I was looking at E5 pistons on eBay and was wondering wether it would be a good option to go for .030 over sized instead of standard.

Would this be worth the extra displacement, or is the a risk with the extra boreing?

That should give you a bore size of 77.75mm which should be fine.
This has been done before and has been covered on this forum many times so search for it and you should get some good info.

You'll need to have the small ends of your rods opened up to 20mm.

30 thou is still within the factory oversizes, usually factory over sizes go up to 40 thou

assuming thats 30 thou over the stock A series bore...cant say i know what A series bores are

u may need to deck block about 1.5 mm
depends on comp ratio needed/head used
e5 piston avalable in flat,2.4 cc bowl,7.2cc bowl.
77mm std,0.50,0.75,1.00,1.50 oversize avalible
comp height 28.60 mm pin size 20 mm

This is the set I was looking at,
http://cgi.ebay.com/ebaymotors/ws/eBa ... em=140386186108&viewitem=

I'm in the process of gathering up my parts before I take them to an engine builder so all this is good info to pass on before it gets machined. I was also gonna get a set of conrods and ARP rod bolts also from the same seller.

Have people checked out this guy?

Curious why those pistons ?
As mentioned they have a dish in them of 2.4cc and their crown is 1.4mm down the bore compared to stock A15 pistons
So your comp ratio might be lowish depending on your head chamber size

They do a flat top version in the same crown height that would give you more comp as no dish

So whats swayed you towards using this Mazda piston ?
Your aware of the 20mm piston pins I assume
I don't see any rods listed.... which ones ?
His prices don't look that hot to me

Those are not the right E5 pistons to use, you get E5 hi and E5 low comp pistons, you need to use the high ones and machine the small 2mm crown off to get them right for the A15, resize the rod and skim the block slightly (which is perfect for those running cut cams where the base circle has been hacked off, and your good to go

pistons i listed start at flat top and go to 7.2 dish
flat top also fits e3 mazda,acl piston no 8048

if your interested ive got a set of flat top pistons 77.5mm acl/rings and rods ready to go. rods have been recon new bolts bushed little ends and buttons made [floating pins] give me a call 0412 864 741 cheers ernie