964 vs GT2 cams for my 930
 

Im looking at cam choice for my 930 build. I was going to use the 964 cams but some people on another board (turbo911.com) have been talking about the virtues of GT2 cams. the general view over there is that the GT2 cam has a broader power curve compared to the 964 which is (apparently) a cam that gives its power higer up the rev range.

my car is to be a street monster with some (but not that much) track time. ingredients as follows:

930 case
shot peened 930 rods
ARP bolts
Supertec head studs
rebuilt mildly ported 930 heads
Carrera inlet
SDS efi
tasty headers
k27 high flow (ideally the MK2 version thats on its way)

What are peoples views?

Andy

I just made the decision to go with a 964 over an EVO cam. The specs show that an EVO cam has more lift and duration. That tells me that it's going to move the power band up. I had SC cams and peak power was about 5500 but it would still pull to redline easily so I figure the 964 cams will move the power band up but not too much.

Web Cam told me that with the EVO cam I'd would start making boost at about 3800. That's too high for me.

I learned in road racing karts that a real peaky engine does not translate to faster lap times even if you're making more hp. On a sprint track with real short gears a real high hp engine helps but I'm planning to run it on the street and large road courses.

I haven't been much into the 930 stuff since I left Andial 12 years ago, back then the hot cam grind was the Gruppe B grind. The SC spec was used for better low and mid range and the Group B was the hot ticket for mid and top end performance.

When I left, the 964 spec was just starting to become popular and seemed to be the best of both worlds.

Whatever happened to the Gruppe B grind? Is it no longer being used or has the name for it been changed?

Ralph

Hi Dave, it was your thread on Turbo911 that got me thinking about the GT2's as a good street choice (actually it was Geoffreys comments) but if its going to push things up high then i think id rather be with the 964's

thanks for your advice

Andy

I was planning on running the SC330 grind in my 930 which will have mods similar to your own. That cam has a total intake duration of 275 degrees and a total exhaust duration of 265 degrees. Its supposed to be a good 930 performance cam for decent midrange and top end gains.

Can anyone tell me what the specs for the 964 abd GT2 cams are?

The Gruppe B grind has low valve lift. Around .060" less than the SC cam.
With EFI you can also consider the Super cup cam. It is in between the 964 and the GT2 Evo cam.

350HP930:
964 "advertised" durations are 280/262
Evo cam advertised durations are 294/274

Advertised duration is measured when the valve leaves the seat until the valve sits back down, typically this would be around
.012" cam lift. Instead of the 1mm valve lift or .050" valve lift number.

Hmm, those are a little too radical for me. Looks like I will be sticking with the SC330 for better mid range and driveability.

I like the 964 over the sport grind for the Turbo. the 964 has more valve lift and slightly less "advertised" exhaust duration. Which can help spool the turbo earlier.

Your boost start RPM will be affected more by the wheel sizes in your turbos than small changes in the cam...

-Wayne

Not that it really makes a difference in this case, but here are the cam specs from my notes at Andial way back when:

911SC for Turbo Use (1.25 @ overlap)
intake is .455 lift and 229 duration
exhaust is .402 lift and 220 duration
113 lobe center

Gruppe B (1.8 @ overlap)
intake is .374 lift and 237 duration
exhaust is .339 lift and 220 duration
lobe center n/a

964 for Turbo Use (1.25 @ overlap)
intake is .470 lift and 240 duration
exhaust is .430 lift and 230 duration
lobe center n/a

934 (3.65)
intake is .408 lift and 250 duration
exhaust is .406 lift and 251 duration
102.5 lobe center

935 (4.6)
intake is .446 lift and 261 duration
exhaust is .446 lift and 274 duration
104 lobe center

I guess John can compare his notes and see if the numbers listed jive with his.

Just for some fun, here are the 962 cam specs as listed by Porsche. I don't have all of the details for the 962C motors, but according to my 1990 962C Motorsport parts spec book the options were as follows:

Option 1 was intake and exhaust cams with 9.3 lift and 276 duration

Option 2 was intake and exhaust cams with 9.3 lift and 288 duration

These were Group C spec, I know Andial experimented with different cam profiles for IMSA. Bear in mind that European tracks are much more top end oriented (i.e. horsepower) then most U.S. tracks. Lots of street races and tight tracks in the old GTP days. Road America and Watkins Glen were really only the "European" type courses run where the cars could really stretch their legs. I'm not counting the banking at Daytona because the infield section is not really all that fast.

Ralph

double post, sorry.

I found this site to have many cam specs: http://www.drcamshafts.com/porsche.htm

I talked to them and they have good prices too. There are several used sets of cams floating around also.

cheers blokes

Andy

...isn't that camgrinders site? :D :D

That is my site!
:)

Camgrinder, did you used to work for elgin?

Yes I worked at Elgins for 14 years.

Hmm, well John, after looking over all your cam specs and thinking about my new motor plans I think I am going to go with the Super Cup grind.

The numbers make it out to be a warmed over SC330 with much better valve lift.

I might as well take advantage of those flat top pistons.

I have had my cams all boxed up and ready to ship to you for months now. Like many other aspects of my project they have been on the proverbial back burner but if I have enough money left after christmas it will finally be time to do business.

What is the total duration on those Super Cup cams?

My Engine Book also has a large list of cam specs too in the Appendix...

-Wayne