Sanding grit in the cooling system never even occurred to me, I can see how that could be a problem. This gasket that Boot77 has shown is looking like a pretty good deal to me now. With the dished pistons of the L-48, I don't think the quench is all that important, anyway. Will a composite cylinder head gasket see any benefit from a spritz of copper coat on each side?

Scotty

 

According to my math, (which, I must admit, could very easily be called into question) on a Chevy 350 with a 4" bore and a 64cc combustion chamber, a .015" head gasket will increase static compression ratio almost half a point over a .040" thick gasket, which is not insignificant to my way of thinking. I mean, if you were thinking about removing the heads to get rid of a .040" gasket and replace it with a .015" gasket for a little more compression, it might not be worth the time and effort involved, but if you are installing new heads, you have to pick a head gasket anyway, so why not pick one that will give you a little more compression?

Also, the 1094 gasket costs about 24 bucks a piece, while the 7733SH1 gasket is only 8 bucks. The 1094 is stainless steel, and the 7733SH1 is plain steel, but other than that they pretty much look identical. Maybe we could save a few bucks? Or is the 1094 actually a superior gasket?

Scotty

 

I would not stop at 64cc chamber if it were me. I'd shave the head down to something smaller get a full point or better of CR improvement. Any amount will help as it increases the efficiency of the engine.
If the cylinder pressure developed can be extracted sooner, then the exhaust valve could be opened sooner and closed sooner so that the intake valve could be opened earlier and closed later. The action of the valves is a big deal when it comes to maximizing the effectiveness of increasing CR.
If you simply increase the CR and do nothing with the cam some gains will be had, and many will be lost due to the poor timing of valve events.

Many dynamics involved in quench and it's use. Again valve timing dynamics allowing for higher cylinder pressures without detonation
A slow opening intake valve slow closing with lots of duration and valve overlap with a low gear ratio drive, (ie 3.70 -4.11 etc) is far less susceptible to detonation than one that opens quickly with less overlap closes early and promotes high cylinder pressures with a higher gear ratio. (2.73-3.08-3.23 etc)
I would agree that quench benefit is lost on the full dish piston.
So if you use a full dish piston on a NA engine,it's better to focus on burn quality,(aka NOT stock 1970"s heads) cam dynamics and intake and exhaust efficiency to maximize the lack of cylinder pressure that can be developed and used in that scenario. And maybe improve the gear ratio.

Oh, and I do not see the benefit of copper coat on a composite gasket, it won't hurt, but no advantage that I can see.

 

OK, so if removing .025" of head gasket thickness gives you half a point of compression ratio, how much would you have to mill off the head to get the other half? Probably more than .025". There are probably a lot of variables here, like the shape and area of the combustion chamber compared to the area of the bore. If you make the head gasket .010" less, you are removing a .010" thick slice of the entire bore area, while if you mill .010" off the head, you are only removing a .010" thick slice of the area of the combustion chamber, which is smaller than the bore. That's just straight milling the head surface, though. What can angle milling do for us here? I think a thinner head gasket is probably the most cost-effective way to increase compression, but you very quickly run out of head gasket to make thinner.

Scotty

 

I wouldn't worry bout grit in the water jackets more than likely you already have some settled at the bottom of your block from the factory. Use to be a machinist around here that would clean the block and then show customers all the junk that came out, he would leave out that most of it was from the water jackets. Now the lifter valley and bores is where I wouldn't want to get much. Why I tell peeps wash your intake manifolds & heads, anything sand cast is gonna have some sand still in/on it.

Quench is important but seal is more important. Never used shim gaskets myself but always read the surface has to be good or you may seep coolant. My last set of heads on my block I used the thick blue felpros and they did seal But I expect the better heads and thinner composite gasket to run better.

Everything I've read bout composite gasket is they work well on an ok surface, some say to spray others say they don't need it. I know my heads will be good enough but my block is meh, so I'll coat one side for my app but if you don't need it why add it to the mix.

More compression is good but I have no idea bout your combo or tuning ability, I've never been a max type due to so many factors(some out of my control like weather). I'd rather have a bit more than these had factory but not so much the car is sensitive.

Just my opinion as always and others have theirs, GL!

 

You can get from the manufacturer how much the chamber is reduced per thousands of an inch removed either angle milled or flat milled. So it can be computed fairly easily before any metal is removed.
I have a flat milled head and my current angle milled head. In both cases the manufacturer gave me specs for doing so. Then I could compute my CR before deciding how much to remove. Flat milling is more restrictive and you run into the intake valve pretty quick. But not too many shops angle mill. I had to have my AFR's angle milled by AFR before shipping.
Neither caused any angular issues with intake manifold sealing or installation.

I've had both low CR, 9.9:1 CR and my now 10.6:1 CR. In each incremental increase performance was enhanced as was throttle response and bottom end torque. CR is a good thing. I should have gone to 11.0:1 honestly.