I have this 87 lt that has a 305 flowtech shorty's holly intake/carb and it is running like crap, it seems since the weather has gotten warm the car has progressivly gotten worse. I rebuilt the carb put in a new fuel pump, new cap rotor and coil (non cc engine got rid of it all a while back and went with HEI) and the thing is running so rough I am getting ready to park it, this car is my daily driver and it sees some miles (about 120 round trip daily) but I am at my wits end any ideas???

 

What do you exactly mean by "running rough"?

I'd start with these things (in no specific order) :

1. Have you done a compression test?
2. Checked the spark plug wires?
3. Checked for vaccum leaks?
4. Checked fuel pressure before the carb?
5. Checked/replace spark plugs?

Finally could you send back a list of what brand of spark plugs, coil, cap, rotor, coil, and wires you are using.

 

Running rough as in, under hard acceleration the car misses horribly and if I get in it hard enough it backfires throught the carb if I stay in it when it backfires it will pop pop pop as long as I stay in it.

I have not done a compression test but I dont believe it has anything to do with it because it still runs strong and this is a problem that litteraly developed over night, parked the car today running find drove it tommorow runs terrible sort of thing no work was performed on anything between the 2 .

I thought about wires and that was going to be my next purchase I just dont like throwing things at a problem at random although that would be the logical next step. There dont appear to be any vacum leaks I sprayed carb cleaner all around the carb with no change in rpm's so it does not appear to be that.

Plugs all look good and they are delco plugs.

Unfortunatly I dont have a FP gauge but I do have a new engine driven fuel pump on the car no more than 2 months old.

everything is a/c delco parts have never had a problem with them in the past so I like to stick with what works.

I guess im gonna try to find some kind of FP gauge today and maybe the plug wires I will post here what I find.