[roland2003]

Hi Guys we have a JCW220 car in at the moment for GTT260 conversion. Whilst the JCW head and manifold were on the bench we 'waved' a vernier over the exhaust ports of the head and manifold .You can see the difference in port sizes .We also measured up the GTT & stock MCS to give comparisons. -See photos.
Pic1) GTT Head -Exhaust ports are CNC milled (3D ball nose profiling ,not just a 'frame').Port size 39mmx25.5mm.
Pic4) JCW Head -Exhaust ports reprofiled (beneath the soot I'd say its CNC milled ,no ball nose cutters, but produced using a 4th axis so is ok but no hand fettling to blend in at the bottom) Port size 34.5mmx23.5mm. I can confirm JCW do nothing else to the stock head aside from this mod.
Pic5) Stock MCS Head -Exhaust ports are just cast finish only. Port size 33.5mmx20mm

Pic2) GTT 2pc manifold.- Ports are 38.5x 25.5mm
Pic3) JCW Motorsport manifold (the one with the cat further back) -Ports are 34.5mmx24.5mm
-Note the out of sequence Pic. numbers above.
Best Regards Roland GT Tuning

[GTT 280]

..assume this is mine?

Like the info on dimensions.

-----------Port------------Exhaust
GTT-----39.0x25.5----38.5x25.5
JCW----34.5x23.5----34.5x24.5
Stock---33.5x20-------???x???

Cheers,
K.

[chrisflyer]

Hi,
Does this mean the JCW motor sport manifold is better on the JCW head and the GTT manifold is better on the larger head due to the exit ports being nearer the exact sizes.