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winstontj

S14 2.5L (87mm) stoker crank in M10 - BAD IDEA???

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About a month ago I acquired a hunk of 4340 steel big enough to make at least two crankshafts. I've got a stock S14 crank that I was planning on using in my M10 for a stroker. I know there are e30 m3 Evo 2.5L cranks out there....

Because of things like rod ratio & just overall enough is enough would using a 2.5L (87mm) stroke be smart, dumb, overkill, stupid, (fill in your thought here)?

AlanM posted that he had a lightweight 2.0L S14 crank made for his specific racing application. Now that I have the hunk of metal and the stock (84mm) S14 crank I'm wondering about the 2.5L (87mm) crank. The metal cost me about $300, machine time will be free and how you harden and prepare machined stock is beyond me but it's relativly low-cost. Should I just stick with the stock stroke S14 crank? Also Pauter *may* be willing to exchange my newly purchased stock 4340 billet rods for the longer Evo rod. If this is the case would using an 87mm S14 crank be dumb in an M10?

Problems?

Thoughts?

Concerns?

Thanks,

TJW

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Guest Anonymous

just moving this back up....

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So where might I be able to source either a loaner 2.5L 87mm stroke S14 crank or buy one that won't cost $2K? I'd love the opportunity to run a 2.3L or 2.4L M10 with ITB's. It may even stray me away from the current forced induction plans. I bet it would be pretty easy to get up real close to 200 at the wheels with that displacement - and the torque!!!

Umm... I think Korman has them or has had them but seriously for well over $1500. Any suggestions?

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While I can't for the life of me understand why you would need to source your own steel, last time I was doing what you are doing I called Moldex, talked to the man, and ordered a crank. I have ordered custom stroke cranks from them in the past, the price was right ($1500 for just about any 4 cylinder last time I asked), the quality was amazing, the lead time was terrible (4 months) but the result was a happy engine.

The reason for the comment is they use a particular grade of specialty steel that might be 4340, but isn't off the shelf - it has special purity requirements, etc. Not that I know that yours isn't the same stuff, but it's kind of like taking a steak to the restaurant, don't you think?

Anyway, Moldex, in Detriot.

Brian

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My girlfriend/fiance's father is a machinist by trade. He works the third (overnight) shift and the majority of the jobs his shop does is DOD contract work. Large parts for things like planes, subs, etc. Once a "certified" piece of metal is cut the remainder can no longer be used for DOD work because it is no longer considered to be up to spec. They are currently working on projects that require 4340 steel in 22" X 22" X 12' (yes 22 inch by 22 inch by 12 foot) The end sections that are not being used are roughly three feet long and they are going to end up with close to one hundred leftover sections. The metal is almost free, the shop time is free and all I need is one crank so the CNC can measure and copy.

They have tools and machines that will inspect every point in every plane and produce an exact duplicate part, or load it up into CAD for changes. I'm looking for an 87mm crank to buy cheap or to borrow so that I can make a copy in lighter steel. The bottom line is the crank will be roughly half the weight of a standard S14 crank. Although the weight of a crank is very centered rotationally, it can and does make a huge differenct to chop the weight in half or close to half. I'm going get a stock 84mm S14 crank made but I'd like to have an 87mm one as well. Going up to 2.4 or 2.5L would make a HUGE difference and be a lot of fun as a daily driver car with a decent cam and a fuel injected ITB setup.

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[quote name="winstontj"The metal is almost free' date=' the shop time is free and all I need is one crank so the CNC can measure and copy.

[/quote]

If you can make two of these, I would be very interested in getting one, especially if you could recommend a rod for the package.

matt

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LOL.... Not trying to be rude by laughing at all but I can understand how everyone would want one. I want one BAD too! The problem is I may have to buy an 87mm S14 stroke crank, at whichpoint it would be fun to have a LW crank but I'm probably not going to spend $1,500 on a crank just to use as a copy.

The only plans I had for anything extra were to put them up on ebay. My other chalenges are hardening... It's not as easy as just cutting the darn thing - you gotta harden it, prepare and balance it... that's not included OR FREE... AND I have NO idea how to go about doing that and no idea what exactly it takes to "harden" a metal. This is getting more and more over my head and all I may do is make a copy or two of a standard S14 crank so I can figure this stuff out at a later date when I have money burning a hole in my pocket.

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Like your self this is way over my head as I'm no machinist/engine builder, but if BMW could have built a crank for the s14 that was half the weight without compromise don't you think they would have?

Half the weight sounds like it's going to break to me - what am I missing here?

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OK OK... Nick you got me. I have NO IDEA about the two metal's densities so I can't tell you about the weight. Why dosent Ford or GM use ARP bolts in every motor? Why doesn't every car come with standard SS exhausts? It's all cost factoring. They are making carbon fiber crankshafts now in some cars - you're not going to see that in your prius anytime soon though.

As you must know, many car manufacturers have to compromise to find their balance between cost, performance, reliability and best means of production. The new M6's have carbon fiber roofs but why don't all the new cars? I don't know about half the weight but I do know that a custom 4-cyl crank costs roughly $1,500 and more for a 6 or 8 so it's all cost. AND torque and ease of low idle. The less rotating mass the harder things are to idle, start and not stall with a manual, etc. think about some random person (male or female) who gets a new BMW but can't really drive a standard... The clutch and rotating mass has to be consistant and solid enough.

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OK OK... Nick you got me. I have NO IDEA about the two metal's densities so I can't tell you about the weight.

ah, so when you said it would be half the weight that was based upon a dream?

As you must know, many car manufacturers have to compromise to find their balance between cost, performance, reliability and best means of production. The new M6's have carbon fiber roofs but why don't all the new cars? I don't know about half the weight but I do know that a custom 4-cyl crank costs roughly $1,500 and more for a 6 or 8 so it's all cost. AND torque and ease of low idle. The less rotating mass the harder things are to idle, start and not stall with a manual, etc. think about some random person (male or female) who gets a new BMW but can't really drive a standard... The clutch and rotating mass has to be consistant and solid enough.

absolutely agree, but we're talking about an s14 here, not a prius. An engine devoloped to win the Touring car championship and homologated through a short production run of road cars. But it's an academic argument as we don't know what weight benefits, if any, you're going to get from your hunk of metal, or whether it'll grenade your engine the first time you hit 7k.

Good luck, you're a braver man than I.

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OK OK... Nick you got me. I have NO IDEA about the two metal's densities so I can't tell you about the weight.

ah, so when you said it would be half the weight that was based upon a dream?

As you must know, many car manufacturers have to compromise to find their balance between cost, performance, reliability and best means of production. The new M6's have carbon fiber roofs but why don't all the new cars? I don't know about half the weight but I do know that a custom 4-cyl crank costs roughly $1,500 and more for a 6 or 8 so it's all cost. AND torque and ease of low idle. The less rotating mass the harder things are to idle, start and not stall with a manual, etc. think about some random person (male or female) who gets a new BMW but can't really drive a standard... The clutch and rotating mass has to be consistant and solid enough.

absolutely agree, but we're talking about an s14 here, not a prius. An engine devoloped to win the Touring car championship and homologated through a short production run of road cars. But it's an academic argument as we don't know what weight benefits, if any, you're going to get from your hunk of metal, or whether it'll grenade your engine the first time you hit 7k.

Good luck, you're a braver man than I.

LOL... Grenade my engine. I really liked that one. I know the stock S14 crank is 9lbs heavier than the M10. No idea what an M10 crank weighs.

Also as I said I have no idea how to properly harden and prepare a crank so if it were hardened and prepared properly it would certanly not "grenade" my motor. The E4340 alloy steel is the same stuff that Arrow, Pauter and a bunch others use for big money custom lightweight rods. Titanium is also an option but that's going to cost me money for the metal. 4340 alloy is the same stuff they make all the high end custom cranks out of so there's no worries at all about blowing anyting up. This is also a certified pure "hunk" not just something pulled out of a dumpster at a metal scrap yard. I asked the question that's all...

AlanM had a custom 2.0L S14 crank made up and I wonder how much his weighs??? Additionally I believe his is made out of the same 4340 alloy which is pretty bullet proof. It's not the metal it's how you treat and prepare the metal.

The S14 in stock form was still tuned down quiet a bit for every day road warriors and there are things that the boys in the back room did to the stock cranks to shave weight as well. Many guys run custom cranks for lots of applications and it's really not a big deal. Also if I blow up an M10 motor it's not like there aren't 50,000 of them laying around. Some PO has already ground off the number stamp on both of my spare motors so the only loss will be my ARP bolts & Pauter rods (almost $2,000) Half the weight is not based on a dream - only I don't know the densities of the metals. If someone could provide either #1-the type of steel used in the stock crank and the weight (in grams) of the stock crank or #2 the type of steel and volume (or displacement - only of the metal crank) I'll be happy to tell you within a few grams how much the new crank *should* weigh.

Any ideas on how to prepare or harden the journals?

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Why don't you post at the S14power.com tech forum. They are pretty over-the-top on S14 madness, and may have ideas on the crank. I've learned a lot reading the posts, including how to simultaneously increase S14 power and decrease my wallet!

Ian

'76 M2

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Those guys are sick! they are making 2.6, 2.8 & 2.9L S14 motors!!! That's just plain crazy! I guess it's doable but it's really insane to think about.

It looks like I'll probaly have to spend the money to buy a 2.5L evo crank becuase no one in their right mind is going to just *GIVE* me their CAD drawings of it. So I'll look around for one and because they are rare and expensive they will hold their value so I can certanly just buy one, hang on to it for a while and then sell it at a later date. It may cost me $1,000 to buy one but hey it's only money!

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