garrett376

Do any of you 964 engine dudes find that boat tailing the case and mooning the cylinders makes any difference in an engine kept under 6800 RPM? I'm trying to decide if I should spend the time with my grinding tools!!

I've heard all sides, but not from 964 tuners...

38D

I would not do it as 1) it cannot be reversed if done wrong and 2) is typically illegal if you ever decide to race.

Larry Herman

Additionally, it doesn't help on lower rpm motors. As you go above 7500 rpm, it becomes more of a factor because the pumping and windage losses rise exponentially.

NineMeister

The first time I did this was to my bone stock 3.2 Carrera engine. In conjunction with Motec and a set of headers that engine made 271hp & 325Nm with standard cams, heads & intake manifolds. I would say that later experience with similar 3.2 Clubsport engines on Motec have fallen shy of this power by 5-8hp. In my opinion, if you have the time and are not restricted by regulations, I would do it but don't go mad. If anyone remembers the ill-fated DOOM project Bob (Norwood) reckoned that the extreme work they did was worth 30hp at 7500rpm.
We have now written a CNC programme to do 95% of the work required (as well as opening up the cylinder spigot to 109mm to take the 102mm RS style cylinders), without this I doubt that I would do every engine myself as it is a very messy job. Be sure to wear proper protective gear if you do and wear a good mask to avoid breathing in the aluminium dust.

jimq

hmmm mooning the cylinders huh. I knew you guys in Kalifornia were a bit strange

Indycam

"I knew you guys in Kalifornia were a bit strange"
Yeah but my governor can beat up your two governors .

garrett376

It's interesting there really isn't much to "moon" on these cylinders! I was surprised. This picture shows how little the cylinder projects past the case - probably 4mm... I thought it would be more until I actually took a look!