Head and Block Milling Questions

[aspekt9]

I had both my head and the block milled to a mirror finish for an OEM MLS head gasket. My question is, with both being milled down, will it affect my piston to valve clearance, or throw off my timing? Are the MLS head gaskets thicker because they require surfaces to be milled? How thick are they? Should I purchase adjustable cam gears to degree my cams? Any other issues I should be concerned about?

 

[DSM_JAY]

To answer your question yes, having both the head and block milled down will effect your piston to valve clearance. one thing about mls gaskets is that they are available in different thicknesses. if you didnt ask or weren't told how much material was taken off of both surfaces now would be a good time to ask or find out, it can be compensated for. I have had many heads and blocks shaved for me and .010 or ten thousandths combined from both sides is still in the safe zone. however if you decide to go with a "standard" thickness your compression ratio will go up, not drastically however. typically a mls head gasket is bought with the intent to run alot of boost. well i dont know if you need adjustable cam gears, they usually are needed when you have after market cams, valves and other mods

 

[FastJetta]

agree with what he said....

be good to know how much they took off of both... if you get a "oh well we had to take off about a 1/4 inch" you may be in trouble

 

[BogusSVO]

ok. according to the mitsu manual, you are allowed to mill a combinde total of .008 from the block and the head

AERA allows .015 from the head
the few 4g63 short blocks I have checked (6bolt) have a piston to deck clearance of .003
Area also lits a new head thickness of 5.200 and a min thickness of 5.185

for appox every .007 milled from the head you close the combustion chamber by 1cc

so if you want OE compression, yes you will want a thicker headgasket that will equal the OE headgasket thickness plus the amount milled

also you may want to do this oil port mod
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html

cam gears will be a good idea to run so you can dial in the cams, stock or aftermarket

 

[herms99gst]

how does 1cc affect the compresion ration? or rather how much would it add to the compression ratio if you decide to stay with the standard size head gasket? if you had a un milled head and block, with a standard size head gasket and you upgraded the pistons to 8:7:1..(using this example cause thats what my arias are) your cr is 8:7:1...what would it be if you had the head and block milled and it caused a combustion chamber decrease of 1cc?

 

[DSM_JAY]

well in order to get an exact number we need a few more numbers, one being if your pistons are dished I imagine they are, that number would help, actually lets check ok -11cc . was the block bored over. deck clearance. however if my math is right, if not someone please correct me it would be around 8.5:1 all in all we could side step all that if we had the numbers on how much material was removed, do some general math and decide on a gasket thickness for you

 

[BogusSVO]

well with casting varances, and how many times the valves and seats have been cut and ground, the head should be CC'ed
http://www.dsmtuners.com/forums/articles-engine-fuel/341621-how-cc-combustion-chamber.html
then the piston to deck clearance needs to be measured...
http://www.dsmtuners.com/forums/cyl...heck-piston-deck-clearance.html#post152107571
then we need to know what the stock cc of the headgasket is, when compressed
also what the +cc or -cc of the piston is
and what the swept volume of one cylinder is from TDC to BDC

then the math can be run and your real world static compression can be found.

 

[herms99gst]

ok now what if it got a little more confusing...im not trying to figure out my cr just wondering how u would est. a giving cr with a certain set up....what if you had a 6 bolt block bored .020 over...85.5 mm..and a piston with a factory stated compression ratio of 8:7:1...that would be assuming you have a 6 bolt block with 6 bolt head...but instead of a 6 bolt head you are runing a 2g head...now a 6 bolt engine with matching head has a cr of 7:8:1, where a 7 bolt motor has a cr of 8:5:1...would their be a way to figure out the size of the combustion chamber giving the cr of the motor if the bore and stroke are giving? and how would you figure out a cr if the head was miled..say .001? or do i just sound like an idiot that is confusing the hell out of everyone

 

[DSM_JAY]

No you dont sound like an idiot, just a little unfamilliar in the ways of determining compression ratios, to find the Cubic Centimeters of the combustion chamber the head has to be off the motor and you have to do whats called CC'ing the head. knowing the bore and stroke of the engine is key but it will only give us cylinder volume, alot of other numbers are needed however if you want to you could do a google search on compression ratio and alot of sites have the formulas.

 

[Thruapole]

What is the typical piston to deck clearance for a 4g63? My pistons are .011 in the hole, but I am running aluminum rods that will stretch at high RPM. I am trying to figure out how thick I need my head gasket to be?????