Short Version:

Swapped the 26915 springs and steel retainers with the 26918 springs and
titanium retainers. The SOTP dyno indicates that the problem is still there
exactly the same. So, whatever it is, it's not the springs. The problem can
be seen in the dyno graph in my sig.

Long Version:

I replaced the Comp 26915 beehive springs with the 26918 springs, and also
upgraded from the steel (795-16) to titanium (794-16) retainers. This was
in an effort to resolve the problem in the dyno graph in my sig. So far, I have
replaced the opti, ICM, coil and spark plugs in the past month. The A/F ratio
is solid, and the tuner removed most of the timing for one pull and no change,
so I would rule out fuel and timing. Not that I belive anything at this point. I
have swapped PCMs too.

I am now going back to square one and checking everything again. So far, I
have run the Comp R lifters at 1/8 turn and figured it's time to readjust them
to near zero lash. I reset them to an estimated 1/32 turn today, but can't drive
the car because of the rain. I'll put up the results as soon as So Cal dries up
a bit and I can go for a test drive.

 

Replaced the coil wire? Definetly looks ignition related due to the up and down nature of the spikes. Something mechanical you would think would just be down, and you didnt list replacing the coil wire.

 

what type of plug wire are you running? some of the major brands have off the bat trouble with bad boots arcing to the block. plug change? gap? i agree with spinner it seems ignition related to me. do you have any fuel system mods ?

 

Mike,
Did you inquire with Jeff about this yet?

 

Check for arcing. Arcing will cause all sorts of weird problems.

 

Yes, it's a new GM coil wire.

New Accel Extreme 9000 wires, new TR5s gapped at .043", no fuel mods other
than AFPR.

Yes, have sent a couple of emails. He is at a loss so I'm checking out everything
again. I could really use some data. I need to find someone locally that can
scan this thing and review the data log.

Have not checked for arching. Once it stops raining in So Cal I'll check it out.

 

Just curious why the gap is 0.043" in stead of the stock 0.050"?

I know you are making significantly more HP than stock, but I'm not sure it's enough to justify that close of a gap. I doubt it's causing your problem though.

Hopefully the lash on the lifters is the culprit.

BTW, I think arcing would show up in low RPM's as well as high RPM's. I doubt that's the problem, but worth a look.

Dan

 

I had a couple of recommendations to go to .035" on the gap, and the tuner
suggested .045" max, so I went with .043". I agree with you regarding the
arching and am keeping my fingers crossed that the lash is the culprit.

 

Interesting. Did they give you any reason for such a narrow gap? I thought our ignitions were pretty good and could handle the 0.050" gap up to the RPM's that we see. I'm not an expert on spark plug gap though, but it seems that I see 0.050" recommended unless people are making SERIOUS horsepower or nitrous.

Granted, I'm making 30 rwhp less than you, but my NGK's are gapped to 0.050" and my engine runs smooth all the way to 6000 RPM. My dyno plot is in my sig. I'm not sure if a narrow gap would cause your issue though.

Dan

 

The closer the gap, the smoother your ignition is going to run. Just less area for the spark to jump. I gap my plugs at .032

 

Did this coure after a cam swap? I saw a very similar graph when someone installed a LT4 HC one tooth off. THe car ran, made 300 RWHP and idled but was severly down on power. Probably has nothing to do with it just throwing it out there just in case.

 

Yes, but I doubt I'm off a tooth on the cam. Dots were lined up just like
the service manual said. I was even trying to verify the install (degreeing)
but gave up once I realized my accuracy was +-3*.

 

is there any way the valves are hitting the pistons? dont look like a huge cam or that the heads are milled or that you have thinner gaskets but thought I would throw that out there....