Questions: New to me 3.3ss with PMO carbs
09-26-2015, 11:51 PM
#1
Questions: New to me 3.3ss with PMO carbs
Purchased a car that just arrived today. It's a 1982 911 with steel turbo flares. It's a beautiful machine, but have some questions on the engine.
Engine was rebuilt 4K-5k miles ago. Specs as follows:
Original Euro 3.0 case
Upgraded pistons and cylinders 100mm slip fit LN/JE 9.8:1
Billet mod s cams
70.4 stroke
PMO carbs
1.75" headers with M&K 2 in 2 out exhaust
MSD ignition - single plug
Wideband AFR kit with LCD display
Now my questions:
1) My two banks are reading different AFR.......one is consistently at 14.2-14.7. The other jumps around, but usually between low 12s and high 13s. I'm guessing one set of carbs is just adjusted to run a little leaner than the other. Is this acceptable or should I make an effort to adjust?
2) Engine has a huge flat spot in the power band after 5600 RPM. The engine has wonderful low RPM torque, but my understanding with mod s cams was that it would pull like crazy beyond 7,000 RPM. The drop in torque is very noticeable from 5600 on. Is this normal or expected with this kind of build?
3). What should I set rev limiter to? I know this engine should love to rev, but what is a good safe number for longevity? Not getting much benefit after 5600 anyway, so I was thinking 6800.
4) Getting harsh vibrations through the car in any gear between 3000 and 3600 rpm. Only becomes really noticeable when letting off throttle in this range. I can tell it is there when powering through during acceleration, but not as bad. Any thoughts? Engine mounts?
I'm coming from a 964 And the difference is astounding. The 964 pulled strong up to redline, but low end torque was lacking. This engine is completely opposite.
Engine was rebuilt 4K-5k miles ago. Specs as follows:
Original Euro 3.0 case
Upgraded pistons and cylinders 100mm slip fit LN/JE 9.8:1
Billet mod s cams
70.4 stroke
PMO carbs
1.75" headers with M&K 2 in 2 out exhaust
MSD ignition - single plug
Wideband AFR kit with LCD display
Now my questions:
1) My two banks are reading different AFR.......one is consistently at 14.2-14.7. The other jumps around, but usually between low 12s and high 13s. I'm guessing one set of carbs is just adjusted to run a little leaner than the other. Is this acceptable or should I make an effort to adjust?
2) Engine has a huge flat spot in the power band after 5600 RPM. The engine has wonderful low RPM torque, but my understanding with mod s cams was that it would pull like crazy beyond 7,000 RPM. The drop in torque is very noticeable from 5600 on. Is this normal or expected with this kind of build?
3). What should I set rev limiter to? I know this engine should love to rev, but what is a good safe number for longevity? Not getting much benefit after 5600 anyway, so I was thinking 6800.
4) Getting harsh vibrations through the car in any gear between 3000 and 3600 rpm. Only becomes really noticeable when letting off throttle in this range. I can tell it is there when powering through during acceleration, but not as bad. Any thoughts? Engine mounts?
I'm coming from a 964 And the difference is astounding. The 964 pulled strong up to redline, but low end torque was lacking. This engine is completely opposite.
