Sputtering and no power

[thisolechevy]

A couple of months ago my truck started to run rough and then would just die, I discovered that it was the cap and rotor and that they were fried. So I upgraded from points to hei style dist. with a little kit by flame thrower, it mounted under the stock rotor, but never got a new cap and rotor. Well about a month later my truck started sputtering and would top out at about 55mph, I talked to an uncle of mine and he said it was either the coil, cap or rotor so I replaced them all at one time and it ran GREAT no problems at all. Then last Tuesday it did it again for about 15miles until I got where I was going, then after I let it sit for a while it worked great??? then again Sunday it did it again going along fine then it just starts sputtering and tops out this time a 50mph and absolutly has no power at all so I replace the coil cap and rotor once more thinking it would work...but it didn't??I am flustered at this what could it be? my plugs and wire are about 6 months old and have 1,100 miles on them and have seen the engine up to 220+ degrees, they are just autozone cheapo's. Could these be the problem at hand? what is causing this?

[thisolechevy]

Ttt

[GMC AMI]

Maybe a fuel filter not letting enough fuel pass at higher speeds and the spluttering is engine not drinking enough gas? Float level in carb should be checked as well.

[ChevLoRay]

If you have only driven it 1100 miles in six months, you're driving yours about twice as much as I drive mine. However, if those are short trips, i.e., less than 5 miles (for instance) your engine isn't coming up to a normal operating temp and condensation can become an issue as in plugs that become fouled because the mixture is too rich. I was taught that a vehicle has to be driven the equivalent of 11 miles, to bring everything up to a normal temp and to eliminate condensation. This would bring the choke to a completely off condition, assuming the choke pull-off is working properly. But, this doesn't mean that running one for short trips causes ignition and carburetor problems. Mainly, condensation is a problem in oil and exhaust systems.

If you have access to an Ignition Analyzer machine, like a Sun machine, you can get a look at what your engine is doing. With the advent of computerized systems, finding a Sun machine may be difficult.

I find that using a higher grade of plugs and wires, is never bad, but that doesn't mean that the cheaper ones won't work. Have you replaced your vacuum advance? What about the timing? Check the oil dipstick. Smell the oil. Does it smell like gasoline? If so, your carburetor could be flooding your engine, by leaking fuel into the cylinders. The gas washes past the rings and dilutes the oil, but puddles in the intake causing a very rich mixture and poor running conditions.

If you are running a Quadrajet, and it is an old, i.e., original, carburetor, they are prone to leakage. It could be the throttle shaft bore, which wears. Or, the plugs beneath the main jets can leak into the throttle bore. Vacuum leaks usually are apparent at idle, but may disappear when you hit the gas (vacuum drops as you open the throttle). If the throttle shaft is worn, you'll have a minute vacuum leak at that bore, plus you may see gas leaking from the shaft.

Usually, a bad fuel filter will starve the engine for fuel as you try to rev it up, but may idle normally. An air filter that is extremely dirty will also have a similar effect. PCV valves can stick, open or closed, and cause vacuum problems.

Look at your plugs. Are they black and wet, like oil-fouled, or do they smell like gas? Plugs that are gas-fouled, will cause erratic running conditions. Again, if they're gas-fouled, the likely culprit will be the carburetor.

When you start your engine, do you see smoke? Could be worn valve guides and oil fouling of the plugs.

These questions are why I suggested someone with a Sun machine may be able to help determine whether or not it is an ignition issue, or a carburetion problem. Sun machines also offer a Balance Test that was good to help diagnose carburetor problems.

Sorry for the long post, but that's the nature of these kinds of questions.

[thisolechevy]

thank you for your help!!! I guess I will take the truck to our local machanic and have him check it. I believe I once heard him say something to the effect of having the equipment you menchend.

[thisolechevy]

O.k. a little background on the truck. its a '68 327 with edelbrock cam, heads and intake. aftermarket pistons rings all that good stuff. and an Edelbrock 650cfm carb, My uncle bought the carb. brand new three years ago then let it sit for 2, when I got it the carb wes re-built about 9 months ago and the place that did it said it was in pretty rough shape, and didn't know how long it would last. I just pulled the plugs and they are black, wet and smell like gas. I guess that the carb is bad :-( and I need to get a new one. Man it stinks this is supposed to be my daily driver and every time I turn around I am having to put money in it...ARGH

[Grim Reaper]

Your choke isn't opening. I bet it's electric. It's proably a bad electrical connection and your disturbing it when you mess with the distributor.

[Robert1970C20rstbukt]

The plugs are getting gas fouled. Check your air filter, fuel filter, the float level in the carb, and your air/fuel mix settings. The choke could be stuck like Grim said so check that too.