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View Full Version : Powervalve not in primary metering block?



The Rudds 88
07-04-2010, 03:07 PM
Does this help? Someone got protested yesterday and disqualified for not having a powervalve. I wouldn't know if there is any advantage to it at all. If there is I'd like to know what it is.

Chuckster421
07-04-2010, 03:21 PM
The only reason for blocking off power valve keeps you from opening carb in a dusty pit when the thing wont idle. Anyone with power valve blocks had the idle circuits altered in metering block and is done in many high dollar carbs. dont just plug your's off and think this is a new speed secret. they probably got hit with illegal carb infraction and the inspector knows this because a stock carb with the power valves blocked would not be in the winners circle. It only takes one good backfire to blow the diagphram out and I have done this many times after setting in distributor. After reinstalling and firing car up with a brand new carb the car wouldnt idle. Carb guys get tired of selling newbies a carb for this reason so they alter idle circuit in meter block so power valve is not needed, therefore no return of carbs that dont idle

stock car driver
07-04-2010, 05:21 PM
The only reason for blocking off power valve keeps you from opening carb in a dusty pit when the thing wont idle. Anyone with power valve blocks had the idle circuits altered in metering block and is done in many high dollar carbs. dont just plug your's off and think this is a new speed secret. they probably got hit with illegal carb infraction and the inspector knows this because a stock carb with the power valves blocked would not be in the winners circle. It only takes one good backfire to blow the diagphram out and I have done this many times after setting in distributor. After reinstalling and firing car up with a brand new carb the car wouldnt idle. Carb guys get tired of selling newbies a carb for this reason so they alter idle circuit in meter block so power valve is not needed, therefore no return of carbs that dont idle

Ive ran blocked power valve on STOCK holleys for years. Not sure at all where you are getting all the above info but its way way off base.

All you have to do when you block the pv is jet up 6-10 jet sizes.

Chuckster421
07-04-2010, 05:48 PM
you are using a crutch to fix a problem that needs a cast. The power valve is used to create the transition from idle to power via the idle circuits of the metering block. When you block the power valve you need more fuel for that transition. revamping idle circuits and accelerator pump cams etc... What you are doing is upping the jet size to "almost" do the same thing, but not as efficiently or with the same results as the way I have described. Chime in dynoman and set us straight. I was explaining that the dqued car was more than likely caught for illegal carb. Not just a pluged power valve. And instead of leaving a short useless explanation I was giving knowledge to someone who may have thought this was the missing link he needed. Now that I have, you come along and tell him he doesn't have to do it right. He can get by with some last page circle track crap you read 20 years ago.

stock car driver
07-04-2010, 05:52 PM
you are using a crutch to fix a problem that needs a cast. The power valve is used to create the transition from idle to power via the idle circuits of the metering block. When you block the power valve you need more fuel for that transition. revamping idle circuits and accelerator pump cams etc... What you are doing is upping the jet size to "almost" do the same thing, but not as efficiently or with the same results as the way I have described. Chime in dynoman and set us straight. I was explaining that the dqued car was more than likely caught for illegal carb. Not just a pluged power valve. And instead of leaving a short useless explanation I was giving knowledge to someone who may have thought this was the missing link he needed. Now that I have, you come along and tell him he doesn't have to do it right. He can get by with some last page circle track crap you read 20 years ago.

Sorry buddy again your wrong. I run active power valves in all of my carbs now. I did however run blocked for about 8 years.

Sounds like your the one with issues if you ask me. Ive NEVER blown a power valve like you claim to do all the time after setting timing or changing a distributor, lol.

stock car driver
07-04-2010, 05:54 PM
they probably got hit with illegal carb infraction and the inspector knows this because a stock carb with the power valves blocked would not be in the winners circle.



This part of your statement is far from true as I clearly already stated. If your going to post blatant b.s your going to get called out on it.

The Rudds 88
07-04-2010, 06:01 PM
He wasn't disqualified for illegal carb size or anything, it was the powervalve! I was there. lol.

Chuckster421
07-04-2010, 06:03 PM
Shouldn;t you be at the track already? Or are you changin another set of plugs from your great reinventing of carb jetting.

Chuckster421
07-05-2010, 09:22 AM
I wish I would have kept the answer that simple instead of explaining the difference to that innerbr#$d, backward a#$, mullberry eatin, country f@#k I was in a pi$$in match with yesterday.

Dirtrace54
07-05-2010, 10:44 AM
The holley book put out by Hayes says the same thing as what stock car racer said. It says the power valve is for off idle performance. When you block the power valve off with a power valve plug, you need to increase the jet size by 6 to 10 jet sizes. Most circle track 4 barrels such Quick Fuel and Barry Grants have the power valves block off on both sides. When talking to Quick Fuel and SuperFlow (who builds my carbs) they say for best performance on circle track, powervalves should be plugged.

But if you want the best answer, I would call your carb builder and talk to them. They will tell you the best setup for your situation.

50j
07-07-2010, 08:42 AM
Power valves are for adding fuel under load or at w.o.t. when vacuum drops. If you block them you have to add jet to make up for the fuel flow you took away by blocking off the power valve channels. Fine for drag racing, not so good for circle track where you're on and off the throttle.

MI Dirt Fan
07-07-2010, 05:31 PM
We put a block in ours for the first time and jetted up from originally 76's to 80's, probly could go to 82's. I know someone who has the same exact carb as us and he jetted his up to 88's. Coming to the green flag give it a quick throttle to clean it out and then go. Under caution he is constantly revving his motor up. I didn't notice much difference in performance. It starts and idles fine.

roybeckett13j
07-07-2010, 07:59 PM
power valves are for richening the air fuel mixture, when the engine is under load. When the amount of vac that the carb is seeing is greater then the vac rating of the valve, it opens and let's in more fuel. Hence the different ratings of valves, for different applications.

Now...circle track...your not going from 1000-8000 rpm once. Your going from 3500-8000-3600-7900. So your engine is seeing a large range of vac amounts, so the power valve is constantly adding more fuel, or being shut.

You could take the time and find the perfect rating of valve your cam/head/intake/carb combo that gives your engine the best fuel curve that will provide the best power. But this takes time, and patience.

Or you could plug...jet up a few sizes...and have an eninge that is lean burning, or too rich at different rpms, since there is nothing to adjust for the amount of different fuel requirements as engine load changes.

Its like a govenor on a diesel engine...more load...more fuel. You could unhook it and just bump the fuel press up...but it will only have that perfect amount of fuel at a small rpm range.

My thoughts...they put a power valve in for a reason...use it, and tune it correctly.

madracer
08-12-2010, 09:50 PM
so how do you know what size powervalve to use?

gadirtracer
08-13-2010, 12:43 AM
so how do you know what size powervalve to use?

By measuring the vacuum at idle. Deduct two numbers and that would be the pv you would start with. 10" of vacuum, 8.5 or 7.5 valve.

madracer
08-13-2010, 03:59 PM
Thanks, does it matter if its 2 or 4 barrell?

50j
08-13-2010, 06:38 PM
Thanks, does it matter if its 2 or 4 barrell?

Yes, it matters.

madracer
08-13-2010, 08:59 PM
what is the procedure for a 4412 2 barrell 602 crate engine?