mls or thin head gasket?
 

I have a felpro gasket set that came with a mls gasket. Im running iron heads on my 318. Both surfaces are unfinished. Should I lower compression with a mr gasket thin head gasket or is it a better seal with the thickef mls?

A thin steel gasket requires retorquing after the engine is run up to temperature. The thicker gasket will lower your compression however.

Does the thicker gasket seal better? Because I would rather have a solid reliable engine than a fast engine thats gonna leak.

If it's the Felpro perma torque blue one you will be fine. It's made to fill small imperfections.

A thicker Head Gasket "may" suck up slight imperfections... like if a motor was overheated and the head is slightly off. ( not my style of gambling though) Felpro make a SD gasket which I believe has a .054 compressed thickness. I was pleased with its performance for service / duty motors.

A MLS gasket needs a finer finish on the deck to seal in most cases. Some guys report no leaks but I have only used as per the manufacturers specs so I cant offer advice on your application.

Increasing compressed thickness increases volume and nets a lower CR.
Decreasing the compressed thickness decreases volume and nets a higher CR.

I just got my 302 casting heads milled about .008 or so because they were a little warped. (im not exactly sure of the amount milled but it was a smaller number.) So i did some researching and found that the stock CR of my 74 318 was about 8.6:1, but ive heard it may actually be lower than advertised. I've heard that my 302 heads should raise the CR about .5-.75 and with them being milled alittle bit im hoping it will increase around .75ish.

So what is the max CR i can use while safely running on regular gas? how about for 91 octane gas? exactly how much will the compression raise if i run a .028 compressed thickness gasket on my 318? Thanks!