Effects of Colder weather on timing?

[chevychic]

Does cold weather affect timing quite a bit?

The past week or so, it's been mild here, about 70° - 80°. Then today it plummeted to 50° and rained a bit... (ok so maybe it didn't plummet, but daaaang was it cold compared to yesterday )

Today my truck ran rougher than it has since I installed my distributer and dialed in the timing. It seems to have a slight miss again. It also started doing it's missing thing on the freeway this evening. The way it was before I installed the distributor but not as bad. I have to admit, I was driving it faster than I normally do and after a bit, I could feel it start to run a bit rough so I backed off a bit. But even after I stopped and it cooled down for a few hours, the miss that appeared today with the cold weather was worse.
I'm going to go out tomorrow and play with the timing a bit to see if I can't get it running smoother.

Anyone have any input to how/if the change of weather is affecting it?

[gchemist]

From the pictures on your web site, I can't tell which brand of carb you have on your truck. My experience, aluminum carbs like the Edelbrocks take more time to warm up in colder climates. To compensate, I adjust the choke to stay closed longer. In freezing nights, it takes my truck almost 15 minutes to warm up. This is mainly due to the setup I have for running in hot weather.

[Mike76251]

If you have a Q-Jet.........I would ditch it and put on a new Holley 650.
I got so fed up with Q-Jets over the years that I put one of these on my truck.
At the same time, I put on a Air/Fuel ratio guage and can report those Holleys are very good at holding it to 14.7

[swervin ervin]

Weather has no effect on timing. I'm inclined to think your problem is more along the lines of wet weather. Condensation inside the distributor or a bad wire, etc.

Also, don't listen to the Q-jet nay sayers. They have no idea what they are talking about. When someone tells you to ditch a Q-jet and stick a Holley on something, this tells me real quick they are clueless what a good carb really is.

[old Rusty C10]

stupid question theres no way any moisture could have gotten into your cap is there i had a problem on an old points system where it woudl gt condensation in the cap and cause what you describe. Someone told me they never heard of this happening but it did for me and when i replaced the cap, the problem disappeared. I discovred the problem cause there was a few beads of moisture in the cap walls

[Mike76251]

Swerve,
I have done back to back comparisions between new Q-Jets and new Holleys and always find the Holleys hold the A/F ratio better than the Q-Jets.
My mileage and power went up with my new Holley too and this would indicate a better carb in the Holley.
The Holley is MUCH cheaper not to mention.
The Q-Jet is a good carb (when new) if you consider Chevy put it on both small blocks and big blocks with little to no changes in the carb but it just doesn't hold a candle to my 650 and 670 Holley according to my A/F guage, mph, and power.
Have you installed each on the same engine and installed a A/F guage to check them?
Most people don't like the Jet because they don't know how to tune it..........I have been tuning carbs for 30 years so that is not the case.
Clueless?
I don't know about that.

[Frank-id]

There is a relationship between timing and temps ONLY on emmissions engines. On those engines, there is a temp sensor on the t-stat housing the restricts vacuum to the distributor. When engine temps are normal, vacuum is not restricted.
Condensation can pass thru 3 feet of concrete. Condensation can travel if there is a temperature difference on each side of any barrier. An engine missing is usually associated with a poor connection, bad plug wires, condensation inside a distributor cap, poorly connected or bad plug wires and/or plugs that may be fouled. The performance between a cold engine and an engine fully warmed is very little with the exception that the carb secondaries will not operate. Checking bad plug wires can be done with engine running or off. Correctly tuning any engine is not to be rushed and is in fact a talent not all have mastered. An engine can have all the "best" parts and still not catch a stocker........ Training and knowledge solve all problems.. Just changing parts is not a solution.....

[Lester]

You didn't say what kind of carb or choke set up you have. Thats kind of important to know.

But not because its one kind or another. Carbs are personal choice like headers or tires with each doing what the owner wants them to do or thinks they want them to do.

The problem you described is rough running and/or high speed miss. Holley, Qjets and Edelebrock are all good units each has strengths and weaknesses. I'd suspect you have a rich mixture problem and not a timing problem. If you have an non-computer controlled HEI setup correctly its almost set it and forget it, hot or cold.

When the temp drops as you describe the air gets denser and adds fuel to the mix. I don't think you have a condensation problem. If your fuel mix is already to rich cold air just makes it worse. At start up it rough idle and high speed it it will feel like a miss. What happens when cold air is introduced the fuel changes from a mist to droplets. Droplets won't burn right if at all, hence the rough idle and miss, mist on the other hand does burn nicely. An air fuel mix gauge won't help identify the problem.

No matter which carb you have you need to better manage the fuel delivery to the carb. Remove all of your spark plugs clean regap and reinstall. Install a fuel pressure regulator. Set it to 5.5 psi for an Edelbrock and you have eliminated that as possible problem. There's nothing else you need to do with an Edelbrock.

With a Holley once you have set the primary and secondary bowl sight levels you will need to watch the fuel level thru the sight hole in the primary bowl particularly when the pump cycles. If the pump cycle over fills the bowl and causes the fuel to run out of the bowl decrease the fuel pressure slightly and wait for the next cycle. Stop when the fuel stops sloshing out. I'd start at 5.5 on the Holley and go up or down from there. Holley says you don't need a regulator with their carb which is hard believe because they make the best low dollar fuel pressure on the market. Buy the one that goes from 4.5 to 9 psi.

For a Qjet, once you are sure the float is set right, set your pressure reg at 5.5 and drive it for awhile and see what it does. There's no other way to match a regulator to a Qjet other than trial and error.

This is problem is a little more complex than a black and white solution so trial and error are in order. Remember if it keeps running rich during you efforts to fix this you need to clean the plugs between each trial. Also, you can get it too lean which is tough on valves and pistons.

Good luck.

Lester