Tennesseejed Posted March 3, 2009 Share Posted March 3, 2009 I admit it, I'm a little smitten by the 3.1L stroker concept. Yesterday I was daydreaming around the Kameari site, mostly oogling the 85mm L6 crankshaft http://www.kameariusa.com/L6_l3_2_85mm_crankshaft.php) and other obscenely expensive parts. Then I recalled defrag010's thread on the the 3.4L LD28 block stroker (here: http://forums.hybridz.org/showthread.php?t=119072&highlight=forged+rods) which lead to some musings over offset grinding. Without dumping $4K+ into a Kameari crank, it seems a pretty comparable result can be had by offset grinding a LD28 crank to 48mm rod journals. If I understand it correctly, this would result in a 85m stroke (clearancing issues). Finding a compatible and reasonable cost rod and piston combination is a little more complicated. Sure, Carillo and JE will build you any rod/piston combination you want if your wallet is deep enough. But a few hours with How To Modify You Nissan, the L6 Engine Caluclator and Google lead me to the Acura/Honda B16A V-TEC rod (48mm, 21mm, 134.32mm) and the Mahle H22 piston (87mm bore, 22mm pin, 31mm pin height, 1cc dish). The above combination gives you are final deck height of 1.57. Maybe that's workable, maybe not. On the other hand, offset grinding the L28 crank to 48mm rod journals gives a stroke of 81mm and saves the cost of finding and buying a L28 crank. Using the B16A rods and the LZ22E (32.5mm pin) gives a deck height of .43mm. Kind of a mini-stroker with a better rod/stroke ratio. The Carrillo version of the B16A rod weighs 441 grams, the Mahle piston 319 grams. I was not able to find the weight of the stock 240Z rods and KA24 piston, but I think these weights are signifcantly less. The two biggest problems with this combo are (1) the BE Width on the B16A rod is .79mm v. 1mm for the Nissan rods and (2) the Mahle piston may not be suitable for long stroke automotive use. For all I know the Mahle H22 piston is a motorcycle piston or designed for some super-sized gas weedwhacker. Oddly enough, after crunching all these numbers I spent some time mulling over/under square engine design. The stock L28 is already moving pretty close to a square engine design (1.09 bore/stroke). Stroking to 83mm or 85mm is almost perfectly square and the rod/stroke ratio is low (1.54) even using the B16A rods. I know a lot of guys are making sick power out of 3.1L engines. There also seems to be two separate camps about whether the whole stroker concept is worth the $. Put me in the latter. I think I'll just bore 2mm-over and put the extra dough into a lightweight rotating assembly. I am by no means an authority on L6 engines compared to the brain trust here in HybridZ. Just thought I would post this in case it might be of some use to anyone else who is researching a stroker build. And if my ideas are junk, no feelings are going to be hurt if this ends up on the 'shed. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 3, 2009 Share Posted March 3, 2009 (edited) You build a stroker because you want to. It isn't about hp to $. Were it so, you'd be dropping in a V6/V8. Dollar for dollar that is way cheaper. There is a lot of info on building a stroker in numerous flavors (including offset grinding) on this site. None are inexpensive! You mentioned the 3.4 LD build too. Sleeves and possibly offset grinding are the only way to acheive displacement like that. My build uses both the LD block and crank. It is only bored .5mm over to 85mm (allows for a rebuild). I'm using JE pistons and L20B rods. Displacement is around 2.85 liters. One thing I'll point out is NO ONE is telling what head bolts with the LD block are being used. I'm still researching a viable bolt. Maybe a Mercedes, Saab, Volvo or an asian/ european diesel (maybe a truck engine) will have something that will work. The BMW 12mm x 1.75 bolts will not work as they're too short. ARP will make a set of studs for around $700-$900! The biggest stumbling block is trying to use the internet for data. The web is slammed full of fodder and floatsum with little viable information. One good hit is balanced with 10,000 hits of garbage. Edited March 3, 2009 by ezzzzzzz added info. Quote Link to comment Share on other sites More sharing options...
Mack Posted March 3, 2009 Share Posted March 3, 2009 I too have run into the same problem you are, Ive been thinking about forged rods and cheap pistons all week now. Ive found out that a honda K series piston (around $400 a set) in an 88mm bore with an SBF ford 347 stroker rod coming in at 5.4" long (and can be had on ebay in H beam forgings for around $300 a set) would be perfect for a regular old L28 block/LD28 crank stroker. The only problem is the BE width of the ford rod. .830" vs a nissan BE width of 1.04" IIRC. the BE diameter is almost spot on and you could bush the SE for the honda sized pin. But, how do you solve the BE width problem? I was amusing myself with the idea of running 6 thrust bearings for a suitable sized crank main bearing to keep the ford rods from sliding around too much on the nissan crank, but thats just a bad idea, I think. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted March 3, 2009 Share Posted March 3, 2009 What's the cost of custom forged pistons? It sounds like after all the time of "custom" stroker setups that would be the way to go. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 3, 2009 Share Posted March 3, 2009 It's one of those you can't afford it if you have to ask...LOL. My JE pistons with rings and pins were close to $1k. Like I said, it's about spending stupid money to build a stroker. Quote Link to comment Share on other sites More sharing options...
Mack Posted March 3, 2009 Share Posted March 3, 2009 thats why Im looking for stuff I can "make work" for cheap. I mean, you get a set of 8 rods for $300!!! forged H beam and what not. With the ford rods, you could aslo get away with RB series pistons in an 88mm bore, which a lot of piston suppliers actually stock. probably looking at $500 for a set of those. with rings and pins. Quote Link to comment Share on other sites More sharing options...
Tennesseejed Posted March 3, 2009 Author Share Posted March 3, 2009 ezzzzzzz, my original post wasn't intended to be a commentary picking sides on the merits of building a stroker v. staying stock. I hope it didn't come off that way. I was only adding that stroking the LD28 crank to 85mm results in an L6 engine that is almost perfectly square (87mm/85mm). IMO, I'd prefer an engine that is on the over-square side. I hadn't realize how square that engine design is until I was done researching it. Mack and I seem to have the same unanswered question: What is the maximum safe tolerance, if any, for undersized rod ends? The B16A rods are .79mm; Mack's Ford rods are .83mm. Maybe one of the many engine builders around here could chime in. Assuming the BE width in the B16A rods are not a problem, the original post seems a plausible design for a 85mm stroker for way less than the cost of the Kameari 85mm crank alone (assuming stock B16A rods over Carrillo). I'm not interested in building it, but maybe someone else can pick up where I left off and make it work. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted March 4, 2009 Share Posted March 4, 2009 Very interesting reading on what you found with the Honda rods being usable in your stroker build tennesseejed. I wondered if there was something out there that was close to compatable in length to a 133mm 240Z rod. You had asked: Mack and I seem to have the same unanswered question: What is the maximum safe tolerance, if any, for undersized rod ends? The B16A rods are .79mm; Mack's Ford rods are .83mm. Maybe one of the many engine builders around here could chime in. Maybe one of the engineers on the site could do a stress analysis with the dimensions of the rod with the different size rod ends. But I would think that undersized diameter would be stronger than oversized diameter though from the original size. So are you are saying that you would be putting in a larger bushing in the rod end, correct ? I am currently building a 3.1L motor and primarily what you will see is a big increase in low end torque, and of course more horsepower due to bigger displacement. But the torque is what will accelerate the car faster. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 4, 2009 Share Posted March 4, 2009 Jed, I didn't mean to imply there was some attitude in my reply. I apologize if it was perceived that way. I was merely pointing out some aspects of building a stroker. Like you and others, I had looked at a variety of rods and pistons. The custom piston seemed the most reasonable approach for me although paying for those pistons really sucked. Mine has been in the works for about 2 years between research and parts gathering. It uses a LD block and LD crank. The 85mm (+.5mm over) bore to 83mm stroke provides a 1.024 ratio while the L20B rod length of 145.9mmm and the 83mm bore gives a 1.758 ratio. I went with the JE pistons to compliment the other parts. There are as many ways to get here as there are stroker builds. With the constant evolution of engines it's reasonable to think that a better off-the-shelf rod and piston combo could be right around the corner. Quote Link to comment Share on other sites More sharing options...
Daeron Posted March 4, 2009 Share Posted March 4, 2009 ezzzzzz: have you looked into subaru bolts? the EA-82 head bolts were about 6-7 inches long IIRC and were 12mm diameter, uncertain on the pitch though. I think the pitch was pretty fine but I may be mistaken. What happened to the original bolts? If you still have them, what length are they? (I presume 1.75 thread count) PalmettoZ: the problem is not big end journal diameter, but big end thickness. The journals on the L series crankshafts are wider from front to back than the honda and for rods being discussed; the question at issue is whether those big ends will slop forwards and backwards on the crankshaft too much, or if there is a way to bush them into place that is actually reliable. I have often wondered that myself in the past, but never seriously thought it would be remotely feasible.... Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 4, 2009 Share Posted March 4, 2009 Daeron, most 12mm head bolts I've seen or gotten specs on are too short and have a 1.5 pitch. I haven't looked at the LD28 bolts in a while but I seem to recall that they were too short or too long (wrong thread placement to use as short). The diesel head isn't as tall as the petrol head. I've been spending money like a drunken sailor (no offense to drunken sailors) lately. Dropping $$$ on studs may be my only choice to cinch the head down properly. With thousands already spent it seems foolish the go half-azz on this critical area. One question that I can't find an answer to is bolt strength. Am I resigned to using a 'head' bolt or would a hi-quality grade 8 or better also work? I'm heading to a diesel repair shop tomorrow afternoon to see what they may have. I'll also go to the PNP and try to find something viable, including the Subi. PalmettoZ, the narrow big ends have been gone over. To make these narrow rods work would probably be expensive such that custom rods would probably be comparable in cost IMHO. Quote Link to comment Share on other sites More sharing options...
Mack Posted March 5, 2009 Share Posted March 5, 2009 so I was thinking about how I could solve the BE thickness issue without a lot of expense and heavy modification, and I think I came up with a solution.... please excuse the crude MS paint pic, but I think it would work. the only problem is that you would need a slightly longer rod bolt. Comments? criticisms? suggestions? IF Im out of line and this is a completely stupis idea, forgive me as Ive beeen up for 20 hours with about 3.5hrs of sleep, so it SEEMED like a good idea. Quote Link to comment Share on other sites More sharing options...
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