You're right about figuring final compression. I'll know more once parts are all together. Would 9.5 and 87 really push it with aluminum heads?

On the header dumps I hear what you're saying. I had considered this but thought (assumed) that with others doing similar this wasn't an issue. I'll need to rethink that a little more. Maybe a much smaller restriction to slowly drain the water? I'm not concerned with leaks since really checking them over, but I had a good amount of water that seemed to make it into the rear ports. I was thinking draining would also limit condensation. I'm open to any and all suggestions on how to go after this the right way.

The cam is the one spec'd for the 500 EFI and it's not in the catalog. Grind number is HR-292-2S-14 IG, .598/.610, 230/236 @ 050, 114 LSA. I will probably run this with a 1.8 rocker on the intakes to help get the exhaust in-line some (so lift would be .633 on the intake). Mine have the tulip-Inconel option so the exhaust port will be very aggressive and potentially over-scavenge. Boosting the intake side would help to get after this. From everything I've read, this is a good direction with that head and really close in terms of the recommended split in duration. I know others here have done similar.

The heads are as-cast with whatever CNC work AFR does to them prior to the full CNC option. They would fall under the partial CNC flow sheets though I think the exhaust flows more because of the valves.

[QUOTE=TomZ;4760964]You're right about figuring final compression. I'll know more once parts are all together. Would 9.5 and 87 really push it with aluminum heads?

Tom, The motors we built for the Monkey were 9:5 with 335 AFR aluminum heads.....I had to run 93 octane fuel...She did not like 87 at all

[QUOTE=badmonkey;4760970]Thanks Chris. If I have to run better fuel that's okay with me. My only concern is finding it. The place I keep the boat in the summer has 93.

What's the cutoff point with octane and aluminum heads? 9.25? 9.0?

[QUOTE=TomZ;4760972]Do not exceed 9.0 is my opinion. I’m sure others may feel differently however.

Even at zero you will need 4 cc of dome to get to 9:1 with a 121 cc chamber and a 040 mls gasket. If my math is right. These Wiseco pistons should be close with a 3.8 dome. Part no. PT077H3. Sorry for not having a link. If you go to 4.25 stroke, a flat top will get you a perfect 9.1-9.2 ha ha. It’s only money. Good luck Tom

Thanks Roscoe. I believe my heads are 118 maybe a touch under. They need to be surfaced to take care of some corrosion spots because of running on GEN VI blocks with open cooling I was going to take them down to 114 to work with the original pistons per the original plan, but since the one piston messed up and required some boring to fix, I got it in my head to Go higher with the compression, etc. I’m still working on the final configuration.

I’m open to any and all suggestions on this so please keep them coming!

My initial rough math based on having the block decked to zero or close to (.001-.002, we’re not final just yet... it may need a touch more than that), using a SRP replacement piston (1cc dome), 039 gasket (FelPro 17048), and the 118 head was putting me at about 9.2. Taking the heads to 114 would put me at 9.4 and change.

Final numbers will be figured out once I have all the measurements in-hand.

Any thoughts on my idea of bumping up the intake side with a ratio change? If I go to a 1.75 Crower rocker, I would be at .616/.610 and probably close the duration spread to 232/236 @ 050 (or 231/236).

I would personally would want dry exhaust to safeguard all of the time and money you will have tied up eventually. Keep posting progress, I can’t wait to see how many prop sizes you have to go up.