Stroker experts Jmort, Drax, DAW

[ToplessZ]

Ok guys Im getting ready to start making some decesions for my turbo buildup I have to get this off the ground soon. I have considered several options 3.0 stroker 2.6 destroker.... Some custom something or other stroker. Alright Ive heard that I could use the 2.4 crank 140mm fj20 rods and vg30det pistons Myth? I want to know if I can run the 140mm rods in an f54 block with my l28 crank or better yet the ld28 crank. I would think that the piston pin height could not be moved up enough to do the 3.1 stroker with the 140 mm rods but it would be awesome. Any words on this. I have everything but the fj20 rods and custom pistons of course. I have all 3 of the above cranks and a set of 133mm 240z rods. I really want to get 400rwhp and to move up from there. Any input would be hugely helpful. Thanks

Jared

[510six]

Jared, my first 3 liter stroker used 240z 9mm rods and VG30 87mm pistons.A 140mm rod can be used with custom pistons,My current setup uses 133mm custom rods and the custom pistons use the same pin heigth as VG 30 dett pistons.The VG 30 and VG30dett both have pistons with a pin heigth that is 6mm less than a L series pistons.Back a few years ago a very common motor combination in 4 cyl L series motors was to use 152mm Napz 2.0 liter rods and block with VG30 pistons and a L20B crank and head.With the longer rods (152mm vs. 146mm) and 2mm overbore VG30 pistons (87mm) this created a 2040.Using a 140mm FJ20 rod would not be possible with VG30 pistons with a LD or L28 crank.With a 73.7mm 240z crank and 140mm FJ rods and VG30et pistons would put the pistons down around 2mm or so in the bore, I would imagine such a motor would rev to the moon.I personally like the grunt torque of a 3 liter .

[Drax240z]

I don't have all the numbers in front of me but I'd try to make some strides towards raising the rod/stroke ratio to 1.7-1.8:1 if possible. (standard 3.1L stroker/LD28 crank being 1.60:1) It sounds like 510six has answered most of your questions though!

[JMortensen]

Might want to ask Dan Baldwin too, but I agree, sounds like 510six has the answers.

 

I'm no stroker expert...

[ToplessZ]

Ok If Im reading correctly I can use the 140mm rods with the ld28 crank as long as I get custom pistons. I was worried about not being able to move the pin height enough to do this. Im in search of the fj20det rods right now. The turbo fj rods are supposed to be stronger then then the non turbo ones. I may try to contact some of our aussie board members to see if they can get their hands on some for me. I looked into custom rods but thats going to be about 1100 dollars for pauter rods. I really want the 3.1 more then the destroker for the off boost torque. Keep the comments rolling in though. I thought that using the 140mm rods with vg30 pistons and 240 crank would only leave the piston 1mm down the bore. Maybe my calculations were wrong though.

[510six]

I had actually looked at putting FJ20 rods in my 3 liter.Vern at Raver Motorsports had a set of FJ rods and I was considering using them and came across a set of Cunnninghams that were 133mm and had not been paid for.A 140mm rod will work but just barely.I also tried to find a set of L13 rods that were supposed to be avalable for 510`s sold in Mexico that were 139.9mm long.Unobtainium.I was talked into using after market rods after a friends race motor put a rod through a block.Stock FJ20 rods are awfully beefy pieces, so with ARP rod bolts I don`t really see that happening.Good luck.I have one other thing to say about 3 liters, in my experience a compition dampner must be used if the motor is to be reved over 6500rpm.ATI now makes a really kick butt SFI race aproved dampner to deal with a 3 liters torsional vibrations.I have had flywheel and crank dampner bolts both come loose with 3 liters and both motors were race balanced both statically and dynamically by a very compitent race machince shop.A Nismo comp dampner can be used but red Locktight the crank dampner and flywheel bolts.

[ToplessZ]

Do you think your contact may still have those fj20 rods. Im not having any luck finding any without going aftermarket. This is a limited budget build with enough allowence for custom pistons but trying to avoid custom rods. Do you have a source for the ati dampner?

[510six]

You have a PM.

[johnc]

IMHO I would stick with a 3L instead of going the big overbore route for a 3.1 or a 3.2. My main reason would be to allow for future rebuilds of that block. Once I've sunk a bunch of money into a block I like to be able to use it again and again and again...

[Dan Baldwin]

My thoughts:

 

increasing rod/stroke via 140mm rods will increase rev potential of a 7000rpm motor to... 7042 (for the same max piston acceleration). Don't bust the bank trying to get a "better" rod/stroke ratio.

 

More stroke is going to improve off-boost AND on-boost torque. Destroker is not a good idea unless you're in a displacement-limited race class. Sure you get slightly more rev potential, but you lose more torque than you gain revs, so power potential drops, and you've lost torque everywhere in the rev range.

 

I ran my 3.1 for YEARS with the stock 240 damper, swapped in the Nismo single-groove (that's all my parts guy had at the moment, I actually wanted the 2-groove) last year due to the rubber in the stock one visibly dryrotting. I shift around 7k, rev limited to 7200. I have had issues with flywheel bolts loosening on me, once after 5 years of usage with a stock lightened flywheel, and a year later with the aluminum flywheel and no washers (dumb). Since had the Al flywheel holes bushed. Fingers crossed, but think I'm ok. No such probs with the damper bolt loosening.

 

IMO, even with a turbo, maximize displacement, subject to how much you're willing to remove (turbo may want thicker cylinder walls) and how much you wanna leave for future rebuilds as John suggests.

[Drax240z]

The draw (at least for me) with the higher rod/stroke ratio wasn't rev potential, so much as detonation resistance. Meh, it was always a "food for thought" idea to me, I may try it sometime.

[ToplessZ]

Well I have a line of 4 fj20 rods need two more. I have to find out if all fj20 rods are the same Ive read that the fj20det are beefier those are what Im looking for. I do plan On going with 87.5 or 88mm pistons thats all the overbore for now. I really hope I can pull off the 140mm rods. The off boost torque and det. resistance make it worth the effort

[510six]

I was mearly stating my experience with 3 liter strokers. Both of my motors were drag raced and were subject to multiple shots of N20.If I was building another 3 liter I would insist on running a comp dampner with it.My current motor has over 150 drag launches on it has over 500rwh and numerous low 11 sec passes with a best nof 10.96 @127.I figured a comp dampner was preferable to having a flywheel come loose at 7000rpm.

[DAW]

In a nutshell, the L24-L28 block is too short to reach a favorable rod/stroke with anything but an L24 crank (or an L28 crank and custom pistons). Do the math. The LD28 block lets you use the LD28 crank (83mm stroke) with appropriate-length rods. There are many possible combinations of rods/pistons depending on purpose, budget, availability, etc.

 

I know, tell me how it can't be done and why a 1.6 rod/stroke is superior to a 1.8 and blah, blah, blah...DAW

[ToplessZ]

Well looks like I can get pretty close to that 1.8 with 140mm rods ld28 crank and some custom pistons. Anyone care to do the math to insure that my wrist pins wont be in the middle of the oil scraping ring. Of course the l24 crank is still an option or using the l28 crank with the 140mm rods I dont think it would rev as well but thats not my main goal Id be happy making power up to 6500 rpms 7000 is def pushing it and the higher you go the more it costs. Custom pistons seem to be fairly reasonable as long as I get them right the first time. Machining and balencing will definatly be the high dollar endevours. Id like to get some headwork done but I may get a spare p90 and go all out with it at a later date and just do a stock rebuild and a little home port and polish work. I wish I wasn't in ohio though Im very leary of sending my setup to be worked on by someone who has never built a high performance engine. Rebello racing is way out of my price range and I guess Im a little nervous about not getting the block torque plate bored. I think this will pay off nicely if its done right the first time though. Id rather draw it out a little and make sure it gets done right then just throwing something together in my back yard. If anyone knows of a reasonable place to have some of this work done let me know. I really don't want to ship the block out but if it means good work at a very good price it would be worth it. Im located near cincinatti ohio currently. Man Im getting excited I should apply for a new credit card and just do this all at once....hmmm guess not. Well Keep the cards and letter...err posts coming

[DAW]

Like you said, you need to figure it all out in advance. Figure out several scenarios or combinations and then look at them in terms of cost, parts availability, downtime for machining work, etc., and what you'll have at the end. If you're going to end up with a huge investment into an L6 by piecing it together, you might consider what sense that makes vs installing an RB 6cyl, SR20, etc.

 

Search this site well and you have to have "How to Modify Nissan/Datsun OHC Engines" by Frank Honsowetz at the bare minimum to figure out the combinations you're considering. Look at L4, LB4 and LZ4 dimensions in that book. The same problems you're faced with re trying to fit a taller performance package into too short a container were solved by Nissan by making the container taller, not by smashing down the contents to make them fit (and compromising performance in the process).

 

L28 rod/stroke was already a compromise from the L24 because they had to use shorter rods when they put in longer crank throws in the same ht block (although a shorter pin ht would have, and does, make more sense to enable a longer rod). This situation was the same as in the L16 to L18 evolution.

 

The evolution from L18 to L20B (same bore, longer stroke) was addressed by increasing the block ht. The same essential thing needs to be done with the L6 as with the L4 if stroke is increased more than that of an L28. Nissan did exactly this with the L6 when they increased the stroke length from 79mm to 83mm. The LD28 block is the same ht as the L20B block. Don't smash down the contents to fit into the container; use a taller container.

 

Simply put, if you are not going to use the taller L6 series block and you want a favorable rod/stroke, you won't be using an LD28 crank. If you use the L28 block and want to increase rod/stroke over stock L28 you are limited by choice of reasonably priced or accessible rods. I'll break up this post and look at some options for using the L28 = L24 = L16 = L18 block ht. DAW

[DAW]

I find the fastest easiest way to figure out combinations of rod length, pin ht. (compression ht.), and stroke length is to assume zero deck ht. with the stock configuration and go from there. e.g., L28 at TDC: pin ht. = 38.1mm. Rod length = 130.2mm (I've always used 130.4 in calcs but I'll trust F. Honsowetz's number of 130.2). You only need these two factors when using the stock crank. If you change cranks you need to add or subtract 1/2 of the change in stroke because the effect at TDC is the change in actual crank throw length, which times 2 is the stroke change.

 

For L28, 38.1 + 130.2 = 168.3mm. You can get 140mm rods (either FJ20 with 22mm pin or LD28 with huge pin [approx. 23.5mm]), so subtract 140mm from 168.3mm and that's what pin ht. you'll need to make it work out at zero deck ht.; in this case = 28.3mm for your custom pistons. A piston with less pin ht. will sit down in the bore at TDC and conversely, more pin ht. results in + deck ht. (and top ring/top of bore distance problems). The LD28 rods are more plentiful than FJ20 rods but the larger pin dia. might pose more of a problem in making custom pistons.

 

Always consider hybrid engine components. Look at specs to find an alternate sources for rods & pistons, especially pistons. There might be sets of Mitsubishi or Volvo pistons out there in JYs for pennies that meet the specs of the $$ custom pistons you're about to have made. If you find some by looking through tables and tables of specs, the least critical factor, and the most flexible factor to deal with, is what bore dia. to make your block to fit the available pistons (as long as you keep the overbore sensible).

 

The best thing about using the taller LD28 block is the expansive choice of stock Nissan rods from L4B/LZ4 engines you can pick from which all give enhanced rod/stroke at low engine-build cost: 145.9mm, 148.6mm, and 152.45mm, and can be combined with readily available factory pistons to yield zero, or near-zero, deck hts. Use the same approach as above calcs but use for LD28 block: 46.5mm pin ht. + 140mm rod = 186.5 as your working distance for a zero-deck, 83mm stroke engine. DAW

[Dan Baldwin]

Can the LD28 block be bored to 89mm? Does it fit (seems like I read/heard the cam cover comes pretty durn close to the hood)?

 

Whatever block is used, I'd still go with the LD28 crank and "worse" rod/stroke ratio *for an N/A build*. Turbo, I'd probably just use a stockish jy L28 bottom end and spend all $$$ on ancillaries.

 

Anybody really *know* how much rod/stroke affects detonation, allowable CR, allowable boost levels on a turbo L-series? For N/A, the benefits of "better" rod/stroke seem to be way overstated to me, turbo might be a different story...

[DAW]

Oh, you might need to use a cowl induction hood or an L88-type scoop, so better forget the whole thing. c'mon Dan do you still believe the world is flat? Just because you didn't think of it, it doesn't mean it can't or hasn't been done.

 

SBC builders often choose 6" rods to achieve good rod/stroke ratios (same rod length as LZ20E) and SBMopars have high factory rod/stroke ratios. This is not a factor that automotive engineers ignore in engine design. If Nissan wouldn't have gone to the V6, I'm certain that the next generation gasoline L6 (with longer stroke) would have had the same increase in block ht as seen in the LD28, L20B, LZ20, LZ22 with rods in the 145.9mm to 6" range.

 

LD28 with N42 head clears my 810 hood with no mods at all, underhood insulation padding intact. For the 240-280Z chassis I have a 240Z dealer-mod hood, which is cutout over the valve cover and uses a riser center buldge/scoop with side openings (inlets/outlets) on it (a Nissan designed remedy for vapor-lock problems) that adds clearance and lower underhood temps as well. I'm using 280ZX headers on the 810 chassis with the tall block and they fit fine, but 280Z headers on the tall LD28-block hybrid L6 might interfere underneath a 240-280Z chassis, which makes turbocharging a good approach at the outset to obviate such problems. DAW

[ToplessZ]

In looking at hybrid rods and pistons I was wondering how much could safely be cut from the ld28 crank. If this can be done there are alot of rod options out there forged and all. I wish I could find an ld28 block around here. Im lucky to find anything datsun at the wreckers much less and ld28 maxima. I wouldnt use those rods though they are way to heavy. Just the crank and block. I have two f54 blocks though so Im probably going to use one of these. Is zero decking the block a requirement. I read about this in my chevy rebuild book but its been awhile. I have the nissan rebuild book and the high performance book Id like to get my hands on the hot rod and race your datsun book if anyone has a copy reasonably.