Head Flow/porting

[Boostage]

This is regarding the 1jz head. clearly cylinders 2 and 5 are the smallest ones on the exhaust side of the head. what kind of difference do you think opening up the ports on just the exhaust side and port matching 2 and 5 to the new size would affect. power range, and overall output?

Couple things I am aware of.

(1)you cant make the ports bigger than the manifold they are dumping into the reason the head ports are smaller than the manifold is so that the exhaust gases will have less ability to reverse back into the cylinder.

(2)because the 1jz is a short stroke motor (not super torquey) you cant go too large inside the ports because you still have to try to maintain good port velocity to maintain good spool up.

I might be wrong on this but the real restriction on the 1jz head is mainly the exhaust side ports. and allowing more flow on that side so that the motor can expell more burnt exhaust gas per exhaust stroke, so there is more room for fresh air per intake stroke.

So my plan is to have all the exhaust ports ported out just a bit(probably gasket matched) on all 6. but leave the intake side stock. do you think this would extend the power range? or do you think the intake side HAS to be done also?

 

[tissimo]

I would do the intake side if you're doing it.. More so if you're going to get cams and rev it up higher.. more flow is always good

You can really open them up that much compaired to the others, Honestly I dont know how much of a difference in flow there are between 2 and 5 and the others. Get a flow test before you port to see the difference.. Ask your porter to try to even them out.

 

[Boostage]

I would do the intake side if you're doing it.. More so if you're going to get cams and rev it up higher.. more flow is always good

You can really open them up that much compaired to the others, Honestly I dont know how much of a difference in flow there are between 2 and 5 and the others. Get a flow test before you port to see the difference.. Ask your porter to try to even them out.

Justin I did some reading.. ALOT of reading and this is what I found out. on a street turbo car you dont want to polish the intake side, it is rough for a reason and needs to stay rough to promote proper fuel atomization. Why? Your fuel injectors work in milliseconds. Ever wonder in 8 milliseconds how many degrees your crankshaft has turned if it is operating at 9000rpm? Your crankshaft has turned approx. 450deg. That means your injector has to start firing fuel way before the intake valve has even opened. Most of the fuel does vaporize as it hits the back of the valve but the rest of the fuel that doesnt vaporize ends up on the walls, short sides and around the valve area until the valve finally opens and draws in the air fuel mixture. Keeping the walls rough in theory helps break up the fuel before it enters the combustion chamber. Atomized fuel burn better resulting in more horsepower and better fuel economy.

However the exhaust side should be ported and polished to a mirror finish. but CAREFULLY because too big and port velocity is compromised. this brings me back to RIC's thread from a few days ago. a 2jz head on a 1jz block is more than likely a bad idea.( for a street car) as the intake/exhaust ports and manifold volume would be too large to fill. but would probably make a Ton of peak hp. but at the expense of even less low end Tq and response.

I'm taking one for the team. I already got a quote on a before and after flow test of my 1jz head, I will see how it flows bone stock, and then a second flow test with all exhaust ports lightly ported,port matched and polished down. this should be done in about 3 weeks.

 

[Rich]

So my plan is to have all the exhaust ports ported out just a bit(probably gasket matched) on all 6.

If I remember correctly the exhaust gasket holes are smaller than the ports.
I was going to port match mine, but ended up only doing the intake side because the exhaust gasket was the bottle neck, not the ports.

I agree with your porting theory above by the way, I think it is correct. Also the rough inside of the intake creates a swirl which helps achieving a better mixture, more homogeneous. Polishing the intake deletes this effect.

 

[tissimo]

yea dont smooth it out, you will need it rough, but I would open it up slightly..

 

[Boostage]

If I remember correctly the exhaust gasket holes are smaller than the ports.
I was going to port match mine, but ended up only doing the intake side because the exhaust gasket was the bottle neck, not the ports.

Dremel..

 

[drewgo]

yea dont smooth it out, you will need it rough, but I would open it up slightly..

Yo that's sound kinda Kinky....:naughty:

 

[Rich]

Dremel..

Yeah, but was it the gasket or the ports which are smallest? Can you confirm the gasket is the smallest?

 

[Boostage]

Yeah, but was it the gasket or the ports which are smallest? Can you confirm the gasket is the smallest?

Im not near my motor but the gasket cant be smaller than the port, it has to be equal or slightly larger. smaller would create reversion. if it is equal sized, then a dremel should fix that.