Crankshaft

[sitnalm]

a friend told me a bored crankshaft of a turbo engine (due to scratches and uneven surface) with oversize engine/conrod bearing (0.5 mm) would not last long and best is to look for another crankshaft without modified.

May i have your comment/experience sharing ? Thanks

 

[kayour]

crankshaft bored??

 

[D7zul]

i think what he means is bore the block..

if u don't want to spend lots of money.. just bore it.. make sure the shop who makes the bore process is a good 1..

and don't forget to get pistons that would fit nicely inside it


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about crankshaft.. u need to send it for balancing along with clutch cover, flywheel & crank pulley..

Gudluck

 

[DanzEterna]

u could 'jack knife' the crankshaft..thats wat i did.

 

[D7zul]

u could 'jack knife' the crankshaft..thats wat i did.

how do u jack knife?

 

[DanzEterna]

dunno that wat my mech said...he some sort like skimm the crankshaft.

 

[^pomen_GTR^]

actually to cut/polish the bearing surface area specific to fit new thicker bearing.....due to old bearing scuffed the surface

like block rebore,crank bearing also got a few oversized type clearance for this purpose...

 

[Katsumoto]

what TS mean is Crankshaft regrinding , this usually done when the surface of the crankshaft is not in good condition

so after regrinding the diameter of the JOURNAL (the place where you put conrod and the crankshaft main cap) is smaller

in factory standard there a option of OVERSIZE crankshaft bearing and conrod bearing .

by fitting oversize bearing you fill in the GAP that grind away from the journal .

---------- Post added at 11:19 PM ---------- 6 hour anti-bump limit - Previous post was at 11:09 PM ----------

[youtube]y0NjkT0mqg0[/youtube]

here a video how it was done

 

[sitnalm]

yes, what i mean was the main and conrod journal on the crankshaft have been regrind, thus need to use oversize bearing. is there any bad effect? as some say, this will not last long and may fail again but just dun understand the logic y it could not last. thanks

 

[D7zul]

oic.. regrind it..

i'd rather get another crankshaft

or upgrade my engine with a stroker kit

---------- Post added at 02:23 PM ---------- 6 hour anti-bump limit - Previous post was at 02:21 PM ----------

yes, what i mean was the main and conrod journal on the crankshaft have been regrind, thus need to use oversize bearing. is there any bad effect? as some say, this will not last long and may fail again but just dun understand the logic y it could not last. thanks

as u can see the work is done by hand with the help of a machine..

if it was done 100% with a precision machine, than it's ok

Gudluck

---------- Post added at 02:28 PM ---------- 6 hour anti-bump limit - Previous post was at 02:23 PM ----------

0.1mm difference can cause trouble at 8000rpm

 

[Katsumoto]

hmm if you ask me , personally i haven seen anyone race with regrind journal

so i cant really tell you if there any other bad effect , just to let you know if you regrind the crankshaft + oversize bearing

sure cheaper then buying another use crankshaft ...

 

[kayour]

dunno that wat my mech said...he some sort like skimm the crankshaft.

or kapak..heheh

 

[virqai]

hmm if you ask me , personally i haven seen anyone race with regrind journal

so i cant really tell you if there any other bad effect , just to let you know if you regrind the crankshaft + oversize bearing

sure cheaper then buying another use crankshaft ...

yeah...we always like big jurnal diameter..i think coz all the rotation part is not full set balancing...so if we go for hi rev then the crank will easy twist,band or broken..small diameter more weak then big right?
only my 2 cent la....:hmmmm:

 

[Rleo6965]

You mean .5mm reduced journal diameter will weaken the crankshaft at high rpm?