MetalThrashingMad Posted May 7, 2009 Share Posted May 7, 2009 I have an l24 that's in rough shape and in the process of a rebuild... I've read that an overbore of 0.078 is safe with these motors with little modification... when I stripped the motor down I saw that the pistons were stamped " 0.050." I'd like to have the walls shaved to fit some new pistons. My questions are, is .055 or .060 over safe for a mild build on an l24? I've seen pistons around for .020 and .040 all over the place; where could I get a set for 50+ thousandths over? Thanks in advance Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted May 7, 2009 Administrators Share Posted May 7, 2009 .050†is not a common overbore, (I don’t recall every boring and engine .050†over in all my days boring and honing blocks). More than likely that is the metric stamp and reads .50 which stands for ½ mm over bore, or .020â€. In that case, the next size up would be .75mm or .030â€, or even 1.00 or .040â€. In short, I am 99% sure you have MORE than adequate material left to meet the next two overbore sizes. Quote Link to comment Share on other sites More sharing options...
MetalThrashingMad Posted May 7, 2009 Author Share Posted May 7, 2009 .050†is not a common overbore, (I don’t recall every boring and engine .050†over in all my days boring and honing blocks). More than likely that is the metric stamp and reads .50 which stands for ½ mm over bore, or .020â€. In that case, the next size up would be .75mm or .030â€, or even 1.00 or .040â€. In short, I am 99% sure you have MORE than adequate material left to meet the next two overbore sizes. Thanks The pistons indeed read 0.50. I feel like such a putz. 0.040 pistons are available all day long so that's what I will probably go with. Thanks again. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted May 7, 2009 Administrators Share Posted May 7, 2009 Thanks The pistons indeed read 0.50. I feel like such a putz. 0.040 pistons are available all day long so that's what I will probably go with. Thanks again. Cool. Glad to hear you are able to move forward with the project. Quote Link to comment Share on other sites More sharing options...
junglist Posted May 7, 2009 Share Posted May 7, 2009 I'll confirm that if the Nissan pistons say .050 they are indeed .020" overbore. My crate-motor F54/P90 L28 from the 80's that I just did a rebuild on had the pistons stamped .050 and I bought new .020" overbore pistons and they fit perfectly. I only did a flexhone honing as the cylinders were still in great shape. Quote Link to comment Share on other sites More sharing options...
josh817 Posted May 7, 2009 Share Posted May 7, 2009 .050” is not a common overbore, (I don’t recall every boring and engine .050” over in all my days boring and honing blocks). More than likely that is the metric stamp and reads .50 which stands for ½ mm over bore, or .020”. In that case, the next size up would be .75mm or .030”, or even 1.00 or .040”. In short, I am 99% sure you have MORE than adequate material left to meet the next two overbore sizes. OR Maybe 4mm or .160" over...... Just kidding, don't do that to an L24. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 8, 2009 Share Posted May 8, 2009 Maybe 4mm or .160" over...... Just kidding, don't do that to an L24. Why not? Seriously! Why not? If sonic testing says you can do it...why not overbore like crazy put an LD Crank in there, and make everybody at the FIA Spec Races wonder how you are getting so much power out of a measly L24... Quote Link to comment Share on other sites More sharing options...
josh817 Posted May 8, 2009 Share Posted May 8, 2009 Why not? Seriously! Why not? If sonic testing says you can do it...why not overbore like crazy put an LD Crank in there, and make everybody at the FIA Spec Races wonder how you are getting so much power out of a measly L24... Because that just makes you a big stroke L28 pretty much. Its kind of like why not get a 350sbc and going crazy on it. Well... They have other blocks that you can just start out with rather than trying to make a certain block go insano. But I guess if you wanted something unique thats the way to go. L24 with 87mm bores and 83mm stroke I think the V03 is..? Like I said, big stroke 1mm over bored L28 pretty much. And you can't beat the tech inspection guys. They baffle me with all their little tools to tell them engine specs. I flag dragged with some guy that did Porsche motors and he said with those things you can have them pump 3L when in tech but actually be like a 3.2L or something crazy like that. Don't think we have that luxury. Quote Link to comment Share on other sites More sharing options...
MetalThrashingMad Posted May 8, 2009 Author Share Posted May 8, 2009 All I'm doing is trying to get around 20 hp more than he stock L24, the car is only gonna be a nice weekend cruiser anyways. I'm not aimed at doing anything hi performance, I just wanted to be more informed on what was going on. I'm mainly planning on a bore job to clean up the cylinder walls (somebody did an awful hone job on it already) but I'll ask the machine shop guys what they think before I start shelling out cash anyhow. Quote Link to comment Share on other sites More sharing options...
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