My banger powered Roadster has a slight but annoying off idle stumble!!! Idles great , after stumble runs great , has a Holly 847 carb and homemade intake manifold. has 34 self advance distributer set to 5 Degree BTC at idle---stock ign system. Carb squirts good on acceleration. Could the stock spark system be to weak to handle the squirt??
power valve may be opening too late. Change it by shimming the spring or stretching it. Holley 847 Diagram 1. Power Piston Assembly 2. Bowl Gasket 3.Nozzle Plug 4. Nozzle Plug Washer 5. Idle Tube 6. Nozzle Bar Gasket 7. Nozzle Bar Assembly 8. Nozzle Bar Gasket 9. Pump Operating Rod 10. Nozzle Bar Screen 11. Retainer Spring 12. Return Spring Pump 13. Pump Assembly 14. Retainer Check Ball 15. Check Ball 16. Retainer Needle 17. Needle Valve 18. Power Valve 19. Power Valve Gasket 20. Main Jet 21. Idle Screw 22. Idle Screw Spring
Thanks Junk yard kid!! Pulled plugs to check---found 2 that were gaped at .020----opened to .035 no stumble!!