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3.4L L28 stroker


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#1 defrag010

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Posted 08 February 2007 - 11:11 PM

I was bored with nothing to do at work today, and got to playing with a L28 crank and block I had laying around. I got 3.500" of stroke (roughly 89mm) out of the crank when I was done welding/indexing/grinding/heat treating it, and bored/honed the block out to 3.5532" (a little over 90mm). After that, I used nothing but modified OEM parts from other makes of engines to make a 3.4L shortblock. It uses dished cast eutectic pistons w/ coated skirts that have been known to withstand over 70hp her piston easily/safely, rods that will easily withstand 75hp per rod, and both at up to 7000 rpm. It has a 1.5:1 rod/stroke ratio, and the pistons sit .011" down in the hole. It will handle as much power as any stock L28 will, and I've used many cranks that I have modified with the same process many times with no casualties. The beauty of this is that you can get off-the-shelf forged pistons and forged H-beam rods for this rather cheap, while only having to modify the rods a little bit. The only custom piece is the crank, and if I can do it then any other competent machine shop can do it too!

the only reason I'm posting this... is because I only built the shortblock because I was bored at work and wanted to keep busy yet explore new possibilities with old motors. What would someone give for a shortblock like this? I know (from trying to sell all of my old L28 parts (which is why I had the extra block and crank!! I couldn't give them away!!)) that there aren't alot of L engine buyers out there, but I figured it might be worth selling if I could at least get my time's worth out of it?

#2 Scottie-GNZ

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Posted 09 February 2007 - 04:45 AM

This should get the attention of the L28et community :D

It uses dished cast eutectic pistons w/ coated skirts that have been known to withstand over 70hp her piston easily/safely?

How about 100+hp (AT THE WHEELS!) per cylinder? That's what I was pushing with the Speedpro hypers/coated skirt running pump and meth-injection.

Scottie

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#3 naviathan

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Posted 09 February 2007 - 04:56 AM

That much overbore is going to make the cylinder walls too thin I think. Hell the 89mm required for a 3.1L stroker make the walls extremely thin.
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#4 dr_hunt

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Posted 09 February 2007 - 05:19 AM

Well, thin thoughts. I saw a guy, Ray Zamora, take a 350 chevy and bore it .125 over to make his own 377" or so motor. He ran it at the drags until a rod let go and windowed the block. Cylinder walls were very thin but it worked. Might of worked alittle better and longer with better rods and some hard block in a short fill.
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I think I have just the right amount of excessive HP!! But I guess there is always room for more!

#5 Mack

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Posted 09 February 2007 - 10:30 AM

interesting concept defrag. If you get bored at work again, take an LD28 block and liner it, then do the same thing. you can actually get a decent rod/stroke ratio out of the damn thing.

oh, If you did this with a linered LD28 block and put together a short block, Id trade you a DOHC head for it, lol!
hey, check my website for pics of my free 280zx.

#6 pete280z

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Posted 09 February 2007 - 10:35 AM

This should get the attention of the L28et community :D


It's got mine! What do you think you would have to charge for something like this?

A couple of issues come to mind though. With that kind of displacement 420 max hp seems kind of limiting. Also, an 87mm or 88mm bore would be much more comfortable.

#7 Challenger

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Posted 09 February 2007 - 04:29 PM

So how did you increase the stroke on the crank, and is there anyway to get a picture of the block?
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#8 defrag010

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Posted 09 February 2007 - 05:06 PM

Mack - I haven't seen a LD28 anything in my life, even with the million different motor cores we have. I was actually going to start messing around with a mitsubishi 4g64 shortblock I had and trying to get 110mm of stroke out of that crank instead of the L28, but it was together and the L28 I had was already apart and I didn't want to tear the mitsu down and clean everything.

mopar69 - The larger stroke is a comibination of welding, offset grinding, and re-drilling oil holes in the rod throws. I cut a thrust cheek to match the size of the rods I'm using. I will get pictures once I'm completely done with everything, and whenever I get around to putting new batteries in my camera. It wil probably be a few weeks though, because next week I have a big queue of things to do that will probably take me a few weeks to get done.

I tore the shortblock back apart today to try a few new things. I figured instead of just unloading an un-tested experiment, I would build one the right way and test it in my car before I gave it away.
For the cylidner wall thickness, I posted the block with 4 posts per side per cyliner (total of 48 posts.. which took forEVER and SUCKED.. drilling and tapping 48 holes), and I plan on partially filling it once I get time and money for some devcon or similar ( haven't decided which filler im gonna use). I'll probably fill the bottom and top half of the block about an 1"-1.5" and fill the area between cylinders so I can still get some coolant flow through the block.
I broke down and bought a set of 6 used Probe dished forged pistons in .020" overbore (which will be just shy of 91mm... perfect to use w/ the HKS 91mm headgasket), so I'll be re-honing the block out to size after I fill it.
All I have to do is find 6 H-beam rods (preferably used, and preferably that have spun a bearing so I can get them for cheap and re-size them because they have to be resized anyways to fit), and drop the crank off at the cryo treatment shop in town for a nitriding treatment followed by a cryotreatment. I want to see how much nitriding/cryoing the crank will improve the strength and hardness of the welded areas on the rod journals.

As for how much I would charge for something like this? I don't know, I had only planned on it being a one-time thing. I was hoping someone would give me a few hundred for the shortblock as I had it w/ the oem parts, but then I decided to improve upon it and keep it to run in my car as a test platform. I only have 2 more L28 cranks and no more L28 blocks, and I can only do this stuff on my free time at work. I could probably build a few more eventually if I come across a few more L28 blocks, but it would be limited to only that unless you can find another machinist to do the same work for you. The cost of all brand new aftermarket/forged off-the-shelf parts, plus the machine work needed to do one, it would probably cost between 2000$-2500$ depending on who would do your machine work/block prep/crank work and what kind of a deal you got on parts.
For now, I'm going to do as much as I can to this and run it in my car as a test bed and see how things go from there!

#9 Mack

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Posted 10 February 2007 - 12:20 AM

the LD28 block is a deisel variant of the L28. it had a smaller bore at 84.5, but a largetr stroke and a taller block with a crank center line to deck height of 227.5mm compared to the L28 deck height of 207.9. SO, you oculd use soem longer rods and get a better rod/stroke ratio.
hey, check my website for pics of my free 280zx.

#10 frank280zx

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Posted 10 February 2007 - 12:29 AM

imagine turboeing that !!!

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#11 SUNMASTER

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Posted 10 February 2007 - 02:51 AM

Nice work there hope it all works out.keep us posted

#12 twoeightythreez

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Posted 10 February 2007 - 11:28 AM

You've got me wondering what kind of stroke you could push the LD28 crank out to....imagine the LD28 block bored to 89-90mm (linered?) with a 3.8 stroke, keeping the same rod/stroke ratio you have now?
(stock LD crank is 83mm stroke vs. 79 for L28)
That would work out to...219cid...or 3.6L...shaweet!
And I'm living here in Allentown...

#13 OlderThanMe

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Posted 10 February 2007 - 01:21 PM

That would ALMOST make it worth staying L6...
;-)
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#14 1 fast z

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Posted 11 February 2007 - 08:16 PM

What process was used for the crank welding. FYI crank welding is very rarley succsessfull, as LOTS of stresses are built up that cannot be taken out, and thus cracking and then the big boom follows. It is NOT the way to stroke a engine. I know of many 22r setups that a company tried and ended up with LOTS of broken cranks. Billet is the best way to go. BTW, I am not buying it, as clearence of the rod on the sides of the blocks and bottom of the bores is impossible, trust me I already looked into it. I would love to see pics and a movie that shows the measurements.
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#15 RTz

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Posted 12 February 2007 - 03:17 PM

1 fast z,

I'm a little surprised. I'm sure you've lost track of how many people told you that you "can't" join two heads together. Or, that it "won't work" and "why". I respect your candor for having the gut's put that monster together....

Whether its the right way or not, you're the LAST person I would expect to kick this under the bus.
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#16 defrag010

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Posted 21 February 2007 - 11:22 PM

What process was used for the crank welding. FYI crank welding is very rarley succsessfull, as LOTS of stresses are built up that cannot be taken out, and thus cracking and then the big boom follows. It is NOT the way to stroke a engine. I know of many 22r setups that a company tried and ended up with LOTS of broken cranks. Billet is the best way to go. BTW, I am not buying it, as clearence of the rod on the sides of the blocks and bottom of the bores is impossible, trust me I already looked into it. I would love to see pics and a movie that shows the measurements.

don't believe it all you want, but I didn't have to clearance much off of the sides of the block, and only about 1/8" off the bottom of the cylinders. The rods I'm using have a 1-3/4" journal and are smaller physically around the big end with smaller rod bolts that sit more flush along with no balance pad, so even with the offset rod throw and smaller journal, the small rod doesn't extend out anymroe than a cunthair than the stock rod setup does. Use a smaller journal, and you can move the journal centerline farther out to increase the stroke without actually moving the rod throw farther out. It's simple math. You wouldn't be able to do this with stock sized journals, which is why I had to use undersized quad4 journals.
As for the welds, The process I used was to grind a 3.5" stroke into the short side of the stock rod journals enough to turn them down to about 1.5" total size. Then, I set the crank in the lathe and used GMAW with 70S wire. Pre-heated the crank to about 300F in the gas oven, then locally heat the journal about to be welded up to about 600F. Had the floorsweep use the big propane torch to keep the crank at temp while I was welding, and didn't let it get below 200F. After All of the journals were welded, quickly stuck it back in the gas oven at about 700F for an hour or so. Took the crank back out, and wrapped it tight in fiberglass to slow the cooling rate down. Took about 45 minutes after the crank was cooled to grind the rods out to 3.5" stroke and to size. No cracks, and the crank itself is being heat treated right now and should be back by the end of the week.
You're right, alot of people have had bad luck with their welded cranks cracking on the welds due to the stress risers, but if you do it properly you won't get much of that. Also, cast cranks are Much harder to weld correctly than forged steel, so it depends on what kind of crank you're welding on. PERSONALLY, I have had Great results with welded cranks, and have done alot of de-stroked and stroked v8's and v6's that were anywhere between mild street motors and wild setups. I did a 390 steel crank for a guy last summer, welded the rod throws up and stroked him out to 4" from 3.75" to make 415c.i.. His FE put down 450something hp and 490tq to the wheels in his stripped down old 70's shortwide bracket truck. He's been running 11.9's for almost a year at the 450+whp level with a welded crank and nothing has gone boom yet. You knew a company that had alot of welded 22R's go bad.... so what, that doesn't mean every crank that gets welded will self destruct -- because it's all in the process. Plus, this motor I put together.. we're not talking about a 10000002304230horsepower race motor that turns 10K rpm, we're talking about a stroked motor that will withstand as much or more than a stock setup would without ever turning over 6000 rpm. Like I said, I've had alot of success with welded cranks in alot of performance motors I've built, what about you?

#17 twistex

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Posted 08 March 2007 - 01:10 AM

i built a 3.2 ld28 block and crank with 6 inch z20 rods and 90 mm ka24 pistons, i have a small video clip of me running it on google video.
http://video.google....6&q=3.2 stroker
I need to put my bigger cam in. im hoping for 100 hp per liter. I have been pulling it up to about 7500 rpm np :P im having issues with my hks copper headgasket sealing with the copper spray. i have to use the copper gasket because i cant find a gasket with 90 mm bore. Only gasket i can find is the hks one!

#18 TABrinn

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Posted 01 November 2007 - 12:08 AM

Twistex, that's one killer engine! It was mentioned it another thread that the LD block doesn't clear the hood with out mods. How did you get yours to fit? Would a cowl induction hood work? I'm scowering every forum and car classified listing on the web for an ld28 crank but now I want the block too!

What CR does that combo give and with what head? Have you had it Dyno'd?

Excuse me while I wipe the drool off my chin!

#19 ezzzzzzz

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Posted 01 November 2007 - 06:27 AM

Twistex, could you provide more info on that LD28 build? Did you sleeve the block? There is the stock 84.5mm bore and only 12mm between bores on that block. The block is partially siamesed with an approximate 3mm gap between cylinders. That leaves approximately 3mm wall thickness stock. Your bore would remove 2.75mm of material leaving only .25mm of cylinder wall. That seems unreasonably little material to hold up to any combustion pressures over time. This based on rough measurments prior to sonic testing of my block. I'm building a LD28 (supercharged) stroker too. I plan to limit overbore to about 86mm to allow for a rebuild and provide adequate cylinder wall thickness. Sleeving was given consideration for a larger displacement but the payoff to payout was not even close to being reasonable. I'm using L20B rods and custom pistons. The mechanical P90a head has been drilled to accept the 12mm diesel headbolts. As for the stroked crankshaft, the limiting factor I see is clearance issues of the rods to block. If power is the only criteria then anything goes. I've had my days of that and look for compromise with regards to longivity. A roaring beast with a thrown rod or split cylinder wall is just a boat anchor.
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#20 rztmartini

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Posted 01 November 2007 - 11:30 AM

...the small rod doesn't extend out anymroe than a cunthair than the stock rod setup does.


Is this a measurement on the metric scale? ;-)

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