Piston to Head clearance and other Q's

[Killer_Mopar]

I need to know the recommended piston to head clearance for an engine. Between decking the block and surfacing the heads, the clearance has gone down substantially on my engine. The problem is that the pistons have a quench pad that sits above the deck (for open chamber heads) and that is where it is tight (30-35 thousandths). I am definetly not going to replace/machine the pistons and getting another set of heads is out of the question(this is my 2nd set), so I am left with 3 options....I could switch to a thicker gasket, shim the one I am using, or maybe take a little meat out of the head. Does anyone know the thickness of the head gasket supplied in the mopar gasket kit is? and more inportantly, is it any good? I know SCE makes thick gaskets but they are really expensive and I would like to avoid that route. Also, since I have never used one before what is the consensus on the steel shim gaskets? Any advice or recommendations are welcomed and thanks in advance.

[Chryco Psycho]

you need .040 between the piston & head minimum , the typical composition head gasket is .038 thick compressed

[70B@rracuda]

CP, what about MLS gaskets?
I  was reading an article on quench and improving combustion while trying to avoid detonation. It recommended the piston/head clearance be .050" to .040 for perfection. "When you get the piston within .050", good things happen." - Engine Masters (I think it was Steve Dulcich)
 Why not closer, con rod stretch? Also is there an enormous distance in stretch between aluminum/forged or I/H beams?

[Chryco Psycho]

MLS works too & you can get a lot of different thicknesses
 yea rod stretch piston can swell with heat etc  you need some clearance fo rsure

[Moparal]

Just the piston dome is .030-035?  What you got for deck Height? Or am I reading it wrong? Zero to .010 in the whole with a .040 plus thick gasket helps one area. As far as the dome hitting inside the head? Have you CC'D the heads and polished the combustion chambers. You will take a few .000 off that way too.

[Killer_Mopar]

Well I took care of my clearance problem. I was around 33 thousandths on cylinder one, 43 thousandths on cylinder 8, and the rest were between 49-51 thousandths. I ended up looking at the heads and found the corresponding chamber for cylinder one must have been casted with a slightly smaller chamber, so with a little grinding and polishing I opened it up and got the clearance to 49 thousandths. Spent forever taping the heads off because I just got them back from the machine shop and didnt want to get any metal shaving in them. I spent too much time and money on the heads to see metal shavings mess them up. I will take a sandpaper roll to the chamber with 43 thousandths for peace of mind even though it is within range. I also decided to get a better head gasket then the cheapies that come with the gasket kit, so if the cheapy gasket was .038 then I will probably buy a .040/.042 and get the clearance around 50 thousandths on all cylinders. Hopefully "good things happen" when I am done Thankyou everyone for the help

[70B@rracuda]

I will try Cometic MLS's next time I do a set of heads. Heard they were the bees knees.

[Killer_Mopar]

I have heard a lot of good things about cometic and when I went to price them I found that summit and jegs dont carry them. According to the cometic website they are 90.85 for a quanitity of one, is that one gasket or a set? If that is for a single gasket, then what advantage do the cometics offer over SCE copper head gaskets that are reuseable and cheaper?

[Chryco Psycho]

Cometic is $90 each [1 gasket]
 they are reusable & are the only way to go with alum heads & the different expansion rates between steel & alum

[Killer_Mopar]

Thanks CP, I remember hearing that they are the only way to go with aluminum heads but didnt know if they had any advantages on iron heads. Im using iron heads and probably wont ever go aluminum on this engine, so looks like a decent set of composite gaskets are what Im going with. Good news for me as they are much cheaper

[Chryco Psycho]

Iron to Iron virtually any headgasket will work ok

[moper]

Quench should be set at a minimum of .035 and a max of .045 with steel rods and hyper or forged pistons. You are using the same pistons I have in one of my builds right now. the quench pads are .059 out of the deck on mine. The one head I've checked so far had .080 deep chambers (surfaces polished) on one end, and .110" on the opposite end...lol. I enlarged the small chambers, and i'm having the head milled to get it to between .035 and .040 quench. What a PITA. I wont be using this design again...lol. Once you get larger than .045", the positive effects of the quench design get diminished. The wider the gap, the less the effect.