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05-09-2005, 06:36 AM
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CC Member
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Join Date: May 2000
Location: Northern VA,
VA
Cobra Make, Engine: Classic Roadsters
Posts: 2,765
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Not Ranked
Aaaahhhhhhhhh!!!!!!!
Need Holley Power valve info!!!
I have had chronic ignition problems for the past week or two. Finally got that fixed, but in the process, experienced a number of backfires thru the carb. Every time a backfire would occur, the car would run worse and worse. I have a Holly 650 double pumper, and I suspect I blew the power valve.
What happens now is that the car will start and run but with the following symptoms:
Barely idles
Sounds a little "off"
revs up but will not take any load
misses and coughs under load
Does this sound like the symptoms of a blown power valve????
HHHEEEELLLLPPPPP!!!!!
 Ed
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LIFE IS TOO SHORT TO WORRY ABOUT GOOD GAS MILEAGE
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Utinam logica falsa tuam philosophiam totam suffodiant!
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Last edited by CobraEd; 05-09-2005 at 07:01 AM..
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05-09-2005, 06:52 AM
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CC Member
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Join Date: Dec 2000
Location: Los Angeles,
CA
Cobra Make, Engine: E.R.A. FIA #2088 1964 289 w/Webers
Posts: 2,151
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Not Ranked
It's a cheap fix. Pull it & replace it! 
__________________
Hyde D. Baker
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05-09-2005, 07:02 AM
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CC Member
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Join Date: May 2004
Location: Rehoboth Beach,
DE
Cobra Make, Engine: FFR Daytona Coupe done to replicate CSX-2299 at the '64 LeMans
Posts: 641
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Not Ranked
Ed,
You didn't let Scott Harrison tune your carb did you? He is famous for his mushroom-cloud backfires!!
Rob
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05-09-2005, 07:09 AM
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CC Member
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Join Date: May 2000
Location: Northern VA,
VA
Cobra Make, Engine: Classic Roadsters
Posts: 2,765
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Not Ranked
HAHA, No, this is my own personal little fiasco.
__________________
LIFE IS TOO SHORT TO WORRY ABOUT GOOD GAS MILEAGE
________
Utinam logica falsa tuam philosophiam totam suffodiant!
________
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05-09-2005, 07:22 AM
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Member of the north
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Join Date: May 2003
Cobra Make, Engine: A Cobra
Posts: 11,207
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Not Ranked
Ed, it is not a fiasco, tuning is a trial and error type deal.
The power valve is cheap, usually if it is damaged, black smoke will be puffing out he pipes and the engine will be loading up.
Sounds like you may still have ignition problems.
Are all the wires on the right posts and plugs?
Is the timing at final in the right range of what it should be? 30 to 36 degrees?
Are all the vacuum hoses connected correctly?
Just my $0.02
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I'm a writer, feed the artist and buy a book.
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05-09-2005, 07:40 AM
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CC Member
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Join Date: Jun 2003
Location: Australia,
Zzz
Cobra Make, Engine: Shelby alum 468 block
Posts: 14,974
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Not Ranked
Don't lean over it whilst tuning.. 
Bernie
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Bernie Knight
KMS 427 #662 Shelby 468 CSX 1026
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05-09-2005, 07:43 AM
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CC Member
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Join Date: May 2000
Location: Northern VA,
VA
Cobra Make, Engine: Classic Roadsters
Posts: 2,765
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Not Ranked
This really has me bugged. The car has run flawlessly for years.
I am going to double check all the wires again.
__________________
LIFE IS TOO SHORT TO WORRY ABOUT GOOD GAS MILEAGE
________
Utinam logica falsa tuam philosophiam totam suffodiant!
________
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05-09-2005, 03:53 PM
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CC Member
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Join Date: Jul 1999
Location: Prescott Valley,
AZ
Cobra Make, Engine: Previous ERA owner on break
Posts: 600
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Not Ranked
You might want to get a power valve tester to see if yours is really blown:
http://www.jegs.com/cgi-bin/ncommerc...61&prmenbr=361
You'll also need a hand vacuum pump with a reasonably accurate gauge.
I know it's a bit pricey, buying a $32 tool to check a $5 part. However, it's nice to be able to check out the fault to see if it's actually a fault, rather than just changing parts and hoping. My 2 cents, FWIW.
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Some folks drink from the fountain of knowledge; others just gargle.
Yesterday's flower children are today's blooming idiots.
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05-09-2005, 09:21 PM
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CC Member
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Join Date: Mar 1999
Location: TACOMA,
WA
Cobra Make, Engine: Everett Morrision FE 427 so 2-4s
Posts: 2,008
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Not Ranked
Holley and other manufactures make a kit with a drill bit and brass pill with a ball in it that instals in the bottom of the baseplate to prevent the backfire from reaching the powervalve. It is easy to install and not that expensive.
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Mike H
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05-09-2005, 09:27 PM
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Senior Club Cobra Member
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Join Date: Jul 2002
Cobra Make, Engine:
Posts: 15,712
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Not Ranked
The power valve tester is nice, but not really needed. The "tester" will tell you precisely at vacuum the PV will open. If it's a 9.5", then it should open at 9.5".
But if you just want to know if it's "blown", simply "suck" on it! Wrap those lips around that gassy bad boy and see if it holds vacuum! If it does, it's working.
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05-09-2005, 11:37 PM
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Senior Club Cobra Member
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Join Date: Jul 2001
Location: Evans,
CO
Cobra Make, Engine: NAF 289 FIA, 347 stroker with Weber 48's, building a '48 Anglia gasser, driving a '55 Chevy resto-rod
Posts: 3,119
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Not Ranked
Quote:
Originally posted by Bernie Knight
Don't lean over it whilst tuning..
Bernie
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Especially if you are smoking 
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"Breathe in... Breathe out... then move on with life. Lifes too short to sweat the small stuff"
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05-10-2005, 06:42 AM
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CC Member
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Join Date: Mar 2000
Location: Fairfield, NJ, USA,
NJ
Cobra Make, Engine: A & C, 351W, Tremec 3550. Exiled Member: Club Cranky
Posts: 5,897
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Not Ranked
While you are in there I would take the whole thing apart and blow out all the orfices. Also check your fuel filters. I assume you have one between the tank and pump and one between the pump and carb. Also blow out your pressure regulator.
Roscoe
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Roscoe
"Crisis occurs when women and cattle get excited!"....James Thurber
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05-10-2005, 06:52 AM
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CC Member
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Join Date: May 2000
Location: Northern VA,
VA
Cobra Make, Engine: Classic Roadsters
Posts: 2,765
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Not Ranked
Well folks, I have the answer. The problem was not fuel related with the power valve as suspected. I knew that I either replaced or bypassed every component in the ignition so I felt that ignition was OK. Plus I knew that during the problem time I experienced a number of backfires thru the carb, so I figured that I needed to look into the power valve.
BUT, . . . . Last night I found that the little iron "starwheel" that is in the Duraspark distributor and triggers the magnetic pickup was spinning on the shaft. The little rollpin that is supposed to hold it in in place was gone. Not sure how or why. I had taken the starwheel and pickup off earlier during the initial problems, and I know I put the pin in there, but it was gone and so my timing was all over the place.
So that is the end of Ed's enigmatic saga!!
Life is good again. No more laying in bed at night sweating and trembling
Thanks to everyone for your help.
Ed
__________________
LIFE IS TOO SHORT TO WORRY ABOUT GOOD GAS MILEAGE
________
Utinam logica falsa tuam philosophiam totam suffodiant!
________
Last edited by CobraEd; 05-10-2005 at 07:04 AM..
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