Case/crankshaft Mods -6, Looking for opinions Options

[Jetsetsurfshop]

Hey Paddock,
I'm heading down that slippery slope (already started) and been looking for information/opinions on case and crankshaft modifications.
I already had my case boat tailed and was looking to complete the task by having the crankshaft knife edged. Then I found this article from Neil at Performance Development.
http://performancedevelopments.com/living-on-the-knife-edge/

Sounds like he's legit and I haven't done crankshaft mods yet. Thinking I should leave it be.
(IMG:style_emoticons/default/beerchug.gif)
Shane

[sixnotfour]

my favorite ....

So why knife edge Porsche crankshafts? I think the answer points to two main reasons. First, the assembler feels good. And second, the customer thinks he is getting something really racy. If you want to feel real racy without compromising your engine, put a number 1 on your door and a racing stripe down the middle of your car. It will be cheaper too.

[stownsen914]

Neil seems to be respected in the Porsche community. As for knife edging a 911 crank, I suspect there are better places to drop your money. The counterweights on a 911 crank are nowhere near as thick and heavy compared to, say, a small block Chevy. I would think you'd have to be at the pointy end of engine development spend before that kind of mod would really make sense. Just my opinion ...

Edit - didn't actually read Neil's article until after I'd posted. He said it better than I can.

[Mark Henry]

I agree, moon cuts, boat tail, knife edging...the gains, if any, are trivial. If your doing a serious campaign, big budget, sure go for it. But if you're mid pack, just having fun I'd spend the extra cash on the heads, twinplug, intake and exhaust first.
For my engine case I just smoothed out sharp edges, flashing, etc

Porting, good cams, pistons, CR, full balancing, intake, headers are the places you need to put the money into.
I reuilt a set of Extreme heads and they had custom guides with 8mm valve stems (9mm stock) SS valves. I almost did this on my engie build, but decided it wasn't worth it on a street car.
The thing I didn't like about the Extreme heads (500hp 930) is it had crazy spring pounds. My engine I used the Eibach sport valve springs.

[Jetsetsurfshop]

I think I'm going to pass on the knife edging. I already plan on spending money on heads, induction, etc. Making power to run in either ST3 or ST4 is the plan.
NASA ST group is a builders class so with good planning you car can be at the top of your class.
My driving skills is the real problem! (IMG:style_emoticons/default/headbang.gif)

I plan on doing the groove and cross drilling to the crank. That seems like a no brainer. Hopefully it doesn't need too much more work. Its been sitting at my dads shop for 25 years. I mean how many hours could be on this thing??

[stownsen914]

I assume 911 motor?

[sixnotfour]

personally, I groove the bearing, crossdrill the crank..

[Jetsetsurfshop]

I assume 911 motor?

Yes sir.
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[Thorshammer]

I haven't posted on here in awhile, but I did a significant amount of work in this area back in the day. I have used a knife edged crank, and a standard (66mm stroke) and found no appreciable difference. However, the theory is correct, and it is standard practice on other models of engine. One only needs to look at GT3 race modded crankshafts to know that the factory crank is indeed knife edged. But, we are (most) amateurs.... Money (and time), probably can be better spent looking at other items. I personally like straight cut gears on the intermediate shaft, although some will argue, that the noise is a detractor. They are period correct for a vintage car, as they were used as a mod, by several competitors. On my spintron rig, they decreased the required wattage by 215 watts, which would equal about a .9% increase in HP, although it wouldn't be linear. One are which is of significant improvement is to build proper velocity stacks with a full radius for the Webers. As well as a vertical stand off for the oil breather and use some fuel tank foam, and a large check valve at the top. This provides for air to exit, and oil to stay in....