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Join Date: Jul 2008
Location: Baltimore, MD
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Crank cross drilling and bearing mod?

Can someone explain to me exactly what is being done when people talk about these mods for high performance engines? Any pics for illustration? Without a picture, i am not sure what this is, sorry.

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2000 VW TDI 224HP/400FT TQ.
Pikes Peak World Record Holder 2007 "Fastest Diesel Car"

1973 Porsche 914/6 2.4L Engine rebuild in progress
Old 07-20-2008, 08:00 PM
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Anyone?
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2000 VW TDI 224HP/400FT TQ.
Pikes Peak World Record Holder 2007 "Fastest Diesel Car"

1973 Porsche 914/6 2.4L Engine rebuild in progress
Old 07-21-2008, 04:55 PM
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Max Sluiter
 
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The search buttom is your friend

Crankshaft cross drill

Cross drilling crank

Case and crank mods: are they worth it?
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911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
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Old 07-21-2008, 06:00 PM
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Thanks. I looked a bit, but am still unsure if it is so necessary on my engine. Just wanted the knowledge for future conversations.

I will not run high rpms, so do i still need the bearing mod? Is that suggested anyway?
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2000 VW TDI 224HP/400FT TQ.
Pikes Peak World Record Holder 2007 "Fastest Diesel Car"

1973 Porsche 914/6 2.4L Engine rebuild in progress
Old 07-21-2008, 06:17 PM
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Max Sluiter
 
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No high RPMs (like 8000), no oiling problem usually. If this is a street motor, you will not sutain the high RPMs like race engines will so you should not starve the rods for oil even if you do wring it out.

The bearing mod goes with the cross drilling to distribute the extra oil, as I understand it.

Did you get a good idea of what the cross drilling is and looks like? It took me a while to read the threads.
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911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 07-21-2008, 06:25 PM
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Yes, thank you I understand it, but I do not think I need this. Good thing as I need to save money for my EFI system.

Everything is so expensive these days. Just how it is, so project just creeps along.
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2000 VW TDI 224HP/400FT TQ.
Pikes Peak World Record Holder 2007 "Fastest Diesel Car"

1973 Porsche 914/6 2.4L Engine rebuild in progress
Old 07-21-2008, 06:55 PM
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Max Sluiter
 
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I agree, your engine is fine without it.
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911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 07-21-2008, 07:02 PM
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We are cross drilling all our cranks. Proper oil flow to all the rods is a good idea at any rpm.
It's cheap and well worth the piece of mind.
The new chrome moly billet cranks that we are building will oil the rods from every main journal. This will allow us to reduce the flow through the number 1 and 8 mains to guarantee even oil flow to all 6 rods.
Is this new /modern oiling schematic necessary ? no, but with a clean sheet of paper why not improve on an old design if you can.
These new cranks are coming soon and will offer a 66 mm 9 bolt crank for very high rpm engine using 3.0, 3.2, 3.3 and 3.6 base engines.
People talk about 8 and 9000 rpm Porsches like that's easy to do. They are easy to build but hard to keep alive. Short stroke engines with proper rod length to stroke ratios are the best way to achieve this goal. Pankl Titanium rods won't hurt either.

As for main bearing movement, the addition of high strength locTite 568 (574 if that's all you have) between the main webs will greatly reduce main bearing moment on lower out put engines. Shuffle pinning as stated here is advised for all higher out put engines. The amount of time spent near redline rather than the total hp out put is probably a better indicator of shuffle pins as a required modification. What I mean by that is a 220 hp mag cased 2.0 that spins 8000 rpm 80% of the time needs shuffle pins. A 3.3 turbo that make 400 ph 5% of the time (short freeway blasts) would be less likely to need shuffle pinning but would benefit greatly from LocTite between the main webs.

As for clearance on the rod bearings as a general rule slightly larger clearances with higher oil pressure/ volume in high rpm Porsches is a good idea. That is why Porsche GT3s run hugh oil pumps and the bearings come color coded for the crank. It is not uncommon to see a GT3 crank that requires three different color code bearings.
That right, with a GT3 you might need 3 bearing sets to build it with the correct tolerances.
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Old 07-30-2008, 04:45 PM
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Henry,

Thanks for the info. Can you send me a message with pricing and more info on what you charge to do this work? Meaning crank and bearing mods.

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2000 VW TDI 224HP/400FT TQ.
Pikes Peak World Record Holder 2007 "Fastest Diesel Car"

1973 Porsche 914/6 2.4L Engine rebuild in progress
Old 07-30-2008, 06:26 PM
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