Just ran my new setup with the Dart aluminum heads in my jet. Spun a Berk mag/bronze A/B at 5,000 rpms, tight pump. No increase over my old iron heads. I run no thermostat and water temperature is less than 120* on my gauge. My specs are below. Questions:
1. With the low compression and aluminum heads, anything to be gained by running higher temperature in the block. Easy option would be to run a thermostat system with 160* stat.
2. How much HP do you think I am leaving on the table with the big impeller? I am reluctant to have it cut down unless my package will generate significant more HP past 5,000.
3. I know I can run up to around 10.5:1 compression with the new heads. If I decide to go that route, mill the heads or new pistons (my short block is like new)?
I saw no increase in rpms with the aluminum heads even thought the ports and valves are bigger in the Darts. I am right around my goal on speed, 72 on the GPS in my 20.5' Caribbean. I may just leave it alone, but you know how it is, if there is some more HP just lurking around the corner, I hate to leave it on the table.
Specs
Gen VI 502 block (casting 10237300) and I am replacing my Gen V cast iron (casting 14097088) heads with Dart Pro 1 aluminum heads with the 310cc intake runners and 119 cc chambers (the mild version). Compression is in the range of 9-9.6:1, not sure.
I have a roller cam with 580 lift, 240 duration, Vic Jr. single plane air gap, Holley 850, EMI Thunder, MSD, Berk 12JG w/ plate, A/B mag/bronze, shoe and droop.