Mack Posted February 8, 2006 Share Posted February 8, 2006 o.k. I dont know much about pistons or what optimal ring land thickness is, but I can tell you what I have in mind, hopefully you can guide me in the right direction...... My engine in my head requires a 28MM pin height. I can have either a 25MM pin or bush the rod to use a standard L series pin. full floating of course... would it be better to use the 21mm pin to have more meat left over for the ring pack? How would you set up the ring pack? how thick of ring lands, spacing, thickness of rings, material of rings, etc...... Im gunning for a 1.75:1 rod/stroke ratio and it will be NA, CR of about 11:1, maybe turbo down the line. not sure. thanks in advance! MSA is coming up soooooooon! lol Quote Link to comment Share on other sites More sharing options...
Guest norm[T12SDSUD] Posted February 8, 2006 Share Posted February 8, 2006 Uh, DEFINITELY get a piston with a thicker 2nd ringland. That is where the ringland WILL break under detonation. AT 11:1 you will be in danger of detonating and breaking a piston. I broke 4 2nd ringlands on one 1/4 mile run at 11.3:1 CR a few years back on stock cast pistons. I had run the car hard for three months with NO PROBLEMS. I was nearly on empty and had just filled up with gas about 5 miles before hitting the track. I guess I got some bad gas because the motor suffered the breakage on the first drag run. BTW, the stock Turbo pistons had thicker 2nd ringlands than the stock N/A pistons. Later,Norm Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 8, 2006 Share Posted February 8, 2006 You could run a 1mm Top ring, and a 1.2mm second ring. It is best to have the same thickness support under the ring for the ring land, as the same thickness of the ring. So if you have a 1.2mm ring, you wanr 1.2mm ring land. Oil rings should NOT go below 3mm in thickness as below that, they cant controll the oil anymore. You want that ring to be down in the bore atleast 2mm. So it depends what pin you run. But with a 28mm pin/2=14mm from the top of the piston to the top of the pin. So 2mm (ring down in bore) + 1mm (top ring) + 1mm (top ringland) + 1.2mm ( second ring) + 1.2mm (second ring land) + 3mm (oil ring) + 2mm( oil ring land) = 11.4mm. BUT your gonna run a .025" negative deck height probably to get proper quench so thats another .6mm, so your right at 12mm ring pack. This is TIGHT, but it will work. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 8, 2006 Share Posted February 8, 2006 As for material of rings, you need to run CHROME STEEL RINGS. MOST DURABLE. BTW, The math I did is tight, so since you have 2mm to play with I would put an extra MM on both of the compression ring lands. (BTW, Youve seen all the pistons Ive design and got forged up, so you know this isnt the first for me mack!!!) Quote Link to comment Share on other sites More sharing options...
Mack Posted February 8, 2006 Author Share Posted February 8, 2006 interesting. thanks for the input.... NORM>>>>> hopefully, the chamber work I am doing will prevent detonation! but the 2nd ringland needs to be thicker? Ill keep tht in mind, especially since this motor may see boost at alater date (with a little less compression, obviously! 1 fast Z>>>>>>>> there is a little more room to play with than 14MM. I have a compression height of 28mm, the pin I use will be either 25mm or 21mm. 28 - (25/2) = 15.5mm or with the 21mm pin 28 - (21/2) = 17.5mm, so how would those numbers grab you? I think 17.5 is a wee bit more to play around with.... just some quick math 1.2mm ring + 1.2mm ring + 3mm ring = 5.4mm . now with the 21 MM pin, 17.5 - 5.4 = 12.1mm which would leave for 6mm for EACH ring land, thats almost 1/4 inch! pretty good, yes? or with the 25mm pin, 15.5 - 5.4 = 10.1. that would leave 5mm for each ring land, still decent, right? Quote Link to comment Share on other sites More sharing options...
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