Refitting pistons.

[dougal9887]

Hi Guys,
I've removed my pistons for the sole purpose of having them machined to reduce compression ratio.
When I refit them, is it acceptable to re-use the piston rings and leave the bores as found? Or should the bores be honed using one of those drill driven stone type hones. Should you always use new rings?
Thanks
Dougal.

[RogerFrench]

I think it depends on the current condition of the bores. If not much worn, refit.
If a bit worn but not worth a rebore, then a light hone and new rings may be in order. I wouldn't hone and use old rings though some do.
I don't much like hand- held hones. Use a drill turned around on a drillstand or a honing machine.

[dougal9887]

I had decided to refit the machined down pistons using the existing rings since the bores look just fine and the rings all had about .002 clearance in their piston channels.
Fortunately I also checked the gaps.These were way out!
Top compressions ranged .016" - .020"
Second compressions ranged .027" - .032"
Oil controls ranged .075" - .094"
I am very surprised to find this. Surely with such large gaps there would have been considerable loss of compression?
Anyway, new rings required and I'm guessing a professional honing job is what's recommended?
I'm hoping QED can come up with the correct +.030 rings. The pistons are the older QED cast type. I'll find out tomorrow!
Dougal.

[englishmaninwales]

Dougal
QED should be able to supply you. I had a set of +030 rings for the later cast AE pistons last week, and according to their website, also suit QED cast pistons.

http://qedmotorsport.co.uk/qed-shop/lot ... ious-sizes

Malcolm

[dougal9887]

Thanks Malcolm,
I see they are quite specific re older type so I'll get them on order.
Dougal.