Ok...got the new heads on the car. Went to the dyno yesterday and the dance began. First...as soon as we would hit the throttle the car would go dead lean...so we lifted. started stesting stuff. Adjusted the fpr and make a run..ok...ran good..ran a back up and loaded up and dead lean again(once again lifted after the car loaded up and the A/F went off the scale on the dyno). We changed the FPR..problem fixed. Next problem, Injectors were 100 % and he a/f was all over the chart...very wavy. Put in some delphi 37s..problem solved and a/f had a nice flat curve. Next problem...I was getting this weird pop mid rpm(4400ish) when making a pull. The car would lunge..then recover and it would happen again up top around 5600. This was repeatable from run to run. Tried different msd box, different coil, checked plugs, different tunes, finally changed the opti. Ok...problem fixed..pulles fine right past where the pop was happening..untill..next problem.

Now at 6700 the car starts to studder. The dyno showes that it nose dives and falls...never recovers. In the dyno graph we didn't lift untill after 7000 rpms. The weird thing is that when the studder starts (6700)my tach goes dead..goes right to 0 then when we lift off the throttle it recovers and starts showing correct rpms again. So..since we didn't get to test anything up top we starting replacing things again with the spare parts we used the day before on the first problem. Changed msd box, same thing, changed coil/coil wire, same thing, changed the opti pickup wire(whatever its called..plugs into the top of the opti), no change, changed plugs..which were brand new yesterday when we started this whole thing...and plug wires, no change. We ran a wire from the alternator right to the power distribution block(battery in rear so it gets power from the rear normally)..no change. So...does anyone have any idea what this could be. What about the pcm, I didn't have a spare 6 speed one to try so I couldn't rule that out. Also..when this happens on my logs my right bank O2s go lean bad. The reading are almost uniform between the two banks all the way through the pull untill this starts to happen. We put the wideband in that muffler(I run dual bullets off the headers) and this problem could not be reproduced on the wideband.

I need help guys...the thunder shootout is next weekend and I have to get this thing running.

Here is the dyno chart...Here is my dyno..remember..we let off after 7000 rpms.

 

Lean makes sense for a misfire because the unburnt mixture of gas and O2 are expelled. O2 sensors pick up that unburnt O2.

Might be fuel pump problems too.

 

did you happen to have the wrong pill in the msd box?....just a suggestion, since stupider things have ruined my day lol

 

good luck with the shootout!!! I wish I had the time and $$ to run my car in it. I had that same kind of thing happen and it was my Ignition Control Module. Just an idea. Good luck.

 

I've read that the stock PCM is only good to 7000 RPM. It is possible that your PCM may not be able to keep pace @ 6700 revs . Your power curve looks pretty smooth to be suffering from any ignition related problems. If your ignition was dropping out it should look pretty ragged at the top end.

I would trust the wide band over the stock O2 sensors, if the wide band says that your not going lean I would bet you hit the wall with the PCM.

 

I had a buddy with an odd miss, they tried everything, the valves tapping the piston slightly was eventually detected after removing the heads.
They clayed the set up and all was fine but up at that RPM i guess things got stretched some....

SOunds really like an electrical problems with the tach falling up there. any new electrical components added? How are all the wires routed? any chance some got nicked or messed up? I had that happen....

 

95Turd,
Have tried just lightly spraying you K&N filter when you recharge it? As opposed to using that Dip pan you normally use?


Nice numbers on the Dyno...
But just think how much better they'd be with an LS1,,, then if ya moved up to a Z28 they'd probably double.


See ya at the shoot out..
Don't worry I'll clean my tail lites for ya.