Need LZ Gurus to help with CR calculation.

[datzenmike]

The U-67 and the open A87 have the same 45.3cc combustion chamber volume. They share the same intake valve size but the A-87 may (or may not) have the same exhaust valve size. I believe the intake ports are also larger on the U67 head.

[RTB]

The U-67 and the open A87 have the same 45.3cc combustion chamber volume. They share the same intake valve size but the A-87 may (or may not) have the same exhaust valve size. I believe the intake ports are also larger on the U67 head.

U67 definitely has a larger intake port and I thought it has slightly larger intake and exhaust valves. Also, I considered using a z22 crank with l20 rods and getting a piston to work. Troy and Rebello recommended against it. They have never gotten that sort of set up to work right. On paper it looks fine but performance wise the rods are just to short for that kind of stroke. Youd be much better off using a z22 crank, 6 inch rods, and custom ordering flat top forged pistons. 

[Kirden]

Thanks RTB. I'll keep that in mind.

 

My setup is actually using the 6" rods now and 28.25mm pin height pistons. Decided against all that huge piston/milling piston crap and found one that should work well with the very limited space that the Z22 crank + long rods leaves you. We'll see how it does once I figure out everything I need to take to the machinist for proper bottom end inspection/modification.

[RTB]

Thanks RTB. I'll keep that in mind.

 

My setup is actually using the 6" rods now and 28.25mm pin height pistons. Decided against all that huge piston/milling piston crap and found one that should work well with the very limited space that the Z22 crank + long rods leaves you. We'll see how it does once I figure out everything I need to take to the machinist for proper bottom end inspection/modification.

Which pistons did you end up finding. I might want to use them too...

[Kirden]

 

Btw, here are the pistons I finally decided to use (The picture is not correct, they are dished with no valve reliefs):

http://www.summitracing.com/parts/slp-h895cp/overview/make/ford

 

So:

87.5mm bore

U67 or open A89 from L18

-15 dish pistons (28.25 pin height)

6" rods

Z22 Crank

1.5mm, 88mm bore Nismo gasket

 

I get around 8.5:1 CR with U67, not sure if the open A89 has a smaller chamber but CR would go up if it does.

 

Ford/Mazda duratec 2.3L pistons. There are also forged pistons for this application that come in many different dish/dome configurations for higher/lower CR but I went with sealed power hyper replacements.

[RTB]

I might do this combo as well except with as flat of pistons as possible and forged of course. If they only have valve reliefs that might work. This is pretty awesome.