Ok, I have an 89 Iroc with an 86 LB9, here is the list of things I have done to it, Crane 262/272 420/442 cam/lifters/spring set installed at 0*, replaced the worn out 416's with brand new 416's, new double roller timing chain, newer style injectors, custom tuned PCM chip, full 3 inch exhaust(no cat) to a flowcrapper, new plugs, wires, cap, rotor, ignition module, O2 sensor, A/C delete, AIR delete, timing set to 8* initial timing, compression test came out to 155-175 with most being 165, 42 psi fuel pressure, no vacumm leaks, no codes, hooked it up to snap on computer and everythings doing what its supposed to. All this has been over a period of time since June. The car just isnt right, I timed the 0-60 twice and it was 9 seconds with no wheel spin cause the car just doesnt want to jump off the line like a TPI should. I got held through first by an 87 2.8 5 spd. The car is an auto with 2.73's but I think it should be faster, I am switching the 2.73's for 3.42's in a week or two. I bought this car to fix up my 87 Sport Coupe but its just sat this entire time cause I've been trying to just get this car right, if I knew all this was going to happen I would have just bought a 350, sorry for the long post I just dont know what else to do? Any suggestions where else to look? Thanks.

 

I would look right here.

 

It has been happening since before the chip and injectors, the chip made it run a hell of alot smoother (PCMForLess burned it for me), and the injectors are still 305 19# injectors, that list of things I did is since this problem has started. It was really bad at one point, I've got it to run alot better, just not where it should. It idles fine, drives fine, stubles a little here and there which the chip took care of for the most part, its just not that quick, I know its an LB9 but it was quick when I bought it and I've done nothing but good to it.

 

What sort of troubleshooting have you done so far?
What sort of fuel corrections (blms) is it showing when you scan it or log data?
Knock counts?

Have you tried acceleration tests with different initial timing? or with the knock sensor unplugged?

Try acceleration test with just 87 octane fuel in it.

Are you still running exhaust manifolds?
Is there any kind of valve between the manifold and Y-pipe?
Did you use new valvesprings when you switched the heads?

Have you tried blocking off the EGR port for a test?
Does the engine have a lot of blow-by?

What do your sparkplugs look like? Do they all look the same?

I highly suggest you sort out your problem before changing any more parts like the rear gears. Increasing the rear ratio will just help mask the problem.

 

The computer I used wasnt advanced enough to show blms, I cant recall what the knock count was but I remember it wasnt to out of the ordinary. Yes I have been playing with timing for a while, it doesnt like 6* it like 8* and 10* is to much. I always run 87 octane. No different with higher octane. Yes I am still running exhause manifolds except the AIR tubes have been removed. What kind of valve between the manifold and y-pipe? Yes I bought a cam/lifter/spring kit. No I have not tried blocking off the EGR, it wasnt hooked up when I got the car and I remember hooking it back up and not noticing anything but doesnt hurt to go back. The engine never had blow-by but its starting to develop a little because of the new heads, but its very minor, nothing out of the tailpipes or anything. My plugs look good, havent got around to all of them but the few I did are burning correctly and are gapped properly. I know what you mean and would love to figure this out before I switch my rear-end gears but its been months and its got to the point where I'm ready to put the gears in and deal with it until the 383 is done.