I have had some stumbling issues with my 292 on occasion, and in general it is not as responsive to throttle input as other carbureted engines I have fiddled with.  When I rev it by hand in park, it is like the engine sucks air for a moment and then catches up speed.  It isn't terribly slow to respond, but I know it isn't where it ought to be.

I have noticed that when I operate the throttle, the overtravel lever does not quite keep up with the throttle shaft's motion.  On other carbs I've examined (a Motorcraft 2150, today) the overtravel lever matches the throttle exactly until it reaches its stop, at which point it stays put as the throttle continues to rotate towards WOT.  If I help the overtravel lever with my finger, the pump squirts more aggressively down the barrels.  I believe this to be the primary source of my acceleration issues.

What I'm wondering is the specific source of this issue.  At first I thought there was a clog in the accelerator pump circuit, increasing the resistance to the fuel flow and thus the motion of the overtravel lever--but now I'm more inclined to think that the spring between throttle and overtravel has merely lost its oomph over 50 years. 

Has anyone ever encountered this issue?  If the spring needs replacing, where would I procure one?

EDIT:  Forgot to specify that the carb is an original '59 Autolite 2100.  I also have a Motorcraft 2150 I could rebuild and use...  it has 1.08 venturis as opposed to the autolite's 1.02 and it also has variable high speed air bleeds.  Perhaps a better option than trying to source a spring?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Your hesitation isn't from your carb, it really comes from your "mechanical timing backlash" from your crank to your points; mostly in your timing chain slop.

When a chain stretches, your cam lags (retards) from its original timing.  When you back off the gas, the cam 'leads' its original timing by as much.  Buy a good ROLLER timing chain set.  I just bought one and I am installing a 4*-offset cam key.  Advancing the cam will bring the torque curve peak to the low to mid-range, instead of the high-rpm range (that I never do around the city).

Roller timing chains don't stretch nearly as bad as original chains, which makes them last three times longer.  You can tell a roller chain; it looks like two rows of bicycle chain side-by-side.  Original chains look like 'fingers' that grow and shrink as they flex around their sprockets.

As soon as your timing is tight again, your gas pedal will feel like it's a new, responsive, engine.  Hope this helps  - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Dave:

I was wondering how the cam advances when you let off the gas.  It still has the same valve spring, distributor, and oil pump load as when you are on the gas.

Peeeot, the spring may be weak as you suggest, but it is also possible that the squirter holes are restricted or are just too small.  Try putting the squirter from your extra carb in it and see if it makes a difference.  Also, if you are trying the spare carb with no fuel in it, the pump will move faster since it is pushing air, not fuel.

John - "The Hoosier Hurricane"

I wish I had some advice to give, but I have the same exact problem.  '59 292 with Autolite 2100 and Ford-O as well.  Engine only has a few hundred miles since rebuild so I know my timing chain hasn't stretched.  I plan on doing some tinkering this weekend and will advise if I make any headway.

Newton's First Law:
An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.  Marry that with kinetic energy from high rpms.

Pistons either push the crank (power stroke with gas), or drag the crank down (all four strokes with NO gas).  Your gas pedal has no difference on your cam train, but kinetic energy does, especially when the cam is running fast.  The cam tends to remain running fast when you let off the gas, so it pulls on the crank.  In other words, the crank-drag slows faster than the cam-drag.

You can see this using a timing light.  Shine the light on your timing marks, and rev the engine to ~3,000, then back off the gas.  A worn timing chain will cause the timing mark to jump all over.  If you do it repeatedly, the timing mark looks so irratic, you will question the validity of the timing light.  Believe me, the light is telling the truth.

For optimum torque curve, ideally you want your cam advanced at idle speeds and retarded at 5,000 RPM.  An old company, Vari-Cam, used to sell a centrifugal cam sprocket that did just that.  I haven't seen them in years, so now I buy offset cam keys.  Drag racers usually retard the cam for more high rpm torque, while cruisers usually advance the cam for more low-end torque.

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

simplyconnected:  The play on my timing chain is comfortably within spec.  I checked it when I had the cover off.  While there is still undoubtably some play in it, I doubt it is the cause of this problem.  I am comparing its behavior with that of other engines that have not been rebuilt and have more than a hundred thousand miles on them, whereas this rebuild almost certainly has less than 10,000.

I still think timing could be a significant part of my problem.  I need to check my mechanical and vacuum advance adjustments again.  Also, I think my vac. advance plate is sticking a bit.  But I know the accelerator pump is putting out less volume than it should.  I know that an empty carb isn't going to provide an accurate comparison, but I was working with a full one.  When I operated the throttle by hand on that "good" carb, the fuel spray was such that it would splatter some tiny droplets out of the carb--my 2100 only squirts that hard if I hold the throttle and the overtravel lever together.  Also, I compared spring tension by pulling the accelerator pump lever away from the carb body on both carbs, and the other carbs I've checked (both 2150s) have certainly been stiffer.

Does this sound more like a restriction or a weak spring?  I can't swap venturi assemblies because my 2150 has the variable high speed air bleed assembly. 

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

It sounds like a weak accelerator pump spring.

If your accelerator pump is working properly, it should give a healthy spray.  The diaphram spring doesn't need to be real strong to return the diaphram for the next pump.  What about your check-valve ball (#39 on pg1a)?  If that's gone, the pump won't work right.

Here are some reference/setup sheets for your 2100:  (RIGHT CLICK on the links below, and choose, "Save Target As..."(fourth item down in the list), then save to your folder of choice.)

http://home.comcast.net/~simplyconnected/59Ford/Carb/59FordCarb.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg1a.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg2.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg3.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg4.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg5.jpg
http://home.comcast.net/~simplyconnected/59Ford/Carb/2100pg6.jpg

Once you save these pages, you can print whatever you like.  Hope this helps - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Peeeot.  You didn’t mention if helping the overtravel lever with your finger actually helped with your initial hesitation issues.  If it did, then all of Dave’s carb suggestions are on the mark but if that checks out, then what John suggests is also a step in the right direction.  Another suggestion is to simply drill out the accelerator pump shooter holes slightly larger to increase the initial rate of pump shot.  Shouldn’t take much as the holes are likely around 0.025” now and an increase to 0.031” will make a substantial difference.

 

If you didn’t get an improvement in throttle response when manually working the overtravel lever, then what Dave brings up about retarded cam timing comes to the forefront but a vaccuum leak could also be present.  A compression check on the cylinders and a vacuum gauge reading at the manifold will help to confirm this or at least help to isolate the cause.

Dave.  My experience has been that the link chains actually stretch at a slower rate than the roller type of chains.  I examined this in detail back in the Seventies and found that the stretch occurs specifically through the links themselves but this only applies to those applications where the link chains are actually wider than the alternative roller chain setups for the same application such as on the Y-Block or FE Fords.  A link chain in most applications simply has more connecting links between each pin thereby making the link belt type of chain more robust and less prone to stretching as compared to a roller type of chain that uses fewer connecting links between pins.  On those engine applications where the link chains and roller chains have the same number of connecting links, then the wear factor at the gears themselves becomes critical thus making a link chain the less desirable setup.  Friction or drag related to the two types of chains is a completely different topic however as the roller type of chains wins this contest easily.  And the different types of roller types of chains haven't even been touched upon here although chain elasticity has been brought up to a small degree.

Lorena, Texas (South of Waco)

Ted:

I have noticed the same thing comparing link to roller chains.  The link chain stretches, or seats in, a little at first, then lasts a long time, usually getting loose as the teeth on the sprockets wear.

Dave, I'm a little confused about your kinetic energy explanation.  Which has more kinetic energy, a camshaft with a diameter of less than 2 inches with a 5 inch timing gear on it, or a crankshaft with a spinining diameter of over 6 inches with a flywheel of 14 inch diameter with a clutch attached, or a flywheel with a 12 inch converter full of fluid, and spinning twice as fast as the cam?  The crank outweighs the cam by many, many pounds.  And you say the cam's kinetic energy is great enough to drive the crank when slowing down?  I can't get my brain to understand how that works.

I have noted spark scatter at constant rpm also, and it varies at different rpm.  I would attribute that to harmonics in the chain.  Have you ever watched a long belt or chain run?  The slack side is not a gentle curve, but rather a series of undulations.  Harmonics?

John - "The Hoosier Hurricane"