I need some help. Last year, I built this combination....
AI 190cc heads
11.3 to 1 CR
Custom Cam
30 LB SVO injectors
Comp R lifters
Comp 1.6 rockers
52MM TB
MSB 8.5 plug wires
Kooks headers
No cats
No Air Pump
CSR electric H20 pump
EGR is still in the intake but tube from exhaust is blocked off and it is turned off in the tune.
Tuned by CAM

It makes about 400 RWHP at 6,100.

Since we built it, I have always had a slight dip at 6,200 RPM and it has been getting worse. It now sounds like a severe ignition miss but it ALWAYS starts at exactly 6,200.

Since I have started troubleshooting this problem I have changed....
OPTI to a brand new GM unit.
New MSD coil.
Replaced 3 of the plug wires that had high resistance.
New TR55 spark plugs
Found a bad injector that was misfiring, replaced all with new 42 SVOs.
Had a little valve float from the first day we put it together and have now repalced the springs AI used with 977s and Ti retainers.
Last week we tried a different ECM and different ignition module.

None of this has helped. At exactly 6,200 RPM it misses. There are no error codes (other than ABS Inop that I have been unable to correct)

I have spent a lot of money chasing this and can not correct it. Other than this, the car runs great. It will pull smooth in 6th gear on the highway at 1,800 rpm and will also run past the miss up to the 6,700 rev limiter.

Any ideas?

I have a scanned dyno graph but am not sure how to attach it.

 

To attach the dyno sheet, use www.imageshack.us and paste the link in the thread. Also, do you have a log of the car as it's doing this?

 

http://img53.imageshack.us/img53/9558/picture004xq6.jpg

Link to Dyno Graph of the last 2 runs. They were done about 2 weeks apart. The red is the first and the blue is the second. It is hard to tell, but they both fall apart at 6,200.

 

do u have any way of logging the car?
mail order tune, or dyno tune? if its a mail-order, it might be something with that?

 

Says tuned by CAM, so I'm assuming it is a dyno tune. Did Jeff datalog the car for you?

 

I know you replaced most everything, but it looks like ignition break-up. How do your plugs look? Any of them carboned up more than the others? I really don't see the miss being in the tune.

 

I do not have a datalog. The tune was done (and redone several times) on a dyno by Jeff at CAM. He has been through everything many times and has no more ideas. The car probably has over 25 dyno pulls on it over the past year since it was built and we have been troubleshooting this.
There are no errors being detected. (other than the ABS Inop that came on 2 weeks while on the dyno and will not go off)

The plugs all look good and look the same.

 

SS MPSTR, I have a datalog file but not sure how to attach it.

 

just curious, but what cam is in there? Says custom, but what parameters are we talking about here? Assuming Jeff de-sensitized the knock sensor with no luck?

 

230/238 - 110
.573 lift on intake & exhaust

We changed the knock module to an LT4 and have set the timing to take out a small amount of knock originally seen in the midrange.

 

Can someone take a look at the datalog for me and provide comments?

 

Any comments on the data file? I have run out of ideas.

 

I got rid of my miss by advancing the timing 2 degrees at the point of miss. You may have to play around with it.

 

Email me the log, and I'll take a look at it.

Sweetred95ta@hotmail.com

 

A shot in the dark, but have you tried an alternate dyno? Maybe your car and that dyno don't get along.

That is quite the list of changes though, I'm surprised you haven't gotten the problem with all of that.

Good luck getting it sorted out. It will be crazy when you get it sorted out.