 by 63RancheroGuy » Mon Jan 11, 2010 11:04 am

Hi Gentlemen,

I did verify that the TDC mark on my balancer is dead-on. I used the "bust up an old spark plug and put a clear vinyl tube into it to make a manometer" method - and verified that indeed the mark is right on. My static timing, vacuum removed from distributor, is set at 6* BTDC.

That's all I got to this weekend. Didn't have much extra time, as I discovered that water has been seeping in from the bed into the cab - so I spent most of my available time pulling the carpet up and trying to get it dried out and sealed. Luckily there isn't much rust...yet <SIGH>.

Thanks for all the help so far, I'll update as I'm able to try more of your ideas.

Adam

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Re: 170 rough acceleration, unless choked.

Post #24 by rbohm » Mon Jan 11, 2010 1:02 pm

8) since you have verified your timing marks, set your initial timing to 12 degrees initial rather than the oem setting of 6 degrees.
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Re: 170 rough acceleration, unless choked.

Post #25 by 63RancheroGuy » Tue Jan 12, 2010 10:11 pm

Quick update -

Adjusted my timing up to 12* BTDC and then I adjusted my idle down to 590-610 rpm by, as Jim suggested, cranking the idle control screw down until it didn't make contact and then back up just a little, I did this slowly as I turned out the idle mixture screw. It took about 20 minutes to get it right. When I was finished, the mixture screw was out about 3 1/2 turns - good call Jim. The idle's so low now that I feel like it's going to die when I stop because I'm not used to the quiet :)

I haven't tested the acceleration yet - tomorrow on the way to work maybe :)

I was looking at my accelerator pump - is there anything to adjust other than just the "hi/low" cam on there? On my old pickup the accelerator pump wouldn't do anything for the first "inch" or two of gas pedal depression - but on the engine in question it squirts with any movement of the throttle...is that normal?

Thanks again guys -

Adam

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Re: 170 rough acceleration, unless choked.

Post #26 by james singleton » Wed Jan 13, 2010 3:14 am

Adam, glad to hear things appear to be going better. As far as setting the "Fast Idle" adjustment, my manual gives a 'fast idle rpm' of "1500" for a 1963 6-170 standard transmission. It has this note as far as setting the fast idle rpm: "WITH IDLE SPEED AND MIXTURE PROPERLY ADJUSTED AND WITH ENGINE AT NORMAL OPERATING TEMPERATURE, PLACE FAST IDLE SCREW ON KICKDOWN STEP OF CAM. THEN ADJUST SCREW TO THE R.P.M. SPECIFIED" (in this case 1500rpm). Hope this helps as well. If you are going to open up your carb to check 'Float Level', or need the 'Dashpot Setting', etc., let me know and I will write the notes given in the Manual for these settings. Good Luck, James

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Re: 170 rough acceleration, unless choked.

Post #27 by 63RancheroGuy » Wed Jan 13, 2010 5:03 pm

Which is the 'fast idle screw'? Mine is manual choke - I'm thinking it might not have one? Does anyone have a pic or diagram?

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Re: 170 rough acceleration, unless choked.

Post #28 by james singleton » Thu Jan 14, 2010 2:11 am

Adam, I forgot you have a manual choke on your carburetor. Yes, I believe you are correct in that the 'fast idle setting' is for an automatic choke. Sorry about that. I also noticed from one of your previous posts that you were inquiring about the "Float Level". My Manual (for the 63' 6 - 170 Standard Trans - Carb) shows a "Dry Float Level - of 1 inch"; which is measured with the top of the carburetor removed and held upside down as you mentioned in your earlier post. They show a 'float level' of 1" w/rubber float, and 1 and 3/32" w/metal float on the "Carburetor Doctor" website. Try the 'Carburetor Doctor' website (http://www.carburetor.ca/carbs/tech); you can click on the following: Carbs Parts Index,....then click on the 1100 series..., then click on "Here" under the 'Manuals Section' and you should be able to get a lot of good information on rebuilding the 1100 carb, along with pictures included. Hope this helps? I know it helped me a lot when I was rebuilding my carburetor. Good Luck, James

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Re: 170 rough acceleration, unless choked.

Post #29 by 63RancheroGuy » Thu Jan 14, 2010 12:35 pm

Update -

So I've driven it a few days now. The acceleration roughness is unchanged with the choke fully pushed in. Pulling the choke out a little fixes this problem, as before.

Sprayed down the carb and all gaskets and I'm pretty sure the spray is just going in through the choke shaft and that's the only area where there is any leakage I can detect.

CobraSix - I think you are on the money with your power circuit identification. As you suggested I got it up to around 2000 rpm (no tach so it's an estimate) and pushed the choke all the way - stomping on the pedal causes definite roughness. It does accelerate but not as responsively or as smoothly as if I had the choke pulled open just a bit. With the choke pulled just a bit - it's fine. So, I think I'm in the market for a new carb - or maybe a full rebuild to see if that helps.

Deceleration in gear from high rpm still causes some ridiculous exhaust noise - so I try not to do that, usually put it in neutral first.

James - thanks for that info, that site is awesome and will definitely come in handy as I work on the carb.

Thanks for all the helpful ideas.

Adam

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Re: 170 rough acceleration, unless choked.

Post #30 by CobraSix » Thu Jan 14, 2010 3:58 pm

The deceleration pooping can be caused by the lean condition being caused with a clogged circuit. Your engine is drawing a large vacuum but getting even less fuel than it should get under normal engine braking.

I'd just rebuild it. Not hard. Or do like I do. Buy a new carb, swap it out and keep the other as a spare. Rebuild it when you get the chance. Swap carbs every few years.
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