Why the JP4 head?

[Loz2212]

What are the advantages of fitting them?

Thanks :)

[qrty]

The JP4 head has bigger valves than the J4 head!

Usually people run J4 cams and springs in the JP4 head but problems can be had when fitting J4 performance cams due to valve clearance!

[Loz2212]

Will that produce more BHP N/A? Or are they something to consider with turbo's?

[qrty]

Depends on other factors!

Some dyno graphs used to be knocking around from a car that had a J4 head swapped to a JP4 but the internals were swapped to J4! Pretty sure the results were positive but I don't think there was a massive difference!

Better results N/A would probably be had if using different cams but as I said you can encounter problems with valve clearance! Not sure about using them with turbos!