Should I do a KLG4 Crank Swap?

[SuperK]

I've got my engine in pieces, so it's now or never. What do you guys think, KLG4 crank swap or not?

I'm thinking it would be nice, less weight. I assume that the strength loss is no big deal.

And let's please keep this discussion to the bottom end. I will go rampaging if someone starts talking about heads and IM's.

[SuperK]

so I'm looking at about 45 lbs for the KLZE crankshaft (the KL01 is like 1-2lbs lighter than the KL01 according to some peoples)

Rockauto lists the steel crankshaft at 43lbs for the KL01.

Rockauto also lists the cast crankshaft at 37lbs for the KLG4.

so I would shave about 5-8lbs off the crankshaft. cost isn't the concern. I think this is good idea?

[wytbishop]

Well I haven't done a lot of work with lightening the internal assemblies of many engines but the one time I did do one was a small block chevy. We put in a forged crank and lightweight pistons and rings. My understanding at that time was that the main performance enhancement was in the pistons. The lighter crank is good but because the weight of the crank is so close to the center of rotation there isn't a huge effect on engine dynamics.

However, 6lbs sounds like quite a lot so I could see that being pretty noticeable in terms of free revving. It would be kind of a similar affect as a light flywheel I would think. I say try it and see.

[Daninski]

The weight saving comes at a cost. The crank is cast iron vs. the forged steel and hard nitrided crank of the standard KL motor. Not as strong. I'd say stick with the KL crank not the KLG4. IMO

[SuperK]

I took that into consideration... but how strong do you need a crankshaft to be when your car isn't hitting 200whp? I'm not turbo or sc'ing this guy.

[RX8SE3P]

I'd stay stock. Not sure if you'd actually feel any difference at all.

As a general rule of thumb, if it was a worthwhile upgrade, you'd have heard/read about it much more often.

[WhiteFinish]

The weight saving comes at a cost. The crank is cast iron vs. the forged steel and hard nitrided crank of the standard KL motor. Not as strong. I'd say stick with the KL crank not the KLG4. IMO

Agree 110%.... especially the nitrided is a very good thing.

[marcdh]

I'm not 100% on this but I'm pretty sure Andy/hppwdn had his klg4 >300whp. I'm not sure what you're planning but I've never heard of one snap, I bet your gearbox would explode before the crank would from too much power. For an NA build or even turbo I'd say go for it if given two cranks of equal condition.

[SuperK]

I also never heard of crankshaft going kabloom. I know that a nitrided forged steel crankshaft is the ultimate noggin smasher but seriously, I don't buy kitchen knives made out of depleted uranium just because they're better...

[MrMazda92]

Mark hit the nail on the head... I was going to reference GoldMember myself, 300+ WHP with a yunkyard G4, under boost.

One thing you need to take into account will be balancing(Not that you aren't already, it's just more important now), between pistons/rods and the crank. If you're going for higher CR. pistons, you could spring for lighter rods while you're at it. You'd have the most rev happy K series in the world, you could call it SuperK.

I've been thinking about this myself, and will probably be going this route as well. I'm shooting for 250 bhp, and a streetable powerband. I don't go for that 7K for power crap... I'd rather make 20 less horsepower and enjoy driving the beast.

[SuperK]

I once considered higher compression pistons but when I saw the price tag I shied away. IIRC it was like 600 dollars or so. Rods would be something a bit custom I think, I don't recall seeing aftermarket rods that were light weight and drop in... But the costs would be something tremendous.
If i had a disposable income with no other projects (house, yard, school, life, wife-hunting) I focus my extra cash on this block of metal.

I believe I have enough information to make a decision. No one has ever heard of a crankshaft creating a crater in their ZE's. Cool. This may or may not make a difference, but I'm going to try it anyways.

[Daninski]

I think you were just looking for people to agree with you and that's fine. I do that from time to time myself. Takes your mind off an arrow to the knee.

[SuperK]

I do everything for attention, dan. E.v.e.r.y.t.h.i.n.g.

I wanted someone who actually did/attempted doing the swap chime in. I don't think it's a very popular mod though.

[crazycanadian]

I do everything for attention, dan. E.v.e.r.y.t.h.i.n.g.

I wanted someone who actually did/attempted doing the swap chime in. I don't think it's a very popular mod though.

I don't think you'll find anyone who has because no one has thought the KLG4 crank would survive with what they were going to put it through...

I say go for it though... I am in your boat and not looking to make big power with my KL swapped 323.. Since I threw a rod bearing in my DE 2 weeks ago I have sourced out a complete KLG4 as a replacement.. In the next week I start tearing into my car converting it from an OBD1 KLDE to OBD2 KLG4... should be fun..

[MrMazda92]

If it bends or breaks, it'll be the first KL crank(of any designation or generation) that I've heard of. Go for it, but remember it cuts out about as much weight as a Fidanza flywheel, so if you're lightening other things as well, you'll really feel it. If you like it, please post feedback!

I'm sourcing a G4 for the block, valvecovers, and IM myself, still debating the crank. If the heads are nicer than the current set I have cleaned and gutted for machine shop time, I'll use them as well.