[hugger6933]

68GMSEE we are looking at his problem as a gen 1 motor and in his fisrt post is states he has a ls1. So the hei that you asked about in your first response won't be an option here. Let me ask this question is there a rev limit switch wired into the msd box anywhere? MSD rev limit switches come in pills similar to the timing pills that you plug into a box or in some cases into the side of a ignition box to limit the rpm and the lowset they normally have and atre shipped with for testing purposes are 3000 rpm's, but that would not explain the no load rev in park. I have seen what you are experaincing on some guys putting together a racecar and it would not rev over three grand and it kept sounding like it was against a "chip" and I asked the question about the box and the low side chip and all that I have laid out here and that was it.So anyone of you been to the track when the bracket cars come to the line and the lights start to drop and the cars are popping and chattering like that is what it called up against the chip. Most of the cars have a box that is a step above the RPM limit switch and it is called a two step. It has a low side and a high side the low side is activated with a lower rpm chip say 3000 when the transbrake is activated and the sw keeps the car from revving past that point until the brake is released. Then on the high side there is a chip to keep the car from over revving on the big end say 6600rpm once in the high end [or any time you rev up that high] it will make the motor misfire causing the popping sound that we are talking of.