I finally got out to drive the car after setting the lash to near zero. The
symptoms are the same (see dyno graph in sig). So the tally so far is
new opti, ICM, coil, spark plugs, valve springs, retainers, PCM swap, and
Comp Rs set to <=1/32 turn. On a full throttle 3rd gear pull on the freeway
the KR was 2* and I could not hear any detonation. Looks like it's time
for some data collection. Where in So Cal can I get some dyno pulls and
an autotap log? What's next in the trouble shooting arena?

The car has 32,000 original miles and the following engine mods:

Crane 104227 cam (210/224 112 .511/.553)
Comp R lifters
LT4 extreme duty timing set
Comp 26918 beehive springs (installed height is 1.75")
Comp 794-16 ti retainers
Comp pro mag NSA 1.6 rockers
7/16" studs
GMPP guideplates
stock 52mm ported TB
AFPR
LT4 KM
NGK TR5 plugs gapped .043"
Carolina Auto Masters dyno tune

 

that looks like a big ignition problem or more along the lines of broken valve spring or something.

 

What are other ignition related components besides the opti, coil, ICM,
plugs, wires, and PCM? All have been replaced with no change. Even
did a dyno pull with most of the timing removed from the program and
it was the same. The dyno curve looks like a sine wave to me which
indicates some kind of harmonic. Unfortunately I have no idea what is
going wrong. I was hoping the dyno curve would be indicative of a problem
that others have dealt with before.

 

Take your belt off on the dyno to rule out any odd accesory problems

 

I noticed youve had a few threads on "LT1 Engine Tech" regarding your problems with this setup.... any particular reason you didn't continue the threads there, where people are already familiar with your issues?

 

Fred,
I posted this exact thread there and received zero response for three days,
hence it's movement over here. I did the same thing a while back with a post
about valve spring pressure. Although my spring change did not resolve the
problem, I'm pretty confident that the valve train is not at fault.

 

check to make sure all your springs are in good condition, then take all the pushrods off and look at the lifters, if you can, get a magnet on a spare pushrod and touch all the lifters, maybe one fell apart, I've seen including on my car the Comp R's falling apart more then ones, I've heard if they last you over 5,000 miles then they are gonna be fine, but its always that one that will come aprt on you like a new set of valve springs. Check that out for sure.

Antother thing, when you have all the rockers off, move the valve springs side to side, and watch the valves, may your valve guides are gone letting in oil, seen in happen on a whole set of valves with the exhaust being most affected when the valve train geometry is way off, the oil coats the plugs fast, so take the spark plugs out and see if they are black too, since you've tried everything do these few things now.

 

The 26918 springs are new (like 300 miles) and I have checked them twice
in that time. The lifters, although I did not inspect each, felt good, as in the
plungers depressed and returned to a positive stop. Pushrods all spin fine and
the valves all spin and move fine w/o extra play. There is only 32,000 original
miles on the engine. The valve train geometry looks fine, both side to side and
front to back.

 

As far as dyno tuning goes....not quite SoCal, but if you don't mind the 2 hour drive, go see Bryan @ Race Prep. 760-200-5155

Their in-house tuner, Tad Banzuelo, is a guy who I consider to be about the best tuner going. He also does mechanical work as well....so your car bascially won't leave until it's right, and kicking butt.

 

Sorry for the off topic question.. But 4drLT4, can he tune with HP Tuners?

 

Rob,

If we are talking HP tuners Suite/Suite Pro, I am not sure if he has that software. I do know he has tuned blower cars with 3 bar MAP. If you have the software, or can borrow, I'm sure Tad can take care of you.

Best to call him and find out for sure.

Take care,
Bob

 

Thanks for the info. I'll call Tad and find out if he can autotap me. For now I
just want to send the data file to CAM (Jeff Creech) and see what he says.