1jz vs 2jz crank.

[jeffro ra28]

Hi,
What are the differences between the 2jz and 1jz crankshafts other then the stroke?
Can i use a 2jz crank in a 1jz block?


Im thinking of a custom built engine, with short rod-stroke ratio. Using custom rods and pistons.

Please enlighten me

[The Real Roadrunner]

short rod/stroke is probly the worst idea ive heard of.
theres no point it just makes the engine less effiecent up top, why would you want to do that?

cheers
linden

[jeffro ra28]

Mate, the pro's and cons never end, how can you judge "its the worst idea ive ever heard of"?

But to answer your qeustion honestly, discuising a 3L as a 2.5L. Passing laws and engineering boundaries.

[jeffro ra28]

Also i may add. It may be possible to stick with the same rod length, and use custom pistons to suit. I havent looked at this option yet.

[The Real Roadrunner]

it wont want to rev properly up top, and because of the chamber design in a 1jz you cant put enough timing in above 5000rpm as they are, let alone doing a short rod motor.
you could do a combined sleeve/spacer arangement (ala OSgiken 3L RB26) to give you the deck height needed for the 2jz but it would be extremely expensive.

short rod designs are not a good starting point for a performance build, it would be the same as pissing into a 45kph headwind.

cheers
linden

ps, for the legalities what car are you looking at putting it into.

[Xistant]

jsut do a 1.5jz lol

same hassles but who's going to know about the bottom end?

[The Real Roadrunner]

Also i may add. It may be possible to stick with the same rod length, and use custom pistons to suit. I havent looked at this option yet.

not a chance the deckheight is 25mm taller for the 2jz getting a set of pistons to change that much i would seriously doubt.

chers
linden

[jeffro ra28]

I agree with what you are saying and yes you are correct in a practicality sense. But bearing in mind this would be a custom built engine, by myself i might add, and all the right tools etc, flow bench, cam doctor would be used.
Everything could be suitably built around the short rod to acheive its gains in the correct department. e.g. higher exhaust-intake flow ratio for less pumping loss and opening exhaust valve early bringing engine on boost quicker. But really the list is long on what is there to work on with a short rod engine.

I have an ra28 in the build. Currently a 1uz is the target engine, which i am building from the ground up currently. But am thinking more towards the turbo 6 style. So i am pondering some thoughts. The 2jz is 2997cc, which is around 60cc larger then alowd.

[jeffro ra28]

not a chance the deckheight is 25mm taller for the 2jz getting a set of pistons to change that much i would seriously doubt.

chers
linden

Ahh yes, thanks for clarifying that, its certainly the early stages of research.

[jeffro ra28]

can anyone actually answer the first question?

[The Real Roadrunner]

can anyone actually answer the first question?

C/C of journals are the same and i would say the bearings on the 2j would be the same sizes or larger which would just be a tunnel bore away.
everything should line up but the counterweights on the 2j may be larger and require abit of work to be done to clearance the block.

lots of work to be different but hey if thats what you want to do then ill be interested to see the results.

cheers
linden

[The Real Roadrunner]

Theyre about 300cc larger than your allowed afaik
cheers
linden

[jeffro ra28]

Thanks linden.
Yeah you are right, it would certainly be a development stepping stone if i could get it to work well. The use of one of the engine dyno's at work would certainly help me out there .

Are you sure we couldnt raise the pin height of the piston 25mm. Iv seen some pins as far up as the 2nd compression ring.
Anyone got a picture of the stock 2j piston?

[jeffro ra28]

Theyre about 300cc larger than your allowed afaik
cheers
linden

[Draven]

have you spoken to an engineer about the possibility of squeezing in that extra 60cc? Some engineers will gloss over things like a 60cc exceed on the capacity. They might get you to get a weighbridge certificate and use that weight instead (because it will be more)