I replaced my old smokey 302 (1979 F150) with a remanufactured 302 long block. This is a stock setup. I got the engine fired up and it seems to run ok at a little higher RPM. At low RPM it doesn't want to idle. I'm guessing I need to adjust the carb to the new motor.

I hooked up my dad's vacuum guage and the engine only pulls about 10 inches. According to the guage's label, more like 20 is normal. At 10 the guage label says late ignition timing or leak at intake manifold.

I'm pretty sure the timing is close. The alternator is in the way of direct view and the only way I can shine a timing light on it is at an angle from the front/side (sort of a 3/4 view). I'm not detecting any obvious leaks at the intake. I have, to the best of my knowlege, connected or plugged all vacuum lines.

Another thing I noticed is a very slight gathering of coolent toward the bottom and back of the engine under the driver's side head. I can't tell where it is coming from but it gathers where the outer lip of the oil pan meets the block. There are no hoses on that side of the engine. Could this be a leaking head gasket (or worse) and would this be affecting my low vacuum? I haven't done a compression check on that head yet.

Will fine tuning the carb bring the vacuum up? After warmup and shut off, I get a little "dry-ice type" of fog out of the carb. Is this caused by too much gas?

I drove the truck a total of about 2 miles, and other than wanting to die when I take my foot of the gas to brake or shift, it runs ok. So far I've only run the engine about 20-30 minutes.

Thanks for any help

 

It sounds like a vacumn leak if the vacumn is that low. As an experiment, while the engine is idling use your hand and cover over part if the top of the carb to restrict air flow to the carb. If the idle picks up and levels off then you have a vacumn leak or a badly adjusted carb. I would guess vacumn if the carb ran ok on the old engine.

 

thanks, I'll give that a try as soon as I can get time to get back at it.

 

Vacuum can be too low and the idle too high if the throttle plates are open too far. Go back and turn the idle speed down and see how the vacuum reading reacts. If vacuum suddenly jumps up close to normal then you have at least found a big part of the problem if not all of it. The idle mixture screws will fine tune the idle and the vacuum readings will show how happy your engine is when fed the proper amount of fuel.

If you are certain that the throttle plate adjustment is not the problem then you will be able to turn in the idle mixture screws all the way in on one side and then the other and the engine will die.