Has anyone used the power valve shield kit ( by Centek) on a holley carb to protect the valve against backfire damage ? I have a 468 BBC dual 750 tunnel setup on the hydro. After a hard run, when almost at a stop the engine will occassionally backfire (anyone know why ?). How do you know if the power valves are blown ?
When the P/V is blown the fuel in the bowl will drain into the engine. It'll be hard starting after being shut off for a short time, say 10 mins to a half hour or more. The engine will be flooded and require WOT to fire the engine. IMO take care of the back-fire problem rather mask the problem with a back fire protection valve. I do not like or use these valves as they can cause problems themselves by reducing P/V response or sticking causing the P/V not to work at all.
From tech article on hotrod.com website:
The way Holley decided to protect the power valve from a blowout was to add a check valve system into the throttle body. This check valve is designed with a manifold reference hole and a check ball that will seal the power valve quickly should a backfire occur. Once closed, the check valve system interrupts the pressure wave generated by the backfire, thus protecting the power valve diaphragm.
The easiest way to tell if your carburetor is equipped with power valve protection is to use a penlight and look through the small hole in the throttle plate. If your carburetor is equipped with power valve protection, you will see a small check ball inside this hole. To help you install power valve protection on an older Holley carb, Holley has introduced a Power Valve Check Ball Kit, PN 125-500.
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