PalmettoZ Posted February 12, 2009 Share Posted February 12, 2009 I just got a set of 89mm pistons for my 3.1L build and am considering shorting the skirts to lighten them up a bit. Has any done this previously with success ? These are stock 89mm KA24 ITM brand pistons. I believe that they are cast pieces. Not very light. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted February 13, 2009 Share Posted February 13, 2009 Why, Are you thinking that lighter pistons will let you rev your engine harder? Personally I suggest you don't do it. The piston skirt is designed to prevent rock or tilt of the pistons as they move up and down the cylinders. Shortening the skirts will upset ring seal with the bore, so you get more blowby and greater oil consumption. This situation is worse with engines with a smaller (numerically) rod/stroke ratio, like the L28 and L26 engines. If you think that you can free up some power because of reduced 'drag', you're wrong. Virtually all the friction is from the rings, not the skirts. Cheers. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted February 13, 2009 Author Share Posted February 13, 2009 Why, Are you thinking that lighter pistons will let you rev your engine harder? Personally I suggest you don't do it. The piston skirt is designed to prevent rock or tilt of the pistons as they move up and down the cylinders. Shortening the skirts will upset ring seal with the bore, so you get more blowby and greater oil consumption. This situation is worse with engines with a smaller (numerically) rod/stroke ratio, like the L28 and L26 engines. If you think that you can free up some power because of reduced 'drag', you're wrong. Virtually all the friction is from the rings, not the skirts. Cheers. Hey Ozconnection- Looking more for the weight reduction without removing material inside the piston. It would be easy to just turn down the skirts on a lathe is what I had in mind. I have heard of some people drilling holes or milling out sections of the skirt to reduce weight. Most of the competition pistons that you see are very short, although I agree with you with what you brought to mind about the piston movement side to side. Wasn't trying to rev harder, just thinking lighter revs up quicker. The crank that I have has the counterweights reduced and I will be using a ligher dampner with single groove. Quote Link to comment Share on other sites More sharing options...
RIP260Z Posted February 13, 2009 Share Posted February 13, 2009 Maybe wrong here, but I thought a good quality front damper like a BHJ one (which is heavy) would be better as it would quell the harmonics with the 3.1L..... more important it is balanced... as even my BHJ one needed a bit of balancing. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 16, 2009 Share Posted February 16, 2009 There is nothing but benifits to lightening pistons, considering you dont take away from the strength of the piston. LIghter piston means a stronger rod, strogner crank, stronger rod bolts, stronger main caps, stronger main bolts, etc. It also takes WORK to stop and accellerate an object, the lighter the piston, the less work it takes to accel and decel that mass. Therefore more "work" can be transposed to the flywheel. Acceleration time is purely dependent on mass. My stroker pisons bare weigh 300 grams after I am finished. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted February 17, 2009 Author Share Posted February 17, 2009 There is nothing but benifits to lightening pistons, considering you dont take away from the strength of the piston. LIghter piston means a stronger rod, strogner crank, stronger rod bolts, stronger main caps, stronger main bolts, etc. It also takes WORK to stop and accellerate an object, the lighter the piston, the less work it takes to accel and decel that mass. Therefore more "work" can be transposed to the flywheel. Acceleration time is purely dependent on mass. My stroker pisons bare weigh 300 grams after I am finished. Hey- I had read your previous post on this and would like to do all of this as well, except there is quite a bit of work for a machine shop and it wouldn't be cheap. I have access to a lathe so I could shorten the skirts up myself, but think I am going to leave them alone. Worried about piston slap if they are too short. Just curious, do you remember the weight you started out prior to machining ? Did you take any off of the skirts ? Quote Link to comment Share on other sites More sharing options...
rsicard Posted February 17, 2009 Share Posted February 17, 2009 Scott: 1 fast Z is absolutely correct concerning lightweight pistons. Suggest that you talk to 1 fast Z more regarding his pistons. Consider sending back your cast pistons for credit and perhaps getting some from 1 fast Z. Otherwise, use a milling machine to take material from the skirts similar to the pictures posted by 1 fast Z. Lastly, SERIOUSLY consider ceramic coating the crowns and moly coating the skirts with CBC2 ceramic coating from Speedway Motors and moly coating from Techline Coatings. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted February 17, 2009 Share Posted February 17, 2009 If you look at the piston from 1 fast z, you'll quickly see that there has been no machining of the piston skirts to shorten them. That is the answer to your original question. Quote Link to comment Share on other sites More sharing options...
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