JoeMag

Looking into the process that CCR (Armando) does on crankshaft cross drilling to get more oil to center rod journals. ...never really looked much into crankshaft stuff so no really familair with this.

Is this the correct option? Other's experience with this?

viperbob

Armando was right down the street from my old shop. He did great work with the cranks of the various model Porsche's to allow for better oil flow (and a lot of other cool stuff that is top secret...).

Tim

We do this frequently...

In addition to the cross drilling, you should get the center main bearing modified also..

Pic of a cross drilled crank with nicely filleted drilling



Fixture in a lathe for modifying the bearing



Finished bearing

Mahler9th

Armando Ayala is the person at CCR. He is right next door to Pacific Performance Motorsports (Mike Stimson; machinist), and they are friendly collaborators. I used both back on my 944 turbo engine building project in 2000 or so. They are both great guys and know a lot about performance engines. I have not discussed 911 crankshaft mods recently with Armando, but you might try searching here or on the Pelican Parts bulletin boards as a next step. And of course you could just give Armando a call. I had lunch with those guys last year sometime ( I think) and we talked mostly about rod bearings as opposed to the crank itself.

On this type of subject, I also like to speak with the fellas at Engine Builder's Supply to learn about their experiences, and Jerry Woods Enterprises (visited with Jerry just yesterday). There are of course many others as well around the country. I feel fortunate to have some of the best resources right near where I live in NorCal.

My engine builder and friend (who has built many of the front-running air-cooled engines which run in our racing group), used a GT3R crank in my current engine, and I am pretty sure it went in unmodified. The initial crank was a 993 unit... not sure whether it had some oiling mods or not. it was replaced as a result of the nose cracking back in '05 or so.

I might converse with these resources about rod bearings as well as crank mods if I were in a building process today. I know that they have all worked through some issues with rod bearings in the past few years, and there are likely various internet threads on this as well. However I am a big believer in speaking to experts in person if possible, over internet communication.

Good luck.

Geoffrey

I do not like cross drilling the crankshaft. You end up with less bearing support on the crankshaft. If you cross drill the crank, then you need to pull all of the plugs to properly clean the oil passages out and if they are not installed properly, they can come out (as you found out). If you don't rev the engine past 7500, then the street crank unmodified will work fine. The 993RSR uses fundamentally a 964 crankshaft unmodified and some of the PMNA engines revved to 8k without being cross drilled. However, if you want to avoid the issue altogether, use a 997 GT3 crank which not only has a larger oil passage, but also has 180 degree oiling on the rod journals. A GT3 oil pump also helps because the pressure side is larger than the 964 pump.

Me personally, I'd never run a cross drilled crankshaft in a racing engine...

JoeMag

Can someone explain to me what this cross drilling does? As I understand it, the crank gets oil from the #1 and #8 bearing and that when it gets to the center rod bearings it is too hot and has lost some pressure. Does the cross drilling allow oil to come from the center main bearing?

Geoffrey -- How does the 993 Gt3 crank do 180 oiling? is there a groove in the rod journal? does it have 964 width rod width? It does not have tapered nose though, right?

Geoffrey

At higher RPM, >7500, there is a less than ideal oil supply from the street based crankshafts. The oil for the rod bearings is fed into the crank at the #1 and #8 main bearings by the case. The main bearings themselves are fed by one of the case halves. If you look at your main bearing you will see a hole which lines up with the galley in the case half.

By cross drilling the crankshaft, you are adding a third hole to the crank in the middle and excess oil from the main bearing is fed into the crankshaft and will supply more oil to the crank and aid in the #2 and #5 rod bearing oiling. You need to groove the main bearing so the oil has a passage to flow around the crank main journal and into the additional hole. I've also see where people groove the crankshaft. It is basically a controlled leak of oil into the crankshaft.

The GT3 crankshaft has two oil holes on each rod journal compared to one of the street crankshafts and the latest version has some additional modifications such as a larger internal oil passage which is really the issue with the earlier crankshafts and it has the oil feed holes at the #1 and #8 bearings angled rather than perpendicular to the centerline of the crank. This helps with the stresses on the crank, and remember these engines run to 9500rpm in the Daytona Prototype cars without cross drilling.

The GT3 oil pump helps with the problem because the pressure side is larger.

The GT3 crankshaft does not have the same rod journal dimensions of a 964/993/930/3.2 Carrera crankshaft and requires custom rods for use with your 993RSR pistons. The earliest 996 crankshaft did have a taper nose, just like the 993RSR crankshaft, although the dowl pinning for the pully is different.