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Wo ist die Rennstrecke?
Join Date: Mar 2004
Location: St Johns, FL
Posts: 1,210
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Oil Leak between Cam Tower & Heads
I seem to have a leak started between the cam tower and heads on the 930 motor. I built the motor, but it makes no sense to me why the leak has started 4k miles after the rebuild. Before I drop the motor and possibly waste a weekend, is there anything else I should be considering? Like, rocker shaft leak? Or re-torque the nuts holding the tower to the heads? Thxb
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04-05-2006, 04:53 PM
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Registered
Join Date: Jun 2005
Location: NJ
Posts: 640
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This can happen when the sealing surface isn't cleaned well enough. Vibration may have parted a crack in the sealant over time if the surfaces never mated close enough. Do you recall how well you cleaned it when it was assembled? Did you check it for flatness?
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-Brian |
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04-06-2006, 04:52 AM
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Can you media blast the head surface that mates with the cam tower. My guess is that you could since a liquid sealant is used between the two surfaces. Anyone know for sure?
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Bill G. '68 911 Ossi Blue coupe |
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04-06-2006, 05:31 AM
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Join Date: Jun 2005
Location: NJ
Posts: 640
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I believe you can, but not the machined surface of the cam tower. My machine shop bead blasted the heads when doing the head job, so that is what I'm going by here.
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-Brian |
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04-06-2006, 05:56 AM
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Join Date: May 2002
Location: Up North
Posts: 1,449
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Can u determine if it comes through the rocker shaft or the actual mating surface?
Its PITA but you can get to at least 4 rockers with the engine in so if you dont mind "wasting" the time, that might worth re-doing & re-test.
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87 930 K27HFS/B&B/Twin-Plug... Megasquirted 
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04-06-2006, 06:01 AM
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Wo ist die Rennstrecke?
Join Date: Mar 2004
Location: St Johns, FL
Posts: 1,210
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I cleaned the surfaces real well and used Lcoktite 574.
I also used the rocker shaft seals and torqued the shaft through-bolts to spec. I've never had these leak before, so I don't know what to look for. Are the leaks similar? The comment about wasting time should have been more like, "where is a good place to start?" I don't want to drop the motor when I could have.... Thanks |
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04-06-2006, 08:10 AM
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PRO Motorsports
Join Date: Nov 2001
Location: Burbank, CA
Posts: 4,580
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This almost never happens. I doubt it is actually leaking from this mating surface.
My bet is that it is you rocker shafts. They will leak down the back side of the cam tower and look like either an oil return tube leak, or cam tower to head leak. It is very common for the rocker shafts to leak, since the bores are usually scratched by careleless shaft removal. I use the 935 rocker shaft seals on all the engines I build for this reason.
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'69 911E coupe' RSR clone-in-progress (retired 911-Spec racer) '72 911T Targa MFI 2.4E spec(Formerly "Scruffy") 2004 GT3 |
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04-06-2006, 08:15 AM
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Join Date: Jul 2002
Location: Atlanta
Posts: 7,125
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Arent you supposed to torque the rocker shafts a bit beyond the torque spec too, as in about as tight as you can get it?
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erik.lombard@gmail.com 1994 Lotus Esprit S4 - interesting! 84 lime green back date (LWB 911R) SOLD  RSR look hot rod, based on 75' SOLD 73 911t 3.0SC Hot rod Gulf Blue - Sold. |
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04-06-2006, 08:47 AM
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Wo ist die Rennstrecke?
Join Date: Mar 2004
Location: St Johns, FL
Posts: 1,210
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Good info - thank you
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04-06-2006, 05:17 PM
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