on the setup in my sig,
surges like crazy and eventually dies at idle
has horrible cam surge/buckin at low rpms
seems to be down on power( less than the 350), and definately pings
switched out to stock computer and it pings just barely and runs a little stronger but still surges and dies. Starts up great and easily so we dont think its timing chain off a tooth.

primary and secondary spark looks good
all sensors check out and have reasonable values
set valve lash twice, even checked lift on valves with dial

im at a loss as what to do because i can have ion retard my timing but whats causing my surge and bucking? Please help i cant figure this crap out.

 

Intake manifold leak or vacume leak. Is the next door I would open.

 

checked everywhere for vaccum leaks and filled the crankcase with propane the engine didnt even blink, no rev up or anything. also checked injectors, but didnt check fuel pressure. % duty looked fine. it runs better at higher throttle positions but the power is still down in that region to it just doesnt buck

 

sure the tune got installed good? know anyone with a car that also has a tune? my MadZ28 350 tune is still in my pc even though I also have a 383. just havent had the time to install the right tune yet, and it still runs awesome on the 350 tune.
also, you can see the spark, but is it happening at the right time? chances are if you can see a strong spark, its proly ok, but could still be the opti is messed up.
you should check cranking compression on all cyl.s to make sure your adj. is close on the valve lash and that the rings are seating into the walls.
you COULD still have the timing chain off by a tooth, it CAN run that way. obviously not good though. but, cranking compression should be really low if that was the case Id think.
new sp. plugs and 02's?
might want to try replacing the map sens. cause it aint that exp. and it could be off its calibration. as in still changing and stuff, but not accuratly.

 

I still think the TC is off a tooth or possibly the opti is damaged.

Its not the tune.

 

checked spark on a lab scope, primary side and secondary side, both looked perfect
pulled plugs and they looked good and clean
checked compression on a few easy cylinders and they were 225psi! all close to each other, how could it be that if my valves were off due to the TC. Also my mechanic friend says every car hes ever seen that slipped over on a tooth will barely start or wont start. is an LT1 different? if the stupid thing just had timing marks on the balancer!
o and the o2s arent new but the values dont seem to stick, maybe just a little slow, but they seem reasonable and my fuel trims seem fairly decent. im curious as to why it would ping so much on the new tune under hard load take offs then with stock tune hardly any ping at all, if any

 

Any idea what the quench height is on the motor? I see your running 7.1" PRs so you must have decked the block and or took some thickness off the heads... Id work out that detonation problem real soon cuz hyper pistons dont like that at all.

Steve

 

Yeah block was zero decked, and heads milled flat. my quench should be right at 39-40 thousandths with the fel pro gasket. compression should be about 11.1 to 1 static and 8.6 or so dynamic, cant remember the exact on that. yeah i know it only detonates like under real hard load, cruising around its fine. zero knock then. now if you go trying to burn the tires of its not good. it was pullin 10 degrees plus when we were trying to do medium take offs in it.

 

also, did you use 5.7 rods, or 6"? I have 6" and used 16cc dished pistons, and decked the block bout .015", and used impala head shims. I figured bout 10.5 - 10.7 SCR. if your getting 225psi crankin, that sounds VERY high. I think pump gas is supposed to be around 185 max to be safe, however Ive never checked mine and Im not positive. I know most stock engines are around the 150psi range. positive the plug wires are on the correct plugs? just another thought thats easy to check.

 

damn, couldnt type fast enough. lol. anyways, try some octane booster to see if that makes it any better.

 

5.7 rods, what is the max on pump gas? i dont understand why its so freakin high. i used the compression calculator on KB's site. my heads are about 57cc, pistons dish 12.5cc after polishing the tops and round over the sharp cuts on them.
and yeah checked wires several times. block height is 9.008, zeroed with my piston height. does KB make a dish 7cc? maybe they shipped the wrong pistons?

 

figured it out on kb's site again
11.09 static
8.67 dynamic
another note, theres not any knock while just cruising, but my temp is about 175-180 its 65 degrees outside and my primary fan is running while at 65mph on the highway? i think the tune has the primary fan set at 175 degrees is it running hotter than normal?

 

What are the timing tables like? How much total timing are you running?

Steve

 

It definitely sounds like your timing chain is off to me. If it was advanced tooth or two the intake valve would be closing extremely early, causing all kinds of low-speed problems, and the high cranking compression you're experiencing. I've installed timing belts one or two teeth off before and experienced the exact same symptoms, especially the knock and surging/ bucking. Pop the timing cover off and see what's happening before something really bad happens. I can almost guarantee that is where the problem lies.

 

okay so could someone explain why my high psi would be caused by that. i thought my pressure would be lower if my timing chaing was off. even though we would have adjusted the valves for the off TC. Also my friend doesnt think its the timing chain because all in all it really doesnt run THAT bad. if you speed the idle up to about 1,000 it doesnt surge and if you drive around town at a little faster rpms it doesnt buck, and on highway cruising its under powered but doesnt jerk or anything.