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About LinkBacksI'm looking to install the Holley power valve check ball in my 850 dp. The Holley instructions show the throttle plate being drilled. I've also see other how to's that show the main body being drilled instead. Does it matter?
Holley PV check ball install
I'm looking to install the Holley power valve check ball in my 850 dp. The Holley instructions show the throttle plate being drilled. I've also see other how to's that show the main body being drilled instead. Does it matter?
just curious...whats the purpose of the check ball?...also...the only time, i have seen the throttle plates drilled was too help with idle conditions!...also...i have been told to plug the p/v's & jet up (thread about that)...hang on, Bob (GN7) will be along shortly!Originally Posted by mrjoshua
Throttle plates are only drilled so that you can get enough air through the plates and still keep the closed enough to keep them out of the transition circuit at idle.
I've never heard of a PV check ball. It's a boat, there's never much vacuum. Plug em and jet accordingly.
GN7: "If you were to have ever had two brain cells you could rub together and make heat, you be dangerous"
I'm no expert but I thought I read somewhere that Holley carbs made after around 1993 already had that blowout protection installed..might want to double check before you start drilling..but like I said I'm no expert.
Last edited by Tittyman; 06-30-2012 at 10:37 AM.
"Bill, if your gonna ride my ass that hard, at least you could pull my hair"....Hillary Clinton
To be honest I do not know how old the carb is. I bought it rebuilt from someone here on the boards. It did back fire through the carb upon startup the other morning. And it ran fine up till almost full throttle. I don't think the power valves blew out or it would not have idled at all. It may very well already have them installed. I would rather block them off anyway but I've been fighting a lean condition and surging at wot. It ran pretty good the other day with the 6.5 power valves and 86 primaries and 90's in the secondaries. That's at 4300' elevation. That should be way too rich for that elevation. But that's where it ran. I don't know what is up with the carb. Fuel pressure I dont believe is the issue as the sight windows on the secondary bowls while near WOT were submerged with gas. I've pulled the plugs and they are still too white
the check ball is placed in the throttle base plate . It is drilled with a specific drill bit that allows a spring loaded ball to be placed in the base plate to allow air to escape during a back fire to prevent the diaphragm in the power valve from being ruptured. The instructions should give an exact location to drill. You drill the throttle blades to lean out the idle mixture if you cannot get enough adjustment out of the idle air mixture screws
armandshammer
Throttle base plate is what I meant. Sorry for the confusion.just curious...whats the purpose of the check ball?...also...the only time, i have seen the throttle plates drilled was too help with idle conditions!...also...i have been told to plug the p/v's & jet up (thread about that)...hang on, Bob (GN7) will be along shortly!
You never posted "throttle blade" Some other "confused" individual put that word in your mouth. I knew what you meant from the first post. You follow the instructions that came with your kit. It can be in the plate or the body, it depends on how the check is built. It is simply a one way check valve that allows vacuum on one direction and block pressure in the other. Its a very simple device and very easy to install.
Most backfires do not rupture PVs. It has to occure when the blades are closed or almost closed to create enough pressure to rupture a PV.
If you have a lean top end surge, its very unlikely you ruptured the PV. Also it would be pig dead rich at anything less than WOT.
If Holley says to drill the throttle plate, then drill the trottle plate.
Thanks. Wilco
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