Well the saga continues (from here: Aluminator/3 valve block guys)
Combo is - 2.9 Gen 3 non-crusher, Nemak 5.0 stroker with about 25-30k miles on it now, fox lake rebuilt and CNC ported heads 60lb injectors, return style fuel system... tuned by me.
Car ran fine for couple years with this setup, took crank pulley off over winter to rebuild and now is down on power with some surges that 'almost' feels like it used to. I corrected the pulley offset and it changed nothing. Brought it to a dyno for some pulls and also to verify the A/Fs on passenger side (my wideband is on drivers side) are still good.
Well the A/Fs are fine so thank god don't have a lean cylinder on my non-monitored side, but graphs say it all, low power and surging wildly. Below is graph and below that is datalog from SCT during the pass, wideband on dyno is passenger side pipe, wideband in SCT is drivers side
Full symptoms:
-Low power overall except "sometimes"
-Airflow maybe slightly less? Hard to judge with the high temps we've been having
-Car idles lower and smoother, almost like there's more load on the engine
-Idle vacuum also lower, about 17.5 inches at 850ish (20ish normally, but also used to idle at like 900-950ish due to single blade TB)
-Idle vacuum does recover to 20 or slightly more with SC belt off
A/Fs at WOT are the same, short terms are right where they used to be
To date:
- I've run a compression test, all cylinders are decent, #1 is down by maybe 10ish psi
- We did a dyno pull with the cap off my catch can and blow-by was negligable
- Re-gapped my TR6s to .028 from .032
- Swapped TR6s for brand new BR7EF gapped at .028
- Swapped MSD coil pack set in the car for spare OEM set
- Swapped BACK to TR6s gapped all the way down to .022 to verify not a spark issue
- Re-aligned crank pulley as described in linked thread above
- Had several different belts on it
0 changes from any of this. The car doesn't break up when it surges, it just feels like someones holding the brakes and letting off randomly, this only happens at WOT. Car runs great, runs as cool as usual, doesn't use a drop of coolant or push any out of the overflow.
Next things to do:
-Maybe refine crank pulley alignment as there is some angular mis-alignment between it and the SC
pulley
-Would like to pull valve covers and make sure no broken springs or popped off rocker arms... is it possible to pull the inlet on a 2.9 non crusher to get the passenger side VC off or do you have to remove the SC?
Combo is - 2.9 Gen 3 non-crusher, Nemak 5.0 stroker with about 25-30k miles on it now, fox lake rebuilt and CNC ported heads 60lb injectors, return style fuel system... tuned by me.
Car ran fine for couple years with this setup, took crank pulley off over winter to rebuild and now is down on power with some surges that 'almost' feels like it used to. I corrected the pulley offset and it changed nothing. Brought it to a dyno for some pulls and also to verify the A/Fs on passenger side (my wideband is on drivers side) are still good.
Well the A/Fs are fine so thank god don't have a lean cylinder on my non-monitored side, but graphs say it all, low power and surging wildly. Below is graph and below that is datalog from SCT during the pass, wideband on dyno is passenger side pipe, wideband in SCT is drivers side
Full symptoms:
-Low power overall except "sometimes"
-Airflow maybe slightly less? Hard to judge with the high temps we've been having
-Car idles lower and smoother, almost like there's more load on the engine
-Idle vacuum also lower, about 17.5 inches at 850ish (20ish normally, but also used to idle at like 900-950ish due to single blade TB)
-Idle vacuum does recover to 20 or slightly more with SC belt off
A/Fs at WOT are the same, short terms are right where they used to be
To date:
- I've run a compression test, all cylinders are decent, #1 is down by maybe 10ish psi
- We did a dyno pull with the cap off my catch can and blow-by was negligable
- Re-gapped my TR6s to .028 from .032
- Swapped TR6s for brand new BR7EF gapped at .028
- Swapped MSD coil pack set in the car for spare OEM set
- Swapped BACK to TR6s gapped all the way down to .022 to verify not a spark issue
- Re-aligned crank pulley as described in linked thread above
- Had several different belts on it
0 changes from any of this. The car doesn't break up when it surges, it just feels like someones holding the brakes and letting off randomly, this only happens at WOT. Car runs great, runs as cool as usual, doesn't use a drop of coolant or push any out of the overflow.
Next things to do:
-Maybe refine crank pulley alignment as there is some angular mis-alignment between it and the SC
pulley
-Would like to pull valve covers and make sure no broken springs or popped off rocker arms... is it possible to pull the inlet on a 2.9 non crusher to get the passenger side VC off or do you have to remove the SC?