WTF: RB30 crank damage (pics)

[robbie2883]

looks fine....as long as the pistons aren't cracked, the skirts are good and the edge of the ringland isn't dinged to where it's touching the cylinder wall you should be good.

[ST240]

Cool.

Just wanted to thank everyone for their input and patience. I'm pretty green with engine buidling but you start somewhere .

The plan going forward is new bearings/rings assuming the pistons/rods/crank/block check out at the machine shop. Unfortunately i have a ton of work upcoming in the field starting tomorrow so this is going to be put on hold for awhile but ill keep you guys posted.

[mott6904]

Are those divots/chips in the piston? If so replace the pistons. all of those little spots will be more prone to melting. If you want to reusing them at least smooth out the damage. I would put new piston in it if it was mine. Arp bolts, stock rods, and forged piston would make a rock solid bottom end. just my opinion.

[robbie2883]

he's rebuilding next summer...just wants it running for now...yes some heavy ridges can create hotspots....but alot of that is in the tuning as well....he will be fine running stock/slightly modified like that.

[mott6904]

I dont know the guy but tons of people dont tune after they finish there build. they will drive it around trying to break it in before going to a dyno. most say that they wont get on but they eager to see what it will do and make a couple pulls. A couple of un-tuned pulls with that damage will not last very long. Plus if he puts piston in it now all he has to pull is the head later and can leave the engine in the car. Im a big fan of doing more now to save time later.

[ST240]

Lol. Trust me I'm not "one of those guys". WOT pulls on an untuned car? . And yes they are small divots/chips but they are prolly 1/16 inch in diameter if that. The sau guys didn't think they were too bad.

I'm going to take it to the machine shop and see what they think. End of story.

Next year I'm going to go with a spool rebuild kit most likely or something else of equal or greater awesomeness .

[synergy]

Dont run that please. Any inperfections that arnt needed are hotspot/knock goldmines. Ive seen hotspots happen for less. Theres not point in putting in a junk piston in a modified engine. And how the hell do you tune around that haha? Going rich because you failed to build your engine correctly is not a good way of doing things.

[robbie2883]

obviously some people don't know how to read a complete thread.

ok...here's the facts of the matter, if you shave those spots you end up with an unbalanced piston so you need to have it rebalanced, not to mention you completely change the flow characteristics of the flame from. anyone who tells you to just shave a piston needs to learn a little more about the flow of a burn cycle before they give advice. for running a STOCK setup (as he has said he's jsut trying to run it stock for now) you'll be fine....if you get any hotspots you'll get a little knock...you don't tune out knock by adding fuel as was suggested. you just back your timing off a little. again...this is for your STOCK setup...if you were building with these parts my opinion would be completely different.

[synergy]

Since when is a boost rb30 stock? He isnt going to run an rb30 stock nobody ever has.

EDIT

He has no head so im guessing this will be a rb25 head. In which case your previous post is useless since it isnt stock. Like i was saying get new pistons. There is no reason why you shouldnt. Your building an rb30det not a ls/vtec

[robbie2883]

^^^HAHA!!!! ST240....u should take advice from the guy who can't even figure out how to route his own vacuum lines!

[synergy]

Just keep your pistons for your stock rb30 build. And robbie im glad you looked up all my post to try to find something that i didnt know how to do.... glad your life consist of looking peoples name up on Nico to find their mistakes.

Sorry i have a life.

[robbie2883]

didn't have to look it up there scooter. i just have a good memory and you haven't been around that long! the point is...if you can't mess with vacuum lines i sure as heck wouldn't trust your knowledge on engine internals! if wanna act like a tool that's your choice, but do us a favor and get some experience under your belt before you start speaking from all your vast 18 years of internet knowledge!

btw...some life...you're on here with me post for post!

OP...sorry to whore up your post. i'm back on topic and won't waste ur time anymore

[synergy]

yup Im going to be the bigger man and just ignore you i guess...

[ST240]

Eh? Yes there is a reason to use stock pistons and rods and that reason is they can easily handle 300 rwkw (400 whp). There's guys on sau running stock bottom end making a s*** load more than that. I plan on running just north of 300 whp which is very attainable.

Again, I'm not expert. I just know what I've read and what others tell me. If the guy at the shop tells me to scrap the pistons, well then i will. If he doesn't, I won't.

[synergy]

ST im not saying swap them for aftermarket im just saying if you going to rebuild it or just build it why take the chance on a piston for no real reason? How expensive are rb30 pistons? Biggest hassle would be the wait on shipping. If your going to do something do it right. Just my philosophy.

[robbie2883]

stock rb30 pistons are not a dime a dozen...and when you replace the pistons you have to replace the rings...file the rings for proper end ring gap, check all your wall to skirt clearances and fit the wrist pins. it's alot of money to just "swap" pistons, stock or aftermarket. it's not worth it if the guy plans on building in a year. the motor will run absolutely fine. either way it'll be a coin flip on if the machine shop tells you to use them or not. some will some won't. let us know what they say though.

synergy...with all do respect...have you ever built a motor from the ground up?
Modified by robbie2883 at 4:18 PM 2/21/2010

[synergy]

Yeah i have From the ground up sir...And i measured everything in it. Plastigauge measured all wrist pins all skirt clearences. Valves in 3 different spots where the wear patterns are different. In the past 3 months i have rebuilt a 420A neon engine and a 3.5 chrysler engine from some old cirrus. So yeah i have....I dont know what the cost is but to put a new piston in shouldnt take more than an hour if its down to the long block right now.

rb30 pistons shouldnt be that hard to get anyways.

[mott6904]

aftermarket rb30 are not hard to find, but i bet finding stock pistons would be a pain in the a**. What would be your goals out of the engine you will be rebuild next year. Robbie is correct, you will get different answer about the piston from different shops. At my shop that is a big no no. And to your comment about the piston balance, I said smooth not shave. Meaning make sure those divots dont have any sharp edges, and the amount of material removed by smoothing the divots not removing them would be less than what is already missing from the damage piston. Im not trying to get in a d!ck measure contest with you bud it sounds like you know quite a bit about the internal workings of an engine, as do i. I just wanted to make sure that he was aware that the damage on the piston will be prone to melting

Back to the topic.What are you doing to the oiling system, crank collar,Oil restrictors, bore out the oil returns in the block,etc? I just bought a rb30 block myself, hopefully when i pull it apart i dont find what you found in your shortblock. Maybe i overlooked it, what head do you plan on running with this setup?

[robbie2883]

mott...i see what your saying...i completely misunderstood you original post. i would agree with you in that aspect.

[mott6904]

I eat my words about finding stock rb30 pistons. I was trolling around for parts for my new block and look what i found.

http://cgi.ebay.com/ebaymotors...97da8

It might be cheap insurance for you.

[ST240]

Im running a RB25DE head with GTR valve springs.

I WAS planning on redoing the collar, but if i do that, i wont be able to use the rb30e oil pump which i hadnt planned on using (was going to use the rb20 pump with extended collar). But ive been reading and from what i understand the rb30e oil pump is actually a very good option if you aren't running high revs even though it has a tiny drive on it (ie tougher than the rb20/25 pump with a short drive, but less flow/pressure so you cant rev it) and you make damn sure you stay off the rev limiter. It has something to do with how the pump is designed internally. Thats a s***ty explanation i know Ill try to pull better info on it.

As far as oil mods go other than what i mentioned above, I think I'll leave the block as is and add one restrictor and leave the other as is. I also have an external head drain on order. I would do more if it was going N1/rb26/tomei.

I'm sure you already know this but, like robbie mentioned, I cant just slap another rb30 piston in there, it will more than likely require a rebalance.

[synergy]

I have a very noob question....How expensive is it to get the crank and pistons balanced? Also this may also be a stupid question... The stock weight of pistons will always be different but what would have a bigger impact in balance a dinged piston or one from a different engine.

Dont mean to flame or step on anyones toes just looking for a real answer.

Thanks.

And also how researched is the rb20 pump on the rb30? I would think taking a smaller engined higher revving engines pump and putting it on a bigger lower rev engine would be a downgrade in two ways.

Revs define the oil pumps output so lower revs on the same pump= less oil. Also id assume the 20 has a smaller pump per revolution than the 30?

[ST240]

And also how researched is the rb20 pump on the rb30? I would think taking a smaller engined higher revving engines pump and putting it on a bigger lower rev engine would be a downgrade in two ways.

Revs define the oil pumps output so lower revs on the same pump= less oil. Also id assume the 20 has a smaller pump per revolution than the 30?

Very researched.

RB30E - low flow & low pressure. The advantage of the rb30e pump is the ring gear is supported better, the other pumps have a "floating" ring gear.RB20DET - higher flow and pressureRB25/26 - at least slightly higher pressure than the rb20 maybe even flow tooN1 pump - higher pressure (same flow?) as RB25/26. The N1 pump has a thinner ring gear for the larger pump cavity, makes it prone to cracking.Tomei, etc - highest flow (pressure same as N1?)

This is why you simply cannot upgrade your oilpump without doing oil control mods. Your head will fill up, starving the bottom end because the oil cannot return fast enough.

[robbie2883]

I have a very noob question....How expensive is it to get the crank and pistons balanced? Also this may also be a stupid question... The stock weight of pistons will always be different but what would have a bigger impact in balance a dinged piston or one from a different engine.

well...when we talk about balancing pistons you're not balancing the piston against the block. each piston is balanced individually. basically when you're balancing the pistons you are making sure all the pistons in the motor are the same weight (within tolerances) same with the crank and rods. if you ever take a second to look at pistons after they have been balanced you will see little dimpled drilled into the bottom of the skirt. this is where they take weight out of the pistons. rods they balance the ends...small end and alarge end get balanced individually. cranks are typically spun up for balancing and little dimples are drilled in the lobes to take weight out. balancing prices vary between shops but typically it's based on a price per cylinder. for instance $50 per cylinder. (just an example)

[ST240]

Guys, they're brazing the keyway back up in it's original position, and putting an oil pump collar on it. Yay! I'll have pics as soon as i get it back.

Ok engine builders, more opinions are needed :

Upon measuring the block:

Out of round: 1.5-2.5 thou, max is 0.5 thouWear: 7-9 thou, max is 7

The shop is highly advising against doing anything other than bore/hone with new mahle pistons and eagle rods, which would net me well over 2k all said and done, which ain't in the budget this year; although she'd be bomb proof then boy. He said that kind of wear is totally normal and that i shouldnt be concerned at all, but it is out of spec.

He also mentioned those divots in the pistons are bugger all really. A bit of emery and they're good. And that bearing wear is nothing. He said if I'm going to be a stubborn bastard, that i should not hone it or anything, and just put it back together as is, as taking more material off will just make clearances worse, increasing oil burn, piston slap, etc.

So I'm thinking of assembling properly as-is, putting the head on, and doing a compression test. If that goes ok, I'll run it like this, and tread lightly. Right now, boring 20 thou over would cure all. Obviously I don't want to increas this to 40 thou or worse, and end up with a boat anchor. Actually, a large part of me is saying to quit being such an idiot. Assembling the engine like that expecting it to perform is wishful.

Opinions?
Modified by ST240 at 3:09 PM 3/27/2010

[robbie2883]

it's iffy, you could assemble it and it run fine...or you could assemble it and you end up doing way more damage and making a so called anchor out of it. i think my main motto applies here. "mod cheap, mod twice."