Supra head flows 1j vs 2j head flow myth

Posted: September 20, 2011 by kemist88 in Tech
Tags: , , , , , , , , , , , , , , , , , , , , , , ,

So ive talked to a few supra heads and owners and I couldn’t figure out why people did the 1.5jz swap(1j head on 2j block). it was a step back words to me. Why. the bigger displacement of the 2jz has to have a head that would accommodate the flow. Now im going to list a BIG reason people justify it. “The 1jz head was made by Yamaha and revs higher”. The head it self isn’t the limiting factor on how the 2j revs but the rotating assembly. that’s really what limits how engines rev. the 2jz head was ALSO designed by Yamaha. the 2jz has the same piston speed @7.5k as the 1jz @9k rpm. the 2jz stroke is too long, and rotating mass is simply too heavy to spin that fast and will throw the balance off and ka-boom “yuh” engine gone.when you de-stroke an engine you can rev higher, when you stroke it you have to rev lower.
Now back to the MAIN topic of the heads flowing

Here you have the un-ported flow chart of ALL supra heads compared to each other

And here you have the ported version of the heads

CLEARLY you 1.5jz fanatics have your shyt alllll messed up. even the NA 2j (2jz ge) flows more than the 1jz gte in alllll aspects.
booyah for more indept info check out the original post on

  1. Ghost says:

    So similar to the argument betwwen Hona heads about the flow rate between a B16 head and a 1.8L GSR head…….B16 head does flow better however…lol

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