SwayBar

Do you know what those specs would end up to be? How much will it cost? Is it just grinding, or is welding involved too? Like you, I have a set of GTS cams sitting around doing nothing, and am considering doing this as well.

Stan.Shaw@Excell.Net

Anyone looking to drill a 5L crank. I have two candidates ready to be drilled

Cheburator

Need to speak to them - they did the cams for drnick's orange car

Vilhuer

Any long term experience on street car with these reground cams? Will they hold up or end up having worse pitting than stock GT cams? Also have one GTS cam set which could be used as core. Latest plan is to use modified S3 set if mods can be done locally.

How about having custom 34-35mm exhaust valves made? I think set of 16 can be made for maybe $700. Would this be worth the trouble? Factory didn't do it to 968 but there might have been financial reasons more than 33mm being perfect size.

SwayBar

Or maybe they just aren't needed. The following is from here:

http://www.rehermorrison.com/techTalk/16c.htm

"Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there."

Spend the money instead on big intake valves. Installing big intake valves with just cleaning up the bowl area with no porting have shown to increase flow without diminishing all-important flow velocity.

Vilhuer

Its little counterintuitive for me at least that 5L and 6.4L would have exact same optimal exhaust valve size. If its true then all the better. Can certainly figure other uses for $$$.

Cheburator

That is certainly not a problem when you are trying to build a reliable endurance racer...

The Aston Martin DB9 N24 laps the Ring in 8m flat. The 928GT in 1990 lapped it in 8:38 in stock form. I hope that a 400Bhp+ race car stripped down to 1335 on slicks should come down to 8-ish flat...

drnick

alex, you are a jammy git for scoring those valves at that price!! there are two things i regret in my GTS engine build - not drilling the crank and not doing any head work.