I've been working on cars for a long time, but this one has me stumped. I have a 1960 Ford F-100 with a 100% original (never been rebuilt) 292 2-bbl V8 and a manual 3-spd transmission. When I first start the engine in the morning (choke pulled out about halfway) the engine runs perfect and real smooth for the first minute or two during the warm-up. After about two minutes, the engine starts to run real rough and will become rougher (like it keeps dropping off cylinders) until the engine either dies or I press on the accelerator to increase the rpms. No matter what I do with the choke or rpms, the problem does not go away until I drive the truck for a few minutes and the engine is fully warmed to operating temperature. It is now to the point that when I first start to drive the truck, it's almost like someone is turning the key on and off, or like the tank is full of water. This problem has been ongoing for a while, but becomes worse the colder the temperature becomes. Again, the truck runs like a brand new fuel injected engine after warm-up and the problem never re-appears after the engine is up to operating temperature. I just performed an annual tune-up, replacing the distributor cap, rotor, points (set dwell to factory 27 specs), condenser, spark plugs (Autolite Platinums gapped to factory .035 inch gap), installed a new coil (oil filled like the original), adjusted the idle mixture and idle (500 rpm) for the cold weather, and adjusted the hot valve lash (to factory .018 inch specs). Other than a very small gain in mileage, power, and idle (when at operating temperature), there was no improvement in the problem I am having. I even changed to my winter jets (went from 50 to 53 jets) and saw no improvement in my problem. The timing is at 6 degrees and I completely rebuilt the carb (original Holley 2300 2-bbl) a couple years ago. At first I thought it was carb ice, but saw no ice formation in the venturis. I then thought there was water in the tank, but even after running one tank down and topping the tank again, the problem is still the same. I also thought the mixture was too lean, but even pulling the choke out further (enriching the mixture) has no effect (even with choke **** all the way out). Plug readings show them nice and tan (perfect) with no deposits (engine doesn't burn any oil). Has anyone had a similar problem or some advice they would like to share?

 

My truck (with a 272) will do that as well. But only below 40 or 50 deg on a humid day. I just thought of it as carb ice. I just think because the air cleaner doesn't have the heat tube comming from the exhaust manifold like modern cars have and also the intake manifold has a open space under it kepping it cool witch is good for power. Mine seemed to have gotten worse when I went to dual exhaust and the heat riser was no longer used. But has gotten a lot better to almost gone when I installed a electronic dist. and now gaping the plugs to 40. So I am thinking you could check the heat riser and the exhaust port under the carb could be cloged and not letting it warm the carb. I find if I just turn off the engine for a minute and start it back up problem is gone.

 

It sounds like we have the exact same problem. Today was worse than ever. It was so bad I had to pull into a parking lot after just going down the road for a few hundred feet because it was cutting in and out so bad. The heat riser was stuck shut (bad spring), so I removed the spring last year, thus rendering it open all the time. I do have a NOS heat riser. I was waiting to install it when replacing the entire exhaust system, but I think I might install it now and see if the results change. I was also reading through the archives and noticed two people with the same problem. One ended up with a cracked head (mine is not creating bubbles in the coolant or consuming coolant) and the other with failing intake manifold gaskets (mine are now 44 years old). I'll do some probing tomorrow to see what I can find.

 

I think you could be on to something with the failing intake manifold gaskets. If there was a small leak, it would happen only when cold. Of course When the motor warms up, thermal expansion seals it up. You covered all the basics with the tune up (getting gas, getting spark, etc). The only other thing I could think of is that those Autolite Platinums are not ideal for an old carb'd motor. Have you ever ran just regular ole autolites?

 

Manifold gaskets very well could be a problem but also; when was the last time the distributor was removed and checked/rebuilt? A leaky vacuum diaphram as well as a sticky advance plate could produce similar symptoms.

 

Before the Autolites, I ran Champions (what the 1960 trucks came with from the factory) and had the same problem. I tune the truck up every year, as it sees a lot of high rpm highway use (3-spd with factory 3.73 rear end gears). The Champion plugs were always a special order item for these trucks, so I decided to run a set of Autolite Platinum plugs (in stock at the parts place), since the platinum tip self cleans and lasts longer (doesn't erode as much metal per spark as steel metal plugs, thus keeping the gap fairly consistent over it’s lifetime). Other than a very minor improvement at idle, the plugs really didn't make much difference. The tune-up parts only see about 5-7000 miles (annual mileage) before I pitch them in the trash. I started thinking about the intake manifold theory last night, but it too didn't make sense. I can start the truck up cold, and it runs beautifully for the first few minutes before the problem starts. It's almost like the distributor is randomly firing whatever cylinder it wants. No matter what rpm I rev the engine to, the problem doesn't go away until the engine is fully warmed up. Like 57_Ford, if I turn the key off, wait a few minutes, and re-start the engine, the problem is gone for a few seconds then returns.

 

The distributor has never been removed or rebuilt. The vacuum advance is on the list of parts to be replaced, but it does work (haven’t vacuum tested it for leaks). Does anyone know who makes an original style vacuum advance unit? All the ones I have found are replacement style units which require the removal of the hard line and replacing it with rubber hose. I really don't think it is the distributor, as the problem only begins after a few minutes of idling (when the mechanical advance isn't even being used) and then goes away once warm. There is a little variation in the dwell at idle (about 1 degree fluctuation), but nothing outside the normal limits (could just be wear in the distributor gear and slack in the timing chain). Today, I tried something a little different. Instead of allowing the rpms to increase as the engine warms up, I kept pushing the choke in to keep the engine speed as low as possible without stalling and without allowing the rpms to increase during warm-up. The problem never surfaced. I'll try this method over the next couple days and see what happens. If this technique does work, it would definitely lead me to believe carb ice was forming at the high idle speeds before the intake manifold could warm up.

 

Sounds like progress. Try some dry gas in the tank and put some road miles under the wheels. When that runs almost empty switch to a different gas station.

 

I also do that with the choke. Some times I think it is just the Maryland climate I have traveled out of state and the problem goes away. I know the last few days have been very humid and rainey those are the worst days for me. Even my 77 f150 did this today. Does your truck have this problem in the summer? I have had 3 different carbs 3 different intakes 4 different dissys and this still happenes. If you do check your intake gaskets I think you might find that the exhaust port that runs under the carb might be cloged. In the late 60s some of the fe blocks had a spacer under the carb that the heater coolent ran throu to keep it warm. I thought about finding one to see if it fixes the problem.

 

57_Ford,

I too live in Maryland (Bowie). I'll replace the heat riser and spark plug wires (the only ignition tune-up item that hasn't been replaced so far) and proceed from there. I'll also order a set of intake gaskets and pull the intake manifold off later to see if there are any restricted areas in the heat crossover.

286 Merc,

I go through about a tank a week. This truck is a daily driver, seeing 40 miles a day (almost all highway). I kind of narrowed out the water in the tank theory, as nothing changes when the tank is filled.

 

try looking for a vacume leak by spraying carb cleaner around spots with the engine running if the rpms go up you have found your leak

 

I just ordered a new vacuum advance and spark plug wire and grommet kit from Concours. Hopefully there will be a gain somewhere when I replace those parts. Tomorrow I am going to replace the exhaust manifold gaskets and heat riser in hopes of solving the problem. I will also to some more testing for vacuum leaks around the intake and carb area.

 

It sounds like you have covered all of the bases. You might want to try something as simple as a fuel additive. They mechanic that rebuilt my motor a few months ago suggested that, and it made a big difference when I was having the same problem. I also did the simple deal of changing gas stations. I did them both at the same time, so I am not really sure if it was the fuel or the additive. Now, that it has been getting down into the teens, the problem is coming back, but it does not die as it did before, and once it warms up, it runs fine. This is probably no help to you at all, but it seemed to help me.

 

I put a 292 in a 46 Ford pickup back in 1970 and I can remember having problems with it in cold weather. I think its just the nature of the beast.

 

UPDATE:

I have solved the problem. Here is the solution to the problem for those with the same problem. I identified the problem as carburetor ice within the idle circuit. Any time the throttle was advanced far enough to engage the transition or main circuit, the problem mainly went away. Upon close observation, I could also see the idle mixture screws (brass) frosted over once the icing began. After reading some of the comments everyone posted, I opted to replace all the exhaust manifold gaskets and install my NOS heat riser (the old one was broken and stuck open). After changing all the gaskets and the heat riser, the problem is solved. The new heat riser is now holding the exhaust from the driver's side back, thus directing more through the intake manifold heat crossover passage and keeping the carb warm. The new gaskets also ensure no heat is lost out of the system. BTW, did the 1960 Ford 292 engines come with exhaust gaskets from the factory? My engine has never been rebuilt or taken apart in any way before it became mine (has been in the family since new) and it didn't have any gaskets or sealant between the exhaust manifolds and the heads (which would explain the exhaust leaks I have had). Did the factory use precision machining between the two parts to make a seal?