Hesitation upon accelerating.

Lots of good advice here. I just want to add that you should also check the point gap or dwell. Most new points are pretty much chinese junk and the rubbing block goes away pretty fast before it gets seated in.
Is the hesitation happening when the engine is warmed all the way up? It might be wrong to assume they cleaned the heat crossover out good when they rebuilt the engine.
 
Good Sunday evening everyone,

Since so many were so kind as to offer up suggestions and point me in the right direction, I wanted to make sure to give an update because I didn't want folks to think nothing has happened with this issue, or think I got it corrected and didn't reply because I don't operate that way!!

Anyhow, here's the latest.

With Christmas coming on, I have been kind of ******* with that and work so the only thing I have done so far is replace the accelerator pump cup. I figured that was an easy place to start first (at least for me)..

I did that last weekend and it did not change anything. The car still has the hesitation and backfire up through the carb.

It still runs good going down the road but it's getting where now once it been driven awhile and warms up, it wants to die when you come to a stop such as a traffic light or stop to turn, etc, when you start to take back off.

Fires back up and runs good down the road again. Also when you start to take off from a stop, the hesitation is like it is bogging down and if you play with the foot pedal, it seems to choke out.

So, the next thing is to check and possibly advance the timing as earlier suggested, and to check the vacuum advance to make sure it is working properly.

I will also have my mechanic check the mixture with a vacuum gauge to make sure things are in check there too.

I am really hoping to get this issue found and corrected because I love to drive my car and it runs too good to have this problem.

Once it's fixed, I will post the findings.

Kevin
 
All probably good advice here, but I think you have two problems going on. Popping through the carburettor in my experience can only happen through a sticking inlet valve and the hesitation is usually due to a poor accelerator pump. I agree with West Coast earlier.
 
I had the same problem, I adjusted my timing after I set the dwell , I set my timing by vacuume gauge to 18 to 22 inches, I am at about 1200 feet above sea level ,It seemed as though the intake fuel air was a little slow to move especially in cold climate, problem solved she starts good when warm and no clatter on acceleration,I later upgraded the dist. to a 57 model with vac. and cent.
advace the old 292 is happier than a new rolls royce . a lot more pep and better milege to boot!
 
So Rick,

Your telling me that you believe a newly overhauled engine has a stuck intake valve? If it did, wouldn't the engine run bad all the time ort at lease have a miss while running?

Kevin
 
Well, it looks like about every possible item has been covered, but you still have the problem. I had the same problem 30 years ago, with a 4160 Holley, on a 312. Turned out it had been shipped with jets 10 sizes smaller than the book said. With all due respect to the carb rebuilder, and the changes in fuel since then, I'd be looking at the plugs for color, and the main jet sizes. You can't cover a lean motor on acceleration with the pump. Today's EFI motors run with the plugs nearly white, but back in the day we needed light to medium brown. I had a big bog, then as the power valve opened, it came back, and ran ok. But after a run down the road, neutral, pull a plug, it was dead white, not light brown. Changed jets, problem solved. Then, I had to undue all the pump changes.

Actually, I did the math wrong. It was more like 45 years ago. Hell getting old.
 
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You mentioned working with the accelerator pump. Did you change the hole by throttle plate to adjust the pump stroke? Generally the "summer" setting is in the hole closest to the throttle shaft. The outer hole is the "winter" setting and provides a longer stroke.
 
Kevin, to have popping in the carby, the fuel has to be exploding when the inlet is open. The only way that can happen is with a stuck exhaust valve. Sometimes with v8s it is hard to pick up one cylinder not firing. You may not even feel the miss. The exhaust gas ignites the incoming induction charge.
You didn't "overhaul" the engine, someone else did and who knows what they did. It is easy to check if it is a valve, just lift the rocker covers. There will probably be a pushrod sitting in the valley.
It is a common problem with yblock engines and the lack of lead in today's fuels and tight valve guides.
A friend of mine shipped a car from the states with a freshly rebuilt engine. Hadn't been run for about 6 weeks and 2 valves stuck open shortly after he first started it. Might run okay the first time you start it, get hot and then stick open. Makes a good case for leaving out valve stem seals.
 
It has been my experience when a valve starts to stick it will do it at high speed as well as r.p.m increses, one thing i do is add marvel mystery oil to the fuel , some of the replacement valves are stainless and when runnig in a cast iron guide tend to stick a little, I started using phosphur bronze giude bushings and m.m.o.in the fuel to compensate for the newer fuel blends we are using today.I have seen a lot of this in the flathead with stainless chevy valves in cast iron guides.
good luck,
Fordestes,
 
Hey guys,

A sincere THANK YOU!! for all the good advice. As mentioned, I still plan to do all the checks as suggested, I just haven't gotten to them as of yet but will soon.

The reason I questioned the sticking valve on the new engine is because I only have the hessitation / stumbling upon acceleration. Driving down the road the engine performs great.

Once I get the other things checked out, I will reply back with what was done.

Jim,

When I put the accelerator pump back in, I am not sure and will have to look, I put the screw back in the same hole and I am thinking the bottom one but will have to look again.

Thanks again everyone!!

Kevin
 
rick55 said:
Kevin, to have popping in the carby, the fuel has to be exploding when the inlet is open. The only way that can happen is with a stuck exhaust valve. Sometimes with v8s it is hard to pick up one cylinder not firing. You may not even feel the miss. The exhaust gas ignites the incoming induction charge.
You didn't "overhaul" the engine, someone else did and who knows what they did. It is easy to check if it is a valve, just lift the rocker covers. There will probably be a pushrod sitting in the valley.
It is a common problem with yblock engines and the lack of lead in today's fuels and tight valve guides.
A friend of mine shipped a car from the states with a freshly rebuilt engine. Hadn't been run for about 6 weeks and 2 valves stuck open shortly after he first started it. Might run okay the first time you start it, get hot and then stick open. Makes a good case for leaving out valve stem seals.
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The popping through the intake on acceleration is a classic sign of a lean backfire. There could be more to it than just the accel pump piston. There is a check ball, discharge needle and sloppy linkage that could be the problem. You need to look behind the choke plates (although difficult), and see if you get a pump shot as soon as the throttle is moved.
If that is not the problem, then need to consider ignition and timing.

A stuck intake valve would not just pop only on acceleration.

Sal
 
"When I put the accelerator pump back in, I am not sure and will have to look, I put the screw back in the same hole and I am thinking the bottom one but will have to look again."


There is only one threaded hole in the pump rod for the screw you mentioned. The hole above it is a vent hole for the hollow pump rod, with another hole at the top of it inside the carb. The adjustment for the length of the stroke of the pump is different holes in the throttle lever. Closer to the throttle shaft is for shorter strokes, and further away from the throttle shaft is for longer strokes.

Sal
 
Thanks again everyone, and Sal!!

I agree what your comment on the valve stuck. If that was so, I would think I would have issues while driving too.

I spoke to my mechanic friend tonight and he agrees that a timing issue will cause the problem I am experiencing so he is going to do the checks on the car soon and I will respond back.

Thanks again!!

Kevin
 
Just so you know, on the accelerator pump holes, the shorter stroke = more pump shot; longer stroke = less pump shot; shorter stroke being closer to the fulcrum.
 
Good Thursday evening everyone!

Well, I think my 56 may finally be lined out so I thought I'd respond with an update since so many were kind enough to offer up suggestions.

I know a top notch mechanic who owns his own business and is a true mechanic. He hasn't worked on too many 56 292 engines, but between these replies, my 56 Ford Car Shop manual, and talking to Mike Suter on the phone, he was able to identify the issues and get the car dialed in.

Here's the issues he found and fixed. Keep in mind the person I bought this car from told me the engine had been rebuilt 250 miles before I bought it.

First, the timing was way retarded which explained the backfiring in the carb when the car was hesitating and stumbling.

JT (the mechanic), using a timing light and vacuum gauge, got the timing set at 10 degrees initial timing with total of 36 degrees.

Next, in the short time I have owned the car, there was a pretty loud tapping in the right head so JT looked into that and found the valve lash to be wrong, and there was still built up carbon around the valve at the rear of the right head and due to that, the back valve was not getting oil and was starting to guald.

I am glad he decided to look into that because I would really be ticked off if the engine would have dropped that valve. He got the valve lash set up properly at .021.

He also got the carburetor mixture screws set properly using the vacuum gauge as per Mike Suter instructions.

Another thing he did was to move the fuel line up off the intake manifold some to keep the potential of vapor lock down.

The car runs so good now I can hardly believe it. There is still and ever so slight hesitation but Mike suggested that the spark plugs could be too cold so I am going to try some Autolite 46's in it and see if that helps. Even if it don't, I can live with the ever so slight hesitation because it's barely noticeable now.

At the end of the day, I have spent an additional $1,000 on this car that supposedly had a rebuilt engine. The largest cost was to fix oil leaks that it had recently, including replacement of the rear main seal.

When the pan was pulled off, there was still sludge in the pan. And now with the discovery of carbon build up still in the heads, I am having a difficult time believing the engine was rebuilt, even though the previous owner provided an invoice for a complete rebuild.

I called the machine shop that did the work in the invoice (Magnum Machine in Chesapeake, VA), and told the owner about the problems and about the sludge and carbon, and he said per the invoice, he did a complete rebuild and the engine would have not left his shop like that.

So, I have an invoice for $2,500 worth of engine machine work and and rebuild. I just don't know who's engine it goes to!

Kevin
 
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