would it be wise to get a crank reground if the mains are just under the set clearances. the crank is already 10/10. could ya get away without doing it, or will cause problems down the track with oil pressure etc as the bearings wear?
Crank regrind
Started by
_holdon_
, Aug 22 2006 03:14 PM
15 replies to this topic
#2
_LH SL/R 5000_
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Posted 22 August 2006 - 03:43 PM
Should'nt be a problem if you get the bearings to suit the amount of grind.
#3
_82911_
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Posted 22 August 2006 - 11:40 PM
If it is a street engine and the mains are showing clearance of more than 0.003" then get the crank ground .020" under and fit undersize bearings.
If you really don't want to turn the crank pins??? then you could, if the clearance is no more than .0035", just shim the pressure relief valve spring in the oil pump and run straight 50 weight oil....Bit dodgy in a "street" motor and you may well have trouble with oil getting into the chambers on deceleration... But hey it's a cheap fix!!!
Cheers Greg..
If you really don't want to turn the crank pins??? then you could, if the clearance is no more than .0035", just shim the pressure relief valve spring in the oil pump and run straight 50 weight oil....Bit dodgy in a "street" motor and you may well have trouble with oil getting into the chambers on deceleration... But hey it's a cheap fix!!!
Cheers Greg..
#4
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Posted 23 August 2006 - 12:34 AM
if you really wanted to you could go to the trouble of mix and matching bearing shells till you got the exact clearences you were after, but this is really race tune blue printing stuff.
10/10 is a good size to run but if clearences are a problem you may want to have a good talk to your crank grinder.
10/10 is a good size to run but if clearences are a problem you may want to have a good talk to your crank grinder.
#5
_holdon_
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Posted 23 August 2006 - 08:13 AM
thanks guys for the responses.
are they arny problems with grinding the journals further (20/20). it just sounds like there is????
are they arny problems with grinding the journals further (20/20). it just sounds like there is????
#6
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Posted 23 August 2006 - 08:22 AM
you dont necessarily have to grind both the big ends and the mains if only one is worn.
i think grinding past 30th will remove the hardened bearing surface.
i think grinding past 30th will remove the hardened bearing surface.
#7
_holdon_
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Posted 23 August 2006 - 08:33 AM
ah i see.
well the reason why the mains are worn is that the mains bearing caps were done up WAY too tight, and basically put higher amounts of friction on the bearings. it had also actually started to spin one of the bearings........
if i can get a bearing to match the clearances - then it shouldnt be a problem should it? or do they only really come in the set sizes.
well the reason why the mains are worn is that the mains bearing caps were done up WAY too tight, and basically put higher amounts of friction on the bearings. it had also actually started to spin one of the bearings........
if i can get a bearing to match the clearances - then it shouldnt be a problem should it? or do they only really come in the set sizes.
#8
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Posted 23 August 2006 - 08:58 AM
^ by matching i mean one 10 and one 20 or trying different sets of the same size and same or different brands.
as i said it really is race only stuff unless you have access to the supplies.
as i said it really is race only stuff unless you have access to the supplies.
#9
_holdon_
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Posted 23 August 2006 - 09:03 AM
really is race only stuff unless you have access to the supplies
the engine is for a street car, but it is a very tough engine and will be used for racing etc. this is why i am concerned.
another thought is to use a different crank??
i have a few spare cranks lying around. (10/10)
could i just use this (just get it linished)?
would this throw out the balance tho?
both cranks have been balanced - but when they are balanced, is each component balanced individually?
i guess they do it as the total bottom end.
so is a replacement crank without rebalancing a option?
Edited by holdon, 23 August 2006 - 09:06 AM.
#10
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Posted 23 August 2006 - 09:14 AM
^ i say race only beacuse the budget usually allow access to the extre parts required.
holden cranks are usually ballanced after weighing the pistons and rings off the rods, then weighing the rod , big and small end seperatly then using some calcs to come up with the correct ballance weight.
sometimes even the pistons are equalised and the rods and ballenced each end equally as well.
holden cranks are usually ballanced after weighing the pistons and rings off the rods, then weighing the rod , big and small end seperatly then using some calcs to come up with the correct ballance weight.
sometimes even the pistons are equalised and the rods and ballenced each end equally as well.
#11
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Posted 23 August 2006 - 06:58 PM
If you are worried about grinding your mains to .020" under then consider that the nascar guys are using a "honda" "IRL" pin size on their BE pins now and they are 1.850" a full .250" undersize from standard.Do you make 800HP and spin your engine to 9000rpm for 2 hours straight??? Then you have nothing to worry about.... 
Please don't try mixing and matching bearing sizes if you don't know exactly what you are doing...It is frought with danger.
GRIND THE BE'NDS TO 0.020 UNDER and know that your clearances are right, even more so if the bearing started to kill itself in it's tunnel.
On that.... How bad did the bearing get? perhaps you had better look at a line hone to make sure that the caps haven't "walked"
Remember... You get 1 shot at the reciprocating assembly...Get it right and it will stay together for a good long time... screw up even the most minor detail and it will eventualy get you... Usually as soon as you turn up the revs...
Cheers Greg..
Please don't try mixing and matching bearing sizes if you don't know exactly what you are doing...It is frought with danger.
GRIND THE BE'NDS TO 0.020 UNDER and know that your clearances are right, even more so if the bearing started to kill itself in it's tunnel.
On that.... How bad did the bearing get? perhaps you had better look at a line hone to make sure that the caps haven't "walked"
Remember... You get 1 shot at the reciprocating assembly...Get it right and it will stay together for a good long time... screw up even the most minor detail and it will eventualy get you... Usually as soon as you turn up the revs...
Cheers Greg..
#12
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Posted 24 August 2006 - 12:58 AM
Bearings used to be available 001" up but I think that was standard only. Check with Repco.
#13
_[BOTTLEDUP]_
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Posted 24 August 2006 - 02:50 AM
A lot of the V8 Supercars run Honda B/E journals as well, SBR in particular springs to mind...If you are worried about grinding your mains to .020" under then consider that the nascar guys are using a "honda" "IRL" pin size on their BE pins now and they are 1.850" a full .250" undersize from standard.Do you make 800HP and spin your engine to 9000rpm for 2 hours straight??? Then you have nothing to worry about....
Please don't try mixing and matching bearing sizes if you don't know exactly what you are doing...It is frought with danger.
GRIND THE BE'NDS TO 0.020 UNDER and know that your clearances are right, even more so if the bearing started to kill itself in it's tunnel.
On that.... How bad did the bearing get? perhaps you had better look at a line hone to make sure that the caps haven't "walked"
Remember... You get 1 shot at the reciprocating assembly...Get it right and it will stay together for a good long time... screw up even the most minor detail and it will eventualy get you... Usually as soon as you turn up the revs...
Cheers Greg..
I'll second what Greg has said here, and would further add, that if the mains were over tensioned, then no doubt the mains tunnel is no longer true. I'd be replacing the bolts, and getting the mains tunnel line honed.
#14
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Posted 24 August 2006 - 11:57 PM
agree with bottledup get the mains tunnel checked, offset grind cranks have been around for donkys and they have heaps taken off the big end journals doesnt seem to hurt reliability. i had a 040 under crank in a chev motor went for 15 years no dramas.
#15
_holdon_
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Posted 28 August 2006 - 08:23 AM
what do you mean by the caps to "walk"
u mean that they have worn unevenly and are no longer perfectly "circular" but oval shaped?
i have had this problem before - i just had to get tops of the caps machined down a touch.
with the mains tunnel needing a hone - how do you mean? also why replace the bolts - would have the over tensioning "weakened" them?
u mean that they have worn unevenly and are no longer perfectly "circular" but oval shaped?
i have had this problem before - i just had to get tops of the caps machined down a touch.
with the mains tunnel needing a hone - how do you mean? also why replace the bolts - would have the over tensioning "weakened" them?
#16
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Posted 29 August 2006 - 08:33 PM
^ the whole piont of tensioning a bolt is th stretch it a predetermined limit, if the bolts have been over streched they may loosen at the mactory setting.
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