PCV question
Thread Starter
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Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,970
Likes: 9,782
From: Rio Rancho, NM
PCV question
Allright you engine gurus,I have a question about Positive Crankcase Ventilation.
My big Caddy engine has a PCV valve in one valve cover with a vacuum hose over to the carb. The other valve cover has a vent tube that connects to the air cleaner.
My question is; Can I run a pcv valve in both valve covers, join them together and then "T" them into the carb?
Does anyone see in problems with this? am I overlooking something?
Thanks
Bobby
My big Caddy engine has a PCV valve in one valve cover with a vacuum hose over to the carb. The other valve cover has a vent tube that connects to the air cleaner.
My question is; Can I run a pcv valve in both valve covers, join them together and then "T" them into the carb?
Does anyone see in problems with this? am I overlooking something?
Thanks
Bobby
You can use a little breather cap on one side instead of going to the air filter.
Thread Starter
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Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,970
Likes: 9,782
From: Rio Rancho, NM
DOH!!!
I'm such a bonehead sometimes. Here I was thinking of getting rid of crankcase gasses and didn't even stop to consider the other end of the equation, that fresh air need to replace what was being taken out.
Thanks Nathan
Bobby
I'm such a bonehead sometimes. Here I was thinking of getting rid of crankcase gasses and didn't even stop to consider the other end of the equation, that fresh air need to replace what was being taken out.
Thanks Nathan
Bobby
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
today's racing engines use a vacuum pump to keep the crankcase at a neg pressure. It gives significant HP gains especially at high RPMs. The engine in my brother's dragster would momentarily bog midrun then take off again. They tried everything to fix it, it wouldn't do it on the dyno tho. He installed a crankcase vacuum pump and no more bog.
Elder User
Joined: May 2007
Posts: 766
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From: south Fl.
Hey bobby, I never thought about not having a fresh air supply when I built the rocket valve covers.
I have driven about 500 miles so far and have noticed no problem. It may be pulling air from the oil fill cap. I will look into it tomorrow.
Rick
I have driven about 500 miles so far and have noticed no problem. It may be pulling air from the oil fill cap. I will look into it tomorrow. Rick
Thread Starter
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Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,970
Likes: 9,782
From: Rio Rancho, NM
Rick,
Cool. Maybe your oil fill cap is a breather. The one on my Caddy covers is a positive seal.
I finally got off my rear and painted my Caddy valve covers and will try and install them this weekend.
I guess I'll just modify my early dual snorkle air cleaner to accept a filter and run things like normal.
Bobby
Cool. Maybe your oil fill cap is a breather. The one on my Caddy covers is a positive seal.
I finally got off my rear and painted my Caddy valve covers and will try and install them this weekend.
I guess I'll just modify my early dual snorkle air cleaner to accept a filter and run things like normal.
Bobby
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
I remember now that some older engines had a separate oil fill tube with a push on breather cap (turn it upside down if it has holes around where it slips over the tube with a steel mesh inside it is a breather cap. (Be sure to soak it in a small container of gasoline to clean it while you change the oil then shake it driy and re-oil the mesh with some clean oil to keep it from getting plugged) Later on the manufacturers moved the breather and fill location to the top of the valve cover about the same time they did away with the road and underside of the vehicle painting crankcase breather tube.
