lammbn

I bought the full color diagram off eBay for my Z. it was extremely helpful when I was tearing my harness out and labeling it, much easier to follow than those stupid black and white diagrams that are spread all over throughout the book. I found only two very minor discrepancies with the whole thing. I did it because the last owner screwed with the heater fan speed circuit and I thought it would pretty bad but just ended up being two wires cut and crossed. If you decide that you don’t want to deal with the harness you have I am selling my harness soon, and for much cheaper than any painless harness is going to cost you. It is in good shape, all new injector plugs and water temp/thermo switch plugs. Problem is I am selling the whole electric system together; body and engine/EFI harnesses, ECU, air flow meter, ignition unit, and switches. You probably don’t need all that but PM me if you are interested.

Thank you guys for your input. Braap: i agree totally that this setup would be completly un-nessesary in 95% of applications out there. But seeing as how i am a hobby machinist/fabricator and a Junior in my bachelors degree for Mechanical engineering i know that i tend to over-engineer things. and thanks for clarifying that the shear stress was not an issue with the washers (i'm not sure if you italicized sheer because i spelled it wrong but i could have sworn that spelling meant see-through. but who would have guessed that english would be an engineer's worst subject. )

sorry, i think you mis-understood what i meant. so i drew a picture, i know that always helps me. i hope this is an accurate depiction of what you have got going on. but before i begin i appologize for such a long post, i tend to look at everything through the eyes of a mechanical engineer. please bear with me. so the red arrow is showing the force of the brace that i was talking about. if this is pulling up on the main bearing cap like that it will skew your torque readings when you are tightening them down. this would make them loose fitting and possibly cause them to pull away from the block a little. but that is all it would take to cause the crank to move around inside the bore. especially at the higher RPMs you are designing this to run at. idealy what you would want is to have it pushing down on the mains so that it is alway pressing them into their slots. but to do this you you have to add more washers to flex the brace out and have it push down. but that brings me to another area of concern. you are building this to help dampen vibrations within the block. those washers can move relative to eachother so i would be worried about the shear stress being put on those bolts right at the top of the mains cap and the bottom of those washers. correct me if this isn't really a problem. i think that the best option would be a solid plate that was welded to the brace that bridges that gap instead of the washers, slightly thicker than what is needed so that it will exert force down on the cap. Then instead of running one bolt through the whole thing i would use a stud, preferably high grade, and use nuts on top of the mains to torque them down. then enough of the stud coming out beyond that to use another nut to secure the brace to the mains. you would have to mill or drill a pocket out on the bottom of the plate to clear the nut holding the cap. like this. sorry for such a long explination. but i dont want to see you to ruin your engine after putting so much work into it. i hope i didn't rock the boat too much.

Nice job on that block brace. I have a quick question reguarding that particular design of it though. since the mains caps are a pretty tight tolerence fit what kind affect would this possible have on torquing the main bolts down? if the brace was in any way flexing and pulling up on those mains wouldn't it affect the how tight those bolts are holding the caps down? are you just going to crank them down a little tighter and hope for the best. this is a pretty critical part of the engine. if they are too lose or too tight it could cause improper oiling, ruin the crank, or worse.

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?

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.

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.

you know if you really want to get it all out and be sure that everything is all good in both the oil and the water passages the best thing to do is get it hot tanked. it doesn't cost that much but it really gets them cleaned up good. it even gets a lot of rust and scale off the block and out of the coolant passage ways. i just had mine done, and with a little shopping around i ended up paying about $35 for the hot tanking part on just the block. about $50 was the average of everywhere i called. I also had the block magnafluxed and the head sonic tested and cleaned, all together it ran me $140. which i am more than happy to pay for the piece of mind that everything is good to go.

Where did you find those wheels?! i've been searching and searching for a five spoke wheel like that in solid black. i haven't been able to find anything without a gay chrome or machined lip, and seeing as how there will be no chrome on the car at all that would look like crap. i had resolved that i would have to find some unfinished and powdercoat them myself.

I think you missed the point of carving out an identical shape of the chamber onto the piston. its to lower the compression to a more managable and sane CR range and still keep the high quenching affect of using flat top pistons with these heads, not to magically make it more powerful or efficent. with the high quench effect it is a so called "fast burn head" because the flame still has a shorter distance to travel than all the way across the cylinder from one side to the other..