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I know this has been talked about in past threads, but I still have questions... I have attached a picture of my timing marks. When timing it with a light, should the timing mark be pointing to the D/C mark in the middle(center chalk line)??

My truck stutters when hitting the gas from idle. Once going it is fine. I have adjusted carb and messed with timing, but can't get rid of this stutter at initial acceleration. I'm thinking that my timing is not right.

Any help would be appreciated... Aaron

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Aaron,

When you say shudder, could you mean a hesutation or stumble? This sounds very much like a carburetor problem to me, rather than timing. With my own truck, I can play with timing all over the place and it will not hesitate on acceleration.

Here's what I would suggest you try. First, take your distributor cap off and look where the rotor is pointing. Then pull your distributor - it's just one wire, one vacuum line and one bolt - and put it in your shop vise. Suck on your vacuum advance unit with your mouth to make certain that it is not leaking and is really moving the point breaker plate. This CAN cause a hesitation if it is leaking. Then put the rotor on the distributor and twist the rotor each dirfection against the shaft, while you hold the shaft that fits down into the engine with the other hand. You should feel a strong spring pressure one way, and it should snap back the whole way with no slop or play in between. This is checking the centrifugal advance weights underneath your points. Finally, with the uinit in your vise, set the points to about .020 thouisandts of an inch. Then take your electrical meter and make certain the points are making contact electrically, before you put the distributor back into the engine. Make sure the rotor iw pointing right where it did before you pulled it out. Set the timing by eye just where it was before - not important you get it exact now. Start it up and drive it with the distribut0r loose enough that you can just turn it by hand if you force it. Try to set your timing so that you can just barely hear a faint ping or preignition on a hard pull over 40 mph in high gear, then clamp it down like that.

Now take your air cleaner off and look down into the thr9at of your carb while you manually stroke the throttle linkage from idle position to full thjrottle. If you do not see and hear a full stream of fuel squirt downwards inside the throat, you have an accelerator pump problem. This area of the carb is the first suspect when you have a hesitation or stumble on acceleration/

If you are lacking this full squirt of fuel inside the top of your carb on acceleration, the only fix is to pull the unit off and find a parts illustration in the shop manual or somewhere else that shows a stack-up of parts inside. There are several small ball checks that must work correctly for fuel to be drawn into the accelerator pump and to be discharged. Each one must be in place properly for the unit to work. Also, while the top is off your carb, find a real flat surface - like a piece of glass - and lay a sheet of 400 grit sand paper down and slide the carb top on this until it shows a shiny line all around the circumfrence, where the gtasket must seat. Finally, fill the carb bowl with fuel and try it on the bench. The accelerator pump must tive a healthy squirt each stroke. You can bend the linkage at the bottom of the piston to increase or decrease the stroke.

Report back to us what you find when you have done this. This is a test, and we are all watching! (grin).

Good Luck

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wow, i better get to work! I will let you know how it goes...

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Mr. Erb, you might need to chime in again here....

When I pulled the head last time there was what seemed to be to much carbon in the combustion chambers. Would this be a result of bad timing? Last time I used a timing light and set it to 2 deg BTDC at about 1200 rpm, hot. For the timing light method, is it necessary to disconnect and plug the vacuum advance line like on most other vehicles?

Also, where could a new distributor vacuum advance unit be found these days?

Edited by John-T-53

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Guest P15-D24
I know this has been talked about in past threads, but I still have questions... I have attached a picture of my timing marks. When timing it with a light, should the timing mark be pointing to the D/C mark in the middle(center chalk line)??

My truck stutters when hitting the gas from idle. Once going it is fine. I have adjusted carb and messed with timing, but can't get rid of this stutter at initial acceleration. I'm thinking that my timing is not right.

Any help would be appreciated... Aaron

99% percent of the time it is the accelerator pump needing to be rebuilt. Do the check Gray Beard mentioned.

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Guest P15-D24

Also, where could a new distributor vacuum advance unit be found these days?

Terrel machine was rebuilding them. Finding a replacement with "fresh" rubber is going to be pretty hard.

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Terrill Machine in DeLeon TX can rebuild the vacuum advance, they also sell fuel pump rebuild kits that replace all the gummed up innerds & rotten diaphragm. I sent my vacuum advance & mechanical distributors to Burton L. Norton in Michigan to be rebuilt. They went through and replaced the breaker plate & mechanical advance weights, rebuilt the vacuum advance, and tested with a Sun Machine to get everything within specs. It cost some $$$, but turnaround time was quick and with a little preventative maintenance oiling & cleaning, they have operated well in the past 10 years.

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99% percent of the time it is the accelerator pump needing to be rebuilt. Do the check Gray Beard mentioned.

Sorry if this is a stupid question, but which part is the 'accelerator pump'??

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Okay Gents, a little clarification is in order here.Fiirst off, initial timing is always set at slow, hot idle - NOT at 1200 tpm. This is necessary so that the centrifugal advance weights under the breaker plate in your distributor do not begin to come out and add additional advance. If you set your timing at speeds above slow idle, you are likely getting some centrifugal timing in the mix, which will affect the reading of your timing lighr.

Timing on our flatties is important but not real critical. You want as much advance - turn the distributor counter clockwise to adance - as the engine will tolerate without preignition. Usually this boils down to four to six degrees before top dead center. Too much advance, and you get pinging. Too little advance, and the engine runs hotter, burns more fuewl and has less power.

As to identifying your acceleragor pump. you really must find a shop manual to know this stuff. It shows a break-down of each part and each circuit. Our Caarter carbs are quite simple and easy to work on, but they must be right to work as they should.

I won't attempt to explain the entire carburetor, except to say that at idle, the engine uses the circuit that you adjust with the small screw on the lower side that has a spring behind the head. At higher speeds, the idle circuit is no longer working and the main metering circuit is used. This includes the main jet in the bottom of the fuel bowl and the vengturi cluster in the carb throat.

When you accelerate from idle to higher speeds, a hesitation will take place between these two circuits. The accelerator pumop is just a squirter that richens the mixture momentarly on acceleration. Nothig more, nothing less.

Terrell Macchine rebuilds old vacuum advances. Bernbaum and Roberts also carry these new. Either way, they are spendy - like $65 to 75 a pop.

Good Luck

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I prefer to do the tests in an opposite sequence of greybeards . Do the accelerator pump test first. Vacuumn advance can be checked on the vehicle with the same method as greybeard without pulling the dist. The accelerator pump works the same way as a pump bottle of glass cleaner does. You should see a spray of gas in the center of the carb when opening the throttle by hand as you would with your foot

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Well, I pulled the distributer and found right away that the vacuum advance does not work. Sucking on it is like sucking on a big fat straw, there is no resistance...

Sounds like Terrell Machine in Deleon Tx, is the place to send it for re-building? Any other suggestions?

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Called Terrill Machine this morning and sending them my vacuum advance pot for rebuild. They want $75 plus shipping and handling and will have it back to me in 2-3 weeks. Wish the turn around was quicker, but...

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I thought I had my rotor marked so I knew which way to put the distributer back in, but now my truck won't start! I have not done a lot of investigating yet, but how many ways can you put the distributer back in? the end that goes in the engine is flat, so it must only go in 2 different ways, right? am I making sense?

If I put the distributer in the wrong way, what do I do now?

Aaron

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I thought I had my rotor marked so I knew which way to put the distributer back in, but now my truck won't start! I have not done a lot of investigating yet, but how many ways can you put the distributer back in? the end that goes in the engine is flat, so it must only go in 2 different ways, right? am I making sense?

If I put the distributer in the wrong way, what do I do now?

Aaron

Yes it should only be able to fit in 2 ways but all that slot on the bottom is doing is running off the oil pump, so when your inserting the dist. you can actually move it and then be out a few teeth before it placed right down. You might be best now to start from scratch and set the #1 cyl to TDC and then put the dist in with the rotor in that spot.

MY biggest question is, how come my 50 and 51 have NO vacum advance? Never seen a dist like it before, but I always worked on newer stuff, so this is all a little strange now.

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My 36 Plymouth has a vacuum advance, but the 49 1 ton does not, but my 53 parts truck has the remnants of 1. Weird! Mike

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A vacuum advance serves primiraly as a boost to fuel economy. It adjusts distributor timing based on throttle position.

Most all industrial applicaion distributors as well as several truck distributors do not have a vacuum advance. Industrial engines normally run at a steady governed speed so a vacuum advance would do no good. My best guess on trucks is they are designed to pull heavy loads and the throrttle would be wide open more than not. So the factory elected to not use a vacuum advance on these vehicles.

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Yes it should only be able to fit in 2 ways but all that slot on the bottom is doing is running off the oil pump, so when your inserting the dist. you can actually move it and then be out a few teeth before it placed right down. You might be best now to start from scratch and set the #1 cyl to TDC and then put the dist in with the rotor in that spot.

MY biggest question is, how come my 50 and 51 have NO vacum advance? Never seen a dist like it before, but I always worked on newer stuff, so this is all a little strange now.

So all I have to do is set the #1 cyl to TDC and then which way does the rotor need to point?

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So all I have to do is set the #1 cyl to TDC and then which way does the rotor need to point?

Needs to point to the #1 spark plug wire in the distributor cap. If you oil pump was indexed per the book the #1 plug wire should be somewhere around the 7:00 OClock position when the engine is at TDC.

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Follow your wire from the #1 spark plug to the distributor cap and that's where it should point.

I believe the usual location for #1 on the distributor is in the 7 o'clock position, but it could also be at 1 o'clock if your distributor shaft is rotated 180 deg.

Edited by John-T-53

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Follow your wire from the #1 spark plug to the distributor cap and that's where it should point.

I believe the usual location for #1 on the distributor is in the 1 o'clock position, but it could also be at 7 o'clock.

Don't want to mess him up...it can't be both, or shouldn't be. Check the online manuals for the tune-up section, should tell you where things should be.

Now as for me...I'm HOOOOOPED! I have no marks on my flywheel anymore...looked real hard and even used some steel wool...their just not there...so I have to try and find zero by going inbetween TDC on #1 and BDC(?) on #6

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That's strange. There is no wear on the outer flange of the flywheel so the marks should not be worn down. Unless the flywheel has been replaced with some generic wheel, the marks should be under several coats of paint. Marks are not that deep so it would be easy for them to be filled in over time.

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You guys are talking about the crankshaft pulley right?

Those marks are pretty shallow, and are easily concealed by rust and paint.

Turn the engine by hand so #6 is at TDC (remove the small pipe plug in the head above #6 and insert an 8" straight piece of coat hanger wire and watch its movement up and down), then try some paint stripper or 220 grit sand paper in the area under the pointer on the pulley. The marks should be down there somewhere.

That's strange. There is no wear on the outer flange of the flywheel so the marks should not be worn down. Unless the flywheel has been replaced with some generic wheel, the marks should be under several coats of paint. Marks are not that deep so it would be easy for them to be filled in over time.
Edited by John-T-53

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Well I can see them plainly on my 51 motor..so that's why I say their missing on my 50...I cleaned...no marks. I think Jim is right, someone changed the wheel and didn't put lasting marks on it.

But I may just switch over to the other pulley, but mine is the (232?) and the other is the 218?...so don't know if that will work or not.

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Well, like I said before, put my rebuilt vacuum pot back on the distributer, put the distributer back in and now can't get the truck to start! I checked and i have spark. Any ideas as the truck started good before I pulled the distributer!

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Well, like I said before, put my rebuilt vacuum pot back on the distributer, put the distributer back in and now can't get the truck to start! I checked and i have spark. Any ideas as the truck started good before I pulled the distributer!

Your either out 180, or just far enough out that your not anywhere near correct or useable timing. I would get a helper and just have them crank while you SLOWLY turn the distb clockwise and counter.

Did you set things back to TDC or just try where you removed it? There are 2 bolts to loosen for maximum adjustment (at least on mine), the one that holds it to the bloack and one underneath...you may need to loosen both to get enough adjustment to find a starting point.

If you have a timing light see if your even anywhere near the marks when it flashes...if it seems WAY off you might be out a whole revolution.

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