Most modern timing lights will work with multiple spark ignition but older ones not so much. I really think before I went and did anything else, I would get a modern timing light and get timing verified in. Usually a big Mopar with stock heads runs no more than 38 degrees total timing. I agree with others suggestions of locking out the distributor and setting the advance curve. I would follow that up by going to Holley’s website and follow the tuning recommendations on the 660s and get them on there. If they have had power valves installed, block them and jet up 10 sizes from where you’re at. The present tune up is hurting your performance more than your converter at present. That weight, gearing etc. should be running closer to 13s than 16s, even if it’s a motor home engine. What spark plugs are you running?
