99 Blue Bird

iTrader: (3)

im in the process of purchasing a lq9 or 4. my question is how many miles are too many for a stock crank to be reused? the long block is 1200 bucks so i dont want to buy it if its not worth. since im puttin in forged rods and pistons it might b worth it to just buy a forged crank as well. my intended use of the car is all street but im rough on my cars and intend to spray a 250 shot and move onto a sts later on. so again how many miles would be too many on a stock crank ?? thanks for any info

Armageddon

iTrader: (41)

You can't really put a number on it. If you pull the caps and the bearings look good it should be fine. Take it to the machine shop and have them check it's straightness and mic out the journals. If everything is in spec I'd use it regardless of how many miles were on it.

99 Blue Bird

iTrader: (3)

ok so if it had 80k on it it would be safe to spray a 250 shot?

DSRE

iTrader: (7)

You cant just go by mileage, it could be 80k of well maintained miles or 80k in a work truck getting beat on daily, if the oil pan is filled with grime and the bearings didn't look ok id be concerned, but either get it magged and checked out by a competent .machine shop before hittin the bottle, truck 6.0 cranks are cheap and can handle big power so if I were you id stay stock or shell out 800+$ for a forging, to make it last under heavy n20 use you'll need a real good tune fwiw, don't skimp on bearings either, I like FM 3/4 groove race mains and the FM CH series rod bearings if you can afford it get them coated by calico, use good steel rings too like hellfires jmho

99 Blue Bird

iTrader: (3)

thanks on the bearing suggestions. so if it checks out fine at the shop than ishould have no worries about it breaking?

99 Blue Bird

iTrader: (3)

ok maybe this will help you guys answer my question. i plan on building a lq4 30 over so it will be a 370. will use a stock lq4 crank with callies main caps. callies compstar rods and diamond pistons. the crank has 77k on it. so as long as it checks out at the machine shop it should be fine sprayin a 250 shot or running 10-15 lbs of boost??

Monte4ever

iTrader: (2)

If it checks out it will be fine. Those stock cranks have been used by some in motors making close to 1000hp.

JS01

iTrader: (10)

You will not be able to break that crank, as long as it's within tolerances for everything and not a junk crank.

KILLER-LS1

iTrader: (18)

using the new mains will cost you a ton. line bore + line hone = big machining costs. stick with the stock ones, and do some ARP main studs which only require a line hone. and yes you will be fine on boost with all this. i have a 404ci truck motor with 10psi boost making around 650rwhp. make sure you have the heads surfaced if they are used to ensure flatness. just take off the minimum necessary. also do some ARP rod bolts and ARP head studs.

Armageddon

iTrader: (41)

I agree... stock caps.

arwokc

Whether or not the crank will work, is all in the journal clearances. The motor I have is an '03 LQ4 that had 80K on it as well and the crank mic'd out like it was new. It was on the tight side of the tolerances. A micrometer sees only dimensions, not miles. I had mine cleaned and a light polish. Don't forget to ask for a magnaflux. I doubt the stock power ratings would crack a crank, but it's just cheap insurance that you don't spend a lot of money and then watch it go out the side of a block. And even though the crank has been mic'd, I'd still check it with plastigage when you start going together with it. I did have my crank rebalanced though because the rods and pistons I'm using are a lot lighter than the stock rods and pistons. I used the stock main caps as well. There's a lot of great information on this forum. I built my engine after reading through this forum for six months, learning what seems to work and what doesn't.

99 Blue Bird

iTrader: (3)

im sorry if this is a stupid question but is a line bore and line hone the same thing as a regular bore and hone? just wondering why using diff main caps would require a diff type of bore and hone sine im already havin the bore and hone done to make it a 370ci motor

arwokc

Since your saying you're making it into a 370cid motor, I'm assuming your boring it out to 4.030", which is exactly what I did. The machine shop will be boring and honing your cylinders, not your crank journals. You don't need to align bore or hone your main journals unless they find a problem with them.

Sometimes a main journal may be slightly out of dimension. So a machine shop will lightly machine the flat mating surface of the main caps and then perform an alignment "hone" to bring them back within tolerance. When you replace the main caps, they rarely create a perfect circle because they usually come with a bit more meat on the journal surface so that it can be machined to a perfect fit. This requires them to be bored to bring them close to tolerance, and then honed to get them in perfect alignment with each other. If you have a spun main bearing, you're nearly always going to need an alignment bore. If this is the case, I'd splurge for aftermarket main caps at that point. Otherwise, the factory caps are plenty tough. So basically the difference between a bore and a hone is the amount of material being removed. It's very much like having the cylinders bored or honed. Sadly, back in the early 90's the engine shop I worked at would throw SBC blocks away if they needed to be align bored. They were a dime a dozen and economically it didn't make sense to bore them. They should have just stacked them up in the back of the warehouse. They're worth a lot more now days than anyone ever expected.

The moral of the story is, have it measured and checked for alignment first. Don't assume you need to have it align honed or bored. If it's within tolerance, it's within tolerance. Taking material off the caps doesn't necessarily make it run any better. Anytime you take material away, you are weakening it.

Just my two cents!

Monte4ever

iTrader: (2)

Good post ^^^^^

DSRE

iTrader: (7)

Also when you add billit main caps they have to machine the thrust surface on the new cap which can be a difficult and expensive! By the time your done putting those caps in you could have sprung for a forged stroker crank! ,ps use the correct dial bore guages and outside mics NOT plasti guage and also check the parting lines where the cap meets the block, you want a smooth transition here no lips fwiw

TJ

iTrader: (10)

at what hp will a stock main cap "walk" anyway?

arwokc

You know, that's a really good question and one that I've researched and researched until I finally just gave up. I don't think there is a posted "magic number" where they just turn loose and say "bye, bye". I have read ALOT of posts where guys are running the stock caps with stroker motors and nitrous that are pushing close to 700hp. I don't know that I personally would feel real confident pushing them to that point, but it does say something about the engineering behind them and these motors in general. Having said that, if you compare them to the old BBC aftermarket main caps, the LS caps provide a lot more meat and more stability with the six bolt system. So, who really knows? It's hard to argue with these guys who are successfully running them with that kind of horsepower. You'll just have to decide what you feel comfortable risking and how much money you want to throw at it.

DSRE is right about the costs. I had billet mains installed on a BBC stroker motor I built, and the machine work cost more than the price of the billet main caps. If you are considering adding billet main caps, talk to your machine shop first. If they have worked with LSx motors before, they'll probably know which caps to recommend. My machine shop wasn't to keen on working with my Milodon caps, because they actually put more meat on them than necessary. This adds to the difficulty of working with them and the amount of time to machine them. They actually charged me a little more for using them. But I had purchased my caps quite some time before and couldn't return them. So, I just bit the bullet and paid the extra that the machine shop charged. Communication is a wonderful thing when dealing with machine shops. Make sure you clearly communicate what your expectations are for your motor with the machine shop. Mistakes at this stage get expensive.


Hope this helps.

DSRE

iTrader: (7)

If you want the ultimate setup for big power with stock caps have them install 8mm dowels in the block similar to a Pontiac v8, doweling is by far the best way to keep the caps still, From looking at the LS Architecture id take a guess the caps wont move till 900-1000hp with arp studs, UNLESS you detonate it, JMHO

NemeSS

iTrader: (127)

i would guess close around 1000rw.
may guys have made over 800rw with stock guts and bearings and report no crank walk.

99 Blue Bird

iTrader: (3)

thnx guys for all the info. it is helpin alot.