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Another crank cross drill question

Here's a picture of my crank with some nice diagramming on top

Am I supposed to intersect the blue galley at the yellow cross or
the green galley at the red cross.

Blue looks like it will be easier to get right and will result in a
shallower hole but the galley may not extend as far down as the
marked main journal.


crank with passages, on Flickr

andy

Old 12-26-2010, 11:18 PM
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I drilled mine straight through the main journal in the middle of the journal. I hit passages every time. Not sure which ones, I think it was the green line one because I could feel a irregular surface once it broke through into the chamber. I used a cobalt bit because of this, a carbide one would have had a good chance to break. I drilled the journal all the way through from one side. I drilled all of mine except #3. The counter weights get in the way.

Good luck,
neilca
Old 12-27-2010, 06:36 AM
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I was just looking at your picture again and realized there is no blue line passage. You cannot run oil as indicated, only green passages.
Old 12-27-2010, 06:38 AM
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Quote:
Originally Posted by neilca View Post
I was just looking at your picture again and realized there is no blue line passage. You cannot run oil as indicated, only green passages.
On this crank there is. I will draw in all the oil galleries tonight. I don't know if
it extends all the way to the yellow X but it does pass allow oil through 2 mains
and 2 big ends.

andy
Old 12-29-2010, 05:53 PM
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Can you explain the benefit of drilling holes in the crankshaft for those of us that wonder why you would do such a thing? I mean, are there not oil passages already in the crankshaft?

Thanks,
Mark
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Old 12-29-2010, 06:27 PM
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Quote:
Originally Posted by lucittm View Post
Can you explain the benefit of drilling holes in the crankshaft for those of us that wonder why you would do such a thing? I mean, are there not oil passages already in the crankshaft?

Thanks,
Mark
Here's some threads that were tagged earlier: cross drill crank - Pelican Parts Technical BBS - Threads Tagged with cross drill crank

The crank is oiled from both ends so it's possible to get oil starvation
on the inner rod journals. Cross drilling the crank allows oil into the
crank at the middle main journal which better feeds the rods at risk.

andy
Old 12-29-2010, 06:43 PM
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My understanding of the crankshaft oiling process, at least in my 965, is that the oil comes from the pump, past the 2 pressure relief valves and the turbo feed oil line, then to the main bearing oil gallery that runs the length of the engine from flywheel to crankshaft pulley. There are eight passages from the main oil gallery to the main bearing supports where the oil flows along the middle case bolts and into each main bearing through a single hole in the bearing saddle and the corresponding bearing shell. So the potential lack of oil would not be in the center of the crankshaft, it would be at, what we called in the Navy - the Most Remote Bearing, or the bearing furthest from the oil pump, and that would be the crankshaft nose bearing.

Each connecting rod big end bearing is lubricated by the adjoining main bearing journal, so in theory, as long as the main oil gallery is large enough to feed all eight main bearings with adequate flow during normal oil pressure and oil viscosity ranges, then all the connecting rods will receive adequate oil flow and pressure.

Am I wrong here?

Thanks,
Mark
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Last edited by lucittm; 01-20-2011 at 06:24 PM..
Old 12-29-2010, 07:30 PM
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Originally Posted by lucittm View Post
Each connecting rod big end bearing is lubricated by the adjoining main bearing journal, so in theory, as long and the main oil gallery is large enough to feed all eight main bearings with adequate flow during normal oil pressure and oil viscosity ranges, then all the connecting rods will receive adequate oil flow and pressure.
The rod journals are oiled via an internal passage that runs the length of
the crank and oil enters this passage from both ends of the crank. This makes
the most remote bearing the two centre rod bearings.

The main journals on the crank have no inlets for oil. Those small holes on the
bearing webs and the main bearings themselves are for oiling the main bearing
to main journal interface.

This modification adds an oil inlet on the centre main journal which accepts oil
right next to what were previously the most remote bearings.

andy
Old 12-29-2010, 07:46 PM
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Andy,
Got it. I didn't know there was a passage through the crankshaft that only fed the rod bearings, it is not on any of the diagrams I have seen. It does make sense because the oil in the middle of the crankshaft does not have to overcome the centrifugal force at higher RPMs in order to get there.

Thanks,
Mark
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Old 12-29-2010, 08:50 PM
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Here's the oil galleries on my crank.


crank_640x480, on Flickr

andy
Old 01-20-2011, 12:29 AM
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Nice diagram, Andy, but where's the no. 1 main bearing in this? I had thought that the no. 1 was also drilled to feed oil into the crank. Am I wrong?

At what level of high rpm use does this become important? I would venture to say that there are two considerations, the maximum engine speed and the time that the engine will spend at high engine speed. Is is something that every 911 rebuild should include?
Old 01-23-2011, 05:09 AM
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Old thread I know, but I still can't seem to find any precise directions all in one place on how to make this modification. I found bits and pieces of the process in a few threads, but nothing I think would make me confident enough to give him as a single process. My crank is with a machinist that has cross-drilled a lot of other cranks, but never one from a 911 and I want to get him the precise specs and procedures before asking him to do it. The motor is going to be used for a daily driver with occasional DE events, and I don't plan to go over 7k RPM. It will be a 3.2 SS with 10.5:1 CR, stock rebuilt rods...I do like this mod as cheap insurance for the middle rod bearings, but I'd rather not do it than have it done wrong.

Does anyone have the precise steps my machinist could follow?

Thanks in advance,

Olivier
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Old 11-26-2013, 08:30 AM
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Helps to give some background for what the oil paths within the crank are intended to do. #8 and #1 main bearing journals have holes drilled in them to get oil into the crank and distribute it to the rod bearings. #8 is the one with the bearing insert (dreaded o-ring leak) at the pulley end of the crank. #1 is the grooved journal at the opposite end supporting the flywheel and providing thrust support.

The primary reason for all of the drilled pathways within the crank is to supply oil to the rod bearings. Since the main bearings are fed by the bores in the case saddles, which connect with the oil passages in the engine case, the mains don't really benefit from any oil within the crank. So what i'm trying to explain here is that the internal crank passages really serve no purpose to feed the main bearings. But we can still take advantage of those crank passages to better serve the rod bearings.

You drill the #4 main bearing journal to allow oil into the crank passages directly from the #4 main bearing saddle oil feed hole. Doing this is basically copying what is already present for #8 and #1 main journals. The key to ensuring oil is well fed into the new hole in the journal is the grooving of either the journal itself or grooving of your #4 main bearing shells.

In conjunction with the #4 journal or bearing shell modification, you have to enlarge the oil supply bore in the bearing and in the case saddle. Be sure to drill the case saddle all the way thru to the main oil gallery, approx. 80mm. This is very important to ensure a path of lesser resistance than the adjoining bores in the other main saddles. 5.5mm is the often mentioned hole diameter. Check the hole in #1 main journal for comparative size of groove and hole.

#2 and #5 rod journal oiling passages (the diagonal lines in ajwans picture) are intersected by the drilling of #4 main and that's what gets the oil to those rod journals sooner. Take a look at the crank diagram and follow the red lines as they flow oil to the middle journals of the crank. I highlighted the red pathways with yellow arrows to indicate direction of flow.

What you should notice is the oil path to get to the #2 and #5 rod journals is a long zig-zag due to oil supply originating from the ends of the crank, regardless of which end the oil comes from. When you drill #4 main to intersect that path, the oil takes a much shorter path from #4 main to get oil to #2 and #5 rods. I've marked the picture with some numbers and arrows to help you know which journal numbers correspond to their locations on the crank.



Here's some pictures of a recent crank I had done by Marine Crankshaft in CA. Pictures are of the hole and groove in #4 main journal and a picture of the removable plugs they install for you.




Another nice little trick/feature Marine provided is they drilled a removable plug in the snout of the crank where the pulley mounts bolts on and also drilled for a plug in the flywheel flange where the dowel pin is placed. Those two additional plug holes make cleaning the crank a little bit easier since you've got a straight shot into those end passages
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Old 11-27-2013, 08:54 AM
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Thanks, Kevin...your post here finally cleared this up for me. I think I was confused about the direction/angle of the hole to be drilled into the #4 main journal on the crank, but now I see that the hole is drilled perpendicular to the center line of the crank in a spot that will intersect the oil galley flowing between the #2 to the #5 rod journals. I assume the ends of this galley are marked by the oil exit holes in the #2 and #5 rod journals and can be used as the guide to find the intersecting point on the #4 main journal.

One more question...does the crank need to be re-hardened if the groove is cut into the crank journal instead of the bearing itself? I think the answer is no since material is only being removed from the journal, but I'm not sure if the new edges, sides or corners of the groove itself would warrant re-hardening.

Thanks again.

Olivier
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Last edited by ohecht; 11-27-2013 at 10:31 AM..
Old 11-27-2013, 09:29 AM
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Actually the ends of the galley serving #2 and #5 rods can be found by locating the plugs on the sides of those crank throws, if there are indeed plugs at both ends. I don't have my crank handy to take a look right now. Going by the sketch diagram, I believe galley serving #5 rod is blind at the #5 end of the galley and does not have a plug on the side. But #2 does have a plug.

So, yes, you can trace the path of the angled galley by using the location of a side plug and the oiling hole in the rod journal. Just keep in mind that the rod journal oiling hole seems like it could be drilled almost anywhere around the journal. All it has to do is intersect the angled galley in order to hit paydirt and receive oil. It would seem the rod journal oiling hole is not necessarily as good of an indicator of the angled galley alignment as is the plug hole. I'm sort of stating the obvious here since the existence of the plug is to close the location where the actual galley itself is drilled in the crank.
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Old 11-27-2013, 09:55 AM
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KTL - Kevin, is there a scope of work you gave Marine Crank or do they have a standard scope for Porsche cranks? Just wondering if I should order the KTL special or what?

Thanks
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Old 12-02-2013, 08:24 PM
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Well my crank work with Marine is limited to one. MotoDelta who I work with typically sends their stuff to a local shop here in IL- AutoMachine in St. Charles. They handle the typical balancing, polishing, crack check of a crank just fine since it's not much different than any other automotive crank work.

But since I was doing the cross-drill thing this time around, I figured i'd send it to someone who's been there done that. Marine seemed like a good choice since they make Supertec's SuperCrank. Turns out David Eden's a real nice guy to work with and i'd send anybody his way. Doesn't mind listening to questions, tells you if you're mistaken, gets it turned around in the time promised (which is sometimes not all that common in this industry). Really top notch work for a reasonable price.

Here's the scope I gave to Marine:

-Crack check (magnaflux)
-Reharden
-Balance
-Micropolish. I meas'd the journals ahead of time so none req'd grinding to a desired bearing clearance. Haven't measured it yet, as i've been fiddling with other people's things to make a few dollars. But the polishing shouldn't open the clearance excessively
-Straighten (if needed)
-Cross drill #4 main and groove main accordingly
-Lighten. This is slight knifing of counterweights to reduce a bit of weight, since it's for a mild race engine. This is pretty pricey so on a stock engine I would certainly forego this. I believe Ollies charges $350 for this.
-R&R crank plugs w/threaded plugs
-Install woodruff key (dang this one is big), spacer, distributor drive gear, intermediate shaft gear & circlip (I removed myself)

Got a message from David when it arrived to let me know he got it and told me they don't "sell" cleaning due to liability and they don't install the gear either. No problem on the cleaning, as I can completely understand they don't want to be liable for any failures due to alleged insufficient cleaning. Nonetheless the crank came back very clean and well sprayed in rust preventative solution. Installation of the snout pieces is just a matter of heating each up and slipping them on one by one. Install is much easier than removal!

Had it en route back to me in just over 3 weeks which I thought was fantastic considering it was going from Midwest to West Coast and back. I don't plan on doing many cranks unless I start helping other locals build engines. But if I had to do another one i'd definitely send it to Marine again.
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Last edited by KTL; 12-03-2013 at 03:18 PM..
Old 12-03-2013, 03:16 PM
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I had Marine Crank handle my crank as well. My hit list looked very similar to Kevin's. Only exceptions were I didnt have it lightened as its a 993 crank and already light nor key'd. I didnt think to ask to have it balanced ... wondering if I should have??? Will get the removable plugs. I figure Ill have the reciprocating mass balanced when I get ready to install the crank. I will have the flywheel, rods, and crank then. Should work out. David is a great guy to work with. He calls you back. Gets busy as I think he works and tries to handle the office jig too. Still havent gotten a price for my work but Im not super worried about it. I figure it pays dividends to have a shop preform the work on a $1-2K crank who was "been there done that".
Old 12-03-2013, 04:15 PM
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Thanks Kevin and Toco!

As I have eluded to in other threads, I am planning a re-build of my 3.2. Will be pretty standard except for straight gear intermediate, 993SS cams and resizing the rods with ARP's. Otherwise will keep as stock as possible. Oh and S. Wong chip.

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Old 12-03-2013, 09:07 PM
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