sourcing 4afe pistons

[Sam_Q]

10:1 or 10.3:1?

[Mr Revhead]

oh whoops 10.3

[Sam_Q]

oh ok just checking, because it makes a big difference to my piston choice.

[oldeskewltoy]

NO... bluetop high compression pistons are 10 to 1. later non TVIS high compression pistons are 10.3 to 1.



In the photo below....
On the left is a 9.4 to 1 CR OEM 4AGE piston.... on the right.... 10 to 1 OEM 4AGE piston(.5mm O/S) note the center section of the 10 to 1 piston is rasied above the machined circumference, the 9.4 piston is lower than the edge. Also note that valve reliefs end flush on the 10 to 1, while on the 9.4 there is a ridge, this is a possible hot spot for ping (suppossion).

[Mr Revhead]

been a while since i payed attention to 16vs let alone a bluetop!

good pics mate

[turbo4agte]

Wait a minute.... I've never seen a 4AFE with a floating pin... you sure about that?

And how come everyone keeps suggesting 4AGE pistons when you have the narrow valve angle FE head? Couldn't it possibly nick the pistons? Also since when can a 4AF non-counterweighted crank spin to 9k?

[Sam_Q]

information is a bit vauge but the later model 4afe pistons have a 20mm pin, floating or not I cant say for sure.

If I were to use a 4age piston I would either leave it alone or have it remachined with shallower flycuts. The main reason why it would likely get away with it is because unlike any 4age head where the valves are at the edge of the chamber the later 4afe/7afe valves are placed recessed high up in the chamber. This means that for the same amount of lift the valves wont stick as far out.

here is something I prepared earlier:



Please excuse the bearing blue and the photoshop dots.

Now how do I plan to make it rev to 9000? well definetly not using any FE parts! I am using mostly a modified 20V bottom end but with 4340 rods.

From what I hear the 20V crank will be ok till 9000 without having fatigue.

Confused? just click on my worklog link in my signitiure