Oil control
08-30-2012, 08:21 PM
#1
Racer
Thread Starter
Oil control
In http://www.928oc.org/tip/tip682.htm it describes using check valves from a 944 to control oil flow to the heads. Ive never heard of this and since im about to have the heads off it peaked my interest a bit. Can anyone explain more about this?
Also when people talk about redrilling the crank, they dont mean cross-drill do they?
Also when people talk about redrilling the crank, they dont mean cross-drill do they?
08-30-2012, 08:51 PM
#2
Nordschleife Master
You might find more info in the original Nichols site - it was last updated in 2011 (the 928oc copy of the tips says it was last updated in 2001 (!!) ).
http://www.nichols.nu/tips.htm
From memory, the 944 mod you mention replaces the oil check valve in each head with one from the 944 S2 (which IIRC is 3-bar?), to reduce the oil flow. However, recent knowledge posted by Greg Brown indicates this isn't a fix, as the true problem on later cars is oil packing into the heads at high rpm's.
See these threads:
https://rennlist.com/forums/928-foru...o-results.html
https://rennlist.com/forums/928-foru...8-engines.html
The crank drilling for oiling can be found under a search for "Taylor crank drilled" - including pictures of the drilling paths.
http://www.nichols.nu/tips.htm
From memory, the 944 mod you mention replaces the oil check valve in each head with one from the 944 S2 (which IIRC is 3-bar?), to reduce the oil flow. However, recent knowledge posted by Greg Brown indicates this isn't a fix, as the true problem on later cars is oil packing into the heads at high rpm's.
See these threads:
https://rennlist.com/forums/928-foru...o-results.html
https://rennlist.com/forums/928-foru...8-engines.html
The crank drilling for oiling can be found under a search for "Taylor crank drilled" - including pictures of the drilling paths.
08-31-2012, 08:55 AM
#4
In http://www.928oc.org/tip/tip682.htm it describes using check valves from a 944 to control oil flow to the heads. Ive never heard of this and since im about to have the heads off it peaked my interest a bit. Can anyone explain more about this?
Also when people talk about redrilling the crank, they dont mean cross-drill do they?
Also when people talk about redrilling the crank, they dont mean cross-drill do they?
08-31-2012, 10:19 AM
#5
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Yes, as Slate Blue as well as Greg Brown has pointed out many times the stock white metal rod bearings are way too soft. There are some tri-metal racing quality bearings (Clevite CB-1628HX or ACL 4B2166HX) available which can be made to fit with a minor machining of the rods (the slots for the bearing tabs). The X stands for 0,025mm extra oil clearance. It is doubtful if the Taylor way of drilling the crank is of any help. For a serious performance engine you better get one of Greg Browns new crankshafts having the right way of oil drilling and smaller diameter (less friction) Clevite H-series rod bearings. New Carrillo rods has to be added for the application.
Ake
Ake
08-31-2012, 06:44 PM
#6
Race Director
928-944's have well documented oil issues.....classic starvation issues, excessive flow to the heads, crap rod bearings that are too soft, crankcase pressure issues....the list goes on and on
While a "chevy" drilled crank is "better"......honestly only at high rpm....928's have proven extremely reliable, even under racing conditions IF they are kept to relatively low RPM...think under 6000....why....well I'm not entirely sure but its probably a combo of flowing less oil to the heads, limiting crankcase pressures and hopefully keeping oil in the sump (need baffles for that)
Want do build a 928 that can turn 8000......it can be done, but it won't be cheap....and would require a dry sump (if it was my $$$ it would anyway)
While a "chevy" drilled crank is "better"......honestly only at high rpm....928's have proven extremely reliable, even under racing conditions IF they are kept to relatively low RPM...think under 6000....why....well I'm not entirely sure but its probably a combo of flowing less oil to the heads, limiting crankcase pressures and hopefully keeping oil in the sump (need baffles for that)
Want do build a 928 that can turn 8000......it can be done, but it won't be cheap....and would require a dry sump (if it was my $$$ it would anyway)
09-02-2012, 02:52 PM
#7
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Carl Fausett has tried diverting oil from the heads for his Bonneville engine.
http://www.enginebuildermag.com/Arti...orsche_v8.aspx
If you are not going to modify the engine for more power and intend not to race the car, you do not need to do anything to the engine. Just change oil and filter, drive carefully and be happy.
Ake
http://www.enginebuildermag.com/Arti...orsche_v8.aspx
If you are not going to modify the engine for more power and intend not to race the car, you do not need to do anything to the engine. Just change oil and filter, drive carefully and be happy.
Ake