|
|
|
|
| Author |
|
|
Registered
Join Date: Dec 2005
Location: Mount Airy, MD
Posts: 4,299
|
Cross drilling replacement?
Being well aware that cross drilling the crank for high rpm oiling of the rods is a proven mod, I still have trouble loosing bearing area to grove either the bearing or the crank journal.
So assuming the oiling difficulty is truly due to the torturous path combined with the crank spinning at speed... Why could one not just drill a 1/4" hole down the length of the crank and press fit a plug on the open end?all the rod journals 'look' like they pass thru the crank centerline - including the two end 'feed' bearings (which are already extra wide). A co-axial hole won't have a flow problem with the crank spinning and it's one long hole thru the unhardened material... And no loss of bearing area, AND best of all, the material removed won't weaken the crank. I mean, it worked on the early camshafts - why not here? Last edited by tadd; 11-26-2009 at 09:07 PM.. |
||
11-26-2009, 09:04 PM
|
|
|
Max Sluiter
|
Are you talking about the same oiling method as the 917 crankshaft? Oil fed into axial drillings in both ends of the crank, meeting in the middle? This reduced oil pressure needed significantly due to not fighting centripetal force.
I always assumed the reason this was not done on 911 cranks was that the clutch on one end and the accessory/fan pully on the other blocked the way for a drilling. The 917 had the advantage of the central, lower power take off shaft from the center gear, which also drove the fan, distributors, and camshafts.
__________________
1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance |
||
|
11-26-2009, 09:32 PM
|
|
|
Registered
Join Date: Dec 2005
Location: Mount Airy, MD
Posts: 4,299
|
Didn't know that about the 917. Is it literally like the early center lube cams... I.e. Filled on one end thru a ceramic thrust seal?
I was just assuming to drill and plug the end that was started from. Given that one only need to intersect the other drillings, I would think the operation could be done on a long quill drill press and use the flywheel to clamp to the table. If you wanted to get fancy, a pipe plug could be set at a depth so that the pully bolt acts as a lock. I would think the 'stock' fill from the end grooved bearings/crank would still be just dandy... Last edited by tadd; 11-26-2009 at 09:48 PM.. |
||
|
11-26-2009, 09:45 PM
|
|
|
Max Sluiter
|
    I think the 66mm stroke 911 crankshaft has enough journal overlap for center-drilling but the later, long stroke cranks with their offset-ground journals do not have enough overlap.
__________________
1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance |
||
|
11-26-2009, 09:52 PM
|
|
|
Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,810
|
Another approach to crank oiling improvement it shown in this thread
Trick for extended high RMP survival
__________________
Don't feed the trolls. Don't quote the trolls  http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others |
||
|
11-27-2009, 04:28 AM
|
|
|
Try not, Do or Do not
|
The best way to cure the inherent bad oil of the Porsche crank is to use modern crank construction.
The Supertec Super Crank does just that. We feed every rod journal from it's own main bearing. Each feel is bored to accommodate the additional oil flow.  
__________________
Henry Schmidt SUPERTEC PERFORMANCE Ph: 760-728-3062 Email: supertec1@earthlink.net |
||
|
11-27-2009, 01:55 PM
|
|
|
1971 Porsche 911S
Porsche
Retor 911
Scarab
Riley
