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Discussion Starter #1 (Edited)
Since the 2j block is compatable with the 1j head, is it safe to assume the 2j head is also compatable with the 1j block?

I am in no position to consider taking on any project like this, but the idea of an ultra responsive 1jz has been appealing to me more and more over the past month for some reason.... I have no idea what car I would like to see it in, though I would definatley be against the mkiv and mkiii due to their weight.

Does anyone know the rough weight of a 2j block, 2j head, 1j block, and 1j head?

Also, I know its still being debated, but does anyone have some hard evidence of the flow potential of the 1j head? From what I have read it sounds like an urban legend that the 1j head flows better/can be made to flow better than the 2j. On another note, does the 1j head do any better at high rpms than the 2j head?

Out of curiosity, how much power would two ct12b's (stock boost) yield in conjunction with a 1jz bottom end? Im thinking full boost wouldnt be seen untill around 4.6-8k rpms.
 

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it has been a while so I don't remember where it was, but I've seen flow charts on another board where a ported 1J head flowed about the same if not worse than an untouched 2J head. I could be mistaken about that, but I know the 2J head faired much better. if no one has posted the info up by the time I get home tonight ill try and find it and post it.
 

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Discussion Starter #3
it has been a while so I don't remember where it was, but I've seen flow charts on another board where a ported 1J head flowed about the same if not worse than an untouched 2J head. I could be mistaken about that, but I know the 2J head faired much better. if no one has posted the info up by the time I get home tonight ill try and find it and post it.
Did you happen to post the same info in another thread a while back? I seem to recall hearing something similar. It just doesnt make sense that a head designed for a 2.5L I-6 would outflow a head designed for a 3.0L I-6...
 

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Akai Suisei - 赤い彗星
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I wouldn't see any reason to take a full 2JZ-GTE and change the bottom end out with a 1J block.

For all practical purposes, the 2J can do everything the 1J can and more. People talk about how high the 1J can rev but how of those people actually have cars that rev to 9k or whatever? Almost none. The 2J has been proven to rev to 7k+, so if you have a full 2J already don't bother with any part of the 1J.

Not to shit on the 1J... It's a very capable motor just like the 2J. I love mine and I wouldn't put a 2J in my Supra if it was given to me. I don't really believe in any of the frankenstein JZ engines except for one or two circumstances. Some people have 2J bottom ends on their 1J but I think this is only worthwhile if you have significant money invested in the 1J head(turbo kit, cams, head work, etc) since none of it would be compatible with a 2J head. Otherwise, if one wanted to upgrade to 3L, just get a full 2J. The assembly isn't as cut and dry as just slapping the head and block together. As far as a 1.5JZ the other way, I see even less reason in that one.

Toyota made 2.5L and 3.0L JZ engines for us already. No need to reinvent the wheel. Instead of worrying whether or not the 1J head will do better, I'd just invest in some head work on your 2J head.
 

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I ran mine to 9k. didnt urbano run to like 10,500?
 

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Discussion Starter #6
Im not thinking about doing any of this, Just got curious.

Im curious as to why you think the 'reverse 1.5jz' would have no merrit? The head would flow a little better and you would have access to the huge aftermarket of 2jz manifolds.

I really dont know much about the 1j block. Is it iron as is the 2j?
 

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I don't have any hard facts like flow charts but I was always led to believe the 1j head flowed so much better because it never had to meet US federal emissions.
 

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Akai Suisei - 赤い彗星
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Im not thinking about doing any of this, Just got curious.

Im curious as to why you think the 'reverse 1.5jz' would have no merrit? The head would flow a little better and you would have access to the huge aftermarket of 2jz manifolds.

I really dont know much about the 1j block. Is it iron as is the 2j?


The engine blocks are basically identical physically except for stroke.

There's actually a member on Supramania that has both engines. A conventional 1.5JZ and the reverse. They have different turbo setups so it would be hard to compare. I'm not sure if he's done with either or both so I don't have any hard results or facts about a reverse.

If you have a full 2J already, what would you gain from a 1J block? You already have the 2J had with access to all the manifolds and turbo kits available and the 2J can rev out pretty high on it's on.


DLM: That rumor has since been debunked. The member Erin Carpenter tested both heads a little while ago and found the 2J head to flow a little better than the 1J head. If search was working, I would link you to the thread.
 

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I thought the only advantage of going with a 1J was weight savings and better throttle response? Like for your hardcore track superstar.
 

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Akai Suisei - 赤い彗星
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There's not much if any significant weight to be saved.
 

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You serious?
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There's not much if any significant weight to be saved.
Then it would be as dumb as someone going with an LS1 instead of an LS7. :sadance:

Maybe the only people who go 1JZ are the ones who can't afford the 2JZ? :wavey: ;)
 

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I wouldn't see any reason to take a full 2JZ-GTE and change the bottom end out with a 1J block.

For all practical purposes, the 2J can do everything the 1J can and more. People talk about how high the 1J can rev but how of those people actually have cars that rev to 9k or whatever? Almost none. The 2J has been proven to rev to 7k+, so if you have a full 2J already don't bother with any part of the 1J.

Not to shit on the 1J... It's a very capable motor just like the 2J. I love mine and I wouldn't put a 2J in my Supra if it was given to me. I don't really believe in any of the frankenstein JZ engines except for one or two circumstances. Some people have 2J bottom ends on their 1J but I think this is only worthwhile if you have significant money invested in the 1J head(turbo kit, cams, head work, etc) since none of it would be compatible with a 2J head. Otherwise, if one wanted to upgrade to 3L, just get a full 2J. The assembly isn't as cut and dry as just slapping the head and block together. As far as a 1.5JZ the other way, I see even less reason in that one.

Toyota made 2.5L and 3.0L JZ engines for us already. No need to reinvent the wheel. Instead of worrying whether or not the 1J head will do better, I'd just invest in some head work on your 2J head.

well said

I ran mine to 9k. didnt urbano run to like 10,500?
why would you rev that high, i doubt either one of you had a turbo big enough warrant that. Also unless the turbo is huge, boost and power will fall off that high.
I rev to 9k only because i have a decently size turbo and alot of nitrous. but my powerband still falls off a little.
 

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Did you happen to post the same info in another thread a while back? I seem to recall hearing something similar. It just doesnt make sense that a head designed for a 2.5L I-6 would outflow a head designed for a 3.0L I-6...
no, I was agreeing that the 2J head flows better just worded it weird probably.. I just don't have the link in front of me showing the proof since I'm in the office on my pda rather than at a pc.
 

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I don't have any hard facts like flow charts but I was always led to believe the 1j head flowed so much better because it never had to meet US federal emissions.

the facts you have are wrong.. With that same logic wouldnt the JDM 2jz head flow better than the US 2j head? no its the same head with differnt cams. Unless you so a back to back comparison, or have flow charts, then dont make a statment like that. the 2j is a step up from the 1j.. not a latteral move, or a step down, there is no reason toyota would make a less flowing head on a bigger motor. and if that was the case Pro cars like ours would build 1j heads to run on our race cars.
 

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Akai Suisei - 赤い彗星
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Then it would be as dumb as someone going with an LS1 instead of an LS7. :sadance:

Maybe the only people who go 1JZ are the ones who can't afford the 2JZ? :wavey: ;)

Well... to be honest, whether I could afford it or not has nothing to do with my engine choice. I've had 2 or 3 opportunities where I could have afforded to go with a 2J Supra had I wanted. I chose not to because of the goals I have for my car.

I daily drive my car and I don't plan to ditch the stock twins anytime soon. To be 100% honest, I don't like a 2J with stock turbos. I don't like the way the way sequential feels with the 2nd turbo comes on and TTC is alot less responsive than my 1J is.
 

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I'm failing to see the advantage here?

Why not just put a full 2J in the project car? Why 1J with 2J head? Less torque, 1J doesn't rev especially higher, parts are easier to get for the 2J.

Also I remember a thread here where flow charts were posted of 1JZ and 2JZ head, and the 2J head flowed better, and had more potential to be ported to flow even better.

From what I can work out the 1J head being better flowing myth came from people doing headowrk to their 1J, and thne keeping the worked head when swapping in a 2J block. The worked 1J head being better than going back to scratch with a stock 2J head.

Dan.
 

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TTC is alot less responsive than my 1J is.
my twins in ttc feel better then my buddys stock twin 1j cars.. yea ~ 3000-3500 the 1jz has full boost where I'm still building, but the extra torque from the 3L makes it hardly even noticable..


as for the flow difference, if you compare the 1jz and 2jz ports.. you can clearly see the 2jz is much better suited for more power.. the 1jz has quite a bit smaller ports for higher velocities for good responce & torque (due to lack of stroke & displacment), but isn't well suited for power..
 
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