Lemming

Now that Franky is all sorted out for this race season, I need to turn my attention to getting a spare engine running out of the two that went down last year. First item is to pull both cranks and have them checked at the machine shop (one spun a bearing and the other broke a rod). Visually both look fine but need to be checked. At the very least I will have the journals polished on both and sell one. I will likely have the crank and rods balanced, probably will include the flywheel, pressure plate, clutch, and harmonic balancer as well.

Has anyone had their cranks lightened and/or knife edged? Pros and cons?

968workaholic

Lightening makes the cranks prone to flexing which turns into bending which turns into not happy driver. Pluses are lighter rotating mass. It is up to you but the cons out wiegh the pros IMO.

RajDatta

There is a reason why the cranks have counter weights on them, they counter weight on the other end of the crank. Unless you are planning to lighten the other end, don't do it.
Raj

FRporscheman

Meaning lighter rods and pistons? Yeah I'd agree, only lighten if you also get lighter rods and pistons. But lightening altogether is something I considered... but in the end I think I would definitely have everything balanced, but not bother with lightening. The priority for me is a smoothly running engine.

Lemming

I finally got around to completely breaking down the bottom end of the engine that blew the #4 rod. If anyone is looking for spare engine parts, let me know. I plan to have the crank checked and if it is ok I will sell to help fund the rebuild of my other spare engine. I may sell parts off of the top end as well.

Jason Judd

Tim,

If you need it...I have a knife-edged crank. I went and got a 2.5 engine, with a 2.7 head. It puts me into GT-3 class, rather than GT-2 class, for PCA...more people to play with.

I've sold the Carillo rods already, but also have the Mahle turbo pistons if any interest too.

Best,

Jason

Lemming

Thanks Jason, but I'm no longer sure that I'm going to knife edge, I'll likely just have the entire rotating assembly balanced.

Anyone have any experience with the racing cams from Web Cams?

KevinD

Hey Lemming, I've been gone 2 years (I have the 924s with the 968 here in Idaho). I was looking at web cams at the time but got distracted. I ended up getting a full rebuilt head from Motorsports Salt Lake. He had his own cam grind there. But with my usual scope creep the cam replacement has grown into a full rebuild.

So I have the 968 crank sitting on the bench now too. You've ruled out knife blading. I've seen many people here have crossdrilled #2 and #3, but most other forums frown on that too, have you tried that? Whatabout just some polishing? Is it worth the effort? I've seen some postings here where they took 4 - 6lb off without changing the rods/pistons, but that is still 10% of the weight so I would think that would still need to be compensated for.
Keep posting what you decide to do. I'd rather copy than experiment.

BTW - shouldn't the 924s - 968 hybrid be a 924s3?

Lemming

I'm still not 100% sure of what I am going to do, I have time as I won't be swapping engines till December. I don't have a bucket of money to throw at this engine so I would like something fairly dependable with an extra 10-15 ponies over what I currently have. I'll likely talk with Pete and a good friend has worked with Milledge over the years with S2 engines, so he is contacting John for me. I'm thinking a well balanced rotating mass (with lightened flywheel and clutch), aggressive cams, and some software will get me where I need to be. I plan to have the head and valves spruced up as well.

S3 has been overplaid, haven't seen anyone use 92468 before

Nurburgring951

Lemming, any ideas what went wrong on those engines? Just under-lubrication because of the wet sump + high cornering forces? Are you considering any corrective measures so this won´t happen again? I´m a noob so sorry if you´ve already covered this in another post.

Lemming

Hard to say, but my guess would be excess RPM's. Last year I was routinely running over 7k rpm for my races, including 3 hr enduros. This year I've keep the rpms at 6.5K, with an occasional 6.8k shift with no issues and I have a lot of hours on this engine (including an 8-hr enduro).

I've never seen my oil pressure drop on track.