finding sticking valve
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Mountain Pass
Joined: Jun 2000
Posts: 242
Likes: 9
From: earth
finding sticking valve
How do I find a sticking valve? I've tried to adust my edelbrock carb via the vacuum gauge method and cannot get an consistent accurate reading. @ idle, the needle will drop 1-1.5" every 2-3 seconds, then smooth, then start dropping again. According to the vacuum chart, this drop means a sticking valve and I need to find the most efficient method. The reading drops from 15" @ 750 rpms. Thanks,
Chris
Chris
Lead Driver
Joined: Nov 2000
Posts: 6,636
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From: Albuquerque
finding sticking valve
If you have a bad valve you should show a dip every time that cylinder tries to fire and then jump back up. Like a pulsation. If it just drops off and then climbs back up something else is unhappy.
Freshman User
Joined: Apr 2002
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finding sticking valve
Hi Chris,
I did the same as you to set my carb and I was getting the same thing. I also noticed on my oil pressure gauge, that it seams to have the same fluctuation. I was wondering if both of the fluctuations were due to a "miss" so the rpm's drop suddenly, resulting in a blurp in the oil pressure and vacuum.
I just assumed that I had a miss and didn't know the best way to fix the miss.
Do you have an oil pressure gauge?
Jay
I did the same as you to set my carb and I was getting the same thing. I also noticed on my oil pressure gauge, that it seams to have the same fluctuation. I was wondering if both of the fluctuations were due to a "miss" so the rpm's drop suddenly, resulting in a blurp in the oil pressure and vacuum.
I just assumed that I had a miss and didn't know the best way to fix the miss.
Do you have an oil pressure gauge?
Jay
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Mountain Pass
Joined: Jun 2000
Posts: 242
Likes: 9
From: earth
finding sticking valve
Jay,
My oil pressure drops about 3-4 psi when the vacuum gauge registers the drop. When I drove the truck this morning, the drop is rather consistent while @ idle (i.e. it doesn't idle smoothly).
Chris
My oil pressure drops about 3-4 psi when the vacuum gauge registers the drop. When I drove the truck this morning, the drop is rather consistent while @ idle (i.e. it doesn't idle smoothly).
Chris
Posting Guru
Joined: Jun 2002
Posts: 1,099
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finding sticking valve
I'm not saying that a sticking valve is the problem, but have you tried pulling a plug wire one at a time? It should run rough, but steady if you hit the right cylinder. Use a tach and vac guage to help see any changes.
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