Stroker experts Jmort, Drax, DAW

[Dan Baldwin]

Oh, you might need to use a cowl induction hood or an L88-type scoop, so better forget the whole thing.

 

If you DO have to butcher the hood to use the LD28 block, that would eliminate it from consideration for a lot of people (myself included).

 

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.

 

Keeryst, DAW, you don't have to be an ass (or maybe you do).

You're missing my point entirely.

 

SBC builders often choose 6" rods to achieve good rod/stroke ratios

 

And at least ONE small-block build-up in Hot Rod way back when found more power with 5.7" rods after doing a comparison study. Not that THAT means SHORTER rods are better, it doesn't. I just haven't seen any EVIDENCE that going out of your way to build a long rod L6 has any measurable benefits. Feel free to demonstrate this.

 

SBMopars have high factory rod/stroke ratios.

 

And they are, of course, the pinnacle of internal combustion engine design...

 

This is not a factor that automotive engineers ignore in engine design.

 

Of course they don't "ignore" it. They also have a lot of other stuff on their minds other than maximum performance. If there is a trend toward larger rod/stroke ratios in the automotive industry, that doesn't *necessarily* imply that that's "better" for US.

 

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.

 

Unfortunately it's also ugly as hell.

 

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

 

So TURBOCHARGING is a SOLUTION to potential interference problems using an LD28 block?!

I think you have overstated the benefits of long rods to yourself to the point that having long rods is the ultimate (only?) goal of your project! If having a turbo facilitates that end, then turbo it is! I hardly think the decision to turbo or not should hinge on whether or not it allows use of the taller LD28 block.

 

In the end, I totally understand that the typical stroker engine has a rod/stroke ratio (1.6) that's low relative to other engines. I can certainly appreciate that there *might* be benefits to having longer rods. I just don't think that they're likely to be worth going too far out of one's way (custom rods/pistons/taller block) for for *most* L6 engine builds.

 

Somewhat interesting reading here: http://www.stahlheaders.com/Lit_Rod%20Length.htm

[JMortensen]

I don't claim to understand everything I just read, but in Dan's link this is one of the first things stated:

Short Rod is slower at BDC range and faster at TDC range.

 

Long Rod is faster at BDC range and slower at TDC range.

 

Is it just me or does this not make any sense? I was under the impression that a piston on a short rod is going to be faster everywhere, and a long rod is going to be slower everywhere given the same engine rpm.

[johnc]

The old rod length arguement. Ron Iskenderian had the best anaylsis of this: http://www.iskycams.com/techtips.html#2005

[Dan Baldwin]

Good link, John. Some people will go to ridiculous lengths just to get the "ideal" bore/stroke or rod/stroke ratio, even if it leads them in the direction of less displacement (and torque/power)! Funny...

[(goldfish)]

I don't understand the short rod beeing slower @ bdc?

 

and my eyes are bugging out, too much reading

[DAW]

Like I said at the outset, "blah, blah, blah."

 

Note Isky refers to going to exotic and extreme measures to do such things as increase the block height. In this case, two blocks are sitting in front of you and all you have to do is pick the one that you feel will work best. With the same stroke and bore, and factory available passenger car rods and pistons equally plentiful to select from, would you pick the block ht that yields 1.6:1 rod/stroke, or 1.8:1? What if you didn't have the inconvenience of using a hood scoop on the 1.8:1 engine...would you still pick the 1.6?

 

I see in Isky's article that he teaches us what Adobe is and I appreciate the cutting edge technology offered, but I think the most appropriate quote relating to this discussion is from Carl Rogers, "When the only tool you have is a hammer, you tend to treat everything as if it were a nail."

DAW

[DAW]

I had an L28 block over-bored to 89mm and all components set to build the typical L6 stroker using LD28 crank but once I looked further into the follow-the-sheep approach of the build and crunched the numbers, I chucked out that plan and arrived at another I feel is more sensible.

 

I was going to do the L24 rod (133mm) on LD28 crank (83mm), r/s=1.6, recipe passed down from grandpa, but worked out other options I feel are better choices for my use:

1) use LD28 block, overbore 0.060" to use std. L28E or L28ET 86mm pistons, or 0.100" overbore to use oversized pistons, stock LZ22E rods (148.6mm) and LD28 crank (83mm), r/s=1.79, or

2) use LD28 block overbored 0.020" for std. LZ22S pistons or Mitsubishi Eclipse pistons (85mm with 21mm pin), or 0.100" for oversized pistons (piston rim needs to be machined down .75mm [several options available for differring dish cc's]), stock LZ20E rods (152.45mm) and LD28 crank, r/s=1.84.

 

Since I'm not using variable camshaft timing, I chose option #1 with r/s=1.79, readily available rods & pistons with no piston machining required, choice of flat-top or dished pistons, easy and cheap build for 2.9L displacement or buy oversized pistons for 2.97L.

 

If a 1.69 r/s is desired (stock LD28 configuration, i.e., diesel), the LD28 140mm rods can be used (I haven't seen any documentation that these rods are significantly heavier than the large-pin Nissan Comp. 140mm rods), with roadster pistons or others with higher pin hts., but why chose 1.69 when you could choose 1.79 for your high rpm engine???

 

I'm bailing out of this discussion and I'll live and let-live re how we differ on what factors are significant, or insignificant, in selecting components for a high r.p.m. engine. I find my current approach more unique and intellectually satisfying to me than my initial choice of 133mm rod/ 83mm stroke. When it comes to rod size, you can say short rods rule but I'll stick with mine. DAW

[Dan Baldwin]

jmortensen and (goldfish)

 

The average piston speed HAS to be the same regardless of rod length, it's only a function of stroke and rpm (long rod or short rod, the piston goes up and down the same amount, the stroke dimension). A shorter rod increases angularity, which causes the piston motion to be sort of exaggerated at TDC, as the rod "standing up" increases the vertical motion of the piston. Near BDC, the rod "standing up" DEcreases the downard speed/motion of the piston. At TDC and BDC, the reduction of rod angularity tries to move the piston UPward.

 

And for the incomparable DAW:

Note Isky refers to going to exotic and extreme measures to do such things as increase the block height. In this case, two blocks are sitting in front of you and all you have to do is pick the one that you feel will work best.

 

I didn't note Isky referring to exotic and extreme measures anywhere, basically he's saying there's no need to bust your balls to get a "good" rod/stroke ratio.

In THIS case, two blocks are NOT sitting in front of the guy we're trying to help, ToplessZ: "I wish I could find an ld28 block around here. " he says. Yet you continue to present the LD28 block idea as the ONLY way to go!

 

From another post BobH (back in town?!) says "The LD28 block had a 84.5mm bore. Those that have actually taken the LD block and tried to get a "larger" bore than the L28 block were only successful in getting it out to about 88-89mm"

So, to answer DAW's question:

would you pick the block ht that yields 1.6:1 rod/stroke, or 1.8:1? What if you didn't have the inconvenience of using a hood scoop on the 1.8:1 engine...would you still pick the 1.6?

 

If the 1.8 rod/stroke ratio block started at 84.5mm bore, and the 1.6 rod/stroke ratio block started at 86, and I wanted a 89mm bore, I'd go with the latter.

 

DAW, the quote you give doesn't seem to be applicable to the current discussion. My point was and is that there's not much to be gained by going out of your way (LD28s apparantly not exactly readily available, possible/likely hood mod required, other potential fitment issues apparently including header clearance?) to put a taller LD28 block in a Z in order to get a supposedly more favorable rod/stroke ratio.

 

The "hammer" of logic, science, and REASONING is a pretty useful tool, you might try it sometime!

[ToplessZ]

Thanks for all the comments guys the sound of the ld28 block is very good but I cannot find one. I know there are also modifications to the block that would have to be done etc. I have 2 f54 blocks. I do believe that with a little creativity that a very good rod and stroke can be created with the l28 block. I was told that honda rods were an option but this requires turning the rod journals down to .1771 but the journals on the l24 maxima were only 1.76?? So Im thinking this can be a safe endevour I may have a line on 8 h beam eagle rods with arp 2000 bolts for under 500 dollars so the price isnt bad for having forged H beam rods. Toyota 3sgte rods are also an option. These aren't going to create a 1.8 rod and stroke but this will im prove it greatly. Also giving more piston options. This has been a great thread that has helped with my research greatly. Hopefully there is still more info out there to be unturned.

[Dan Baldwin]

Just a couple more points (I appear to be a post or two behind...):

I had an L28 block over-bored to 89mm and all components set to build the typical L6 stroker using LD28 crank but once I looked further into the follow-the-sheep approach of the build and crunched the numbers, I chucked out that plan and arrived at another I feel is more sensible.

 

"follow-the-sheep"? It is MORE stupid to discount out-of-hand a proven reliable method just because so many have already done it as it is to follow same method without understanding WHY.

 

I was going to do the L24 rod (133mm) on LD28 crank (83mm), r/s=1.6, recipe passed down from grandpa

 

Grandpa? Again we gain insight into DAW's totally unscientific reasoning. It is an "old" recipe, therefore it is no good, huh?

 

Since I'm not using variable camshaft timing,

 

Yeah, no kidding! (got a chuckle out of that one)

 

but why chose 1.69 when you could choose 1.79 for your high rpm engine???

 

FWIW, max piston accelerations are equivalent for the following:

1.6:1 r/s engine @ 7000rpm

1.69:1 engine @7044rpm

1.79:1 engine @7089rpm

 

There IS SOME theoretical redline increase to be had with longer rods, it just ain't MUCH.

 

I find my current approach more unique and intellectually satisfying to me than my initial choice of 133mm rod/ 83mm stroke.

 

"more unique"? No such thing. Something either IS unique (only one) or it is NOT unique. To quote Ecclesiastes: "there is nothing new under the sun". Another good one: "all is vanity". I wouldn't get TOO caught up in trying to be different for no other reason than JUST to be different.

 

Promoting "your" idea (and it AIN'T your idea, old as the hills...) of maximizing rod/stroke ratio at the complete disregard of practicality to OTHERS who seek advice doesn't seem warranted to me, though.

 

When it comes to rod size, you can say short rods rule but I'll stick with mine. DAW

 

I NEVER EVER SAID THIS!!!! My point all along has been that there is little to no *evidence* that rod/stroke ratio (over a reasonable range) makes a significant difference in engine performance. Longer rods make for less side-load on the piston, that's good. Longer rods reduce peak piston acceleration, also good. I just don't think it's worth fussing with an LD28 block to get these small benefits, and any PERFORMANCE benefits are more a matter of quality than quantity. Supposedly shorter r/s is better for low-midrange and longer r/s better up top, but not by any significant margin.

 

All that said, I wish you the best with your LD28 build, and I hope it fits OK. I just don't think you're doing anyone any favors by INSISTING that a longer r/s motor is going to be demonstrably better-performing than a shorter r/s motor, without having ANY evidence whatsoever. Someone TOLD you big r/s is better, you reasoned in your head "yessss, it IS better, MUCH better, FAR better!" But you haven't presented a CASE.

[ZROSSA]

Jared,

I have never played with the l6 so take this as an idea only. If you are going to have to grind the crank why not offset grind it and get a little more stroke? This woould, off coarse, mess with the precious rod lenght/ stroke ratio........... ! You are turboing this, right? Make the block strong and run more boost that with make up for displacement any day. In a n/a situation the most hp you would gain but overbore and stroking would be around 20hp. Mabye double that for a turbo. I think the money would be better spent on a strong bottom end and head work.

 

Douglas

[ToplessZ]

Zrossa I had though about this. I am looking into the cost of doing just that. Would be awesome to have a 3.1 without the 89 mm bore. I want to go 88mm max. I would really like to hear input of grinding down the rod journals to .1771 but I am no engineer so I dont want to make a statement of truth in that respect. Im hoping someone will chime in about that. Soon

[dapiper]

OK gurus, what model do these fj20 rods come on? What about the front cover and oil pan. I have one of the comp baffled Design Products pans I wud like to use.

[510six]

FJ 20 rods came in early 80`s Skylines.The cars were never sold in the USA.AS DAW said the LD 28 and the L20b both share the same deck height.

[ToplessZ]

The LD28 and L20b may share the same deck height but the l20b uses 145.9 mm rods and the LD 28 uses 140mm However the LD28 uses a huge wrist pin when compared to most others (if trying to source stock pistons) The fj20 rods may provide a better selection of compatible pistons such as the vg30 pistons. Zrossa now that I think about it having the crank offset ground going down to a 1.771 rod journal from a 1.9670 is not really going to produce anything noticable other then a chance for error. I think you could have a custom crank made by crower or similar if you had really deep pockets to give you more stroke....Hmmm wouldnt that be tasty. If I can use the 1.771 honda rods I can have a forged h-beam rod and custom piston set for about a grand. Not to shabby.

[ToplessZ]

3sgte rods would be another good option. There is one set on ebay but I dont know where I could find another set cheaply. They are almost 138mm with a 1.899X rod journal size. They wouldn't be hbeams but they are forged from the factory and look plenty beefy. Maybe I should find an mr2 forum to join. Anyone have any helpful hints for finding a set of those cheap

[texasz]

Dan Baldwin...you have PM

[z-ya]

I'm sure people have said this before, but If this going to be a turbo build up as stated in the original post, I think you are wasting money on any internal mods except forged pistons and o-rings. Spend your money on a good engine management system, stage 5 hybrid turbo, and intercooler, and be done with it. Any additional power you get with a turbo stroker certainly won't be worth the additional cost.

 

Here is what I'm planning for my next turbo motor build (I'm running a stock L28ET now):

 

Bore to 87 or 88 mm

Forged pistons

stock l28 rods, crank.

P90 Head

 

Wiseco makes an 87mm foged L28 piston with a 9cc dish which should yeild around 7.8:1 CR, which would be good for high boost (20psi) applications.

 

This should yeild a reliable crank 400HP.

 

No offense, just my $0.02

 

Pete

[ToplessZ]

I dont take offenses on this board just advice thanks zya. This is going to be a max performance build for a turbo app for sure. I am hoping for more like 400rwhp with the possibility to get a little more after I completly upgrade the drivetrain and chassis. I want reliability I know of people getting 400 or more crank hp on a stocker block but I like to feel comfortable doing it. Im not planning on going way out of my way to do this but there appears to be some viable options that would not be a burden to add while having the motor built such as longer rods. I just bought a microtech engine management system for the fuel and will be using the msd btm for ignition control.

[z-ya]

ToplessZ ,

 

I know a few people getting 350HP at the wheels on a stock long block.

 

Doesn't the Microtech have ignition control? If so, don't waste your time screwing with an MSD BTM, ditch the distributor a just go for crank trigger direct fire ignition. You will have more control over timing than the BTM can ever give you. The BTM will not allow you to change the timing curve of the distrbutor, just retard under boost.

 

I'm installing a Wolf3D V4 in a friends turbo 240Z now, and we are using the MSD GM twin tower replacements coils with a Nology three channel ignition amplifier in a wasted spark configuration. The ECU can drive the Nology module directly.

 

We're shooting for 300HP at the wheels with a stock long block (stage 3 hybrid turbo, intercooler, 14psi).

 

Pete