Technical Banger---off idle stumble!!!

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??

 

Try changing or cleaning your spark plugs. Mine never last to long.

 

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!!