1973 911 T 2.7 upgrade
08-30-2003, 07:25 PM
#1
Racer
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1973 911 T 2.7 upgrade
OK, I've got a great set of 2.7 RS p's and c's, Weber carbs, MSD......now for the cams. From what I've read it seems the "S" cam is recommended quite often, but it seems to me this is rather outdated. Does anyone have any input on the best cam for a track car that is never driven on the street, except freeway driving to get to the track? How about GE 40's or 60's ?, Maybe solex ? I realize I may need to remove material from the valve pockets, and I plan to bump the CR up to 9.8:1 . Thanks in advance !
08-30-2003, 10:03 PM
#2
RL Technical Advisor
Hi Howard:
Well sir, everyone has an opinion about things like this and I'll simply offer mine,...
I don't think "S" cams are outdated at all. In many applications, they are THE thing to use and still outperform a lot of others.
Its all a matter of choosing cams to match the car's primary mission. Factors that must be considered are:
1) Displacement
2) Compression ratio
3) Usage (street/track or race only)
4) Gearing
5) Weight
6) Head flow capabilities
GE-60's are a fine choice for a track car, as are the Web-Cam 120/104 in engines like these. Solex cams make better mid-range torque than "S" or the others above, but do not make the same peak power or have the same RPM range. GE-40's are similar to Solex's.
With stock 90mm RS P/C's at 8.5:1, you will not have a piston-to-valve clearance issue with any of the above cams. Set that deck height at .038-.040 and you will be fine.
Well sir, everyone has an opinion about things like this and I'll simply offer mine,...
I don't think "S" cams are outdated at all. In many applications, they are THE thing to use and still outperform a lot of others.
Its all a matter of choosing cams to match the car's primary mission. Factors that must be considered are:
1) Displacement
2) Compression ratio
3) Usage (street/track or race only)
4) Gearing
5) Weight
6) Head flow capabilities
GE-60's are a fine choice for a track car, as are the Web-Cam 120/104 in engines like these. Solex cams make better mid-range torque than "S" or the others above, but do not make the same peak power or have the same RPM range. GE-40's are similar to Solex's.
With stock 90mm RS P/C's at 8.5:1, you will not have a piston-to-valve clearance issue with any of the above cams. Set that deck height at .038-.040 and you will be fine.
08-31-2003, 02:05 AM
#3
Racer
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Thanks Steve ! As usual, your opinion is welcome and appreciated.
I think I'll try the GE 60's, the track ( WSIR) is a high speed high RPM track , so mid range is not that important. The rpm range will be 6200 to 7000 with a stock early 915 gearbox, approximately 2300 #.
Thanks again !
I think I'll try the GE 60's, the track ( WSIR) is a high speed high RPM track , so mid range is not that important. The rpm range will be 6200 to 7000 with a stock early 915 gearbox, approximately 2300 #.
Thanks again !
08-31-2003, 05:02 AM
#4
RL Technical Advisor
My pleasure, anytime!
P.S....
The 120/104's are just as good as the GE-60's,...
P.P.S,....You'll need close-ratio gears for either one to work effectively.
P.S....
The 120/104's are just as good as the GE-60's,...
P.P.S,....You'll need close-ratio gears for either one to work effectively.
09-01-2003, 03:56 AM
#6
RL Technical Advisor
You bet!!!
All 911 cranks are forged steel,......the "T" crank is just lighter since it has no counterweights but it isn't very smooth. This is a consideration when using a magnesium case which are always crack prone.
FWIW, I NEVER use that thing in any engine; I've seen far too many cracked cases to consider it,... Further, all race cranks get cross-drilled, micropolished, and balanced.
All 911 cranks are forged steel,......the "T" crank is just lighter since it has no counterweights but it isn't very smooth. This is a consideration when using a magnesium case which are always crack prone.
FWIW, I NEVER use that thing in any engine; I've seen far too many cracked cases to consider it,...
Further, all race cranks get cross-drilled, micropolished, and balanced.
09-02-2003, 05:22 PM
#7
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The old "T" crank shaft was replaced 3 years ago with a 2.7, along with 2.7 cylinders and pistons. The case was boat tailed, shuffle pinned, new rods (carrilllo ) and raceware rod bolts, AASCO springs and Ti retainers.. The upgrade now is to remove the CIS, add RS p and c's, swap cams, add Webers, port the heads to 34mm....bump the CR to 9.8:1 . the next upgrade will be new gears and a GT LSD. Hopefully we'll end up with 190-200 hp at the flywheel.
