Originally Posted by Red16
Originally Posted by chip-3door
Originally Posted by Red16
chip - could you do a little post on plastiguages and how to use them.
from my understanding you basically put them on the bearing shell and tighten up the rod end / main cap bolt, then check the width of the strip against a chart to gauge the clearance between the bearing and the journal face. but do u use new bearings to do this? as if you used old ones it would give a different size to the new ones.
You just did it mate, i cant really write that any better than you did then!
Other than to state that when dry building any engine you use EXACTLY the parts you will use in final assembly, so therefore when you plastigauge the bearings you would use the new ones.
does the plastiguage chart tell you when the clearance between bearing and journal is too large or do you have to check some other form of manual for that info? basically i want to know this for my upcoming zetec turbo build
and if for example the gap was too large i assume you would just regrind the crank and fit oversize shells.
it means you could end up buying a set of new shells only to find out theyre no good for youre engine surely
or is this just an occupational hazzard
The plastigauge just tell you the size of clearance, it cant tell you if thats good or bad as it doesnt know, so you need to know the required clearance and compare.
As for if its wrong, depends on why its wrong mate!
Could be that the bearing tunnel is oversize, so you dont have enough bearing clamping force (there should be a small amount of crush)
Could be that the crank is undersize
Could be that the bearing is too thin
If you get the wrong reading, you need to check why.
But before buying bearings in the first place, you should KNOW the other two are correct anyway, so you would NEVER regrind a crank as a result of a plastiguage result, only because you mic'd the journals and they were tapered or undersize.
Does that make sense?