Matadem Posted July 15, 2007 Share Posted July 15, 2007 to lower compression? I have 2 l28 blocks 1 from a z 1 from a patrol the patrol has dished pistons(use thicker rings too)(this is what I am going to use) the z has flattop I was wondering If I machined the top of the pistons to lower compression a bit I would have a spare set I would use these with p90a head... p90a stamped but has no hydraulic lifters... You can laugh if you want but this is my junkyard technology project the only performance parts are a professional ported head and arp conrod bolts...+ the turbo stuff Thanks Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 16, 2007 Share Posted July 16, 2007 Are you trying to machine a dish into the flat tops, or machine the dish out of the dish pistons, just for curiosity's sake? Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 16, 2007 Share Posted July 16, 2007 if you're thinking about machining a dish into a flat piston, you're much better off trading those flats to someone who wants them for an NA aplication and get some dished from them. makes both parties happy Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 16, 2007 Share Posted July 16, 2007 The problem is the piston, although flat, would be way down in the hole if you shaved the top. I think Norm (former member, now banned) milled some pistons down and then ran a longer rod to get them back up to the deck height. It was either him or DAW. You can do it, but you need to cut just the right amount off the top, and then to get the height back run a longer rod, which gives a better rod/stroke ratio anyway. Much much much easier to just get the right pistons though or swap as e_racer1999 suggests. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 16, 2007 Share Posted July 16, 2007 Somebody had a thread going about doing some extreme piston lightening as well, was that the same build do you know? I was just wondering about that the other day and hadn't gotten around to trying to search for it yet... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 16, 2007 Share Posted July 16, 2007 That sounds like 1 fast z's build where he machined the inside of piston to lighten it, but that is not the same idea as cutting down a dished piston to make it a flat top. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted July 16, 2007 Share Posted July 16, 2007 Keep a .187" thick dome for NA cars, and .25" thick for Turbo Cars. I have done LOTS of lightening, as well as dishing, custom domes, etc. NA pistons Notice the extra strut inside the TURBO pistons for support: Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 16, 2007 Share Posted July 16, 2007 Yes - it was Norm (the 12 second SU dude) that "ground" the dish off his pistons. Believe he used his driveway concrete, and then counted the number of passes he made with his first piston until it was flat, and then performed the same # of passes on each subsequent piston. Believe he made like 10 passes or so and then changed angle 45 degrees. This is from memory (fading) only though, so it might not be totally factual. The post was over on Z-Car.com. Quote Link to comment Share on other sites More sharing options...
Matadem Posted July 16, 2007 Author Share Posted July 16, 2007 Are you trying to machine a dish into the flat tops, or machine the dish out of the dish pistons, just for curiosity's sake? Machine a dish into the flattops Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 16, 2007 Share Posted July 16, 2007 Believe he used his driveway concrete, and then counted the number of passes he made with his first piston until it was flat That can't really be the way he did it, is it? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2007 Share Posted July 17, 2007 Yep. I know a guy who shaved his head on his go kart the same way. Might not be the most precise way to do it, but it will work if you're careful and cheap. Hard to argue with results... Quote Link to comment Share on other sites More sharing options...
bschiltz Posted July 17, 2007 Share Posted July 17, 2007 What if you got a piece of glass and some wet and dry paper? That'd improve consistency and still be really cheap. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 17, 2007 Share Posted July 17, 2007 No such thing as the wrong tools if you've got the determination I guess...I would think that would actually be harder to do than to just machine the things properly! You'd have to make sure your pressure was consistant, and the swipe was the same length...I've done some sketchy mechanic-ing in my day, but my hat's off to Norm! Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 17, 2007 Share Posted July 17, 2007 No such thing as the wrong tools if you've got the determination I guess...I would think that would actually be harder to do than to just machine the things properly! You'd have to make sure your pressure was consistant, and the swipe was the same length...I've done some sketchy mechanic-ing in my day, but my hat's off to Norm! try searcing the archives at Zcar.com sometime for his name.. "norm (the 12 sec dual SU dude)" The guy is WILD as far as how low-budget he goes with things, but he pulls out results. I am not 100% certain I trust my judgment of his BS factor; he is the type that makes you second guess belief as well as doubt in him.. You just can't decide whether to believe him. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2007 Share Posted July 17, 2007 I don't think I've ever seen a technical post from Norm that I thought was BS. Maybe overly political (which is why he was banned from here), but I never looked at his methodology and thought "There is no way that happened the way he said it did." Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 17, 2007 Share Posted July 17, 2007 I can attest firsthand that Norm's bulid pulls phenomenally. 12 second car built at home without fancy tools and runninng SU's to boot. I feel a kinship with him in that both his car and my wifes 260Z (AKA "The Blue Turd") have similar...er....'patina'! Having supported Turbomachinery in the third world, I can tell you firsthand that 'the proper way to do it' takes a back seat to 'it works' any day. I watched aghast as a guy with a hand grinder took swipes at a Turbine Impeller Stud, and then randomly swiped against pieces in his stock rack until he got a 'spark pattern similar'---nothing like precise metalurgical analysis for 'torque to yield' fastener fabrication! I had gotten into that situation when no less than FOUR OEM-Manufactured pieces failed on pull-up. I was not happy with their OEM machining, as I could see lines in a radius, and it didn't look like it was shot-peened for stress relief. This guy, in his little shop, with his 'benchtop tools' resting on the FLOOR with operators squatting in front of them piled with chips all around...produced a part that looked like it was CHROME. I simply had them 'make it as smooth as you can' and they did. Torqued up, held, and is actually running today at a Refining Location now four years later! Never put too much faith on a 'clean and proper shop'---put more faith in the backlog of work the shop has...if they have a lot of work, there's a reason for it: They probably do a pretty good job! Amazing things can happen with ingenuity and simple hand tools. In the Phillipenes during WW2, they made Colt 1911's using little more than hand labor, chisels, and files! Barrels were drilled using a bit, then broaches for the rifling and final bore were made using broken file pieces woven into bamboo arbors! They didn't place at any International Pistol Shooting Competitions, but they put lead downrange when they needed to! I digress... Side Thought: New Discovery Channel Program for Maching Geeks: Extreme Machining of the Third World! First Edition: Norm squatting on his driveway in the hills of Western N.C. machining his pistons! LOL Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 17, 2007 Share Posted July 17, 2007 I will make clear two things: one, I had NO IDEA why he wasn't here as well as "the other place" and two, that I feel his name alone carries undeniable clout; I have seen one or two MEAN z setups on dual SUs and those are the ones that really got the heart pounding, because there was an echo in the exhaust note only produced with the twin carb setup; a hi-po motor based on the same induction as the original 240Z has a specialized tone to it that is STILL very stockish and that appeals to me more than anything else about Zcars. Thats why I want dual TBS for FI. Quote Link to comment Share on other sites More sharing options...
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