Check your coil and injector wire harnesses also as they may have been damaged during the rocker swap. Sometimes weird issues can be traced to something simple and seemingly unrelated to the problem at hand.

 

That's a good point! Lots of pins have gotten bent over the years at that coil pack connector

 

Good idea. We certainly haven't ruled out that this could be electrical rather than mechanical.

In my last post, I didn't go into detail on the scan results, but I did several. Almost all cylinders are involved, but #6 is clearly the worst offender.

 

Good point, I had one drive me crazy for a couple days once backfiring etc and finally I disconnected each main coil connector to see which side of the engine was causing the issue. My buddy that owned the car had pulled the coil bracket and coils and mixed up the wiring/firing order when he did, I got the order straightened out and it was golden.

 

I don't see how anything like that would be possible on a 99-02 LS1 F-body without disconnecting the individual coils from the brackets. The complete coil/bracket setup only connects one way. Pins in the connector being bent, yes, might be possible. I don't know if the brackets are mirror image and thus not swappable, but otherwise I don't think it would matter what set of coils would be mounted on which side.

 

Ive heard of the harnesses for the brackets reinstalled 180 out, which even then seems difficult to do but i guess possible.

 

In my situation the dude pulled the coils off the brackets and had them 180 off like mentioned below. If you didn't pull the coils off the bracket then this wouldn't apply. I just threw out things that related to what others have posted.

When you have someone else in the mix messing with things they shouldn't it's easier than you think. Prime example of why I don't like people helping me unless they're fetching things for me. Otherwise the help usually translates to more work for me.

 

But in this case you'd really have to go out of your way to screw it up. With the retaining clip and the little security strap, it couldn't be more obvious. Plus it naturally lines up. You'd have to twist the harness pretty seriously to get it backwards.

 

I agree with you. I can't tell you how it happened, I didn't mix them up, I just fixed the mix up.

Pretty sure that the harnesses got swapped from one side to the other because installing them in the "obvious" way that they laid didn't work out. Either that or the dude twisted up the wires so bad they no longer laid in their natural state.

I think you're taking this as if it's applicable to you, it sounds like it's not, I'm just referring to what others stated about the wiring. If you didn't disconnect your coils and didn't accidentally swap coil brackets from one side to the other then it doesn't apply to you.

 

No, not at all, just discussing it generally.

 

Gotcha. Well if you've ever had someone help you that has no experience in that field and doesn't pay attention to how they did it, you'll understand how easy it is to make something simple very difficult.

 

Believe me, I've been and can be that guy In spite of trying to approach tasks carefully and systematically, and double check everything, it can be the second or third time before it's right.

 

After spending a couple of hours at my friend's shop going over and rechecking everything today, with the same result, I came home tonight, did a search, and found this in an old thread:
I noticed today that the upper walls of the replacement arms are thicker and they seem heavier in general than the stockers. The backfiring and cutting out at high rpms is valve float, pure and simple. With 158k on the stock valve springs, this shouldn't come as too much of a surprise.

This is my latest theory.

 

Seems plausible...

 

The negligible weight difference wouldnt mean anything there. They are talking about a much larger "full roller" setup.
What springs are you running?

 

The original stock springs

 

You could be floating the stock springs but not because of a rocker arm. did you find the cause of the misfires?

 

We haven't identified any electrical source for misfires. Remember, the car runs perfectly fine in normal driving including moderately high throttle and rpms. The misfires are limited to high rpm backfiring ... if you keep pushing it, it feels like a rev limiter kicking in.

And as I've said, kind of a rough idle, (but not a consistent miss) and at times, a slight tip-in stumble. None of this was happening while driving around with the bad rocker; it's only been since the new rocker install.

I have extremely limited time to mess with this, but I hope to get to it again in the next couple of days.

 

Ive always seen valve float as tapering off of power in the upper rpms, NOT backfiring.

 

Most of the time it's a coil/mag/wire issue but I've seen it before in race engines and a few street applications, Typically when the engine has weak/damaged spring(s) due to being over revved. Or in some cases the engine is long overdue for springs or someone drops in a cam and doesn't bother to upgrade the springs.