![]() |
|
|
|
Registered
Join Date: Nov 2004
Location: Munich, Germany
Posts: 62
|
Use of 993 camshafts in 3.0 SC?
I have a set of good used 993 camshafts and a SC engine which is in need of a little improvement in power.
Originally I planned to buy a set of 964 cams for the SC, but now I´m wondering if it would be possible to use my 993 cams instead. (The timing and lift should be pretty much the same) But I worry about the fact, that the 993 has hydraulic lifters and therefore probably different beginning ramps than the 964 version with rigid rockers and 0,1 mm play. On the other hand I know of guys who replaced their hydraulic lifters on the 993 with the old type of rockers without changing the cams. Who is able to help? Do I risk premature wear or noise or burnt valves?
__________________
it`s not the speed that kills, it`s the sudden stop! Last edited by 911TE; 11-23-2006 at 12:12 AM.. |
||
![]() |
|
Registered
Join Date: Jan 2005
Location: KENDAL,CUMBRIA, UK
Posts: 1,580
|
HI give John a ring (if he do's not pick this thread up) at Dougherty Racing Cams as he is your man, www.drcamshafts.com
regards mike |
||
![]() |
|
Registered
Join Date: Feb 2004
Location: California
Posts: 926
|
The 993 cams are similar to the 964 profile as far as lift and duration are concerned. The lobe seperation angle is increased from the 964's 113 angle to 115 degrees. Also, the clearance ramp is shorter in height for the hydraulic rocker arms.
I have also seen people use the mechanical rockers on the 993 cams. But, the cams are sometimes noisy. And the valve seating velocity is higher because your off the clearance ramp. As the 911 engine heats up, the valve clearance increases. The normal "mechanical" rocker arms increase in lash, so the clearance ramp built into the profile is taller (.008"-.010"). The hyd rockers keep the system preloaded the entire time, so the clearance ramp is shorter (.004"). The clearance ramp is the section of the profile which gently loads the rocker before opening the valve, and on the closing side slows the system down before the valve hits the seat. The 993 cams can be reground to a 964 or other mechanical profile. The best ones to get are the early 1995 style with the timing gear keyway. The later cams do not have a key slot and are tough to time in the engine without the factory tools etc.
__________________
John Dougherty Dougherty Racing Cams |
||
![]() |
|
Registered
Join Date: Nov 2004
Location: Munich, Germany
Posts: 62
|
John,
Thank you for explaining it in detail! My cams are very early 993 (10/1993), so they still have the old style keyway and the engine also had the old chain wheels. So if I understand you correctly, you wouldn`t risk to use them as they are? Regrinding at your place isn`t easy for me because of shipping costs, so its probably cheaper to buy a new set of 964 cams. Thanks, Sebastian
__________________
it`s not the speed that kills, it`s the sudden stop! |
||
![]() |
|
Registered
Join Date: Jan 2005
Location: KENDAL,CUMBRIA, UK
Posts: 1,580
|
HI Sebastian , I get cams of John in the USA and the shipping is not that bad , just get some new from John.
regards mike |
||
![]() |
|