I'm building a standard 440 for a friend of mine.
It has been a absolute pain in the ass from day one. It was originally built in the early 90's by Blair Machine locally and stored since then. I was given the motor to look it over before we installed in into a fresh painted body. The white assembly grease used was rock hard and the motor had to be pried apart. It had low compression cast pistons on stock rods, the cam had to pounded out. It would not turn over until all the mains were pulled.
I sent it to the local machine shop to be cleaned, new cam bearing installed and my buddy bought probably the last set of Arias flattops made Lol. They are supposed to be 2.077 compression height and should be about .010-.013 below deck depending on how much was milled off the block to square it.
As we start assembly, everything is going okay, the endplay is on the outer limits at .006 but the mains are at .002 across all of then and the crank turns nicely after being fully torqued. I mocked up a piston and rod to see the assembled height so I could order the right head gasket. Turns out the piston is .013 positive deck ! That's nice.... I believe the original shop decked the motor to crutch the crappy cast pistons.
I have a set of Promaxx heads that are ported with 85cc chambers (measured) and am trying to figure out how much and what gasket I need for this thing. I am leaning towards a .051 MLS Cometic. I would have 10.43 cr and only .038 piston to head clearance. I could run a Felpro .039 composite that I have a stack of and end up with 10.7CR and only .025 piston to head clearance. I have some friends that have done this with no issues. But being this is my friends motor, it would probably turn into a greek tragedy. Also, the block deck surface is not the magazine centerfold in engine builders digest as for as smoothness for a MLS. I have only used MLS on our Cummins 5.9 and 6.7 motors and copper on race engines with nitrous. I have always been warned about how picky MLS gaskets are when it comes to surface finish.
BTW, the cam is a Hughes solid with .576/.588 lift 246/250 duration and ground on a 110 center now.
Warming up popcorn waiting for reply

Mine is about the same. but its a 512 lowdeck, .016 above the deck I went with .051 Com gaskets, any closer would hit the head, I have run 10k miles & all is good

.025 is risky in my books. .030 is bare minimum to me and still hold your breath at high rpm.

I have the same dilemma. +.016 deck height. I currently have .051 gaskets in there but not totally happy with the quench. There is an alternative other than MLS - which I also can't use because of the surface finish. These guys make a broad range of head gasket thicknesses for Mopars and other brands:

https://www.scegaskets.com/

Tightest I've ran was an LS7 with .027 piston to head. Passenger side pistons showed signs of just touching the head at that point.


I like the .051 cometic idea.

Felpro 1039 possibly? Also .051" gasket.

I've read about quench as close as .025", but:
1. Tight piston to wall, small bore, and long rod ratios limit contact at TDC rock-over
2. How fast did the engine turn?
3. Did a leak-down test show the same results as with more clearance? The first damage to occur with only slightly too little is a slight collapse of the vertical clearance of the top ring groove, it may even be invisible but a feeler gauge will show below the usual .006". This restricts the ring's access to combustion pressure and reduces seal.

Anything less than .035" makes me nervous.
Grumpy said 50 years ago that if you don't need that much anti-knock, you can reduce pumping loss by increasing it to .060". Pulling those CC in the quench band in & out constantly uses power, think of quickly separating 2 flat pieces of glass.

I was going to use a 3/16 s/s spacer and two .030 cometics to get around .250 thick, but got another block instead.

There is no way I would run any less than .037 piston to head clearances unless I knew the piston to cylinder wall was at or less than .003.
I've tried things like having less than .037and had to fix it after the testing
As far as the main bearing clearances are you using a dial bore gauge or how are you getting those tight clearances on the main bearings
I like and use the old rule of .0010 clearances for each one inch of crankshaft journal size so that means at least .00275 on 440 size mains, I like and use looser bearings to get .0030+ all the way up to .0042 on high rev race motors with thin oil
To little bearing clearances, a tiny bit to tight, will cause a lot more issues than a lot to loose

Has anyone used the .051 head gaskets that 440 source sells ? They are only $15 each and would work for a while. This car is never getting nitrous.
It would give me enough room for the heads decent compression.

You can take a thin cut off the pistons if you have a certain combo in mind. I had a set of pistons cut. .008 to get exactly what i wanted on a 408 stroker. Cost me $80.

I have not used them, but I have seen them, they look good, I would have no problem using them in your case, I had my surfaces done for the cometic gaskets,

Thanks,
I'm going to give them a try. The block surface looks like I would need to use copper coat or something to promote a better seal.
Plus they are really, really attractively priced.

If the surface looks like you would need copper coat to seal MLS I would not use them. JMO

he is not using MLS, the 440 source are coated composition

When I read posts or articles -- where ever, magazines, etc -- and they are leaning towards most concern about gasket thickness, they are missing the most important concern of all -- combustion seal.

Unless the head gasket is MLS, a composition design head gasket must have a durable combustion seal for the sake of defending itself against pre-ignition and detonation -- both of which will practically always exist in hi-performance race engines.

Wire ring combustion seals will act as a dam, fortress... against detonation and pre-ignition.... and that's what's needed with composition head gaskets for performance/race applications

IF you want to change CR, then change the pistons or change the cylinder head's chamber volume.

I'm a former gasket engineer from a major company.

I have 0.051" Cometic head gaskets in my small block, as a means to gain some needed clearance. I can't for the life of me remember which year he ran it, but I remember Jon Kaase ran a MLS gasket that was around 0.060"-0.070" thick.

The main reason different head gasket thicknesses should be considered is to correct dimensional geometry of an assembled engine >> deck height. There are thin metal "spacer shims" (dead soft copper) also available from different sources.. to adjust the deck height after excessive and/or repeated resurfacing of the deck. Older engines are prime candidates for this usage. Similarly, that's the reason why gasket manufacturers have slightly increased their composition thicknesses of their head gaskets. In other words, the past common ~032-038" thicknesses, have become up to ~050-058... in that range.... strictly for geometry corrections to the block assembly for deck height.