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Author
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Topic: blowby/vaccuum leak theory
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CHIPSBAD67
Gearhead Posts: 396
From: LOU,KY;USA
Registered: Sep 2003
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posted 11-12-2003 11:39 PM
   
i was told today that my 232/240 @ .050 duration cam with the 110 split should have more than 8inches of vac. at idle. the guy then explained that this may be my entire problem with the slight power loss and engine running tad rough upstairs and the oil stick blowing out. he said it could be pulling oil out of the valley into the intake and the vac. loss at wot could be causing the pcv valve to close at not pulling the crankase pressure down thus blowing out the stick. ok, i might buy the first part of that, and the cam probably should have more vaccuum. the part i dont buy is the pcv stuff. if the pressure is enough to blow out up top then it would be enough to open that pcv, the little metal disk would not block that. i rechecked my cranking comp. and got 148-150 psi on all but #1 cyl. that one is closest to the stick and it pumped out 145 psi. i sprayed oil into the cylinders and they all pushed 160. this is supposed to show if there is a problem with the rings or valves. just thinking out loud here. would oil getting in the intake passage kill your engines resistance to detonation? im thinking i read that somewhere.------------------
306, 4speed, 4.11's....best 1/8 mile 7.58 at 92mph with 1.72 60ft. PUMP GAS/NO ADDERS/STREET TIRES
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Hans olsson
Gearhead Posts: 622
From: Sweden
Registered: Apr 2000
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posted 11-13-2003 06:32 AM
Upper end oiling is very bad and kills the power.Pull the intake and look for oil in the runners.The dip stick can be secured with a small spring.When we have a intake leak oil in to the runners it slows the car down a couple of tenth��.
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- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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Mike_R
Gearhead Posts: 176
From: Indianapolis, IN 46237
Registered: Feb 2001
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posted 11-13-2003 08:07 AM
I don't have an answer for the intake charge question, but...When you start making good hp you're going to have blowby under full throttle conditions. The first thing you'll see is the dipstick tube blowing out and blowing oil all over the place. That's normal for a high hp engine. That's why people install crankcase evac systems. When you start having blowby while cruising around town at normal speeds that's when you should be worried. The PCV by itself is not going to totally eliminate this problem. I'd suggest somehow securing that dipstick so it doesn't blow out. That will stop it from blowing oil out all over the place. That's probably the best you can do unless you decide to install an evac system or a vacuum pump. But this blowby is not necessarily a sign of any problem.
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CHIPSBAD67
Gearhead Posts: 396
From: LOU,KY;USA
Registered: Sep 2003
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posted 11-13-2003 06:34 PM
i recently read that blowby can cause hp loss anywhere from 10-25 ponies. i dont know where they get the numbers but i can imagine its not good for power to have pressure on the bottom of the pistons. definitely pulling the intake for good measure. i cant remember if i used the cork gaskets on the ends or not but since i did have the block decked i hope its not causing a problem. i know whenever i drop an intake on i really stress about putting it on evenly and not letting the gasket to slide down to block the top part of the intake passage. i wonder how many people with good flowing heads have unknowingly blocked the port with the gaskets.------------------
306, 4speed, 4.11's....best 1/8 mile 7.58 at 92mph with 1.72 60ft. PUMP GAS/NO ADDERS/STREET TIRES
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