1jz vs 2jz heads

[Starfire]

Has anyone bothered trying to flow the heads with positive pressure going through them? As a turbo engine I would have thought that flow under boost would be more important than numbers taken under vac?

I may of course be speaking out of my ass here...

[gianttomato]

they did some decent work on the exhaust there GT

The exhaust ports were absolutely terrible. The valve bowl was awful and the ports themselves were just too small. That said, they outflowed the a lot of the old pushrod heads by a country mile.

Intake flowed 360ish hp in standard form, but the exhaust only flowed 230 hp! Now intake flows close to 400 hp, whilst exhaust is closer to 330 hp.

[TheToyman75]

Nice gain there GT,

Good ot see the low end lift didn't suffer as is the case with soooo many port jobs.

[1JZ.747]

i woul ddo a 1.5jz swap based on keeping my existing bolt ons and cost saving a new manifoled etc.

having said that. from speaking to bruce at hardcore racing in slacks creek who i would say is very clued op on jz series engines as they have run the fastest jz powered pass in australia. he tells me infact his flow bench testing has shown a 1j head flows superior to a 2j when the port work has been done, 1 mm oversize vavles and cams added, this is why he as been putting 1j head on his 2j customers engines.

at the end of the day full 2js are making good power, so are 1.5jz's.

make the decsion from a economic point.

[petespipes]

another way of plucking this chicken is the turbo'd 2jzge.there are manifolds getting around to turbo the NA head,I presume you just chuck a set of turbo pistons and rods in,add fuel and do big skids,blitz the dyno shootout and leave victor bray a humiliated wreck behind you all for $99 worth of chinese manifolds and a coupla gaskets.........

really I did hear its being done,relatively good power for small cost [comparitively]

all hearsay though,definitely cant verify any of it.Interesting though.

[oldcorollas]

has anyone done a back to back dyno comparison between a 1.5J and a 2J?
could this be one of the cases where higher port velocity from a smaller port actually makes for a better engine package? (just thinking after reading motomans ramblings again)

[chris davey]

How could the test be done though? They would have to be running the same everything including tune to prove anything. I think it may be hard to find 2 people with EXACTLY the same setups especially as there aren't that many 1.5jz's around compared to 2jz's.

[oldcorollas]

yup too true
i suppose for forced induction the situation gets more complicated... i guess you could fill in a 2J's ports until they are same size as 1J and see how that works... but in reality, no-one will bother doing it

[1jzracing]

Heres some food for thought on the topic of heads

there was a levin sports sedan getting around a year or 2 back with a 1jz twin garretts 30psi and over 600hp

they did a fare bit of development and found the best head of all was the 2jzge it has bigger valves and bigger ports and bolts straight on ...yeeha!

on top of that they played with some aftermarket cams too and found the best ones for racing were the std atmo 2j ones

[petespipes]

fits in with what I heard re 2jzge engines getting good power being turboed [not first hand info]

[Norbie]

1JZ-GTE and 2JZ-GTE heads are pretty restrictive on the exhaust side; this is done to keep gas velocity high and thus spool the turbos as quickly as possible, which was obviously a high priority when those engines were designed. It makes sense the atmo versions flow better since they have nothing to spool up.

[ReQuieM]

Ok so this is all heresay and speculation, But I've heard a couple of times that the 1.5jz is a 'torque monster' could the differnce be similar to the difference between the 2-4valve windsor heads? One for torque, one for hp? I realise that the number of valves makes more of a differnce then a small amount of flow, and also the design as well. But it is a real world similarity that i could draw on. Could also explain why the tuner that 1jz747 see's uses the 1jz head as a preffered basis. 1jz747: is the work shop that recommends the 1jz head specialise in drag racing? To me torque is goooood

[ReQuieM]

Whoa hey, i just noticed how old this thread was. Sorry 'bout dredgin it up!

[crownman]

Hi fellas, Can somebody tell me the cc"s of a standard 2JZGTE and 2JZGE combustion chambers ?????????? PLEASE -- I have cc'd a 1JZGTE chamber 45 cc's. As a sports sedan racecar I am not allowed more than 2,5ltr.multi valve turbo. Maybe I would be better off with a 2J head on my 1J block without expensive headwork.?????????? Regards crownman.0412 711 481.

[Mr DOHC]

the 3l motor is just a torque monster naturally, i'd say its the extra 500cc and just a generally good bore/stroke combo that makes it so good