OST-093: My, My, Mystery

[oldeskewltoy]

2 down... (leftside) 2 to go.....





after discussion about his build, my client decided on a new set of pistons......




more to come.......

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The pistons I just showed in my previous post.... This is essentially a stronger smallport piston.



Full size image - https://gallery.ostportworks.com/albums/..._large.jpg


Stock valve sizes because more than 80% of 4AGEs built are built with standard valves. The biggest flaw in OEM type 4AGE pistons (9.4:1, and 10.3:1) is they have a slit for oil return. These forged pistons support the 2nd compression ring far better with a series of holes.

Under a stock chamber, and a stock 1.25mm gasket, they are 10.3:1, under a tighter squish (.032"/ .8mm) they calculate out to 10.9:1.

These are also customize-able, want less/more compression height - done, want more, or less compression(dome volume) - done. These are available in .25mm overbores (81.0, 81.25, 81.5, 81.75, and 82mm)

One of the "olde" reasons for not using forged pistons were they tended to slap in their bores until they warmed up,because piston to wall clearance had to accommodate the pistons expansion. The piston to wall clearance on these pistons are 0.0025" (0.064mm). If you look up the stock piston to wall clearance you'll note it is 0.0039" - 0.0047" - so these should not "rattle" in their bores.

For more info send me an email: oldeskewltoy at yahoo dot com please include "OST/Traum piston" in title