bebbetufs

I'm thinking I need a cross drilled crank. No local machine shops do this kind of work, so I'm considering my options, so for starters you could think of this an intelligence gathering post.

1. If you have a nice cross drilled crank for sale let me know. This will be the easiest option. I will consider knife edged cranks as well.
2. If you have a nice crank that could work as a core let me know. At least this will save me the cost of shipping my core back across the Atlantic.

Thanks.

Darwantae951

I have a good core.

gpr8er

I have a perfect crank on the shelf that came out of a 89 2.7 with 45k on it. I can get it machined to your specs. But shipping to Norway?? That will probably be more than the crank.

M758

Really? Did are there any race prep shops around? Someone has to have a crank maching shop in Norway. The crank is heavy and will cost you a ton to ship.

Look for shops that do race prep on any car. Then call about crank work. They may not do it in house, but probably have a machine shop that does work on cranks for them. The 944 crank is nothing special so any shop that knows how to work on a crank should do just fine with cross drilling.

Chris White

Just keep in mind that cross drilling won’t do anything for the 944 oiling problem – no help at all.
Might as well buy 50 1/4” drill bits and do it with your handheld drill……

bebbetufs

Thanks for offering to help guys.

Chris. Could you please explain? EDIT: I did an advanced search on crank and your name and found a post where you explain.

I made a few calls today and found some companies that can do it, but not in my region. Trouble is that labour is expensive over here, and I'll have to ship it anyways so it might still be cheaper to look for solutions abroad.

M758

Greg Fordhal did some testing where flowed the crank and based this he recommends drilling the number 2 and 3 rod journals. This created the best flow balance. Drilling all 4 is good because it improves flow to all bearings, but in his opinion drilling all just 2 and 3 is the best since in the stock condition they are weak.


Greg Fordhal for those that don't know is from the Northwest and runs 944 cars in the area. He also has been race engineer for several proteams and ran semi-factory 944s years ago.

I tend to trust him quite a bit.

Chris White

I don’t doubt that Greg is right, but how is getting more flow in the crank going to help? (note that I said ‘in the crank’ since it does not increase oil flow anywhere else in the system)
That’s like adding a 4” fire hose on to the end of a garden hose. You are not going to get more oil out of a system that is having a problem upstream.

What actually keeps your rod bearings from failing is the hydrodynamic wedge principle. The pressures at the hydrodynamic wedge are not created by the oil system pressures, in fact the rod bearings will survive with as little as 5 psi (at the bearing). Rather than go off on an engineering discussion of hydrodynamic wedges you can google it or check out http://en.wikipedia.org/wiki/Fluid_bearing
The problems with the 944 oiling system all lie upstream of the rod bearing –
1) 951s run high oil temps – loss of viscosity
2) 951s suffer from oil aeration due to poor oil control in the crankcase
3) All 944 oil pumps will cavatate at higher engine speeds
4) There is a 90 degree corner in the crankshaft oil passage
Put all of those together and you have some problems that cross drilling will not help.

bebbetufs

Do you know how this has been established, and has anyone been able to fit a different pump?
would not drilling a new exit hole 90 degrees from the existing hole straighten out the passage a little?

Do most bearings spin when accelerating after heavy braking? If so that would suggest aereation is the main culprit.
I have installed a crank scraper. Would not knife edging the crank in addition help further combat aeration?
Perhaps the best solution is to make a crank scraper shaped to the knife edged crank, or am I just dreaming? Seems likely the oil will be turned into foam very rapidly when contacting a spinning crank even with the above fixes.

V2Rocket

Serious oil cooling, crank scraper, and cross-drilling the mains and the 2/3 rods...shouldn't be too expensive.

How high of RPM does it take for oil cavitation?

Chris White

Yes, dry sump systems do a nice job…..not cheap and not really compatible with a street car.


There are a lot of ‘little’ things you can do to minimize the problem. IJ crank scrapers makes a custom fitted scraper/windage tray that I use on most high end builds. It helps. Knife edging may help a little – but I actually believe that reducing the max counter weight diameter is better.

Oil cooling is very important!

Darwantae951

My engine has a knife edged crank with IJ crank scraper/windage tray:

bebbetufs

Thanks Chris.

I run IJ scrapers both on the upstroke and the downstroke. Darwin's windage tray looks better.

Reducing the diameter is probably something I can do on a lathe myself? I will only need to have it balanced afterwards. How much do you recommend to take off without ruining driveability?

I have decided to buy a Rx7 oil cooler. Is this sufficiently big? It never ever gets hotter than 86F, and that was in 1901

So no way the oil pump housing could be machined to accept a better pump then. What about machining a billet oil pump housing which could accept an updated, high rpm pump mechanism.

flipo

Dry sump is the only way to resolve all oiling issues ,it does not look the cheapest option but believe me it is in the long run

savvas944

bebbetufs
i have a virtually unused spare ,cross drilled crank,micropolished,lightened ,and rebalanced to zero
gms at 2000 rpm,which makes it suitable for removal of balancer shafts as well.
and for high reving.
Made 2 numbers ,one fixed it on my RUF prepared 2.5 turbo engine,with excellent performance.
email me on j.savvas46@gmal.com for more details.The crank is boxed and can be sent to Norway
with little courier cost as opposed to courier charges from USA.