Truck runs rough, help!

[Johnathan25]

Hello everyone. I have a 1985 Chevy c10 that’s been running pretty rough here recently and I cannot for the life of me figure out why. When you try to crank it up you have to hold it for awhile before it fires up, and then as soon as it fires up it acts like it struggles to stay cranked, every now and again it won’t even crank and you have to wait awhile and then it will. Once it’s warmed up it idles pretty rough and jumps around, and when in gear it does it even more. Turning the air on makes it jump around way worse to the point where it almost wants to shut off. It doesn’t jump around while going up the road, but when you start off from a stop or slow down and start to pick up speed again it really feels like the engine is struggling to keep up and won’t pick up speed very quick, almost like it’s lost it’s power. Occasionally it’ll bog down so bad from a stop that it’ll almost stall out.

Here’s some info on my truck:
-the engine is completely stock minus a Holley carb that was added not too long ago and the emission stuff gone.
-just replaced spark plugs, wires, distributor cap, coil, and rotor.
-just replaced valve cover gaskets
-nothing else has been modified or tampered with.

If anyone has any idea on what could be wrong I’d really appreciate it!

 

[Johnathan25]

Also forgot to add that the engine is a 305.

 

[Charlie]

 

[75gmck25]

Did it ever run right with the Holley? It sounds like the carburetor is way off and is making it run bad. I don't have enough experience with Holley's to make suggestion on what to look for.

Bruce

 

[Johnathan25]

Yes it ran right with the Holley to begin with. The carb is tuned about as perfect as it can be, this problem just started manifesting itself within the past two or so weeks.

 

[bucket]

Check for vacuum leaks? Were the new plugs and wires before or after it started running rough? Did the problem come about all at once?

 

[Johnathan25]

Check for vacuum leaks? Were the new plugs and wires before or after it started running rough? Did the problem come about all at once?

There are no vacuum leaks, made sure of that. The problem started a few days before I changed the spark plugs, and it pretty much just started out of nowhere.

 

[bucket]

What did the old plugs look like?

 

[Rusty Nail]

Battery cable.

 

[Johnathan25]

What did the old plugs look like?

If I remember correctly they were light brown in color.

 

[Johnathan25]

Battery cable.

I checked the battery cables and they looked fine to me, I’ll double check though.

 

[Frankenchevy]

every now and again it won’t even crank

As in you turn the key and nada?

If so, I second Rusty’s opinion

 

[Rusty Nail]

Lol wtf u mean "opinion"?

 

[Johnathan25]

As in you turn the key and nada?

If so, I second Rusty’s opinion

I mean when I turn the key it turns over but won’t start occasionally.

 

[Mr_Ryumaru]

Did somebody put the wrong fuel in? Maybe theres something in the tank? I almost wonder if something happened to the carb. Could you have missed a vaccum leak? Try the old spray bottle of soapy water. Check the fuel filter. Double check firing order and such.

I know it's all no brainer stuff, but what harm can double checking do. Also, how old is the engine? Could it be wounded? Did it get put under heavy load or get revved out? Did someone maybe borrow it right before the problem start?