LS376-525 with Truck Norris camshaft tune problem

[Eiksaa]

Hello

I am trying to tune my dads C2 with a LS376-525 with a BTR Truck Norris camshaft.

under light throttle/no throttle and in gear the timing oscillates wild from 0* to 26* degrees. See log file: https://drive.google.com/file/d/148T...ew?usp=sharing

The car is undrivable as it jerks so hard you get thrown around in the seat.

Only problem I can find is that the acc pedal position only ranges from 18% to 84% wot.

Other than that I believe there is something that takes control of the timing and cause this... but what?

Current tune: https://drive.google.com/file/d/1N9B...ew?usp=sharing

All help is much appreciated!
1963 Corvette LS3 E67 Thuck Norris - Help.hpt

[Alvin]

Most of us don't want to download from external links. You might want to post the log here.

[Eiksaa]

Fully understandable!

Here is a log i made today. clearly showing the ignition timing issue
28.06.2025 oscillating ignition - LS3 Truck Norris E67.hpl

[Alvin]

There are far too many changes that don't need to be made in this file. Put back all the idle airflow tab except for the Base airflow final minimum and start up airflow.

Put all the prediction coefficients back. There are a ton of things changed that just don't need to be.

As a general rule.. don't change anything you don't understand fully.

[Eiksaa]

There are far too many changes that don't need to be made in this file. Put back all the idle airflow tab except for the Base airflow final minimum and start up airflow.

Put all the prediction coefficients back. There are a ton of things changed that just don't need to be.

As a general rule.. don't change anything you don't understand fully.

I have tried changig it all back to the stock LS376-525 tune, but does not help.

Is it possible to flash a stock LS3 file on the E67 ECM and try that?
Im confident in tuning regarding ignition and fuel, as I do tune alot of other ECUs, (simpler gen 3 ecus or standalone) but this E67 just dont make sense to me regarding idle settings.

[Alvin]

Change those settings back.. then tune the car.

I'm not attacking you when I said you don't look like you know what your doing. I'm pointing out you shouldn't change things you don't understand. For example.. could you give a reason why you change the prediction coeff?

[Eiksaa]

Apologies, not intended to sound like that.

I have tried copying settings from other files, LS376-480 crate engine stock tune, and also stock LS3 settings.

I can try and change it all back to the stock LS376-525 file and start from there again in case I have messed something up.

Here is my "as found" file. 1965 Corvette 525 LS3 As found.hpt

[Alvin]

Yeah don't copy out of other tune files. We are only able to see a portion of the calibration. 2 + x = y. X might be 2 in one calibration and 3 in another.

Start with your as found GMPP file and tune from there. They are quite capable. The only bugs they have are related to idle not being able to go less than the stock file (some select) and fans not returning to low speed. I've got real wild setups on those controllers doing just fine for years.

[Eiksaa]

01.07.2025 as stock as possible, big shake.hpl

Here is a new log with as close to stock tune I could get it.

Feels better, but still jerks hard under very light/no throttle.
still oscillating ignition timing.

Fuel is not tuned for the BTR Truck Norris cam, but I belive I wont get the correct tune anyways on low load as the ignition is going wild.

All help is much appreciated

[gtstorey]

Always post the tune and log as a pair.

[Eiksaa]

ad1965 Corvette 525 LS3 Restart.hpt
Here is the tune