mr/griffin

i see people post on here asking questions alot, some get help they want and some get the "search is your freind" line

i have been just searching for a reliable 400-430 hp using toyota oe parts stock or modded plus

large fmic
msd
custom exaust

i am searching for people who have pushed the c15b to its limits and if anyone had one for sale

anyway my main point was i keep hearing mixed replies on exhuast diameter so i am just gonna go with this guy from a supra forum bcus he posted number and junk


I'm currently building a bullet proof 1JZ, and I ran into the following problem;

Maybe there is someone who actually put dual valvesprings in a 1jz head, and 1mm oversized 2jz valves, (because this is not a 'drop in') could help...

So first of all 2jz valves are different. The 1jz exhaust valve is stock 30 mm while the 2jz exhaust valve is 29 mm. The 1jz intake valve is 32 mm while the 2jz intake valve is 33,6 mm. So I upgraded to 1 mm Oversized 2jz valves from supertech. This makes my 1jz have an intake valve of 34,6 mm and exhaust stays 30 mm. Anyone who says 2jz valves are a drop in, obviously don't know where they talking about. Of course, it can be done but it takes a lot of work to machine the head.
Thought I share this with other people, becouse I couldn't find anyone on the web who has actually done this personally...

I have some supertech dual valvesprings, wich are actually designed for the 2jz. But the inner valvespring (the little one) doesn't seem to fit the 1jz head.
The problem is that the area just around the valveguides is not machined, it's cast alu. So the inner valve spring doesn't lay flat on the head. I looked at some pictures from a 2jz head and there the surrounding area is machined. Now my question is, if anyone has an 2jz head laying arround, can measure up the distance from the top of the valveguide to the surface just next to the valveguide. Not the surface where the original spring is located, but closer to the valveguide. Here's a pic of what I mean.

The pic is a little unclear but you know what I mean

Mike552

Wow, that's so odd.

The 1JZ is 33.6mm intake / 29mm exhaust
The 2JZ is 32.0mm intake / 30mm exhaust

Now, I wonder if by "2JZ" they mean FTE or FE? This would be the next thing to check, if the FTE and FE have the same valve diameters. They could very well be different...

Also, for any engineers out there, is there a way to calculate normative airflow between the two above heads? I'd like to see what results in more flow. I'd assume that you want more exhaust flow for a turbo application in order for it to spool at lower rpms. Unless you're running full boost, I'd think this is the way to go, right? (I.e, rather have bigger exhaust valves than bigger intake valves)

MDSC

iTrader: (3)

i though i was going to see flow bench numbers in this thread.

good2go

iTrader: (6)

+1

I don't see how this has rendered the "headflow debate finally over"

Launch1

+1............

charley240

iTrader: (6)

+1
I figured same thing

kdick91

Valve diameters are only a tiny fraction of what goes into head flow. Just to name a few details, you also have to consider the shape and size of the port, how clean it is (polished/cast), how air flows through the port, and the behavior of airflow when the valve is at different lifts. Even then a flow bench doesn't provide information on how the head will flow with whatever intake manifold you use. Don't get me wrong though, flow benches usually help me decide what I'm buying Good job on finding these details though!

mr/griffin

well if i am not mistaking bench results have been posted some where on here i cant remember where

Klaus

iTrader: (1)

Crickey this debate was over a LONG time ago.

mr/griffin

part of the debate was valve diameter falsely quoted, it just to clear up misconceptions

MKIVS374

iTrader: (2)

Just cause the valves are smaller or larger is irrelevant.

soardrft

iTrader: (8)

My 1jz head just came back from the machine shop. I put 2jz titanium valve springs and 2jz cams so it can be done.

While things were apart the 2jz springs were a tad less than a mm larger, but not enough to worry. As for the width they were a straight drop.

Now I'm no gear head, but I trust the machine shop that has done the work. They said I did not need modification, however I decided to mess with the ports for more power and no price difference so might a well right?

Now for pricing. Without my hookup I would have paid $250. Not bad if you have the head out.
As for results well um yea. Once I stop buying things for this car maybe I will strap it to the dyno. Sorry no bench test that I know of, but I never asked the machine shop. BUT my point is it can be done.