Question about PCV?
Thread Starter
Cruising
Joined: May 2004
Posts: 12
Likes: 0
From: denton tx
Question about PCV?
I have a '74 with a 350 that has after market valve covers and air intake. The PCV was routed to the vacuum tower at the rear of the manifold. My question is do I need the PCV at all, or is a filler/vent cap on each valve cover enough. Or should I drill a hole in the base of the air filter housing and run a line from the PVC to there?
Le Mans Master
Joined: Feb 1999
Posts: 6,807
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From: Hoosier
Cruise-In III Veteran
Do a forum search, there have been many posts about this. Bottom line, you want the PCV. A breather on the other valve cover is ok, you don't necessarily have to pipe to the air cleaner on that side.
Safety Car
Joined: Feb 1999
Posts: 3,630
Likes: 14
From: Fountain Hills AZ
Originally Posted by wsnider74
I have a '74 with a 350 that has after market valve covers and air intake. The PCV was routed to the vacuum tower at the rear of the manifold. My question is do I need the PCV at all, or is a filler/vent cap on each valve cover enough. Or should I drill a hole in the base of the air filter housing and run a line from the PVC to there?
Melting Slicks
Joined: Jul 2004
Posts: 2,577
Likes: 2
From: Long Island New York
Originally Posted by Vetterodder
The air cleaner housing, while a good source of fresh air into the crankcase on a PCV system, is not a vacuum source as the PCV valve needs. The only source of vacuum is the intake manifold, preferably through the carb base as it was designed for. Routing it directly to the manifold works but the crankcase fumes to be reburnt will be distributed more equally to all cylinders, rather than just the rear ones, if hooked to the carb.
Melting Slicks
Joined: Oct 2001
Posts: 2,320
Likes: 2
From: Salem Oregon
Lol, this forum is great. I am just putting in a engine with a bunch of changes, and had not got to the final hooking up, the pcv etc. And here you guys answer me even before I could wonder about it. Thanks, Randy
Thread Starter
Cruising
Joined: May 2004
Posts: 12
Likes: 0
From: denton tx
Thanks for the advise, I will be hooking the PCV up today or tomorow. However does anyone know what type of Holley I have?(unable to post pictures). There are only 3 vacuum ports on the carb; 1. large opening at base on the pax. side at rear, I plan to run the brakes here. 2. on the front fuel bowl, now runs the dist. advance. 3. Small port below the front bowl.
My plan is to run the head lights, and transmission to the vacuum tree on the manifold. The dist. advance will stay on the front fuel bowl. And the power brakes to the large port on the rt. rear base of carb. If it would be enough vacuum I will run the PCV to the small port below the front fuel bowl.
And finally can someone recommend a good book on Holley carbs that might show some of the vacuum line setups.
My plan is to run the head lights, and transmission to the vacuum tree on the manifold. The dist. advance will stay on the front fuel bowl. And the power brakes to the large port on the rt. rear base of carb. If it would be enough vacuum I will run the PCV to the small port below the front fuel bowl.
And finally can someone recommend a good book on Holley carbs that might show some of the vacuum line setups.
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Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
That port on the rear passenger side is for the PCV. I would not use that for the brakes. Install a T-fitting on the rear manifold and get brake vacuum from there. My pic shows brakes and transmission vacuum modulator at that source. With a four-speed the latter is obviously not needed.
Here is that carb barebones. It is a model 4160/3810.
Here is that carb barebones. It is a model 4160/3810.
Last edited by Paul L; Dec 30, 2004 at 10:21 AM.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
You want the blowby/crankcase gases coming through the PCV to be reburnt. Hence the connection to the carb. Connecting the brake vacuum there will defeat the purpose of the PCV.
As to its purpose there is an informative article here.
http://www.autosite.com/garage/encyclop/ency08b.asp
As to its purpose there is an informative article here.
http://www.autosite.com/garage/encyclop/ency08b.asp
Last edited by Paul L; Dec 30, 2004 at 10:38 AM.