I am in the process of ordering +2mm flat top pistons for an A15, the 76mm pistons that came out of the motor have hand ground valve reliefs and a pin height of 29mm.
I believe the correct pin height for the A15 is 30mm, do the standard A15 pistons have valve reliefs machined into them or has someone done a dodgey job on these pistons.
I am looking at flat tops with a rally cam, std h89 valves and need to know if I do need reliefs cut into the pistons or not, if std pistons do not have them I won't bother, thus making life easier.

Cheers

It depends on the cam specs, comp ratio and other specs (etc etc) but seeing as it's a rally engine I would think yes they need reliefs.

Factory pistons did not receive valve reliefs on the crown instead they were dished this means the ones you have aren't factory. There is a relief (exhaust) cut into the perimeter of the piston bore on the deck, that's about it.

I think the pin to piston deck height of those pistons 32.5mm, you'll need to confirm that. If those pistons come flush with a 29mm height then your new ones at 32.5 will protrude. That's sounds like alot to hang out.

a15 piston comp high is 30mm.
a14 is 32.5mm.
i've got a set ross of forged 78mm flat top pistons with valve reliefs (a15 -30mm c/h) (new is stock with total seal race rings. pm me if interested.)custom made.

also got a12/a14/a15 "rebuild kits" with cast dish pistons/rings/bearings/gaskets/timing kit. starting for $450.00

also a s/hand set of forged 77.5mm a15 on rods(slight crown damage,but still can be used no problems.

also a15 new 77.5mm flat tops (no reliefs) 29mm c/h cast pistons/rings/buttons, 18mm bushed rods to suit

where are you located. cheers

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