[Erin Carpenter]

It has been a very common rumor on here for a long time that the 1JZ head flows better than the 2JZ. This has lead to alot of people doing the 1.5JZ swap or atleast wanting to. Over the last few weeks I have been building a 1JZ, including porting the head, for a customer. I flowed the head on our SF-600 flow bench before and after I ported the head.

A stock 2JZ flows about 238in and 154ex at .400 lift. A stock 1JZ head flows 215in and 133ex at .400 lift. After I did a good street port job including reworking the chamber the 1JZ head flowed 230in and 152ex at .400. This should put to rest the idea that the 1JZ head is better than the 2JZ, because the fact of the matter is that it is not better.

Erin

 

[BlackMatter]

Nice work and good info. +1

 

[SuprAng]

you only flowed it at one lift value though, shouldnt you have done more to make that kind of conclusion?

 

[airbats801]

Since im going standalone, maybe I should track down a 2jz head while im at it.

 

[Erin Carpenter]

Obviously I would not have gone through the trouble of flowing it at only one lift. I was using peak lift as an example that 1J is 20cfm down compared to the 2J.

Erin

 

[Ckanderson]

wow... finaly... the truth comes out!

 

[jbsupra89t]

Finally! +1

 

[Turbo Drifter]

Thank you for the work you have done. I'm glad I went full 2jz .

Jeremy

 

[JustAnotherVictim]

When they say flows better are they saying flows more or as a ratio. Or does that even matter

 

[toyotech01]

Excellent info
Jake

 

[rgguy]

Good info. Too bad I sold the 2J head that came with my 2J block! Oops! Oh well the VCs and the intake were already polished and everything so a little head work will get me back on track!
Cary

 

[Saleen00_227]

i heard that it was because the 2J had the runners on cylinder 1, 2, 5, & 6 leading to the valves slanted and the 1j had them all lined up straight letting the air come in quicker. naoto from blast racing told me this. dono how right he is

 

[chris davey]

So just to clarify: In a head you want as much flow as possible and also velocity. I see that the 2jz head flows more but wouldn't this decrease velocity which can be worse. Or am I on the wrong track here?

 

[becauseican]

Well looks like its time to put a 2j head on my 1jz

 

[ZaZZn]

well that about sums it up... very intresting... Thanks Erin....

Funny thing is the 1jz has a bigger exhaust port then the 2jz. 31MM vs 30.

 

[NecroCyde]

so maybe the 1jz just has better port velocity rather then better flow then, hmmm i wonder if there are any more tests that can be done for more information between the two heads.

 

[Erin Carpenter]

i heard that it was because the 2J had the runners on cylinder 1, 2, 5, & 6 leading to the valves slanted and the 1j had them all lined up straight letting the air come in quicker. naoto from blast racing told me this. dono how right he is

This is not true. The port configuration is the same on a 1J as a 2J.


As far as velocity is concerned, it is true that port velocity is important but it takes a more expensive flow bench than I have access to to calculate. Velocity is dictated by the port size and there is very little difference in port size between the two heads. The difference being a slight difference in shape of the ports even though they are configure the same.

Dont get me wrong and think that Im bashing the 1j head, because Im not. It is just not as good as a 2J head by around 20cfm. Niether head is really that great of a head to begin with. It is way better than a 7M though :bigthumb:

Ill try to post some pics of the head I just finshed next to a ported 2J in the next few days.

Erin

 

[Jewishjalopi]

can you put a 7m head on your flow bench and see what you get?

 

[Erin Carpenter]

We have before. Ill dig up the flow sheet for it tommorow.

Erin

 

[chris davey]

Definitely didn't think you were bashing the 1jz head. Brilliant info. that MANY people have been wondering about for a long time