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Discussion Starter · #1 ·
Could someone please identify this strange canister connected to my carburetor in the top right of the attached picture? (on a 1978 GMC 350). It looks like a pcv valve but is not connected to the crank case. Does not do anything when blocked off.
 

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x2 fuel filter
where is it connected???


someone probly used it on a vent line to keep the big rocks out..
 

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Discussion Starter · #5 ·
x2 fuel filter
where is it connected???


someone probly used it on a vent line to keep the big rocks out..
Thanks. I knew it wasn't a pcv as the goodwrench crate engine doesn't have one. A fuel filter though, that's kind of strange to be connected to a vacuum line.
 

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farther down behind the radiator core support. is the carbon canister.. the separator layer in there sometimes fails.. causing carbon granuals to get blown/sucked into the carb bowl vent and the vapor control valves..

leave it in place..

you may need to replace the carbon canister.

by the way the fuel vapor system does a lot of good also.. catches gas tank vapors and absorbs them in the carbon granuals.. so when you start the engine the purge control valve opens and allows them to be pulled in a burned.. instead of escaping to the atmosphere.
 

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Thanks. I knew it wasn't a pcv as the goodwrench crate engine doesn't have one. A fuel filter though, that's kind of strange to be connected to a vacuum line.
Whoa!! Back up!!
Your goodwrench crate doesn't have a pcv!
If you like lots of oil leaks then leave it as is.
But, you need a pcv for several reasons.
1. Release crankcase pressure.
2. Help remove blowby gases.
3. Help remove moisture.

Wayne will pop back and tell me I missed a few but the bottom line is
'You need a pcv system'!!
 

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Discussion Starter · #8 ·
Whoa!! Back up!!
Your goodwrench crate doesn't have a pcv!
If you like lots of oil leaks then leave it as is.
But, you need a pcv for several reasons.
1. Release crankcase pressure.
2. Help remove blowby gases.
3. Help remove moisture.

Wayne will pop back and tell me I missed a few but the bottom line is
'You need a pcv system'!!
I was a little hasty in saying it doesn't have a PCV. What I meant was that I hadn't ever seen one on it and it probably has one. I always think that a PCV valve is something integrated in the smog era and is bad, but I have it confused with an EGR most of the time which, luckily, this truck never had.
 

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Discussion Starter · #12 ·
Then you've got a PCV. I agree with Rwenuts that running a pcv is a good thing. Breather can also be placed on there in place of pcv but would go pcv route as suggested,
It has a hose to the carb and also a breather. The breather most likely decreases the effectiveness of the PCV if my thinking is correct. Also will a PCV decrease power output?
 

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It has a hose to the carb and also a breather. The breather most likely decreases the effectiveness of the PCV if my thinking is correct. Also will a PCV decrease power output?
the PCV flow pulls excessive oil and fuel vapors from the crank case...

the Breather filter allows air to be pulled in when the PCV is pulling more than the piston rings are bypassing.. without a filter in the breather.. you will be pulling dirt from the underhood area into the crankcase... not a good thing.

the crankcase breather not only filters the usually incoming air into the crankcase. but it also also allows the excessive blowby to escape the crankcase.. this keeps the crankcase pressure right at zero...
 

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Discussion Starter · #15 ·
does the extra fuel filter hose go to the big port on the top front center of the carb??
I haven't looked at it in a while but I believe it's somewhat off center and angled toward the driver's side. It is at the top though.
 

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It has a hose to the carb and also a breather. The breather most likely decreases the effectiveness of the PCV if my thinking is correct. Also will a PCV decrease power output?
Not running a PCV can bring the potential of oil build up/sludge. Most cars run a breather on one valve cover and a pcv on the other. In my opinion it really does not matter which sides you choose. I have run breathers on both covers before due to some edelbrock valve covers I bought 20 some odd years ago but that's the only time I ran a set up like that. Again though, its best to run a breather on one cover and a pcv on the other,
 

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Discussion Starter · #17 ·
Not running a PCV can bring the potential of oil build up/sludge. Most cars run a breather on one valve cover and a pcv on the other. In my opinion it really does not matter which sides you choose. I have run breathers on both covers before due to some edelbrock valve covers I bought 20 some odd years ago but that's the only time I ran a set up like that. Again though, its best to run a breather on one cover and a pcv on the other,
It's got a PCV on the passenger side and a breather on the driver's.
 
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