Theo, I wonder if you need to find out why the engine is detonating at 18-2000 rpm? You may not be able to “tune” your way out of this. It might be in your best interest to recheck the mechanical side of your rebuilt engine.
For example, my old school distributor ramps up advance from 27-32 degrees in that rpm range (w/no ping). Even the slow accelerating early S2 emission engine runs 20+deg.@2000rpm. (all-in degrees measured at crankshaft)
I would start with an old fashion warm engine compression test with throttles open.
Think about pulling the cam covers, check cam timing and valve lash.
Good luck,
Dave
It’s a good point. My 123/TUNE distributor before ramped up very quickly and I didn’t notice pinging at this same RPM. Nothing in the engine has changed since them but something could have. I have not attempted a valve setting as the whole process is intimidating. Other than high compression, are there any mechanical issues that can cause this?
My most likely scenario would be excessive (or a history of) head skimming to flatten the head surface. Did the car have a history of overheating? Do the warm WOT compression test for sure.
A scenario of the cam timing being so far out that it causes detonation…I’m not sure that is a possibility.
I wasn’t suggesting you adjust the valve lash. Just pull the cam covers, check the lash. At the same time you can view the timing notches in the cam at TDC and verify that cam timing is correct.
I also have to ask: are you sure you are hearing detonation? That’s an odd rpm to have it happen. Torque peak / max cylinder filling is around 2800. But anything is possible. Get another set of knowledgeable ears to listen.
Who rebuilt your engine? Let them listen too?