[HSC-ZL1]

I don't know if these are comparable but I have a heritage ZL1. I ran just 8 degrees of initial timing for break-in and moved up to 10 degrees at 500 miles. This motor ran at about 195-200 at this timing. This is a factory billet HEI distributor. I bumped the timing up to 12 degrees initial (about 35 total) and immediately gained 5 degrees in running temp. It will elevate to about 220 in traffic on 90 degree days but return down to 200 when moving with the 10 degree initial timing.
Might be worth trying for break-in on new motor and a quick test to see if temps come down with less timing.
cooling system carries about 4 1/2 gallons of 50-50 dex-cool.