I think you better pull the distributor and start from scratch--sounds like timing is way out of whack

 

check firing order, if that checks out check static timing then get inot air fuel mixtures as a hyper lean set up will create most of your symptoms.

 

You asked this question over at Stovebolt too.

I think you need to start with the low hanging fruit. Check the plugs, compression, plug wires. Then check to see if your timing is accurate. That TDC is actually marked accurately as TDC on the timing tab and/or that you do not have the timing accidentlialy too far advanced. Might consider readjusting the valves. Also, see if any vacuum leaks. Spray some WD 40 or something aroung the carb base, vacuum advance lines. Check to see if the vacuum advance can is intact and not ruptured.

One other thought, might be a ruptured power diaphram. The YF uses a mechanical/vacuum rod arrangement where vacuum applied to the power diaphram over comes spring pressure keeping the rod in the jet at idle and part throttle. When the vacuum is over come by the spring, the thick part of the rod moves up and out of the main jet. If the diaphram is ruptured, which is a distinct possibility given the NOS status of your carb (i.e., not ethonol resistant) the thicker part of the rod will be out of the main jet feeding the motor fuel through the main jet that it may not be able to use, rich condition, which you are trying to compensate by making adjustments in idle speed, timing. So you may need to take it apart and check that the diaphram is not bad. I know its been rebuilt, does not mean a thing. Could also be the main jet is loose, or the rod got bent somehow. Its just a matter of pulling it apart and double checking

 

I have the timing set at 10 degrees BTDC. I read somewhere that a I6 250 should be 4 degrees BTDC with not vacuum connected to the distributor. What is your recommendation?

 

I think your issue is carb related but if you want to eliminate a few things first, I would deal with the low hanging fruit first, then the timing. If the distributor has say 12 degrees of mechanical, which is 24 at the motor, and the factory specification is 5 degrees advanced, that is a total of 29 degrees. You are currently at 34 which is not a an outrageous amount and may very well be fine but I might go back to the factory specification just so you can have a baseline for your diagnosis. Then, If the other low hanging fruit checks out, and the timing is right, I would head to the carb.

 

I have been working on my car, but it still is not running right. I can get it to start when it is cold, but within 1 minute as it warms up it begins to run rough and starts to backfire. I must constantly keep feathering the accelerator to keep it running and then it will just stop.
I have checked these things: The wiring firing order is correct, and wires are new. The plugs are not fouled, but I replaced all of them anyway and it still did not fix the problem. I found no vacuum leaks, and the compression is good. There is 10V at the coil. The plugs have spark. I put in a different known good MST hotter coil. I reset the points gap a bit wider. I removed the YF single carb and opened it up and it is clean with no debris or gunk in it. I drained all the gas and put in fresh 93 octane fuel. The vacuum advance can is new and seems to be working. I have not been able to check the timing because the engine will not run long enough for me to be able to do that.
So, I am now wondering if either the fuel pump is bad and not pumping enough gas into the carb or the distributor is not creating a hot enough spark at the plugs. When I checked the plug spark on 3 different plugs, the spark was a “red” color and not the normal “blue” color. I’m wondering if changing to an HEI type distributor would be a better choice. That is my next step. If that fails, I’ll replace the fuel pump.
Any other suggestions? What’s odd is that when it’s cold, it seems to run okay for a short time. As soon as it heats up it runs very rough and then dies.

 

You say you put on a hotter coil? Have you checked voltage at ballast resistor and at coil and points? Have you looked at points and set the dwell? You say you got spark but is it correct?

 

Did you confirm that the accelerator pump diaphragm was still intact? How did you check the operation of the choke? Did you confirm that the float level was set correctly? What were your numbers when you did the compression check? When you say the advance can seems to be working, what did you mean? Did you check fuel pump pressure?w

 

Did you confirm that the accelerator pump diaphragm was still intact? How did you check the operation of the choke? Did you confirm that the float level was set correctly? What were your numbers when you did the compression check? When you say the advance can seems to be working, what did you mean? Did you check fuel pump pressure?w
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Why 93 octane, is it a high compression engine? If you have money to blow, just start replacing parts, if you want to learn, then test first. What is your fuel pressure? Can't say I've ever seen a red spark. Yellow or maybe orange yes, but red? You should be seeing a blue spark. Check the spark when the engine is cold, crank it without pumping the throttle. If the spark looks good, start it until it won't run anymore then recheck the spark to see if it is colder (yellow instead of blue).
After it stalls and you try to restart, does it seem to start but then die as you let it go from cranking position to run position?

I got 93 octane to help prevent the dieseling when I turned off the ignition. That no longer seems to be a problem. I'll check the color spark again on several plugs and advise. Yes, when I try to restart, it seems to start but then dies as I let go from the cranking position to run position. If I pump the pedal it tries to run rough and may backfire then die.

 

Why 93 octane, is it a high compression engine? If you have money to blow, just start replacing parts, if you want to learn, then test first. What is your fuel pressure? Can't say I've ever seen a red spark. Yellow or maybe orange yes, but red? You should be seeing a blue spark. Check the spark when the engine is cold, crank it without pumping the throttle. If the spark looks good, start it until it won't run anymore then recheck the spark to see if it is colder (yellow instead of blue).
After it stalls and you try to restart, does it seem to start but then die as you let it go from cranking position to run position?

 

Did you change condenser?

 

No, have not done that yet. Will check today.

 

You still have not answerd the question as to whether the accelerator pump diaphram is intact. The condition you describe is indicative of a ruptured diaphram. One of the reasons I have been harping on this is that the diaphrams supplied with later rebuild kits were made of a not so durable rubber and were a constant source of trouble. I ran Carter YF's for years (dual carbs) and this was a constant issue. Also, the little cast cover that secures the diaphram is also prone to warping from uneven screwing down with the four screws. If the diaphram is not sealed by the cover, or is ruptured, fuel gets under the diaphram where it cannot be, and thus renders the pump and main jetting essentially inoperative.

As for the dwell, you should check it. If the needle is bouncing all over the place, suggests the lobes are unevenly worn on the distributor causing eratic dwell which is also a cause of this kind of running issue.

Compression check, the actual readings can tell you a good bit, including whether the valves are set too tight.

 

The compression results: #1=152, #2=155, #3=152, #4=155, #5=155, #6=155. seems okay.
Now that I know how to check the dwell, I'll do that this weekend.
I understand what you are saying about the accelerator pump. I'll check with Jon Goodman about this as he rebuilt this carb for me recently.

As of yesterday, I may have fixed the problem. The motor now starts and idles fine. It revs up without hesitation also. I plan to drive it a bit today. I did 4 things since I last reported. First, I replaced the fuel pump. Second I bought and new condenser from Jon G. and installed it. Third, I had some dirty gas in the tank. When it pumped through the filter it was dark orange in color. It seems that all the dirty gas has been purged from the fuel line and pump and now I'm getting clear gas through the pump and filters. Fourth, I set the idle up a bit.

I am thinking the motor was trying to run to lean. Not getting enough fuel or good clean fuel. Maybe a bad pump?

 

Excellent work! Jon is a good man and an excellent technician. A ruptured YF diaphragm would not be a Jon issue, just the state of the quality of parts we can get these days. I would not mess with it if it’s idling and accelerating fine. It’s sounds like you have sorted out the issue.

 

Well, my Belair was still not running right, wouldn't start and began backfiring again. After going back to basics and checking lots of things, it turns out that the timing was way off. Perhaps as much as 40-50 degrees. That was causing the starting difficulty, backfiring and engine running hot. The cause of the timing problem is a misaligned harmonic balancer. I set the motor on TDC and made a new alignment mark on the balancer and redid the timing. After doing that, I turned the key and the motor started immediately and runs very well.

Now the question becomes, why is the harmonic balancer that far misaligned? Could I have the wrong HB on the motor. The motor is I6 250 and maybe the HB is for a 235? Would a 235 HB fit on a 250? Or could the HB have slipped on the shaft? Sheared off the key pin? I'm going to pull this current one off and replace it and want to get the correct new one.

Thanks again to everyone for the help.

 

Wow! If you chasing your tail on this car was a movie this would definitely a must see! Sometimes its smacking you right in the face but your eyes never see it.Good job !

 

Sounds like I'd start with timing.

 

Hopefully, it's running by now. This thread is almost 2 years old.