I just pulled my perfect running small block out of the moth balls and dropped it in an S10. I pulled the intake to sandblast it and then re-installed with a Holley 600cfm. It would not idle, I replaced the carb with an Edelbrock 600 electric choke. It idled but ran a little rough, then after driving for a few minutes started to miss on 4 cylinders. I discovered that the intake gaskets were for a later year or something because the ports looked too big so I replaced them with 1205 gaskets. Still runs rough. The pattern seems to be every other cylinder on the cap or all cylinders on the lower plane of the intake. My compression is ok, all cylinders have spark (hei distributor), oil pressure good, fuel pressure 6psi, idle 800 rpm, base timing 14 degrees, no vacuum advance hooked up, all new plugs and wires, carb brand new. I know this has to be something really stupid. Some one please five me some guidence.  

Carb not working on both circuits(fuel/jets)You did clean all the sand out of the intake right?? Bad intake gasket on one side of engine not sealing to head.(vacuum leak)Dist not installed properly 180 deg off?? perhaps.4 bad spark plugs on suspect side.Good luck.Hope this helps.  

I did clean the intake in a water jet washer (big tanks with lots of hot water and detergent pressure) for 2 hrs to remove the stains from fuel, oil, ect. I do not suspect an intake problem again just because I actuall test fitted everything this time (I used and identical set of gaskets sprayed with copper coat and looked for transfer patterns). The missfires are not on the same side of the engine, they are actually 2 on each side the only thing they share in common is being on the lower plane of the intake and the pattern of every other cylinder on the cap. I don't think its 180 out just because it ran ok then just happened, does any one know if that is even a real possibility??? I have puit in several distributors 180 out but they never ran smooth at any time. I have replaced the plugs three times now so I can kind of rule them out too.  

Gotta be fuel distribution.Carb has a problem.Its not feeding the lower half of the plenum.  

1.visually check that all 4 carbie jets are squirting fuel ,do this in nuetral with the air filter off.(if the engine runs correctly at higher rpm definitely means a vacuum leak.............2.faulty distributor,rotor button,coil,ecu,leads not in properly pushed in even though they may look like they are. Check the distributor cap and ensure that ALL under terminals are clean and not corroded. Ensure that you dont have 4 or 6 cyl electrical components in your aftermarket ignition system.Even though all plugs are sparking ,they may not all be recieving the same charge. Check compatability of distributor and coil and ECU.Check that the engine is well earthed and all ignition and spark wires not loose and correctly fitted.Check the alternator and charging system that all electrical components functioning correctly.........................3.ALL fuel gaskets should be BRAND NEW! Why,old dried gaskets leak or are prone to when not used for a long time(even though they worked last year),many people keep the entire carb submerged in petrol when not in use in an airtight container.Even carb to manifold gasket should be new.Ensure that all unused carb ports are tightly plugged.....................4.Remove all plugs completely and crank the motor,pump the throttle;now have a visual inspection to see if fuel is coming out from each plug hole.Also compression test the motor,you may have ring or piston failure. ................5.lastly remove the inlet manifold and make 100percent sure that there isnt even a tiny hole anywhere.NO SAND ANYWHERE!You may need to have it pressure tested for leaks,cracks etc.Make sure that the heads,valves,lifters are'nt to blame for this problem ,as they could well be.An internal oil blockage or air lock.On a hydraulic cam if the lifters dont get oil,those valves wont open causing splutters and misfires. I hope this helps.  

you did not say which manifold that was... is it possable that one of   egr passages opened up or let sand loose in the intake????


if one side is dumping in full egr flow it will act almost exactally what you describe..

can you fab a block off plate and blow compressed air in...


if it is a dual plane manifold with the full divider.. put the carb on backwards... if it is the carb the problem will be on the other cylinders...