crank woes and bearings help - kind of urgent

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mikeyp

New Member
hey people,

right just had a call from the engineers and it's not quite the news i'd wanted. the crank needs a grind of 0.25mm and he can't find a supplier of the bearings. even his supplier of ACL bearings said there isn't any in the country.

i'm speaking with another member about his crank which is going to get inspected and hopefully only needs a polish, if this is the case then i will go with the better crank.

but if the second crank isn't any better than mine once measured, is it usable with a .25mm grind? i've spoken to some people that say it won't last and it will kill the bearings if it's had a grind.
my inteded use of the car is a standard engine and turbo etc running around 280-300hp @ 1-1.2bar.

just to compound this problem i've now got to find bearings, i've got the part numbers for both nissan and acl bearings at both the standard size and undersized but i've not contacted any suppliers yet to see if there is any stock. where do you lot get your bearings from, or where should i be looking?

as i need to call the engineer back with my decision to grind or don't bother, this is sort of urgent. any advice will be much appreciated. thanks.
 
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Gtirchris

Member
Hey buddy if you get the crank reground for undersized bearings then it will need to have the nitride coating put back on in, this is a fairly expensive process, best option is to get a known good crank and either get acl standard sized bearings from erics performance parts in america or get the bearings fron nissan themselves, they're not that much money but you will need to get the journals measured by the machine shop and grade the bearings accordingly re the workshop manual to ensure the correct oil clearance, I hope this helps you out mate. ;-)
 
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mikeyp

New Member
thank chris, yeah i was wondering about the nitriding. apprently the original depth of the hardening is .3mm so just slightly more than the grind needed on my crank. a few people have said that any more than a polish is enough to need it doing again or the bearings wont last.
i've not found anywhere to get the nitriding done. a lot of people say it's expensive but no one has ever said how expensive "expensive" really is. is this £100 or £500??
where does this treatment?

if the sencond crank turns out to be good then i'll forget even trying to grind mine and go with the better crank. i'm just trying to plan ahead incase the other crank isn't any better than mine. so far it's coming from a non-knocking engine but the condition is currently unknown till it goes to the engineers.
 
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Gtirchris

Member
Hmm, yep that sounds about right re the nitriding, as to how much it costs i personally don't know as it's not something that i have had to have done buddy. As far as who is able to re-do the nitriding for you, again i don't know anybody that does it for sure, but it might be worth giving automotive services in northampton a call as Simon,(the guy that runs the place) is extremely knowledgeable and always willing to help, and i'm fairly sure that he does a lot of work for the drift boys with their sr20's in the 200sx's etc, and his work is top notch and he doesn't charge the earth.;-)
 
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mikeyp

New Member
ok cool found eric's performance parts on ebay, they seem to do acl bearings at a fiarly good price. hate to think what the delivery is but who cares when things need doing.

been searcing around the internet and not found anything about nitriding services yet. have any of you ever had it done?

are there any people on here running thier car with a crank that has been ground and using oversized bearings?
 
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mikeyp

New Member
right so i have heard back about the possible replacement crank... same story as mine so i'm back to square 1.

a few people are quite sure that a properly ground crank will be fine to use again, so long as the clearances are all ok. but a number of other people have warned me off using a ground crank and some have had bearings fail again from 500-2000 miles.
i've found one owner who is running a ground crank and has done a little over 2k on it with some drag racing and hard track use, no problems to report so far. the crank was not re-nitride hardened before use.

so i spose i'm stuck for choices, i have a crank that needs a 0.25mm grind, i can get bearings for it and it seems i have a choice of weather to use it ground or get it re-nitride hardened before using it.

i don't want to build my engine back up again and find it won't last as i can't afford to have to go through all this again. so the fear of the crank chewing up the bearings in a couple of k is what's stopping me just going for it.
my engineer is a very long standing reputable business and does top work on engies (southern rebore services) so i know the grinding is going to be up to par.
but i have heard it from an engine builder that a ground crank has failed on him more than once and he will not use them anymore.

what's my next move?
have any of you got a decent crank for sale?
 
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pulsarboby

Guest
ive got a very good crank in but not cheap mike as said the other day as i wont use ground cranks in rebuilds either unless its just main bearings that need grinding as they are just under rotational load some will dis-agree with me but its what ive found for myself so i go with what i know and have done.
if its a normally aspirated engine then no problem as the loading is linear throughout the rev range but 300+bhp on a 4wd turbod car = a big punch on the crank when that turbo spools up lol

its either that or just get it ground, if others have used them and they are ok then just go ahead with it and keep the power to a sensible level
 
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pulsarboby

Guest
ive got 3 in total 2 of those i need for builds were doing shortly plus im buying in stuff all the time so by next year im bound to have located other good cranks, so il have one spare if you want it.

im quite prepared to let you have it on the basis that your engineer checks it over and if he thinks its unsuitable for whatever reason then send it back to me and il give you a full refund minus the postage costs there and back
 
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mikeyp

New Member
well i've just had a very interesting conversation with longwear surface treatments which basicly ended in them being very surprised if any cast crank would be sutable for nitride hardening. nearly every crank they harden is made of an alloy which has been designed for nitride hardening and is only available in billet form, and so billet cranks are what they hardern.

they were willing to take my crank and treat it but they said i would most likley be wasting my money. there are other nitride processes that are not as effective and only give an increased level of carbon to about 2000th or an inch. he highly suspects that this is the process that nissan used for the cast cranks.
so without further material information of the makeup of our cranks, gas nitride hardening is probably a waste of time.
he did day that other processes maybe useful for hardening the surface and are much more cost effective also.

so just been on the phone to nissan and of course their parts department didn't know anything but the guy said that the kind of data i needed would cost a lot of money to get from nissan and they tend not to be very forthcoming with it. great help, thanks nissan.

with people like bob saying that cranks have gone west after a small grind, this tends to surgest that the hardening is only the thinner version and would also explain the damage to cranks with failed bearings. my own crank had lost 1000th just from bearing wear and the depth of overall damage was 10,000th, which couldn't happen with proper nitride hardening.

next up speak to my engineer and see what hardening he can offer and what costs i'm looking at. then give up and phone bob for a new crank.
 
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mikeyp

New Member
balls and now my engineer is off sick.. so won't be getting anything sorted this side of next week. ffs.
 
red reading

red reading

Active Member
The gtir crank is not cast and is nitrided, you have been told all this before as standard these cranks are handling in excess of 1000bhp, and you will get deep scoring on a crank nitrided or not if the standard aluminium bearings wear thru, you get bearing wear from shite oil supply's to the crank from the oil pump or from dirty/debris in the oil. the standard aluminium bearings do not absorb the debris like white metal bearings will therefore you are more prone to get scores in the crank journal, that info was from vandervell bearings (the owner) who are the largest crank bearing supplier in the world!

So to sum it up if you have crank to bearing contact the engine will go pop, for what you want a ground crank will be fine if it and the bearing clearence's are set correctly the oil will be the bearing media,
 
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mikeyp

New Member
thanks danny.
i am well over panicking about all this but as it's my first go at it i like to work things out 100% before i do something.
been speaking to a number of people today who have proven to me that many a ground crank has gone on to do great things in the gtir engine. i just need to speak to my engineer about it and then i think i'll just go for it.

i do have one questions.. if i have clearances that are too large due to crank and bearing wear, then the crank is ground back and undersized bearings are used of the same undersizing as the grind, before fitting i should be using plastigauge to check the clearances.. what happens if they are not right?
if it's too tight (not likley) i can have a bit more ground but if it's a bit loose then i'm stuffed as the bearings don't get any thicker.

or am i being a numpty and because they are new bearings and a properly ground and polished crank, it's all going to be super tight and bang on anyway?
 
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mikeyp

New Member
oh and do you know the chemical makeup of our cranks? or where i might find out?
 
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stumo

stumo

Active Member
so just been on the phone to nissan and of course their parts department didn't know anything
Click to expand...
you'd be surprised how little info the dealers get from Nissan.

Next time you're there get a print out of a page, apart from a part number, that's the extent of the info....

All the service departments get is the service books, that's it. Nothing more.
 
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