carburetor question
Cargo Master
Joined: May 2004
Posts: 3,007
Likes: 5
When you push on the accelerator pedal, the power valve shoots some gas into the air stream going thru the carb.
Have someone step on the accelerator while you look down the carb, if you see a small stream of gas shoot out, it's working.
Have someone step on the accelerator while you look down the carb, if you see a small stream of gas shoot out, it's working.
Senior User
Joined: Aug 2002
Posts: 108
Likes: 0
Honestly, I am not sure a stock motorcraft carb. has a power valve. I know my holley does.
If the power valve is blown, it would run fine for a few seconds, then start to "load up" or flood then die because the fuel flow is not being cut off when it should. That is the easiest way of knowing when a power valve is blown.
Honestly, I have never blown one in either of my two Holley's that I have had on my truck, and trust me, it backfired up thru the carb. hundreds of times.
Hope this helps.
If the power valve is blown, it would run fine for a few seconds, then start to "load up" or flood then die because the fuel flow is not being cut off when it should. That is the easiest way of knowing when a power valve is blown.
Honestly, I have never blown one in either of my two Holley's that I have had on my truck, and trust me, it backfired up thru the carb. hundreds of times.
Hope this helps.
Senior User
Joined: Aug 2002
Posts: 108
Likes: 0
G-k90, you are thinking of the acell. pump, which is conrolled directly by the pedal. Yes, you will see gas if you step on the pedal. The power valve he is talking about controls the flow of gas from the fuel bowl into the venturi's and there is no way to visually check it.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
The power valve dumps fuel when you really need it, so if it's blown, it's going to be dumping fuel all the time. You're going to be running very rich and probably blowing lots of black smoke. It's located a little more "in" the carb so you're not going to be able to see it while looking down the barrels.
Newer Holleys have power valve blowout protection, so yeah, you could back fire and not damage them. But if it is an older carb, it may not, and a single back fire and *poof*, blown power valve.
Newer Holleys have power valve blowout protection, so yeah, you could back fire and not damage them. But if it is an older carb, it may not, and a single back fire and *poof*, blown power valve.
Senior User
Joined: Aug 2002
Posts: 108
Likes: 0
I know the 600 I have on it now has protection and I think my 750 did as well. Never delt with a really old holley. Can rebuild one in an hour too.
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
No kidding. Rebuilding my new 4bbl took a fraction of the time it took me to rebuild the 300's original 1bbl. Holley's are a sinch.
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