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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,126
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Cam tower bores and effects on oil pressure
Thought has crossed my mind. I've been trying to figure out why my oil pressure has been lower than I like on my 3.2 (3.4) at idle when hot (it'll dip below 1-bar at 900RPM). It has a turbo, so oil pressure is feeding the turbo and it already has the restrictors on the cam tower lines.
What dawned on me, is the bores for the cam journals are pretty grooved. Anyone have any insight on the effects on oil pressure due to this? Second, has anyone sleeved these bores?
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Cory - turbo'd '87 C3.2 Guards/Blk, 3.4, 7.5:1 CR P & C's, 993SS cams, Borg-Warner S366 turbo @ 1.2-1.5 bar, depending on mood  , Treadstone full bay IC, 70mm TB, TiAL F46 WG, HKS 1 1/2" BOV, twin 044 pumps, MicroSquirt AMP'd w/GM smart coilpack, Bilstein coilovers, Tramont wheels (285's rr, 225's frt), Big Reds frt, 993 rr., tower brace, MOMO wheel
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09-01-2017, 08:21 AM
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Registered
Join Date: Apr 2007
Location: wisconsin
Posts: 2,553
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Quote:
My motor is in pieces, will need to check... I told my cousin, a mechanic, that the 930 cams rode in an aluminum bore, with no bushing... He didn't believe me... |
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09-01-2017, 09:58 AM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,126
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Hmm, I always assumed pressure fed, but you might be right? If that's the case, this is the most useless thread ever! 😂 😂 😂
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09-01-2017, 10:18 AM
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Under the radar
Join Date: May 2007
Location: Fortuna, CA. On the Lost Coast near the Emerald Triangle
Posts: 7,129
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I think this is a good question, since no one ever talks about cam bearing clearances.
The cam journals are sort of pressure fed. That is, the pressure in the squirter tubes feeds the cam bearings.
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Gordon ___________________________________ '71 911 Coupe 3,0L outlawed #56 PCA Redwood Region, GGR, NASA, Speed SF Trackrash's Garage :: My Garage |
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09-01-2017, 10:56 AM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,126
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Yep, that is what I found too. I had to Google at work.
The spray bars feed. I'd thibk with that much surface, it'd have to be fed and not splash if you will, no? |
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09-01-2017, 10:59 AM
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Registered
Join Date: Apr 2016
Posts: 1,176
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The cam towers are spray bar fed and there are really tiny bores that spray oil here. The cam tower bores being scored will not affect your oil pressure.
If you have low idle oil pressure (i.e. below 1 bar) it's not really a concern unless you don't also have 1 bar per 1K rpm running oil pressure. The gauges aren't that accurate in the first place. If it is a concern, there are 2 things you should check: 1. Whether you have the spacer in the oil pressure relief valve (the one on the bottom of the motor) 2. What kind of oil are you running. Lower weights mean lower pressures. |
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09-01-2017, 11:33 AM
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My Garage
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