Thanks man, so last night I went out and tested a different engine, not the GRP. I have to finish installing that in another truck.
But last night I tested my Novarossi .28 in the meantime because I was having a separate issue with that. The GRP .28 was sticking at higher revs once it got to like 20k rpm.
The Novarossi .28 was pinging hard coming down to idle off high speed passes on a rich tune. This tells me (I think) if its pinging hard on a rich tune, then it's gotta be either too much compression,
too hot of plug, or both at the same time? My question still remains- How do you know if you have only a too much compression symptom, or only a too hot of a plug symptom, or both at the same time? This is the tricky part.
What's the best way to distinguish between either too much compression or only the plug being too hot or too cold? I know head shims dictate compression and plug number is the heat range. Does higher nitro content increase compression (I think it does), and too much compression can blow plugs. But my issue I usually see is Ring aping pinging. It was happening every time very consistently. I added the shim back in it that I took out. Its back
to the factory shimming now at .9mm shim stack!! I was shocked. That's the biggest shim stack I've seen. I didn't think taking a shim out would cause that drastic of a running change
but it did. It was ring aping pinging. Adding the shim back in (used the same plug the whole time) calmed it back down almost 100% until the tank got down to almost empty and started
1 or 2 pings every so often which I didn't like. Id like to get all pings gone. With this Novarossi .28 I think Ill just leave the shim stack even after its broke in fully, and maybe go to a #6 plug
from the current #5 Im using. But it was running and idling like a champ and had a lot of power with the factory shims and a #5 plug. I guess I ended up answering part of my own question of distinguishing some of the symptoms. I only added a
head shim and the engine calmed down noticeably at idle. Id say its good to go. Next up is finishing the GRP. Getting that running well again.