lammbn Posted February 28, 2008 Share Posted February 28, 2008 Alright, i give up. i have spent the last hour searching and found nothing and i know as soon as i post this someone is going to pistol whip me with a thread that has exactly what I'm looking for. I have just finished the teardown on my engine and it is off at the machine shop right now getting a chemical bubble bath and magnafluxed. Now the re-build can finally commence soon. Now the quick and dirty plan is currently as follows Hone and bore the block if absolutly nessesary get crank checked and possibly heat treated or something bla bla bla Flat top pistons MN47 head (with the Braap makeover.... hopefully) i want the quench of the MN47 but also a reasonable compression ratio, i know, not the straightest line of reasoning there is it? and seeing as how i already have obtained the head i don't want to go looking for another. I would like to have the head all done by Braap (I still need to get around to getting a rough estimate so i know how much to save up) but basically i am looking at port and polish to match custom intake manifold, bigger valves, and some unshrouding. sorry for the novel but my question is this. if the CR isn't low enough for my tastes after the head work, is it possible to mill the shape of the combustion chamber into the top of a stock flat-top piston? And if so how deep can i go? I currently am getting my mill honed in and a intake flange whipped up. i would really like to do the pistions myself seing as how custom pistons are way too expensive for me and i can get a better match for each cylinder this way. and the CR i want. i also have the help of my father-in-law who is the head of a very large machinist shop and a very good source of info. (and no i cant get free work out of him, i already tried. he runs a private shop for a very large production company locally.) any help or experience is welcome. Quote Link to comment Share on other sites More sharing options...
Matt K Posted February 28, 2008 Share Posted February 28, 2008 Why not just toss in a 2mm headgasket? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 28, 2008 Share Posted February 28, 2008 A braap head?!!!! Cooooooollllllllllllllllllllllll. I want pic's! Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 29, 2008 Share Posted February 29, 2008 A 2mm head gasket will defeat ALL purpose of a high quench head. PLEASE search before posting, if your not sure on what your posting about. Quote Link to comment Share on other sites More sharing options...
lammbn Posted February 29, 2008 Author Share Posted February 29, 2008 Ditto what 1 fast Z said about the head gasket. i want to keep the quench affect. Dr Hunt: sorry but i don't have it done yet. i still need to get around to finding how much it will set me back so i can save it up. my wallet is already cowering in the corner with fear. but good news might be around the corner. i am working on getting a '73 240Z and a '75? 260Z for cheap to possibly part out. 1 fast Z: you are very Knowledgeable with this kind of stuff with Z parts. do you have any idea how deep i can mill a pocket on a standard flat-top piston safely. I've seen it done with a sbc piston before but this is the first Z engine for me. of course this is all dependent on whether the chamber work removes enough material for my tastes. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 29, 2008 Share Posted February 29, 2008 I rework ALL of my pistons to the lightest as possible. You can go a MINIMUM of .187" thin in the top dome on a NA motor, and usually I shoot for .200" thick. All piston manufactures are different, so that will vary on how much you can take out of the dome to maintain that thickness. ALSO do NOT make ANY dish below the quench pad of the MN head, as you WILL defeat all purpose of that head. Make a reverse mirror image of the combustion champer for max quench. Quote Link to comment Share on other sites More sharing options...
lammbn Posted February 29, 2008 Author Share Posted February 29, 2008 yes, i know. thanks for the very usefull info. it answers my question of how thin i could go safely. my plan was to set the head on the block and hand tighten it down without a gasket and one by one slowly run the pistions up till they touch the head. then either spray machinists blueing in the spark plug hole or put it on the piston beforehand and see if the head will make marks on the piston where the combustion chamber is. then mill the same depth and shape that will fit within the space under the chamber on all of them. from there i would hand blend the outline of the chamber into that pocket and carfully cc them so that they are all the exact same volume. something like this. the blue area is the mirror of the cobustion chamber onto the piston and the red is the identical pocket i would mill into the top of each one. i would blend the blue part into the red pocket so that they where all the same volume and there where no sharp edges to cause any pre-ignition. nothing is to scale and it is just meant to be a visual aid. does that sound like the fundamentaly right way to do it? Quote Link to comment Share on other sites More sharing options...
1 fast z Posted March 1, 2008 Share Posted March 1, 2008 Perfect. Quote Link to comment Share on other sites More sharing options...
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