Quick Quesrry about 4AGE Bore Size!

[FYADUP]

Hey guys,

I am selling these pistons on trademe -

http://www.trademe.co.nz/Browse/Listing ... =390950151

I haven't answered it yet, but have a guy asking if these would fit the standard blacktop bore?

On the net I have found the standard bore size of 81mm

On the box of my pistons its says 3.209 inches, which when converted to mm is 81.5mm - does this mean no, it won't fit standard bore and is 5mm oversize? or is 81mm I keep seeing on the net just a rough whole number as opposed to being to so many decimal places?

Would be great if someone could shed some light on this


Cheers,

Jason

[Vertigo]

yep, oversize. standard is 81mm.

[Bazda]

Meaning he would have to get the bores re-bored.

Anyhow ALL bores should be honed to suit the new piston no matter what.
Esp if using forged pistons as they require certain tolerances.

The only time you can just drop a piston in there is when you buy another stock one of the same size.

[KIPH8N]

What if you have a silvertop block and drop 4agze pistons in there? Do they go under stock pistons?

[Bazda]

What if you have a silvertop block and drop 4agze pistons in there? Do they go under stock pistons?

I would say no.
n/a piston clearance and forced fed clearances are different.
n/a being much tighter.

[4agtepwr]

Normally as a rule, the clearance is built in to the piston, for example with a 81.5mm os 4agze piston the bore can be finished at the nominal size 81.5. I think from memory they run just on .05mm clearance or.002 thou in old school terms and that is built into the skirt of the piston if you get what I mean. But yes that block will have to be bored and honed to suit those pistons as there .5mm oversize.
There are exceptions to this and piston to bore should always be checked before assembly by someone who knows what there doing.