2 engines, a 350 and a 400, want to run 40 and 42 deg. on the street. Less than that and they are dogs. 350 is a crate and the 400, home built. everything double and triple checked. Only common ground is the distr. They are from summit. Initial timing set @ 10 and 12. No pinging, hard starting, or overheating. Called Summit and they are baffled also. Any ideas. BTW the 350 runs 89 octane and the 400 runs 93. The plugs are clean and the right color.