fujack103

Hi ppl about 3 months ago i rebuilt my 94 sti engine using arius pistons eagle rod had the crank ground and acl uprated mains and big end bearings, when changing the oil you could see metal fillings in it which i was not impressed to see!!!!! so today i took the engine out and stripped it to find the main thrust had eaten into my crank :O it took me a while to work out that the clutch pulls on the crank not pushes this is the side it has worn out. has anyone come across this before using a uprated clutch and uprated bearings? oh its a single thrust by the way.

RAMP

Did you replace the oil pump,cooler and sump at the time of the rebuild as these may have had metal particles in them which could have picked up the shell,But if it is only the main thrust bearing worn out then are you sure that there was no swarf in the oil ways of the crank? Did you dry build the engine and or measure the crank to see if the bearings where the right size?

Heple

I was always under the impression that you should never re-grind the crack and always buy new.

Could it not be as "Ramp" says that the bearings were not matched to the crank

Craig

fujack103

there was no metal fillings in the engine before rebuild it has come from the crank i guess where i have a uprated clutch its put too much stress on the bearing but seeing that their uprated i thought i should take it, i just didnt know if this is a common plroblem?

fujack103

all the mains look ok (still gray suface) apart from the thrust side ( down to copper) which has eaten into the crank would this be down to a uprated clutch or do u think there was some other course?

RAMP

Can you mike up all the main journals and see if there is a difference in size,Maybe the thrust bearing is bigger or smaller than the others?

fujack103

in what way do u meaqn bigger or smaller?

RAMP

Are all the mains the same size,Just a thought maybe the problem lies in the thrust bearing surface being a different size to the other mains?

fujack103

i still dont know where your coming from? theres only one thrust in the center and as far as i know its the same size as the rest internally.

RAMP

The diameter of the thrust journal on the crank,Does it differ to the other mains Journals?

fujack103

im not sure without checking but how would this have an effect on the thrust side of the bearing?

fujack103

im going to go and take some pics it might be easier to see whats happened

scoobysmiff

iTrader: (2)

i was under the impression that you cannot regrind subaru cranks because the hardness on them is so thin, once a crank needs grinding then it's good for the bin and nothing else i've been told?

fujack103

sems like that might be the case!!! So whats the best route now then, new crank new shells the only thing is i dont wnat this to happen again!

Eprom

I would be looking at why it failed, was the thrust clearance checked on build up. I have built a few engines although not Subaru, if you had any contamination due to the crank re-grind this would have show up on the shells and mains.
If you are re-building with new crank and shells, it will now require a major strip down due to the metal particles.

Strip heads and clean, replace oil pump and modine? Oil cooler.
Inspect and measure every thing before assembly, my rule is measure twice fit once.

Good luck.

fujack103

TBH i didnt measure the end float as i had the crank ground and they supplied the bearing ( i know school boy error i hear you say) so i didnt think there would be a issue.

Eprom

No you live and learn, anyone who has not made a mistake has done nothing.

Hope you get it sorted.

st3v3

So ive been lead to belive the cranks are only case hardened, so that would be about .020" a side(.040" on dia) i wonder if for some reason the regrind has gone through the case hardening,leaving softer material underneath in contact with the bearings,

but yeah they shouldnt be re-ground,unfortunately a throw away item.

scoobysmiff

iTrader: (2)

I would have a chat with a reputable engine builder and get an opinion from them, someone like RCMS. Speak to Olly - He WILL know without a shaddow of doubt as to whether you need a new crank of not, would be a good time to fit an Sti 9 crank anyway, crossdrilled apparently and better for strength, like i said though speak to Olly.

fujack103

Oh its a new crank without a doubt! theres no room for a regrind on the thrust side. what the common price on a sti 9 crank and will it fit straight in or does work need to be carried out on the block?

jaytc2003

iTrader: (1)

with it being a 94 engine I dont think a sti9 crank is a straight drop in, I am sure something needs to be machined. Have a word with the likes of API or Zen. Think a new crank is around the £250 £300 pound

fujack103

come on lads prices and ppl?

scoobysmiff

iTrader: (2)

rcms do them, check their web site

APIDavid

iTrader: (4)

NEW crank at APi £365.00 + VAT NEVER grind a Subaru crank.

David APi

fujack103

thanks for the response guys and i just wanted to add that i have 4tho wear on the center part of my wrist pins and 1tho on the piston ends these were supplied with the arias pistons, to me this seems too much wear for less then 3000 miles of driving but i cant work out why unless the pins are of a sh*t quality, what do you think?

thedeester1

not sure what the tolerance is but hey can i borrow yout tooling?

Eprom

How have you measured the wrist pins, have you taken them off the pistons, and measured with a micrometer, at various points across the length.

I would have a chat with API, they have a good reputation on here, you could be throwing good money after bad, trying to rebuild this, you will need to know all the specifications and tolerances to perform a good build, and also have the correct measuring equipment, this is required on just a standard build, you cannot always rely on the machine shop to get it right, that is why you measure every thing before assembly, even down to gapping the piston rings if needed, and checking bearing clearances.
Cast pistons for instance require different bore clearances than forged, due to expansion properties, but if you don't know these tolerances you will have an engine that will be slappy or could even pickup a piston in the bore when hot.

Get as much information as possible before you start again.
Regarding the thrust side, I know that some blocks, have a centre thrust and some have rear, you may have to have the block machined to fit the later crank, but there are people on here that would help you there.

Hope you get it sorted.

fujack103

Borrow me what? 0.o

fujack103

Eprom, i measured them using a caliper gauge and a mic and they both show the same on the unworn parts either side of the center that runs on the small end that is still showing the grinding flatness so thats my datum. also i have arias forged pistons and i gapped the rings using the measurements given by the arias putting them in the bore and getting a feeler gauge then filling them to suit.

Eprom

Looks like you have done the right thing, but something is not right, the gudeon pins should not have that wear on them after 3000 miles, have they gone oval where the gudeon pin meets the little end? Do have they any flat spots on them?

Do you know what the deck height was when you re-built the bottom end?
I am just trying to ascertain what may have gone wrong; it could well be faulty components.

Would be worth talking to API or RCMS