Suction
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Freshman User
Joined: Aug 2006
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Suction
I was changing the oil and filter on my newest acquisition; 1966 f-100 4x4 stepside. While the engine was running i pulled the dipstick and noticed a lot of suction coming from the dipstick tube. I then pulled the breather off of the valve cover and the suction stopped at the dipstick tube and was present at the breather, the engine did pick up in rpm's but no apparent "miss" like you would find with a vacuum leak. The engine is a 390 with an edelbrock performer 4v manifold. I looked for a pcv valve but there is not one. Could this be the problem? Any info would be appreciated.
Thanks
Ion Kendall
Thanks
Ion Kendall
Cargo Master
Joined: Apr 2004
Posts: 2,574
Likes: 4
From: Golden, CO
If you are absolutely certian about not having a PCV, it sounds like an intake leak.
Time to check the plugs, look for an extra white one, or an oily one. Start reading up on intake leaks in this forum.
Keep us posted.
Time to check the plugs, look for an extra white one, or an oily one. Start reading up on intake leaks in this forum.
Keep us posted.
Fleet Mechanic
Joined: Aug 2007
Posts: 1,836
Likes: 261
From: Piney Woods of East Texas
The PVC valve should be in the passenger side VC, connecting to the base of the carb. Your drivers side may have a breather cap to pull air or connect to the air filter. It sounds like something is missing on the fresh air draw. If it is supper strong vacuum it may be a intake leak like hypoid mentioned.
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Post Fiend
Joined: Dec 2003
Posts: 6,658
Likes: 4
From: "Islander"
You should get a strong crank case vacuum over time, place your palm over the left VC breather hole and wait 5 to 8 seconds you should start feeling crank case vacuum slowly increasing provided you don't have a high blowby motor. Without a PCV valve the motor should not idle very well if at all and as the above reply stated white plugs from too lean in the rear.
PCV is a variable controlled manifold vacuum leak to the crank case and yes the idle will go up when the breather is removed.
PCV is a variable controlled manifold vacuum leak to the crank case and yes the idle will go up when the breather is removed.
Last edited by "Beemer Nut"; Nov 17, 2007 at 02:47 AM.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 787
From: Simi Valley, CA
Originally Posted by iontkendall
I was changing the oil and filter on my newest acquisition; 1966 f-100 4x4 stepside. While the engine was running i pulled the dipstick and noticed a lot of suction coming from the dipstick tube. I then pulled the breather off of the valve cover and the suction stopped at the dipstick tube and was present at the breather, the engine did pick up in rpm's but no apparent "miss" like you would find with a vacuum leak. The engine is a 390 with an edelbrock performer 4v manifold. I looked for a pcv valve but there is not one. Could this be the problem? Any info would be appreciated.
Thanks
Ion Kendall
Thanks
Ion Kendall
Last edited by NumberDummy; Nov 17, 2007 at 04:50 AM.
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