Still popping back through carb... after thorough tune up..?

[steveeoaktree]

Here I am again turning to the experts... I methodically went through everything that I thought was necessary on a vehicle that is 40 years old and had sat for a while.. New plugs, cap, rotor, carb rebuild, fuel pump, oil change (and filter), and some seafoam in the tank along with adding a few gallons of fresh fuel. She's still "popping" or "stumbling" when I open the throttle. Runs perfectly smooth at idle, and "cruise" speeds. It's possible I reckon that I could've got the float drop set wrong or the float level..? I also am going to check the dizzy tomorrow along with checking all vac lines with the best diagram that I have so far... Fuel filter has also been changed.  Due to how smooth it runs normally, I was trying to avoid looking into any serious valvetrain issues, well and the fact it has only 66,000 on her. I don't really know the tendencies or weaknesses of these particular years' of engines though. Any direction is appreciates! I was considering possibly there may be build up on the valves?

 

Stevee

[steveeoaktree]

Well after I got the sunroof hole temporarily sealed, I tackled the vaccum lines and carb issues again. Bought new vac line and installed all as the diagram stated. (with the exception of the pcv as I have it on back order) The popping is gone, but if I even touch the throttle, it tries to die. ? The carb is rebuilt, although I didn't have the solvent or equipment to soak it like others do... I just cleaned it out with carb cleaner and checked as many ports as I could get to. I also couldn't replace the float as it's on baqck order too at o'reilly's. The old float has a "line" where it must've sat and the material even feels different from above to below that line. Checked fuel filter again too. Pump is new. It's almost acting like their isn't an accelerator pump at all...? (it came pre assemblewd in the rebuild kit). I guess that it's going to be another hefty $300 expense to get a rebuilt one... ha ha. She idles so smooth with no smoke or ticks... which is what throws me. If it were valvetrain oriented it'd have more symptoms.

[steveeoaktree]

Another update... I stumbled upon the ac delco spark plug boxes in the trunk that the seller had installed prior to shipping the car. They were marked .085...? Now even before looking it up, I knew that seemed awful wide. The factory spec is .060 for the plugs, which is considerably narrower. I hadn't considered that to be a variable, but at .085, it makes it nearly impossible for the coil to send a spark across that gap at anything more than an idle. Next day off, and they're getting re gapped, and replaced if they look bad.

[JUSTA6]

No way the gaps on the plugs are that large. I'm thinkin .45 ,tops, check N regap.  From what you said you've changed.....Recheck your firing order on the plug wires. Don't forget Pontiac rotor's rotate counterclockwise.

[steveeoaktree]

I wouldn't have thought it, but they checked out between .085 and .090 !! I knew that he put a new set in before shipping the car, but I can't believe that he gapped them that wide. I went through so many other things before checking this... ha ha. The recommended gap on the new plugs that I just installed was .060, but there were a few brands/styles that were .045 though. I guess that I shouldn't be surprised after the crankcase full of gasoline (fuel pump), or the mismatched set of plug wires that were on the car when I got her... I replaced the wires, cap, and rotor when I first got the car along with the fuel pump, (after smelling the fuel in the oil during the oil and filter change). New inline wix fuel filter, replaced all of the rubber fuel line with new gates 3/8' line, and rebuilt the carb (twice). The only thing that I'm still waiting on is the new brass float to replace the black foam type...

[steveeoaktree]

No way the gaps on the plugs are that large. I'm thinkin .45 ,tops, check N regap.  From what you said you've changed.....Recheck your firing order on the plug wires. Don't forget Pontiac rotor's rotate counterclockwise.

Yeppir, all the plug wires are new, and correct. It always idled perfectly, but I just didn't consider that someone would install plugs with a gap set at .085... Thanks!

[steveeoaktree]

Well another update... After the plug gapping, I finally decided to pull both valve covers and do a bit of investigating... Besides the fact that the valve cover bolts were barely finger tight, I cannot find any issues with the valvetrain. Every rocker arm has basically the same amount of oil sitting in the "cup" above the valve springs, and it's obvious that there is plenty of oil flow to all 8 on the top end. I could spin some push rods where the valves were closed, but nothing sloppy or broken. Before re installing the valve covers though, I'm going to have a friend start the engine while I watch the movement of the valvetrain just to be sure. My brain keeps going back to the 2 c's though. Carb and Coil.... Well if all is well with the valvetrain, I'll get the new brass float installed when it arrives, and go from there. BTW, does anyone know how many wires should be plugging into the bottom of the H.E.I.? There was a single multi plug (that goes across the unit) and then a single wire plug that plugged in behind it...

 

 

Thanks y'all