JRL 31x

I have a 2001 5.3 in my truck, 180k miles on it when I bought it, everything looked good. Now has 799 heads, comp cam and sprins, victor jr, holley 750 dp all controlled by an MSD 6010. 12 volts to the box, all connections grounds are good, checked for continuity, etc.

Other night I slowly brought it up to 2500 rpm and held it there after it built oil pressure to let it warm up, then all the sudden bad misfires, backfired out of the carb, now it pops really bad, misses on all 8, timing seems to be jumping and the tach bounces all over.

I've tried 2 different crank sensors, oil looks good so nothing was probably shaved, pulled the pan and everything looks ok, and I can't spins the reluctor wheel or anything and it APPEARS to be where it's supposed to.

-How do I check for sure that the reluctor wheel is exactly where it needs to be, at TDC?
-How likely is it that the wheel is what went bad?
-Could it be a ground in the MSD box?

JRL 31x

So here's what it doing now, me and a buddy checked reluctor and everything appeared to be ok, and he didn't think it was very likely it had spun or anything and neither did I. Bolted everything back together, stuck crank sensor in, now the tach is (for whatever reason) reading accurately and I no longer think it's a crank sensor issue.

How often do cam sensors go bad? It starts right up, revs up to 2k on it's own and I don't know why, then bogs back down, misses like hell, and dies.

n20transam

iTrader: (5)

That backfire through the intake could have screwed up the power valve. Might want to check it.

JRL 31x

I can check it tomorrow I guess, but since it's a brand new Street HP I'd hope that's not the case.

n20transam

iTrader: (5)

Yea, I would check just to make sure. I've seen it happen more than once with intake backfires.

JRL 31x

Solved the problem (so I hope).

Got it to idle, but kept missing like hell and would instantly idle up to 2000. Chased every vacuum leak in the book and no dice. So, decided to do a compression test, and low and behold cyl 5 had no pressure. Pulled valve covers and founds the spring on the intake valve of 5 just sort of hanging there Spring is ok, but appears that the comp retainers had been worn through by the stock rocker arms and allowed the valve to pull out of the keepers (sorry for terminology). Not only that, but every single other comp retainer had this same wear pattern, just happened to be this was the first one to let go. This explains the huge vacuum leak, miss, etc.

I still have a full set of factory LS6 retainers, and I'll throw them on tomorrow provided the valve is ok and the cylinder holds compression. Glad I caught it when I did.

gagliano7

Nice catch that could have went horribly wrong.

JRL 31x

My sentiments exactly. Looks like the Comp retainers are a hair shorter than the stock ones and it caused things to bind up. I'm assuming they'd have been fine if I'd have used roller rockers.