![]() |
|
|
|
911 OCD
|
964 v 20/21 cams
Can anyone explain (or direct me to a thread) the difference between the 20/21 and 964 cam grinds. I have an SC w/ 3.0.
Thanks in advance. Cheers, John
__________________
jk 82 SC Euro 82 SC Targa 69 912 62 AH 3000 97 740il 'If you are under control, you're going too slow' Parnelli Jones |
||
![]() |
|
911 OCD
|
cams
TTT
Thanks
__________________
jk 82 SC Euro 82 SC Targa 69 912 62 AH 3000 97 740il 'If you are under control, you're going too slow' Parnelli Jones |
||
![]() |
|
3.4 Bigger is better
Join Date: Nov 2003
Location: South Dakota
Posts: 1,497
|
I have no direct experience with the 20/21 can but is more aggressive than the 964. It would move the power band up higher in the rpm range. Emailing or calling John at Dougherty Racing Cams would be able to tell you what cams he has that would be close to the 20/21 and the characteristics of the cam. I went with a DC-22 regrind from John and am very happy with it. Power comes on strong around 3900 rpm through 7000 rpm. Check out the specs at Web Cam Inc. - Performance and Racing Camshafts and the 964 cams and what John offers here. Dougherty Racing Cams
__________________
Michael 88 911 Diamond Blue CE Carrera 3.4 HC3.4 member 2020 Honda Passport |
||
![]() |
|
911 OCD
|
Thanks
__________________
jk 82 SC Euro 82 SC Targa 69 912 62 AH 3000 97 740il 'If you are under control, you're going too slow' Parnelli Jones |
||
![]() |
|
Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,310
|
Quote:
__________________
Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
||
![]() |
|
911 OCD
|
I use mine strictly for the track, so I'd like to have my power band higher in the RPMs. My car is a Euro with the larger 78-79 intake/exhaust heads. I think the 964 is what I'm looking for. Thanks for the input. I'll search out the thread.
John
__________________
jk 82 SC Euro 82 SC Targa 69 912 62 AH 3000 97 740il 'If you are under control, you're going too slow' Parnelli Jones |
||
![]() |
|
![]() |
Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,310
|
I've heard the differences between the 964 and 20/21 cams are subtle. They are similar cams. The 20/21 is sometimes referred to as "964+" cams.
And as you probably know, CIS systems won't work with radical cams. Specifically, they won't work well with cams that allow much overlap. The cams we are talking about here (964 and 20/21) have a modest amount of overlap, and plenty of lift and duration. In order to move the power band much higher, overlap is necessary.
__________________
Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
||
![]() |
|
Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
|
The Web-cam site sucks for comparative purposes (which is probably intentional) to see what compares to what Dougherty makes. The 964 is a good choice for a basic bump up in performance. Anything above that will see better results by improving your pistons to something more aggressive than the stock smoggy smushed dome pistons.
Plus the more aggressive you get with your cams, the more cognizant you need to be of the piston-to-valve clearance. Those cams with higher lift @ overlap spec want to have relieved piston pockets. With that comes higher compression ratios and more power and then more risk of pre-ignition if you don't have twin plug or run high octance racing gas. And as Supermain alluded to, the 964 and 20/21 cams retain basically the stock lobe separation/overlap spec. Which limits the power you can gain with them. A cam NOT based off the stock SC/Carrera lobe separation is where you need to go (up to a point, to allow the fuel injection to still operate well) to find more benefit from your cams. It all boils down to a matched system from the injection, be it carbs or individual EFI throttle bodies, to the cams and pistons. Just changing cams on a stock 3.0L isn't going to do earthshattering things for you.
__________________
Kevin L '86 Carrera "Larry" |
||
![]() |
|
911 OCD
|
I'm planning a 3.2SS with 9.5, maybe 10.5 JE pistons. The 20/21 cams came with the car with engine ready to assemble.
I have ghl headers n muffler, CIS, single plug. I'll use 94 octane for the track. Thanks for the input.
__________________
jk 82 SC Euro 82 SC Targa 69 912 62 AH 3000 97 740il 'If you are under control, you're going too slow' Parnelli Jones |
||
![]() |
|