Hm. It's been over 30 years since I actually stuck my head under a hood and set points and timing, adjusted valves, and rebuilt a carb, or even thought about doing so. I suppose I can be excused for getting fuzzy on diagnostics. I solicit the input from you who have remained sharp in the techniques of diagnosis by observation.

Harley Earle had its points set professionally within the last 4,000 miles (on the way to Florida from Seattle). I don't now how long the plugs or wires have been on, but after the points were set it ran as smooth as molassas and got excellent gas mileage.

Now it is running rougher and rougher immediately after start-up for a longer and longer time, and taking more turns to hit fire the first time.

Today was typical: It ran rough for the first 1.5 miles, getting a little better as the distance went by. I shut it down at a restaurnt and had a liesurely lunch; it fired up promptly and ran very smoothly all the way home.

The heat valve is frozen and I've hammered it around to fully open.

Is the rough running until really fully warmed up most likley to be plugs, wires, points, condenser, or coil, on probabilities, or to involve valve settings (no audibles there, but I think I've got hydraulic lifters--'49 Super (Dynaflow)

Aw, c'mon, gurus--what is this, a case of "no guts, no air medal"? :confused:

im not into points an condensors , i have a 53 str8 8 an installed a 12 volt pertronix ignitor electronic ignition conversion fits under the stock distributor cap hooks up with 2 wires , an hooked it to a 2nd hand accel super coil i liberated from my mustang , no more points an condensor,

What's the outside temp where you’re at? If it’s above 60deg, your heat valve probably isn't doing much anyway. Your dwell (points) won't change with temperature, but your spark plugs may need to dry out (nighttime moisture) before they are firing correctly. If you have a spark plug wire tool you can pull each wire off in turn and see which of them doesn’t change the way your engine is running.

Good idea, GB . .hadn't remembered nighttime moisture, but not sure how much of a factor. The car is covered at night. And new information is gas mileage has fallen off significantly, down 25%. I'm suspicious of points wearing, I think, because the trouble came on over only about 250 to 500 miles, progressively. Maybe the condenser, not functioning properly until it gets good and hot?

you might want to spritz the carb and intake gaskets with wd40, carb cleaner, etc. if the idle picks up, you have an obvious air leak. consider a compression test and leak down test also. if you are the least bit suspicious of the coil, plug wires, points, change um. probably wouldn't hurt to go through the carb either.

Electrical parts get worse, not better with heat! If it was sporadic, I'd be more inclined to look there. Look at the carb like HG says or maybe a fuel problem?

!!! I replaced the intake/exhaust manfolds and the block gasket beneath the carb recently. Maybe something's loosened up, now leaking when the parts are cold and not when they expand with heat. Thank you, heidigirl--I'll "spritz" tomorrow before I start it and see what happens. I'll also check the tightness of the mainfold stud nuts (sounds a little kinky . . . redface.gif ) and the carb nuts. It that doesn't do anything, I'll spritz the inside of the distributor cap, just in case there's a bit of moisture there.

do the spritz with the engine running, but before you retighten anything. otherwise, how else will you know if you have an air leak?

Yes, ma'am . . .

You can use water for the spritz test also, if the engine stumbles then you've found a leak.

Ty, GB. Haven't gotten to it yet.

Funny how well it runs once it's warmed up. I took it to the Mississippi/Louisiana line and back earlier this week on a hot day; had to stop twice to pour water on the radiator due to very slow heat buildup; but is ran smooth as silk and returned almost 18 mpg, running between 60 and 70.

Those Straight 8s don't even think about smoothing out until about 60 MPH :D

Haven't spritzed, but found the three carb mounting nuts loose. I'd but a new gasket under the carb, and I suppose it compressed. Tightened them, and the rough running improved, but has not been eliminated. Don't think I've got any leaks between the intake manifold and head . . more later when I delve deeper.

Found the problem: air leaks between intake manifold and head.