Kachow! Offset-dish forged pistons

[Pocket Chant]

Ugh. I want to build my M20 so badly. After I get new front tires I'm going to start collecting parts.


Oh, and it's Voila ;)

[digger]

any chance in getting these for an 89.6mm crank? They're almost as common as 2.8 cranks.

should be able to get it to work

stock stack height is 37.5 mm crank throw +135 mm rod +34.2 mm piston comp height = 206.7 mm (deck height is 206.2mm so sits 0.5mm above deck)

with 44.8 mm throw you need a 26.9 mm compression height instead of stock 34.2 mm.

MM do this with a 138mm rod on their 86mm bore rally motors so the piston comp height is even lower again!. The bigger the piston the farther the valve relief is away from the edge and and ring grooves (with stock valves)

you can use smaller wrist pins, thinner rings and the pin into the oil ring.

[deutschman]

Oh cool. Id like to use these in my next m20.

[SkiFree]

dang Andrew! if i didnt now have a s14 i would be placing an order right now.

Eric, having an S14 around is not to be wasted! Lets get you an 02 to go with it.

[Cabriolet]

dang Andrew! if i didnt now have a s14 i would be placing an order right now.

[SkiFree]

any chance in getting these for an 89.6mm crank? They're almost as common as 2.8 cranks.

Yes, depending on a couple factors.

The three things to balance is the pin height, ring package, and the meat available above the top oil ring (along with valve reliefs). In a nut shell with a 89.6mm w/135mm rods you're crunching all these things closer together (as with any stroker piston).

digger - A stock short skirt 8.8 piston was used in conjunction with the mold.

Matt and AlphaE - Thanks guys.

[AlphaE]

some jerks have ALL the cool toys:) :) super jealous! especailly of the fact that you have the means to do that kinda work. VERY COOL!!

[MR 325]

Wow Andrew, nice!

[CarsSuck]

any chance in getting these for an 89.6mm crank? They're almost as common as 2.8 cranks.

[digger]

Any reason for not simply mapping the 8.8 or 9.7:1 piston?

[SkiFree]

Jaywood -- The mold was made from 80a urethane. Would have liked to use epoxy but the stuff is getting difficult to get in small quantities. As it turned out the sensors picked up everything fine.

Digger -- Went conservative; 85mm bore.

Lorin -- Thanks, just one step closer.

The other upside to these is we'll be able to use them for the stroker kits and custom piston orders without bumping the price up.

[LJ851]

Kachow indeed!

Nice work Andrew.

[digger]

Looks good :)

85 or 86mm bore?

[jaywood]

Oooooh, looks very nice. What material did you use for the mold?

[SkiFree]

So after a couple weeks worth of fiddling around I'm happy to say that the new design is finished.

Started with a mold of the 885 chamber ....



popped out ....



Little solid works love ....



and wah-la these little babies pop out! (these are speced for my stroker build running the 2.9L kit running 84mm crank and 9.75:1 compression)