Wierd PCV system!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sjarrett71 · 07-09-2010, 10:54 PM

Hey guys, check this out and tell me what you think. I have removed the oil fill cap and replaced it with a breather. That's the best I could do for now because the other two holes where the pcv valves are were too small to do anything with. Also, what hose is supposed to be connected to the metering block on a Holley carb? I'm posting some pics of the PO's damage. Any advice on how to clean this up would be great!

Longhorn Man · 07-09-2010, 11:04 PM

why are you running 2 PCV valves?
remove one of them, install the breather in the now empty hole, and then put the cap back on the front hole

sjarrett71 · 07-09-2010, 11:06 PM

It's the way the PO had it. I got a breather and put it in the oil fill hole because I couldn't find one wiht a small enough shaft to fit in the PVC hole. Can you tell me what hose is suppose to go where on a Holley carb? I've had several Edelbrock carbs but never a Holley.

71swb4x4 · 07-09-2010, 11:08 PM

Get a smaller bushing to run your breather in.

sjarrett71 · 07-09-2010, 11:10 PM

It's not the bushing, it's the actual hole. The breather wouldn't even fit without the grommet.

sjarrett71 · 07-09-2010, 11:15 PM

If you notice where the brake booster vacuum house mounts to the carb, can I take it off there and mount it to the intake manifold and then attach the PCV hose in that location on the carb? What hose is supposed to be mounted to the metering block or can I plug it off? The vacuum advance hose is attached the front bottom of the carb.

QKENUF4U · 07-10-2010, 12:54 AM

WOW WHAT A CLUSTER FUDGE THAT IS !!!!
1. remove the hoses from the carb thats run to the two PCV's (think i either used that for my distributer or plugged it)
2. the PCV's can go to the back of the intake in the first pic (in front of the dist. where the brass line/fitting is between the hoses) make up a T fitting there and plumb brakes off that
3. ONLY ONE PCV needed.. the other side needs to be the breather (they make new rubber plugs to fit the holes with the correct size hole for the breather)

[IMG

cdowns · 07-10-2010, 01:15 AM

that craks me up an excellent illustration of what can b done by a parts changer with no clue as to what the proper way is . who needs a service manual, just friger it out

vectorit · 07-10-2010, 01:49 AM

No wonder the carb intakes are all black...

sjarrett71 · 07-10-2010, 08:38 AM

Quote:

Originally Posted by QKENUF4U

WOW WHAT A CLUSTER FUDGE THAT IS !!!!
1. remove the hoses from the carb thats run to the two PCV's (think i either used that for my distributer or plugged it)
2. the PCV's can go to the back of the intake in the first pic (in front of the dist. where the brass line/fitting is between the hoses) make up a T fitting there and plumb brakes off that
3. ONLY ONE PCV needed.. the other side needs to be the breather (they make new rubber plugs to fit the holes with the correct size hole for the breather)

[IMG

That WAS the fuel line. I just moved it over there to get it out of the way. I ended up replacing it. There was a metal line from the fuel pump then a rubber line then the fuel filter then a rubber line then a metal line then a rubber line then the metal line into the carb. Can you see why I replaced it?

sjarrett71 · 07-10-2010, 08:46 AM

QKENUF4U, THANK YOU for the info!!! If we could still give rep points I'd load you up!

jorgensensc · 07-10-2010, 10:44 AM

QKENUF4U,
The only thing I'm not sure I agree with on what ou said was the manifold vacuum. If he has an automatic he needs to run the tranny off that port. I'm not sure with holleys, but I always run my brake booster line off the carb ( maybe where it's at now on the carb) and run the PVC off another port that comes off the carb. ( maybe that's also on the same port it's on now). For sure you need to have one PVC on one valve cover, and a breather on the other. Right now the PVC's are pulling major vacuum on the engine. The breather is needed to create that inlet flow of air, so the PVC can pull air through the engine. However, be ready for some smoking to occur. I had somebody tell me once doing it this way was a way to pull vacuum and help reduce oil by the valve seals. When you take it off you may have more oil consumption and smoking.
Shawn

sjarrett71 · 07-10-2010, 11:20 AM

Thanks for the input Shawn. The truck has a 4 speed tranny so no need for a vacuum line for it. I'm gonna hook the brake booster up to the rear of the manifold, the PCV valve to the large port on the rear side of the carb, the vacuum advance to the small port of the front/underside of the carb, and block off the port on the metering block. I guess I'll look for another breather assy with a smaller shaft to fit in the rear hole in the valve cover on the driver side of the engine and put the oil cap back in the front hole.

Camaro_nut2001 · 07-10-2010, 11:34 AM

Ok, you need to run one of your PVC"s to the big port on the back of the carb, it's in the base plate. Do away completely with the other PVC. Put you Dist. on the port on the front metering block and plug off the small port on the bottom right side front of your carb. Put a 90 degree fitting in the intake behind your carb and run your booster off of it. Before you hook up your lines correctly, clean out the metering block port and both base plate ports with carb cleaner as I would say if the motor has been run this way for a while you have gumed up oil in your carb. Good thing you replaced that fuel line setup. JM2C

Tomahawk30 · 07-10-2010, 12:41 PM

I got a laugh out of this.... I picked up a 78 Chevy 3/4 ton 4x4 last year that had that same dual pcv valve setup for some odd reason. I admit to a WTF moment when I first saw it...

RichardJ · 07-10-2010, 02:28 PM

PCV systems are really quit simple. Fresh air enters one side of the engine, mixes with the crankcase fumes, exits the other side of the engine through the PCV valve and goes into the intake manifold. The engine burns the fumes along with the gasoline. The PCV valve controls the rate of flow of the crankcase fumes.
The drawing below is flipped left for right from what you are probably going to do.

You will notice that in the drawing there is a hose from the air cleaner to, the valve cover. The air entering the crankcase through the carb air filter is going to be filtered better than a seldom cleaned or replaced valve cover filter.
There is another thing to consider. When an engine gets older and worn, the PCV system cannot handle all the crankcase fumes and blow-by. Under high load conditions such as on a hill or WOT , some of the excess fumes will reverse direction in the hose to the air cleaner. The carb will suck these fumes in and they will be burned. If you only have a valve cover breather, the excess fumes will spew into the engine compartment.

This is called a Closed System and ALL crankcase fumes and blow-by are consumed in engine combustion.

In case you missed Camaro nut2001's post, the upper metering block port on a Holley is "ported" vacuum. That is the port generally used for distributor vacuum advance. The front bottom port is used for other emission systems if present.

sjarrett71 · 07-10-2010, 03:09 PM

Thank you RichardJ. I'm gonna get this thing straightened out tonight after I get off work and after I mow the yard.

Rollie396 · 07-10-2010, 03:31 PM

You mentioned that your breather is too big for the hole in your stock valve covers.Seems that most aftermarket valvecover breathers are for 1 1/4" holes but the stockers are only 1".I had the same issue and after some looking around I found a chrome breather made by RPC that worked for me.I don't have a part number for you but this is their website http://www.racingpowercompany.com/in...cPath=0_14.The Bumper to Bumper here stocks them.

sjarrett71 · 07-10-2010, 04:43 PM

Thanks for the info! I'll probably end up changing the valve covers anyway but it's another link to add to my "favorites"!

C20-67_N_MO · 07-10-2010, 04:56 PM

RichardJ the system you have shown is the CLOSED system. But most PCV systems these days just have an open breather that is NOT attached to the under side of the air cleaner and is considered an OPEN PCV system.

just a FYI for everyone.

Longhorn Man · 07-10-2010, 06:31 PM

the closed system is prefered, and required for the smog police if your state enforces it (1964 and up on cars, and 69 and up in light duty pickups).

sjarrett71 · 07-11-2010, 11:42 AM

Well I got everything fixed with the PCV system! I got a new nipple for the rear of the manifold for the brake booster, I only have one PCV valve now with a hose to the rear bottom of the carb, the distributor hose is attached to the metering block and the small nipple on the front of the carb is blocked off. I also found a breather with a small shaft to replace the "extra" PCV valve with so I could replace the oil cap. I'll try to post picks up this evening.

07-09-2010, 10:54 PM	#1
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Wierd PCV system!! Hey guys, check this out and tell me what you think. I have removed the oil fill cap and replaced it with a breather. That's the best I could do for now because the other two holes where the pcv valves are were too small to do anything with. Also, what hose is supposed to be connected to the metering block on a Holley carb? I'm posting some pics of the PO's damage. Any advice on how to clean this up would be great! __________________ -Scott-

07-09-2010, 11:04 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Wierd PCV system!! why are you running 2 PCV valves? remove one of them, install the breather in the now empty hole, and then put the cap back on the front hole

07-09-2010, 11:06 PM	#3
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! It's the way the PO had it. I got a breather and put it in the oil fill hole because I couldn't find one wiht a small enough shaft to fit in the PVC hole. Can you tell me what hose is suppose to go where on a Holley carb? I've had several Edelbrock carbs but never a Holley. __________________ -Scott-

07-09-2010, 11:08 PM	#4
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Wierd PCV system!! Get a smaller bushing to run your breather in. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

07-09-2010, 11:10 PM	#5
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! It's not the bushing, it's the actual hole. The breather wouldn't even fit without the grommet. __________________ -Scott-

07-09-2010, 11:15 PM	#6
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! If you notice where the brake booster vacuum house mounts to the carb, can I take it off there and mount it to the intake manifold and then attach the PCV hose in that location on the carb? What hose is supposed to be mounted to the metering block or can I plug it off? The vacuum advance hose is attached the front bottom of the carb. __________________ -Scott-

07-10-2010, 12:54 AM	#7
QKENUF4U Senior Member Join Date: Jan 2005 Location: SUNNY WARM BIKE RIDING COTTONWOOD ARIZONA Posts: 2,097	Re: Wierd PCV system!! WOW WHAT A CLUSTER FUDGE THAT IS !!!! 1. remove the hoses from the carb thats run to the two PCV's (think i either used that for my distributer or plugged it) 2. the PCV's can go to the back of the intake in the first pic (in front of the dist. where the brass line/fitting is between the hoses) make up a T fitting there and plumb brakes off that 3. ONLY ONE PCV needed.. the other side needs to be the breather (they make new rubber plugs to fit the holes with the correct size hole for the breather) [IMG Last edited by QKENUF4U; 07-10-2010 at 01:06 AM.

07-10-2010, 01:15 AM	#8
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Wierd PCV system!! that craks me up an excellent illustration of what can b done by a parts changer with no clue as to what the proper way is . who needs a service manual, just friger it out __________________ 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 Last edited by cdowns; 07-10-2010 at 01:15 AM.

07-10-2010, 01:49 AM	#9
vectorit What? Join Date: Jun 2007 Location: Southern California Posts: 7,617	Re: Wierd PCV system!! No wonder the carb intakes are all black... __________________ Chris 1968 K20 Suburban 1972 K10 LWB PU

07-10-2010, 08:46 AM	#11
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! QKENUF4U, THANK YOU for the info!!! If we could still give rep points I'd load you up! __________________ -Scott-

07-10-2010, 10:44 AM	#12
jorgensensc Registered User Join Date: Jul 2003 Location: Cypress, Tx Posts: 4,005	Re: Wierd PCV system!! QKENUF4U, The only thing I'm not sure I agree with on what ou said was the manifold vacuum. If he has an automatic he needs to run the tranny off that port. I'm not sure with holleys, but I always run my brake booster line off the carb ( maybe where it's at now on the carb) and run the PVC off another port that comes off the carb. ( maybe that's also on the same port it's on now). For sure you need to have one PVC on one valve cover, and a breather on the other. Right now the PVC's are pulling major vacuum on the engine. The breather is needed to create that inlet flow of air, so the PVC can pull air through the engine. However, be ready for some smoking to occur. I had somebody tell me once doing it this way was a way to pull vacuum and help reduce oil by the valve seals. When you take it off you may have more oil consumption and smoking. Shawn __________________ 1972 C20 Suburban- Big Blue Betty '56 Chevy Bel Air Sedan- Frame up Restoration -What would you attempt to achieve if you knew you could not fail?- -I Refuse To Tiptoe Through Life, Only To Arrive Safely At Death's Door- R.I.P. EAST SIDE LOW LIFE

07-10-2010, 11:20 AM	#13
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! Thanks for the input Shawn. The truck has a 4 speed tranny so no need for a vacuum line for it. I'm gonna hook the brake booster up to the rear of the manifold, the PCV valve to the large port on the rear side of the carb, the vacuum advance to the small port of the front/underside of the carb, and block off the port on the metering block. I guess I'll look for another breather assy with a smaller shaft to fit in the rear hole in the valve cover on the driver side of the engine and put the oil cap back in the front hole. __________________ -Scott-

07-10-2010, 11:34 AM	#14
Camaro_nut2001 Chevy Lover Till The End. Join Date: Dec 2009 Location: Mascot TN. Posts: 795	Re: Wierd PCV system!! Ok, you need to run one of your PVC"s to the big port on the back of the carb, it's in the base plate. Do away completely with the other PVC. Put you Dist. on the port on the front metering block and plug off the small port on the bottom right side front of your carb. Put a 90 degree fitting in the intake behind your carb and run your booster off of it. Before you hook up your lines correctly, clean out the metering block port and both base plate ports with carb cleaner as I would say if the motor has been run this way for a while you have gumed up oil in your carb. Good thing you replaced that fuel line setup. JM2C __________________ 1969 Chevy SWB Big Block - Under the knife as of 12/26/2011 1989 Chevy Silverado, 4X4 - Daily Driver 1996 Chevy Suburban K1500 - 4-Wheeler, Campin Truck 1968 Chevrolet Impala Sport Coupe - 327/350hp, TH400, all original. Members I've met: BamaBaxter, My Build: http://67-72chevytrucks.com/vboard/s...d.php?t=500359 Last edited by Camaro_nut2001; 07-10-2010 at 11:36 AM. Reason: Just saw something I missed.

07-10-2010, 12:41 PM	#15
Tomahawk30 Registered User Join Date: Jun 2010 Location: Russellville, KY Posts: 956	Re: Wierd PCV system!! I got a laugh out of this.... I picked up a 78 Chevy 3/4 ton 4x4 last year that had that same dual pcv valve setup for some odd reason. I admit to a WTF moment when I first saw it... __________________ 1979 Silverado C10 Shortbox - Photo Album 1977 Silverado K20 Camper Special - Photo Album 1972 C10 Custom Deluxe Highlander - sold 1971 Cheyenne Super Longhorn -sold 1972 Cheyenne Super SWB 4x4 -sold, bought back, sold again... I'm dumb. 1970 Chevy C10 SWB "Sprout" -sold 1972 Cheyenne K20 -sold 1969 GMC Shortbox Stepside 4x4 -sold 1972 GMC Jimmy 4x4 -sold

07-10-2010, 02:28 PM	#16
RichardJ Registered User Join Date: Apr 2010 Location: So Cal Posts: 1,466	Re: Wierd PCV system!! PCV systems are really quit simple. Fresh air enters one side of the engine, mixes with the crankcase fumes, exits the other side of the engine through the PCV valve and goes into the intake manifold. The engine burns the fumes along with the gasoline. The PCV valve controls the rate of flow of the crankcase fumes. The drawing below is flipped left for right from what you are probably going to do. You will notice that in the drawing there is a hose from the air cleaner to, the valve cover. The air entering the crankcase through the carb air filter is going to be filtered better than a seldom cleaned or replaced valve cover filter. There is another thing to consider. When an engine gets older and worn, the PCV system cannot handle all the crankcase fumes and blow-by. Under high load conditions such as on a hill or WOT , some of the excess fumes will reverse direction in the hose to the air cleaner. The carb will suck these fumes in and they will be burned. If you only have a valve cover breather, the excess fumes will spew into the engine compartment. This is called a Closed System and ALL crankcase fumes and blow-by are consumed in engine combustion. In case you missed Camaro nut2001's post, the upper metering block port on a Holley is "ported" vacuum. That is the port generally used for distributor vacuum advance. The front bottom port is used for other emission systems if present. Attached Images __________________ '67 GMC 2500, 292, 4spd, AC



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07-10-2010, 03:09 PM	#17
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! Thank you RichardJ. I'm gonna get this thing straightened out tonight after I get off work and after I mow the yard. __________________ -Scott- Last edited by sjarrett71; 07-10-2010 at 03:09 PM.

07-10-2010, 03:31 PM	#18
Rollie396 someday it will be done! Join Date: Sep 2004 Location: Lloydminster,AB. Canada Posts: 1,620	Re: Wierd PCV system!! You mentioned that your breather is too big for the hole in your stock valve covers.Seems that most aftermarket valvecover breathers are for 1 1/4" holes but the stockers are only 1".I had the same issue and after some looking around I found a chrome breather made by RPC that worked for me.I don't have a part number for you but this is their website http://www.racingpowercompany.com/in...cPath=0_14.The Bumper to Bumper here stocks them. __________________ '72 C-10 Proud owner of a million new and used pieces that used to be and will once again be(god willing) a testament to the term "they don't build em like that anymore. '80 LWB 2wd beater '67 GMC long fleet (cab donor) '66 long step (parked till it's turn comes around) '65 short step (parts truck that will donate it's bed and possibly frame to the '66) '06 Grand Prix wife's car (she hardly lets me touch it) my pics

07-10-2010, 04:43 PM	#19
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! Thanks for the info! I'll probably end up changing the valve covers anyway but it's another link to add to my "favorites"! __________________ -Scott-

07-10-2010, 04:56 PM	#20
C20-67_N_MO Champagne Taste on Beer Budget Join Date: Dec 2008 Location: High Ridge, Missouri Posts: 2,190	Re: Wierd PCV system!! RichardJ the system you have shown is the CLOSED system. But most PCV systems these days just have an open breather that is NOT attached to the under side of the air cleaner and is considered an OPEN PCV system. just a FYI for everyone. __________________ Coming Soon: Project 1970 Country Truck

07-10-2010, 06:31 PM	#21
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Wierd PCV system!! the closed system is prefered, and required for the smog police if your state enforces it (1964 and up on cars, and 69 and up in light duty pickups).

07-11-2010, 11:42 AM	#22
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: Wierd PCV system!! Well I got everything fixed with the PCV system! I got a new nipple for the rear of the manifold for the brake booster, I only have one PCV valve now with a hose to the rear bottom of the carb, the distributor hose is attached to the metering block and the small nipple on the front of the carb is blocked off. I also found a breather with a small shaft to replace the "extra" PCV valve with so I could replace the oil cap. I'll try to post picks up this evening. __________________ -Scott-

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