Okay, I get the new 460 engine all tucked in (pix and new gallery coming, honest...) and everything runs perfectly... except when the thermometer drops.

For two mornings in a row, the outside air temperature flirted with the freezing mark. When I go to start the beast, it runs ungodly rough, and simply will not warm up unless it runs for 45 minutes or more. The first time I came across this, I was scared that I may have blown a freeze plug from the sudden engine death and clouds of white smoke that bellowed out when I put the transmission into Drive. (they weren't... but dayam it was rough.)

When the thermometer climbs above 60 degrees F (or so), everything runs fine again.

So... how the #$@! do I get around this temperature dependency? I have some ideas, but I was curious as to which ones have the best chance of working, and if I maybe missed something:

* get higher octane gas (it had two tanks of regular-grade in it... still burning that crap off, and I'm down to 1/2 of the aux tank. I'll prolly have to go get premium now and mix it all together; was hoping not to do that...)

* dry out the gas w/ HEET or some other chemical (it's prolly full of condensate, judging by the missing, coughing, clouds of utter crap coming out the exhaust, and outright cussedness that's temperature-dependent)

* tinker with the carb mixture to compensate? (err, my house is at 4500' ASL and the hunting grounds flirt with 10,000' or so, so I already had to lean it out a touch... judging by how easy the motor floods when it gets cold, I doubt the mixture is too lean, but could it be too rich still?)

* buy a block heater (not as funny as it sounds - I live in a fairly cold part of Utah when winter shows up.)


Any other suggestions? (and perhaps serve as a warning and prep guide to those of us who aren't yet used to driving old trucks in cold weather?)

TIA,
/P

 

Are you running a choke and if so is it electric or manual? 30 degrees or so shouldn't be enough to cause this but if you've got a choke make sure it's working properly. Also check that your timing is set properly. Lastly if you have OLD gas get rid of it and try some fresh stuff. You don't need to use higher octane gas (unless you've got a high compression engine). Just make sure that your gas doesn't have moisture in it.

Last year I could run my truck at subzero temps with no problem . . . other than the extreme cold toasting my battery. I replaced it with dual Optimas and never had a problem since. I have a Holley carb with an electric choke. It just keeps running once it's started. Getting warm IN the cab is another story.

 

Had the same problem with my 460. I replaced the carb with a Holley 750 and adjusted the electric choke and it does not do it anymore. I am in Buffalo NY so I know about cold mornings.

 

Pen,
45 minutes seems to be a long time to warm up? Are you running a thermostat? Have you got an aluminum intake manifold? Headers? Dual exhaust? Why is this thing running so cold?
Chances are: it isn't the gas? It's just running too cold and you don't have your choke setup right. You could try a hotter plug, but that's a stretch.
What kind of cam do you have in it?
KingFisher

 

Although diagnosing such a problem over the internet is difficult, here are a few things you can try:

On the next cold morning, prior to attempting to start the engine, press the accelerator pedal to the floor, this sets the choke. Next, remove the air cleaner and verify that the choke plate, located on top of the carb, is fully closed. If not, the choke needs repaired or adjusted. When you crank the engine, a vacuum motor opens the choke plate slightly to allow the engine to start. As the engine heats up, the choke should open. If it doesn't, a quick tap in the accelerator pedal should settle the idle back down.

Note: I am not saying this is your problem, but with today’s electronic fuel injection systems on new cars, some people forget how to start a car with a carburetor. One method that always works for me is to pump the accelerator pedal 2 times, press it all the way to the floor, and then release it. Then, crank the engine without touching the accelerator pedal. If the engine fails to start, I repeat the process. The mistake I see lots of people make is pumping the accelerator pedal while cranking the engine. This process doesn’t allow the choke to set properly.

One other thing to check is the condition of the air filter, the flexible hose coming from the exhaust manifold to the air cleaner, as well as the air cleaner valve that the hose connects to. This valve should be closed allowing only hot air from around the exhaust manifold to enter the air cleaner. This warm air provides better fuel atomization. As the engine warms up, this valve opens allowing cool outside air to flow through the air cleaner.

Please write back and let us know what you find.
Happy motoring,
John24255

 

Your carb is icing!! It took me forever to figure this out on mine. You need to run a stock style air cleaner in cooler weather with a working hot air inlet on the snorkle. If not, the cool moist air will freeze up in the idle circuit of the carb and cause it to act like it is flooding. I made an aluminum piece for my header on my truck to hook up the hot air hose in the winter.

 

LxMan - you hit it on the head. I'd spoke with a buddy of mine about it and he had the same problem as well... I'd neglected to mention that I'd seen water droplets all over the butterfly valves on the morning I was stuck trying to fix the thing, and ice wouldn't have been out of the question on Mon. and Tue. mornings. I'd have replied last night, but the stores were close to closing.

I had the stock intake cover on it, but never installed the heat-vent pipe coming up to it from the manifold heat-plate (nor was the vacuum line for the snorkel door flap/valve attached... I'd never thought that I would need it, since I never did on my Jeep.) So, I had to make a run and get all that put back in, then I filled the tanks up with decent gasoline, and just in case, chucked in a bottle of fuel dryer into each tank.

That cured the warmup times. I started the beast this morning ( same temperatures as the past two mornings), and it warmed up in less than 10 minutes.

Some asides: The choke is a manual, and it sets well enough. the only real discrepancy from the previous engine is a mismatch in port size between the exhaust port and the carb's choke-stove attachment (something that wasn't a problem on the old engine, and I'm using the same carb that was on the old engine.) I'd rigged an adapter of sorts when I put the carb on, and gave it no real thought. It doesn't leak, so I doubt it could be that, but I'll peek into it just in case (the rebuild engine came out of an old Mercury, and I'd only swapped the oil pan and exhaust manifolds to make it fit the truck.)

The cam and intake manifold are both OEM. Nothing hot or fancy there (I built the truck to tow, not race )

ivanribc - I have dual batteries as well, and though not Optimas, both are brand new (I bought the truck itself just this past July.)

My thanks for the help, guys

/P

 

Glade to hear your back on the road. Far too often we forget that some of these devices on our engines are actually good for something.

Happy Motoring,
John24255

 

Mine may ice up when it is as warm as 60 degrees if it is real foggy or high humidity.
Glad I could help