Just a quick note 2jzr31, the section you are posting in here, is for conversions only.
Any tech questions/posts go in the tech section.
When you muck around changing heads on RB's the CR changes. Like a 9:1 RB25 head on a 9:1 RB30 block ends up with a 8.5CR. But what about JZ's? Are the combustion chambers different volumes on the 1JZ and 2JZ heads?
What CR do you get from the following?
2JZGTE long block with 1JZGTE head.
1JZGTE long block with 2JZGTE head (mate is doing this becuase his 2JZ bottom end is stuffed)
2JZGE long block with 1JZGTE head.
Just a quick note 2jzr31, the section you are posting in here, is for conversions only.
Any tech questions/posts go in the tech section.
Peewee
1985 MZ12 Soarer - 1UZ Powered
2013 86 GTS
OK, thought that this would be related to engine conversions No probs
Originally Posted by CrUZida
HEY WHAT THE??????? ...... the title at the top of my page says: "Tech and Conversions Discussion of conversions and other technical automotive topics"
sounds like the right section to me .... plus I have an interest here as im playing with similar information atm too
would love to know the chamber volumes for 2jgte and ge heads.... ANYONE????
i have the measurements for a 1j ... head is 40.5cc, piston valve cutouts are 3.6cc, 1.2mm gasket is 6.9cc and 1 cyl displacement is 415cc
note std 1jzgte is more like 9:1 believe it or not! .... i KNOW thats not what they claim but if you actually measure it thats what it works out to be!
will have the volumes for 2jzgte pistons soon too.... and comp if fitted to a 1j .... thats if they fit!
.... think they are the pistons from your mates stuffed 2j bottom end
Its been moved from the other section to this one.Originally Posted by 1jzracing
Peewee
1985 MZ12 Soarer - 1UZ Powered
2013 86 GTS
.......
Nice work 1JZracing and thanks for sharing your findings.
re-checked the vol's for 1jzte heads and pistons with a more accurite burette ... slight update still works out to be 8.9:1 for a standard 1jzgte
plus have piston volumes for 2jzgte, they do drop straight into a 1j the deck height is perfect!!
2jzgte pistons in a 1jz works out to be 7.7:1 ... fine for 36psi and racing only maybe
1jzgte head = 41.4cc
1.2mm gasket = 6.9cc (edit: its 87mm x 1.3mm = 7.7cc)
1jzgte piston = 4.2cc 498gms
2jzgte piston = 13.8cc 504gms
who has the chamber volume for a 2jzgte head?????????
Last edited by 1jzracing; 12-07-2006 at 06:55 PM.
Cool. Did you get the pistons from Al? Maybe he can do the tests on his 2J head?
mmm the large difference in piston crown volume might suggest the 2JZ has smaller combustion chamber to achieve a 8.5 CR. What are your thoughts?
Some people have reported 1JZ engines with 2JZ heads to be sluggish. Whether or not this is BS, I have no idea. But if it results in a low CR it might explain it. I know the VVTi 1JZ has a cr of 9:1, you are not measuring one of these but hey?
Wouldn't the 2J head on a 1J give a higher comp ratio given the smaller piston volume? Or will the different swept volume change that? That's assuming the head volume is the same or similiar to a 1J.
I would measure the 2J head volume but I don't have any accurate equipment to do it with.
I think all you need is a piece of glass with a hole in it and syringe??
I am a bit hazy on this so please correct me someone if I am wrong. The way see it is the 2JZ piston needs more volume as its pushing up more air because the extra displacement (assuming the same chamber volume) IE the capacity is bigger so there needs to be more volume somewhere to accommodate the extra air to maintain the same CR of 8.5. The fact that there is extra volume in the piston is promising as it hints towards the chambers being similar sizes to achieve the same CR. If the piston volumes were the same it would impossible for a head swap to not alter the CR's because of the difference in displacement. (IE the combustion chambers would have to be different to get the same CR or 8.5:1)
Clear as mud? My head hurts.
Last edited by 2JZR31; 11-07-2006 at 09:21 PM.
1jz racing: So 2jz pistons are direct fit into 1jz and you reckon about 7.7:1 CR. That is interesting
yes 2j pistons are a direct fit into a 1j... i havnt checked the little oil squirter but it doesnt foul anyway
I will say it again 1JZGTE are all close to 9:1 .... i have 3 to measure and they are NOT v vti engines
a quick calc for a 1j head on a 2j - will yeald the same comp of 9:1 so it looks likely the heads are almost identical, if anything the 2j may be ever so slightly larger
to measure a head:
small piece of perspex with 6mm hole near one end, put grease around the hg surface of the chamber on your 2jzgte head to act as a seal, place the perspex over the chamber and set the head up on a very slight angle with the hole at the high end, now fill the void with kerosene using a syringe or better yet a burette, note the volume .... write down the figour and rush back to toymods forum to post youir findings
someone must be a member of www.supraforums.com someone there will know chamber vol for a 2j surely
Give it a go Al
I posted some threads on other forums looking for the chamber size. Lets see if we get answers.
Strange shit about the high CR I wonder why they would state 8.5 if its not true?
Interesting, but relies on assumptions. But there is also claimed specs of the factory stated volume.
http://www.supraforums.com/forum/sho...chamber+volume
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