Crankshaft vent - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ChevyRatRod · 04-17-2011, 08:52 PM

i have a 67 chevy that had a two barrel carb. i took off the old carb and intake manifold. i replaced the intake with one i had #3927184 ( new intake manifold). the new intake doesnt have an oil fill tube so i replaced the valve covers with new edelbrock valve covers and put a breather in them. now i have no place to run my crank shaft vent hose to so i was wondering if i could just cap the hole since i have the breather in the valve cover???? any advice would help!!!!

cableguy0 · 04-17-2011, 09:12 PM

Are you talking about a road draft tube or a pcv? You need a pcv to stop the engine from spewing oil and keep the gasses out of the crankcase. You should have a breather in one valve cover and a pcv valve in the other valve cover.

ChevyRatRod · 04-17-2011, 09:33 PM

i have a breather in one and i dont have anything in the other yet what is this pvc? can you explain it more please?

ChevyRatRod · 04-17-2011, 09:38 PM

pcv

cableguy0 · 04-17-2011, 09:47 PM

Positive crankcase ventilation. It uses engine vacuum to suck the fumes moisture and other bad stuff out of the crank case. If pressure is allowed to build up inside the engine it can cause oil leaks by pushing out the gaskets. Way back in the day they used a road draft tube which basically just let oil blow out of the engine onto the ground which served as the vent but that isnt the best way for obvious reasons.

ChevyRatRod · 04-17-2011, 09:51 PM

so do i connect the old crankshaft vent (that went to the air filter before) to the pcv valve in the other valve cover? i would post a pic but i dont know how. sorry

cableguy0 · 04-17-2011, 10:11 PM

Ahhh i understand now. Forget about the tube that went to the intake. Its not needed with the aftermarket breathers that go into the valve cover. The other valve cover should have a hole about the same size as the one you put the breather in. INstall a pcv valve into that hole with a grommit. Then run a vaccum hose from the pcv to the large vacuum port at the base of the carburetor.

ChevyRatRod · 04-17-2011, 10:43 PM

ok cool but what about the old hole? it is still open so can i just make a cover for it and plug it or do i need to do something else with it?

GASoline71 · 04-17-2011, 10:50 PM

Pictures would be great...

Gary

ChevyRatRod · 04-17-2011, 10:57 PM

no the hole going into the block next to the distributor. i would post a pic but i dont know how to post it. i have one on my comp right now, everytime i try it asks me for a http: for my pic or something

cableguy0 · 04-17-2011, 10:59 PM

Ohhhh your engine has a road draft tube. If you run a pcv and breather you can eliminate the road draft tube by plugging the hole.

ChevyRatRod · 04-17-2011, 11:05 PM

is there a recommended way of plugging it or can i just make a metal plate and throw a gasket on it to plug it? i really appreciate the help.

cableguy0 · 04-17-2011, 11:08 PM

As long as you seal it up you shouldnt have any problems. As I said you need to make sure you have a good working pcv system in place or you will start have bad oil leak issues.

**Captainfab** · 04-17-2011, 11:21 PM

You can plug the breather hole in the rear of the block with the correct size of freeze plug. I believe the correct size is 1-1/4", but you might want to double check that as it's been a long time since I've done this.

04-17-2011, 08:52 PM	#1
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Crankshaft vent i have a 67 chevy that had a two barrel carb. i took off the old carb and intake manifold. i replaced the intake with one i had #3927184 ( new intake manifold). the new intake doesnt have an oil fill tube so i replaced the valve covers with new edelbrock valve covers and put a breather in them. now i have no place to run my crank shaft vent hose to so i was wondering if i could just cap the hole since i have the breather in the valve cover???? any advice would help!!!!

04-17-2011, 09:12 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Crankshaft vent Are you talking about a road draft tube or a pcv? You need a pcv to stop the engine from spewing oil and keep the gasses out of the crankcase. You should have a breather in one valve cover and a pcv valve in the other valve cover. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-17-2011, 09:38 PM	#4
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent pcv

04-17-2011, 09:47 PM	#5
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Crankshaft vent Positive crankcase ventilation. It uses engine vacuum to suck the fumes moisture and other bad stuff out of the crank case. If pressure is allowed to build up inside the engine it can cause oil leaks by pushing out the gaskets. Way back in the day they used a road draft tube which basically just let oil blow out of the engine onto the ground which served as the vent but that isnt the best way for obvious reasons. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-17-2011, 09:51 PM	#6
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent so do i connect the old crankshaft vent (that went to the air filter before) to the pcv valve in the other valve cover? i would post a pic but i dont know how. sorry

04-17-2011, 09:33 PM	#3
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent i have a breather in one and i dont have anything in the other yet what is this pvc? can you explain it more please?

04-17-2011, 10:11 PM	#7
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Crankshaft vent Ahhh i understand now. Forget about the tube that went to the intake. Its not needed with the aftermarket breathers that go into the valve cover. The other valve cover should have a hole about the same size as the one you put the breather in. INstall a pcv valve into that hole with a grommit. Then run a vaccum hose from the pcv to the large vacuum port at the base of the carburetor. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-17-2011, 10:43 PM	#8
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent ok cool but what about the old hole? it is still open so can i just make a cover for it and plug it or do i need to do something else with it?

04-17-2011, 10:57 PM	#10
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent no the hole going into the block next to the distributor. i would post a pic but i dont know how to post it. i have one on my comp right now, everytime i try it asks me for a http: for my pic or something

04-17-2011, 10:59 PM	#11
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Crankshaft vent Ohhhh your engine has a road draft tube. If you run a pcv and breather you can eliminate the road draft tube by plugging the hole. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-17-2011, 11:05 PM	#12
ChevyRatRod Registered User Join Date: Apr 2011 Location: Ventura, ca Posts: 8	Re: Crankshaft vent is there a recommended way of plugging it or can i just make a metal plate and throw a gasket on it to plug it? i really appreciate the help.

04-17-2011, 11:08 PM	#13
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Crankshaft vent As long as you seal it up you shouldnt have any problems. As I said you need to make sure you have a good working pcv system in place or you will start have bad oil leak issues. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-17-2011, 11:21 PM	#14
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,251	Re: Crankshaft vent You can plug the breather hole in the rear of the block with the correct size of freeze plug. I believe the correct size is 1-1/4", but you might want to double check that as it's been a long time since I've done this. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE



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