Not quite sure what to look at here. On my '65, I replaced the rotor, cap and plug wires but it only helped slightly. When I start the car when the temp is around freezing, it will start ok and run fine for about 10-15 seconds and then begin to misfire on a cylinder (maybe two) and stall if I don't keep my foot on the gas some. I have to sit and let it warm up for about five minutes, but as soon as I head down the road or put it under load it will begin missing badly again. I find that if pull off and rev the engine high once or twice it will clear up and run fine after that.
I haven't checked the points or the shaft for play yet but I'm suspecting it. Once it's warm it'll run almost perfectly- though I can detect a very slight miss as I cruise along sometimes. Any ideas?

 

How's your choke?

- Eric

 

The fact it clears itself says dirt in the carb to me or at minimum its fuel system related.
But read on…
Look at the fuel system first. Is the filter good? Is the carb getting sufficient fuel? Is the accelerator pump shot weak? Look down the carb while actuating the throttle. Should see a good strong squirt throughout its travel. Main fuel pump weak? Are the lines from the tank ok? Pick up in the tank ok? Carb tight on the intake? Dirt in carb, sticking float needle etc...(The plugs would show lean here).
Could be a vacuum leak, incorrect choke setting or a combo of all of this.

If you had a mechanical ignition problem (bad dist shaft bushing, bad cam shaft) it wouldn’t be sensitive to temps nor would it "go away". Unless it’s an intermittent short?
Check the coil primary & secondary windings with an Ohm meter. Could be a coil failing or a bad connection from its power supply or to the distributor. Check the wires on the breaker plate and where the negative wire passes through the bottom of the distributor to the neg term on the coil. The wires will fray from the breaker plate rotating with the vac advance causing intermittent grounding of the ignition system. Also clean ALL grounds. An almost 50 year old car will need to have all grounds re-established.
Does the vac advance canister work properly? When you pulled the rotor did the weights and springs move freely?
How do your plugs look (read)? In your case if their white you’re lean which is insufficient fueling. If the plugs are black your coil could be weak or its some other ignition related problem.
Let us know what it is when you find it.

 

Ahem.

Does the choke close?

- Eric

 

Your symptoms mimic a choke pulloff problem. Dont know if that carb uses one though. If pulloff does not crack choke plate open a hair after cold start the engine will do exactly what you describe.

 

Definitely sounds like a lean condition to me, either choke or choke pulloff or lean mixture caused by vacuum leak or to lean a mixture at all times. The colder the weather, the worse a lean conditiopn would be. Do you know what jet/rods you have and what was original? I'd start with checking and adjusting as neccessary the whole choke and choke pulloff and also make sure there are no vacuum leaks.

What engine and carb are you working with?

 

Yes, probably the choke!
Kinda had to explain the proper way to set it.
Should be about $20 at a garage, if they now how!

 

If you have the point distributor I can tell you from 40 years of working on these old beast that one of the little culprits in tune up jobs have been overlooked many many times in the past and especially now in this modern world of high tech and computers. The condenser has caused many people to think it was a carb problem when it was just the 2 dollar condenser. Buy a real good one, Accel, Jacobs electric, Mallory. It worth trying instead of a carb rebuild or a new carb which I have seen in the past. It may be your choke sticking also.

 

Low octane?
railguy

 

as stated above, choke, vacuum break mechanism(it may be inside the choke housing), fuel pressure/volume issues, carburetor float failing, ignition issues, etc.

pix of the carb. would let us know what type you have.


bill

 

Yep once again you guys nailed it, the choke blade was getting stuck on the air horn from the air cleaner being overtightened by a previous owner. This is just a 2bbl on my 330. This would explain why revving it once or twice would open it (from the engine shaking it loose). It's a rebuilt carb by the looks of it so everything seems fine. Wish I had some receipts come with this car to see what was done. I always seem to go to worst case scenario mode, the distrib is fine. Thanks everyone for the detailed replies.
I'll be looking at the points next, they work fine but the cap and rotor had seen some wear so I'd bet these need it too.

 

You're welcome.