Topic: When reboring for over standard size, is one piston measurement used?

[denward17]

I have ordered a new set of over size (0.5mm) pistons/rings from CI. 

I was thinking about this earlier today and have been unable to find an answer.  Invariably all 4 pistons will probably be different sizes, one can only hope they would be the same.

When I take it in for a rebore, I assume I take all 4 pistons and the machine shop will match a specific piston to a hole, is this correct?

Or is it common place to just take one piston and all 4 holes match that one piston.

[Tracksnblades1]

A good machine shop will require all of them to verify proper clearances…

Check your min/max specs of your cylinder bores then the min/max specs of your pistons.
Compare the smallest bore with the biggest piston to the piston to wall clearance.
It will quickly become apparent..

[bryanj]

Technically all the above is true BUT in the 70's when using Honda pistons it was very rare to find any measurable variation is size between pistons

[Henning]

I did the CI 0.5 over re-bore a couple of years ago, and supplied a reputable shop with all pistons along with the cylinders. When I picked it up there were greasy fingermarks all over one of the piston boxes while the others were untouched. Clearly they'd measured one and bored based on that. 6k miles in and thankfully it's gone well. Bottom line, what the salesman tells you and what happens on the shop floor are two different things.

You need to worry more about piston to cylinder clearance; I had a discussion with the shop regarding this, they weren't happy with what I was asking for. Clearances for the CI pistons is less than for Honda pistons, I don't remember the numbers but there are several threads about this.

[Tracksnblades1]

Sometimes the smallest piston gets the most action during the initial boring..
Hopefully they all get their own home once the honing begins..?

Some shops were notorious for .002 cast piston clearance regardless what OEM recommended.

[dave500]

it also depends on who does the bore n hone job,i have a friend with an engine shop,he always goes the extra mile and does it all properly,i had him rebore a 550 motor for me using a david silvers piston set first oversize,he does each bore by itself,you might not notice any more power but longevity and smoothness plus easier balancing of carbs.
i have old hard drive magnets on the filter to monitor the break in,starts out pretty sparkly then diminishes each short oil change.

[bryanj]

I have just bored 3 500 blocks and not one cleaned at 1st oversize, at least one bore on each was barrelled i.e. worn more in middle than top or bottom

[RAFster122s]

I have just bored 3 500 blocks and not one cleaned at 1st oversize, at least one bore on each was barrelled i.e. worn more in middle than top or bottom

I bet it was cylinder 2 or 3 that was barreled, due to less cooling than the outer cylinders.

Interesting data you have given us.
Thanks!
David

[dave500]

another thing is thrashing,pushing or lugging a motor untill its fully warm,thatll cause wear unevenly,also the 550 is more over square,that keeps the piston rock down.

[bryanj]

One of the inners yes, just went to o.5mm