Composite - head and block have to be flat.
MLS - head and block have to be flat and finished to an RA of at least 60 and some require even better surface finish.

What's the power goal?

I've put a fresh 9627PT composite on a deck that's already had a few headgaskets on it and even on a head where there was one season of "bite" into the surface. I cleaned up both surfaces carefully and it still sealed just fine to 23lbs+ on a b16g w/ standard ARPs at 90ft/lbs. That's not big power, though.

I'm planning on putting the same composite on this build as well, with a 6851S and forged pistons & rods, 21-25psi depending on the octane I'm running at the time. RockAuto was selling them for like $10 each so I picked up a few a couple years ago.

I use composite head gaskets on stock piston/rod combos. The headgasket serves as a fuse.

For piston/rod motors, mls and some experience tuning. Another reason to run mls is to lower the compression or get the cylinder head height correct.

Alot have changed to the sce cutring gasket. Its a composite and o ring thats crushable. People seem to like it as a next step for more power and boost.

I'll be updating the tuning calibration and timing curves to optimize the setup, same as done with the 16G. I feel like my setup is pretty stable, and the knock sensor with E25 fuel is helping me find the sharp edge of the tune.

Power goals: 6-Bolt - 1G rods, 95 pistons, Standard ARP studs, TDO5H Bastard 20G

Currently running 300-380hp with a Big16G @20psi (29psi if I use all the boost spike.) The 20G will be a little more power, hopefully less spike. If I can find 400hp I'll feel good about it.

I'll be happy with a little more compression ratio - but I need to know the block prep.

The head prep can be done at the machine shop, but the block prep is going to be in the engine bay. It's already running with a multi-layer metal head gasket, which won't survive disassembly. I'm wondering if I just need to clean the block well, or bust out some other tools to prep the surface.

Justin

If it tells you anything the sbe record car has gone 8.90 at 151 on a felpro composite and some standard ARP studs, doesn’t mean it’s the best option for everyone but says a lot for the guys who thing they need an MLS gasket for their stock street car that rarely sees wot. And I’m also with danl, it serves as a fuse of sorts, he couldn’t have said it better.

you gotta have the head and block prepared for metal my friend runs one and hasnt had a issue with block or head he just slapped it on. But everyone car can be different , you got some insurance for the composite versus the mls.

Composite. Only con if you can even call it that, is it’s a pita to scrape it all off when you change it.

Stock OEM is more than fine. If you get a mirror finish then you can opt for an MLS. I like the EVO III unit but they are so high now.