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Author Topic:   ? for KP
posted November 09, 2004 02:34 PM
In a 5200 Weber, have you ever heard of anyone blocking the power valve? Also I was told I need no more than 4 pounds of fuel pressure. Well I put a regulator on it at 3 pounds and ran out of fuel on the straights. Came in and turned it up to 5 and same thing. The car runs great without it with a carter 13 pound pump. What's the deal????????????

posted November 11, 2004 01:24 AM
You should be able to block p/v out but you'll need to jef it up between 6-8 sizes to compensate for the enrichment circuit. I don't know for sure but around 5 1/2 to 6 1/2 psi of fuel should be adequate. I'll check my resources and write back.

posted November 11, 2004 06:09 AM
I would NEVER block a power valve in any carb, as it ruins the fuel curve thru the rpm range. The carb becomes too lean at one end and too rich at the other. No matter WHAT jet you put in, it's not going to have the proper air/fuel ratio at anywhere but in one narrow location of the range of use.
That said, the proper float level has a lot to do with your fuel starvation, as well as it wouldn't hurt to check what your fuel pressure is doing out on the track (particularly right before it seems to run out of fuel). You might have another problem that is being masked by the excessively high pressure pump. Look for things like a cracked or loose fitting or any other area where the fuel system could be pulling air where it shouldn't be.
Next, proper jetting isn't going to factor in to the problem unless you're WAY out of the ballpark (like far too lean for top end fuel consumption).
Proper ignition timing and top end performance characteristics of the ignition system is important too, since an ignition problem could show a symptom on top end that "seems" like a fuel starvation problem, but when you bury the thing with fuel, it becomes masked again.
The point here is, that it's true that you should not need (IMO) more than 6lbs ever in ANY gas 2bbl carb, no matter WHAT flavor carb it is.
Keep me posted, and let us know if any of this rambling helps. :-)


[This message has been edited by KPLugnut (edited November 11, 2004).]

posted November 11, 2004 06:35 AM
we don't run power valves in our holley carbs. ruppert carbs.


posted November 11, 2004 07:14 AM
I seriously think there is something else going on. The thing is without the regulator it is flawless. Only one car can pull us down the straights. If we're 1 or 2 car lengths behind someone else I'm beating they're doors off before the next corner. BTW Earl Parker is the one that suggested putting the regulator on it because it idles very erratic. So I'm pretty sure it should be on there. The reason for asking about blocking the power valve is we run a cam with 274 deg dur @ .050 with .425 lift which I think has the power valve open while it's idling. SO I took the power valve out and stretched the spring a little and it idled a lot better and is a little more crisp on restarts. Now the problem for me is that I want all I can get from this carb but I will have to prove to the car owner we need a regulator but since it runs good without it I don't know if I can talk him into putting it back on and looking somewhere else for the problem.

posted November 11, 2004 10:07 PM
make sure that if you are running an adapter for the carb to the intake that it is tight. I have had one that the adapter bolts were bottoming out and the adapter was a little loose. causing it to **** air and right as I was about 3/4 down the straight it would start cutting out. Bobby

posted November 12, 2004 06:08 AM
Thanks b4. We have to use a stock intake, egr plate and 5200. We've checked all over this thing for leaks. It didn't cut out with the regulator, it cut off then middle of the corner it was fine till 3/4 down the other straight then die again.