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#1 |
Registered User
Join Date: Jan 2007
Location: Garland,TX
Posts: 431
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pcv question
Hi everybody. the other day i got the bright idea to get rid of my pcv and put a breather cap in its place. on the carb were the pcv hose was connected i put a little tuner breather/paper filter. now the truck seems to idle really high obvouisely, you can really hear the carb sucking in all that extra air. it almost sounds like i have a blower. anyways my question is wether theres any advantages to running a setup like this. the motor should still be getting vented properly through the cap breather on the valve cover right. one thing i noticed is that my truck is a little harder to start, i have to give it some gas so it wont stall.
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#2 |
Registered User
Join Date: Aug 2006
Location: Bakersfield,CA
Posts: 7,893
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Re: pcv question
if youre having to give it gas so it wont stall its because the hole where the hose went to under the carb isnt sealed good enough, but it should be fine cause my pvc is there but not working, i stuffed it full of silicone and my truck runs fine
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-steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME |
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#3 |
Registered User
Join Date: Aug 2006
Location: Bakersfield,CA
Posts: 7,893
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Re: pcv question
i just noticed that you said you put a breather on the carb where the hose went and thats why it wants to stall, you need to go to the parts store and get a little cap to put over it then it wont stall
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-steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME |
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#4 |
Registered User
Join Date: Apr 2006
Location: MinneSNOWta
Posts: 1,381
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Re: pcv question
![]() You have to seal off the PCV port on your carb/throttle body. essentially you have a huge vaccum leak leaving it open, and that's the sound you are hearing, all the air being sucked through the little filter you installed. Get a cap from your local parts store. ![]()
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2003 GMC Sierra 1500 WT 1995 Nissan Hardbody 2016 Hyundai Veloster Turbo DC2 (SW/AW) Clyde W. Harvey USN "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery" Winston Churchill |
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#5 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: pcv question
dumb idea
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#6 |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,872
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Re: pcv question
Don't be surprised when you start getting a miss,and discover a burnt piston.You are running WAY lean like that.
There is a very good and sound mechanical justification for the PCV system and it should be installed and working properly. What is gained by disabling it anyway?
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
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#7 |
Dave's not here, man
Join Date: Jun 2004
Location: Winder, Georgia
Posts: 2,000
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Re: pcv question
I agree with working Longhorn. With that breather attached to the carb base, you are sucking additional fresh air into the motor; it's acting like an extra air cleaner which will affect your fuel air mixture. I also don't think the breather you have installed on the opposite valve cover will extract hydrocarbons as efficiently as a PCV system. They've been in use for 40+ years for a reason, but it's your truck.
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- 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 |
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#8 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,526
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Re: pcv question
If I was disabling all the smog systems on my truck, that would be the one thing I left alone. It removes the hydrocarbons from the unburnt fuel that finds its way into the crankcase and also removes moisture thus helping to keep the oil clean
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#9 | |
Registered User
Join Date: Sep 2006
Location: League City, Texas
Posts: 732
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Re: pcv question
Quote:
![]() Just leave the pcv hooked up, I can't see how it would hurt the engine or performance in any way. Plus it is not big enough to be an eye sore. |
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#10 |
Registered User
Join Date: Jan 2007
Location: Garland,TX
Posts: 431
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Re: pcv question
thanks for all your input, i guess its going back on.
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#11 |
Senior Member
Join Date: Nov 2006
Location: Yukon Oklahoma
Posts: 2,647
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Re: pcv question
Great idea, I had a 350 w[o a working pcv and it ran like crap and I had v/c seals leaking and lots of oil blowing thru the breather on my valve covers. Put a working pcv in problem solved.
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Happiness is towing your "new" truck home. 1972 C-10 1982 GMC (parts truck??) ![]() 1969 c10 parts truck 1969 C-10 ( my sons) 1992 Silverado 4X4 (now the boys truck)(now mine again ![]() 2002 Tarus (my wife loves that car) |
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#12 |
Registered User
Join Date: Dec 2004
Location: Northern AZ
Posts: 7,271
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Re: pcv question
They came up with the PCV (positive crackcase ventilation) because cars caught on fire and some blew up. The fumes (blowby) need to go somewhere and back into the combustion chamber is the best and safest, it can marginally help mpg, but will keep you from having a big fire ball erupt under your hood!! You need a breather on one valve cover and the pcv on the other. I had a front seal make a weird noise once when I had suck on one side and no inlet on the other!! I was baffled by that one!!
Last edited by 70rs/ss; 02-21-2007 at 01:26 PM. |
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#13 |
Semi-Senior Member
Join Date: Feb 2003
Location: Washington, MO
Posts: 390
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Re: pcv question
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'68 50th Anniversery LWB Custom Fleetside, '77 305 v-8, turbo 350, factory speed alert (still works), '71 drivetrain w/front discs. Some call it ugly yellow, others call it Ochre '83 Jeep CJ-7, <80,000 miles, original owner '04 Chevy Suburban, 4x4, 2500, 6.0 ltr, Predator Diablo programmer '95 GMC K1500 Extended cab |
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#14 |
Registered User
Join Date: Aug 2006
Location: Bakersfield,CA
Posts: 7,893
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Re: pcv question
after reading about the sludge and mpg and the others i think ill put mine back on becuase id never heard any of that before all i heard was that it was just a breather and figured why bother with if its just a breather but thanks for the new outlook on it and ill go get a new one and put it in this weekend
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-steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME |
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#15 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: pcv question
Plug the big vacuum leak, on the carb.......
Can you give us an idea of why you put a filter on the carb's PCV connection port? |
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#16 |
To The Levy
Join Date: Jan 2007
Location: california
Posts: 391
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Re: pcv question
The P.C.V system is not a power robbing component, (positive crankcase ventilation) It's purpose is to remove crankcase pressures built up in the crankcase from blowby gases that produce during combustion. by removing this and just venting to atmospher is ok, but , why just be ok, why not be better and have the engine just pull em out and reburn? As far as your high Idle, I will agree with above mentioned, you have to PLUG it off completely, not filtered. but in my opinion, I would want the pcv on and working.
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#17 |
Junior Member
Join Date: Jan 2007
Location: Dallas, TX
Posts: 246
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Re: pcv question
yeah my pcv lines are not hooked up, and mine idles REALLY high when its out of gear. i wonder if thats why it idles so high?
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#18 |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,872
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Re: pcv question
Yeah that's probably why. Hook it back up! You will damage your engine running so lean.
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
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#19 |
Registered User
Join Date: Dec 2004
Location: Saskatchewan, Canada
Posts: 1,371
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Re: pcv question
The stock PCV things are a complex looking little unit with moving parts in them and such, where the aftermarket ones are just an empty tin can with a hose barb on one end (like a breather with no guts in it and a hose barb out the side). Is there any advantage/disadvantage to either style?
Also, on the other valve cover, is it better to run an open element breather, or a pipe to the air cleaner? Thanks!
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1964 Chevy Short Fleet: Tornado 1972 Chevy C10: Fast Orange Secondaries Wide Open |
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#20 |
Account Suspended
Join Date: Mar 2003
Location: ** THE FALL GUY **CHICAGO IL
Posts: 5,883
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Re: pcv question
guy's you half to have a pvc valve.. it's like a truck with no brakes
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#21 | |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: pcv question
Quote:
I stand by that one should always have the PCV valve in the flowpath--it does a couple of things: 1) provides a back flow check valve in case your engine backfires and, 2) it gives a restriction (throttled orifice) for the vacuum flow from the engine crankcase--so you won't have that fast idle condition. It is a designed vacuum leak, not a gaping hole in your intake manifold. That way you control the leak and do not run lean. If you so choose, you can run the engine, as they did in the old days with just a breather or two on the crankcase. I don't recommend it, because the design of the PCV system maintains a slight vacuum on the crankcase, thus eliminating all of those unsightly oil leaks and making the engibne work less. |
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#22 |
Registered User
Join Date: Aug 2006
Location: Bakersfield,CA
Posts: 7,893
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Re: pcv question
i dont know about the high idle thing becuase mine idled the same before and after i plugged up the pcv, the idle screw needs to be turned down to lower the idle
so is there a real advantage to running a pvc vs not running one? the reason im thinking of putting it back is becuase i saw something about better mpg other than that i have 2 breathers, and about the backfiring, my truck backfired a couple times before i plugged it but since i plugged it up it hasnt backfired, i dont know im just confused, like usual ![]()
__________________
-steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME |
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#23 |
Dave's not here, man
Join Date: Jun 2004
Location: Winder, Georgia
Posts: 2,000
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Re: pcv question
Your truck most likely backfired as a result of hydrocarbons igniting. As mentioned earlier in the thread, the PCV rids the crankcase of these flammable gases, which are a byproduct of combustion. You're lucky you didn't have a catastrophe. The PCV also helps to prevent sludge from building up in the motor. This system would not be omnipresent in the automotive world if it didn't serve a purpose. I would put it back if I were you, but that's just my opinion.
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- 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 |
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#24 | |
Semi-Senior Member
Join Date: Feb 2003
Location: Washington, MO
Posts: 390
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Re: pcv question
Quote:
As to the question as to if you should run it...... The board members who are telling you to run it are either mechanics, have been mechanics, or know a lot about engines. I've seen some of their posts in the past , for what it's worth, they know their sh*t. You decide who is right......I already do.
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'68 50th Anniversery LWB Custom Fleetside, '77 305 v-8, turbo 350, factory speed alert (still works), '71 drivetrain w/front discs. Some call it ugly yellow, others call it Ochre '83 Jeep CJ-7, <80,000 miles, original owner '04 Chevy Suburban, 4x4, 2500, 6.0 ltr, Predator Diablo programmer '95 GMC K1500 Extended cab Last edited by 68speedalert; 02-23-2007 at 11:03 AM. |
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#25 |
Registered User
Join Date: Sep 2005
Location: 9000' Mountain Man
Posts: 326
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Re: pcv question
The military started using pcv back in the 1940's on their vehicles....long before anyone even thought of emission controls. There is a reason for them.
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