lexus_sc400_n20

my friend is thinking about a 1.5jz in an sc3. the question is what the comp ratio would be. a 1jz would be boost friendly, but would a 1jz head and 2jz block be as well? if not, what would it take to change that?

Dew23

iTrader: (1)

2jzgte bottom end you compression should be about 8.5.1 or somewhere close.

T51R

actually.. with 1jz head... compression would be sky hight due to the 1jz head has less combustion chamber than 2jz head..
so if you would do 1.5j then.. either you make the combustion chamber larger or you can put the 2jz stock head gasket X2... I have done twice with this.. and compression is about as close as 2jz.....

I hope this helps

motorheaddown

The 1jz-gte stock compression is 8.5:1; however, the stroke is less than the 2jz-gte motor (common knowledge). That means that the clearance volume (compressed volume) is less than the 2jz to achieve the same ratio. *However*, the 1jz-gte pistons are *NOT DISHED*; they're FLAT. That's at least 10cc's of volume alone that's removed to achieve 8.5:1. My "guess" is that a 1jz head on a 2jz-GTE bottom end is about 9:1. While a 1jz head on a 2jz-GE bottom end is closer to 10:1.

There's a SF member who has the goods on this stuff. I believe his screen name is "Orin". Search on SF; you'll get good info there.

-scott

T51R

2jz stock bore and stroke is 86X86mm
1jz stock bore and stroke is 86X71.5mm
which come out to be 14.5mm stroke difference, and 506cc difference.
even with 2jz TT block.. without droping compression..it would be 10.4ish. one that I messured
Easyest way to drop the compression is to put double OEM head gasket.. many of japanese tunner has used this method as well as I have used them myself..
or if you want to keep stock head gasket, you can make combustion chamber bigger ...
when you put the 1jz head on 2jz block... which would be about 70mm different on hight.
which means that there would be some parts would be short ,but this is based off from if you have complete 1jz engine... if you have all the 2jz parts.. which mainly , you need couple water passage(between head and block) on the side of the block.. would be short, timming belt has to be 2jz's,

best thing for you to do if you going to ndo 1.5j... try to have as much as 2jz parts you can so that you dont have to fight to get a parts later on....

anyway this helps.. and email me if you have any more questions.
tonishi21@yahoo.com

P.S orin..... hehehee he is to busy to putting his motor back together...