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Re: Removing power valve
[Re: varunner]
#2648653
04/24/19 09:22 PM
04/24/19 09:22 PM
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Joined: Aug 2003
Posts: 43,913
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,913
Bend,OR USA
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Which end of the carb are you removing the P.V. from? Why aren't you wanting use it?
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Removing power valve
[Re: Cab_Burge]
#2648665
04/24/19 10:24 PM
04/24/19 10:24 PM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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"Why aren't you wanting use it?"
THIS^^^
Boffin Emeritus
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Re: Removing power valve
[Re: varunner]
#2648706
04/25/19 07:13 AM
04/25/19 07:13 AM
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Joined: Jan 2003
Posts: 13,053
Benton, IL.
DaveRS23
Master of nothing...
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Master of nothing...
Joined: Jan 2003
Posts: 13,053
Benton, IL.
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The change in the main jet will depend on the size of the PVCRs under the power valve. You can take drill bits and measure the PVCR size and then with a little math figure how much bigger the mains need to be. It won't be exact, but will get a good close starting point for the rest of the tuning.
Power valves and PVCRs are good tuning tools. Rarely do they need to be eliminated, at least on the primaries.
Master, again and still
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Re: Removing power valve
[Re: Clanton]
#2648707
04/25/19 07:13 AM
04/25/19 07:13 AM
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Joined: Jun 2006
Posts: 703
Virginia
varunner
OP
super stock
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OP
super stock
Joined: Jun 2006
Posts: 703
Virginia
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so I'm having a heck of a time getting this engine to idle decent. Seems way too rich. Plugs are wet, inside of intake usually looks wet. It's 383 stock eliminator engine. It has 7-9 in. of vacuum at idle. The carb, R4668, w/vac secondaries, came from a carb guy with a 3.5 PV, I put a 2.5 in there, and it may have helped, not sure. So at this point I'd just like to get it out of there and see how it responds. The mixture screws seem to work right, and all butterflys have had a hole put in the them. Secondary block doesn't have a PV. Also the motor seems to run lean at WOT, this was seen on the dyno, 13.2, and inside of headers are white.
Last edited by varunner; 04/25/19 07:13 AM.
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Re: Removing power valve
[Re: varunner]
#2648708
04/25/19 07:17 AM
04/25/19 07:17 AM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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It should NOT idle on the PV, something is wrong.
Reason#1 for "Take it out" advice: doesn't understand what it does.
Boffin Emeritus
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Re: Removing power valve
[Re: polyspheric]
#2648723
04/25/19 08:29 AM
04/25/19 08:29 AM
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Joined: Jun 2006
Posts: 703
Virginia
varunner
OP
super stock
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OP
super stock
Joined: Jun 2006
Posts: 703
Virginia
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agreed it shouldn't. if removed, it won't. not sure how much you actually know about a holley on a stocker motor, but if you check around, most people remove them, just to simplify things. This engine will either be at idle or WOT, nothing in between. It should NOT idle on the PV, something is wrong.
Reason#1 for "Take it out" advice: doesn't understand what it does.
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Re: Removing power valve
[Re: varunner]
#2648727
04/25/19 08:48 AM
04/25/19 08:48 AM
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Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
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Often times, removing the PV will slightly improve the “hit” on the line.
I’d take it out and see what happens........ easy enough to put it back in.
Do the OE bowls have site plugs?
If not, I’m guessing the floats are a little too high, and/or the fuel pressure is slightly too high.
Holes in all 4 butterflies?
Better check the wording on that in the rules.
We had an issue with that years ago.
We had to replace the rear blades(with some that had no holes) before we could continue running, and they disallowed our qualifying runs.
An easy test is lift the carb off the manifold an inch or so, and block it up with something.
Turn on the fuel pump and see if any fuel starts dripping from anywhere underneath.
I’ve seen fuel dripping out from places where it theoretically “couldn’t”.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: Removing power valve
[Re: fast68plymouth]
#2648735
04/25/19 08:52 AM
04/25/19 08:52 AM
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Joined: Aug 2006
Posts: 614
Michigan
Get-X
mopar
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mopar
Joined: Aug 2006
Posts: 614
Michigan
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Often times, removing the PV will slightly improve the “hit” on the line.
I’d take it out and see what happens........ easy enough to put it back in.
Do the OE bowls have site plugs?
If not, I’m guessing the floats are a little too high, and/or the fuel pressure is slightly too high.
Holes in all 4 butterflies?
Better check the wording on that in the rules.
We had an issue with that years ago.
We had to replace the rear blades(with some that had no holes) before we could continue running, and they disallowed our qualifying runs. Yup, I've seen guys get bounced for having the wrong head on the butterfly screws, let alone modding the butterfly's themselves.
'65 Belvedere
'68 GTX
'57 Dodge pickup
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Re: Removing power valve
[Re: Clanton]
#2648754
04/25/19 09:23 AM
04/25/19 09:23 AM
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Joined: Jun 2006
Posts: 703
Virginia
varunner
OP
super stock
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OP
super stock
Joined: Jun 2006
Posts: 703
Virginia
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1 1/2 How many turns out are the idle metering screws?
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Re: Removing power valve
[Re: fast68plymouth]
#2648756
04/25/19 09:26 AM
04/25/19 09:26 AM
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Joined: Jun 2006
Posts: 703
Virginia
varunner
OP
super stock
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OP
super stock
Joined: Jun 2006
Posts: 703
Virginia
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I agree, easy to do. no site plugs in this day and age in stock, holes in butterflys I'm not worried about. will definately lift the carb and if it drips. fuel pump pressure is 6 lbs. Often times, removing the PV will slightly improve the “hit” on the line.
I’d take it out and see what happens........ easy enough to put it back in.
Do the OE bowls have site plugs?
If not, I’m guessing the floats are a little too high, and/or the fuel pressure is slightly too high.
Holes in all 4 butterflies?
Better check the wording on that in the rules.
We had an issue with that years ago.
We had to replace the rear blades(with some that had no holes) before we could continue running, and they disallowed our qualifying runs.
An easy test is lift the carb off the manifold an inch or so, and block it up with something.
Turn on the fuel pump and see if any fuel starts dripping from anywhere underneath.
I’ve seen fuel dripping out from places where it theoretically “couldn’t”.
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Re: Removing power valve
[Re: dvw]
#2648757
04/25/19 09:26 AM
04/25/19 09:26 AM
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Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
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Unless the wording in the rule book has changed, drilling holes in the primary blades is legal....... and no mention of size limits, so they can be big enough to get plenty of air thru to attain a decent idle.
Generally the idle circuit in a factory carb will need some enrichment to supply enough fuel to achieve a decent idle with a cheater cam that has low vacuum.
Perhaps the mods that were done are a bit on the rich side already.
But I strongly suspect there is fuel flowing that’s independent of the motor running.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: Removing power valve
[Re: DaveRS23]
#2648758
04/25/19 09:28 AM
04/25/19 09:28 AM
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Joined: Jun 2006
Posts: 703
Virginia
varunner
OP
super stock
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OP
super stock
Joined: Jun 2006
Posts: 703
Virginia
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I'll measure that and record. I only have a very small amount of the transfer slot exposed. thanks all. The change in the main jet will depend on the size of the PVCRs under the power valve. You can take drill bits and measure the PVCR size and then with a little math figure how much bigger the mains need to be. It won't be exact, but will get a good close starting point for the rest of the tuning.
Power valves and PVCRs are good tuning tools. Rarely do they need to be eliminated, at least on the primaries.
Last edited by varunner; 04/25/19 09:30 AM.
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Re: Removing power valve
[Re: varunner]
#2648761
04/25/19 09:34 AM
04/25/19 09:34 AM
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Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
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I wouldn’t be trying to get it to idle at a low-ish rpm either........ 12-1300 in neutral, hot...... is where I’d be.
And, unless the car was moving........ it wouldn’t be in gear.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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