Guest Confederado120 Posted August 30, 2003 Share Posted August 30, 2003 Can a rod longer than the 240 rod be used in a 3.1 stroker (diesel crank)? I realize that this would require a custom rod. But what the heck, if going forged pistons. Were not talking off the shelf anyway. Just wanted to know if the pin height can be raised to accomplish this. Or is the 240 rod the max for pin height? Thanks, Walt Quote Link to comment Share on other sites More sharing options...
Muskrat Posted August 30, 2003 Share Posted August 30, 2003 If I am not mistaken, pin height is a measurement taken from the piston, not the connecting rod. I believe connecting rods are measured center to center; while piston pin height is measured from crown to pin center. The FJ20 conn rods have are 140mm, as opposed to the 133mm of the L24 rods. I believe the L20A conn rods are 135mm. Its worth looking into, though you would need a shorter piston. I'm currently looking into this myself, though I'd like to try the setup on a L24 block. Hope that helps. Quote Link to comment Share on other sites More sharing options...
jeffp Posted August 30, 2003 Share Posted August 30, 2003 I went with longer rods in my 3.0 build, yes you can increase the rod length, and it is worth it in the torque figures. Quote Link to comment Share on other sites More sharing options...
Guest Confederado120 Posted August 30, 2003 Share Posted August 30, 2003 JeffP, how much longer did you, or can you go? Walt Quote Link to comment Share on other sites More sharing options...
TimZ Posted August 31, 2003 Share Posted August 31, 2003 I'm using 5.3" rods (134.6mm) rods on mine and was able to have a piston made that didn't require anything particularly funky. It is possible to actually put the pin right through the oil ring groove for additional rod length - they have oil control rings that have a special support rail on the bottom side that allow this, and I am told that this is streetable. What I don't know is if this type of oil control ring is available in a size that would work for us. If you went this route you could conceivably go a fair amount longer on your rods. Quote Link to comment Share on other sites More sharing options...
jeffp Posted September 1, 2003 Share Posted September 1, 2003 I went with a set of crower rods and they are 5.350" that is about the longest you can go without putting the wrist pin in the oil groove. I thought about going with 5.400" but decided the gains would not be worth the potiential trouble I may have had with the oil ring. I realize that I could have easily gone longer, and yes they do have ring sets that make provision for this, but I wanted to play it safe because it is a street engine. Quote Link to comment Share on other sites More sharing options...
HS30-H Posted September 1, 2003 Share Posted September 1, 2003 The classic Japanese route ( back from the mid Seventies ) to a 3.1 stroker using the LD28 crank was always to use the L14 rods and Honda XL500 ( motorcycle ) pistons. They used to bush the pin bore and offset drill it for a 138mm centre-to-centre length. The XL pistons had a pin height of 29mm - leaving 0.5mm above the stock deck surface ( 41.5mm LD28 crank throw + 138mm rod length + 29mm pin height = 208.5mm ). I have been gathering parts for my own 3.1 engine project for far too long now. I keep selling the cranks because friends need them, so its slow going. However, I have a set of new Japanese-made rods with 138mm centre-to-centre and a set of forged 89mm pistons with 29mm pin height. This is a tried and trusted route in Japan. The Japanese parts are very well made but a little on the expensive side. http://alansphotos.fotopic.net/photo.php?id=1121032 Quote Link to comment Share on other sites More sharing options...
DAW Posted September 2, 2003 Share Posted September 2, 2003 Why don't you just use an LD28 block? You won't need custom pistons or rods, as there are many combinations of Nissan rods (LD28, L20B(=LZ20S), LZ20E, LZ22S, LZ22E), and myriad Nissan pistons with 21mm pins to combine with these pistons depending on which bore and rod length you choose. The stock LD28 rod(140mm) and piston(46.5mm c.ht., 84.5mm bore, huge floating pin) can be used for a budget shortblock. With an adapted N42 head with f.i. it makes 10:1 c.r. and pulls harder than a stock L28E; with a turbo and P90 head it provides a stout bottom end capable of routinely handling 21:1 c.r. stock. Anyway, if you do the math, you can put together many combos to suit your rod/stroke of choice and bore. I don't know the maximum LD28 overbore but the cylinder walls feel (through water passages) thicker than L28s, which would stand to reason for the higher demands of the 21:1 c.r. The question is going to come down to whether you want a 3.1L with a 1.65:1 rod/stroke or a 2.95L with a 1.8 rod/stroke. If you're insistant on the L28 block, look into the LD28 rods...same length as FJ20 rods but with larger pin bores which could be rebushed. DAW Quote Link to comment Share on other sites More sharing options...
Bob_H Posted September 5, 2003 Share Posted September 5, 2003 DAW, I actually talked to someone who did do a sonic bore testing of the LD block. It starts out with a smaller bore than the 2.8, but the largest they could get the bore was in the 87-88mm range as they were sonic testing. If I remember correctly, they sometimes found individual cylinders they could get out to 89mm, which is equal to the 3.1 effort, but they never found a whole block they could do that with. In the end, they spent a lot of effort to find they couldn't exceed what they already had with the L28 block. -Bob Quote Link to comment Share on other sites More sharing options...
Guest Confederado120 Posted September 5, 2003 Share Posted September 5, 2003 Thanks for all the info guys. Walt Quote Link to comment Share on other sites More sharing options...
DAW Posted September 6, 2003 Share Posted September 6, 2003 Thanks Bob. I wasn't expecting the overbore to exceed what could be had with the maximum overbore of an L28. I figured any increase in bore over 84.5mm is golden when you're working with an 1.8 plus rod/stroke. I'd trade 87.5mm bore for 89mm bore any day to have a 1.8 rod/stroke over a 1.65 rod/stroke. DAW Quote Link to comment Share on other sites More sharing options...
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