Merc 1075 is actually 7.9:1 comp

Other thing to keep in mind you can always open up your chambers about 5cc's and lose .3. Every little bit helps. Btwn that and .060 gasket
Should get you in the high 8's.

7.9 is right,,I'll have to look at the receipt for the gaskets I ordered.they were cometics.if you can't wait till tonight,,maybe give cometic a call.

I can wait, great info guys!! Thank you.

1075 has .051 head gaskets in it. You can get .125 head gaskets from cometic but they are pricey. Or what ever you want made just next day ship them and they are don in three days at least the last ones I ordered where.

I'd go with a .060 head gasket if you have a .040 on it now and call it a day. Those blowers are really big for what you're doing. In fact, you might be better off with a smaller blower for distribution purposes on such low boost. I would think 9:1 compression and 4-5 psi would easily be 800+. You might actually struggle to get the power that low and wind up with a 900hp engine with low boost.

For comparison purposes, I have 572's. I used to run Merlin Grumpy Heads years ago and my compression was 8.3:1 on a cam that's somewhat close to what you have but solid and made 838HP at 6K rpm with an 8:71 blower and 6psi boost, no intercooler. Fast forward a few years ago, I put AFR 357CNC heads on it and I never dyno'd but I estimate the power was close to 900 hp since I picked up 300 rpm and didn't change anything else. Then two years ago I completely rebuilt the engines with new blocks and pistons, running 8.4:1 compression, 8:71's and 6psi boost netted me 965hp on the dyno. That was also good for another 200 rpm gain in the boat. I also installed a methanol injection system in place of an intercooler and with Meth the boat runs 95.4 mph and without it activated the boat ran 94.5 mph. All 572" stuff...

This amazes me!! Are we 100% sure a factory 1075 has flat tops .075 in the whole and a .051 gasket? NOT doubting your knowledge or intelligence in any way shape or form!!! But if I am basing my build off of those numbers I want to be certain of it. I love this site, you guys are all great:)

I am not certan of the .075 in the hole but its deep and no doubt they are flat tops. I do believe I have a few pistons here from a rebuild I did before. I can figure out how deep it was if you want to know. Compression height take me a minute later tonight.

Just looked up gaskets they are .051 head gaskets and .051 for intake. Intake uses a MLS also.

If you wouldn't mind double checking the hole depth I would really appreciate it!!

For what it`s worth , run it rich. According to my knock sensors and AFR gauges the motors are quite a bit happier at low to mid 10`s then they are at low 11`s. @WOT

With that set up I'm coming closer to 8.24 however go to Wallaceracing compression ratio calculator and play with the numbers. Merc might use a flat top also with a bit more valve relief. Either way you can get some ideas