Your biggest thing is to find a piston with oiling holes not slots, those slots weaken the landings. Your next thing is to open the ring gaps, your normal off shelf pistons were never spec'd to rev very high or be used in a setup with lots of compression/combustion pressure so you want to open your ring gap a little to prevent ring bind which also cracks the landings off due to the incredible drag created by a bound ring.

I have 4mm valve clearance at minimum and an adjustable cam gear and timing cover with removable window to make the best of the setup once its complete.

My problem is/was valve spring seat pressure, it is to soft, busy machining up some titanium lower spring seats 2mm thicker than stock.

FYI, CP and JE charge almost half the price of the pitroad or Kameari to make sets of one off forged pistons. tough im going to try stay away from forged if I can. I have my hands on a set of B6 pistons, will try them in my spare block

Some amazing prices coming up, My 800hp GTR's pistons are 30% cheaper! , looks like ill go back to using good (OE) B6 or E3 pistons, i could buy and build 3 motors for the price of one set of forged pistons,,, that said forged isnt ideal in a NA motor anyway do to a larger expansion/contraction rate (up till a certain power level obviously)

That is exactly why i free rev'd it, ignition problems tend to be more load based/show up more under load,,, one free rev is a quick way to work out probability of ignition causing it

For now ill have to build up another motor with mazda pistons, this time ill try find a set that had drilled holes for the oiling not slots, I knew those slots would cause drama but honestly this motor was a "trial and error" setup and cost me next to nothing, wanted to find out what would work for me and my power goals, now its time to do it right, pity no one seems to have stock of the A15 high comp's so ill build a 3rd forged motor when i have time!

because I have ran from 28deg to 36 deg total advance and it did the EXACT same thing at EXACTLY the same RPM,

I have also tried using my old points dissy, same thing, same RPM, and I have also changed coil same thing same RPM.

Fair to say its not likely to be ignition?

Actualy it will tell you if its load based or not, in my case it isnt load based which cuts down my searching for the solution by about 50%

I would think that one rev up to 7000rpm is one whole heap better than the extended time it takes to get the car up to 7000rpm in 2nd or 3rd gear let alone the difficulty in actualy listening to the problem due to wind noise.

Either way I already know its valve related, will play with shimming and clearance this weekend and drive the motor into the grave, already purchased a replacement A15 (cheap as chips here) and will build a bottom end with better pistons than the "trial and error" setup i did first time round.

Leda have a very poor reputation here,

Will give Dundee a PM also Paeco industries.

Thanks guys

Who sells good A15 race pistons with 11.5-12.5 odd compression? forged preferably. Would also be nice if they are set to accept a 300 odd degree cam.

thanks

Even in neautral it hits a wall at 7000rpm and wont rev any higher,,,

i can turn the spring and i can push the retainer down,,, hard to gauge KG's though, will see if i can find a push scale, what i did do is check that i only have about 4mm from full open to valve bind...

Had somone helping changing my jets while i was playing under the valve cover, and yeah, in went the wrong air correctors and well, my Machined flat top mazda pistons took a break... blowing crank case vapour out like mad.

ehh, I killed the unkillable,,, funny that its a mazda part that failed lol

its on the intake mani,,, you can just see it in the pic

those stacks have been changed for decent ones that hold my "air flo" simple foam filters in place,

LINK FOR PIC