XB12 crank in xb9 cases

[Machinetools1]

Hello there

I was wondering if an xb12s crankshaft would fit in an xb9 crankcase years being the same.

 

[loose1]

Yes. Cases are the same

 

[Machinetools1]

Thank you

 

[theMelvster6]

differences between the 12 and 9 are as follows...

Stroke: xb12 has 3.812" stroke and a 3.498" bore flat top piston with a small button in the center to bump
compression up to 10:1. xb9 has 3.125" stroke and a 3.498" bore piston with a +12.3cc rectangular dome
to get it back to' 10:1 compression with the short stroke.

xb9 left xb12 right

Primary: the xb12 has a higher geared primary drive than the xb9.

Header: xb12 has a 1 3/4" header and the xb9 has a 1 5/8" header.

Throttle Body: the xb12 has a 49mm throttle body bore the xb9 has 45mm throttle body bore.

ECM: of course the ecm tune is different between the two, but you could load the xb12 tune (fuel maps and ignition timing maps) into the xb9 ecm via ecmspy or tunerpro

you can use the xb9 piston with the +12.3cc dome on the xb12 crank. the compression ratio will go up to 12:1...a bit much for the street unless you can afford the high octane gas.

 

[Machinetools1]

Fantastic...Thanks for the information. So the heads are the same for the 2003 through the 2010?

Thanks for the info.

 

[xb12rs]

I have a xb12 crank with 6900 miles on it. To my knowledge the heads never changed.

 

[theMelvster6]

Heads are the same...I believe there were slight differences in the rocker boxes through the years, but that is mostly a concern when you buy gaskets.