3k Big Port Head

[Lukey]

I was just wondering how to tell if my 3k has a big port head can some one pleese have one because i think i have two :D thanks heaps Lukey

[Felix]

If it has a round welschplug on the back of it, it is a bigport. If it has a plate with 4 bolts it isn't.

 

Bigport heads are overrated, unless you want to drop the compression of a dished piston motor for forced induction.

Edited August 30, 2007 by Felix

[Lukey]

thanks bud :D

[camerondownunder88]

What Felix said a welsh plug on the back. Off top of my head I think it is 45mm Diameter.

 

Also over rated. If you look out for them they are easy to get and the original big ports the port is to big for the valve so if you have one you can/should run the better later KE70/55/late30 head valves they are a bit bigger and later valve seals then it will be better.

 

As I belive Toyota went to smaller ports to increase torque of the motor in the KE30 as it got heavier and needed it. So higher velocity air flow from smaller ports will give more torque. So the best head to get is a 3K-H one they are stock high compression and some were mild ports. Not the normal small nor where they large like a small port but they have a better matched port to valve size and 3K-H was shaved more factory to bump up compression.

 

But a big port if you have it can still be a fast way to get more air into the K motor for mods eg SC or turbo.

 

Cameron

[old corolla bloke]

[ if you do change the head don't forget to port match the manifold .....smal port manifold runing into bigport head loses gas veloctiy and causes port wetting......no not that sort of wetting.ttt

 

port wetting is where the atomised fuel condenses into bigger droplets at low engine speed this shows up as a soogy engine response and some times misfires at light throttle cruising.

 

its not as drstic as going the other way of big manifold small ports but is a pain to track down

 

cheers

 

brian

[snot35]

So what sort of compression does the 3K-H have? I've been told that it has higher compression. Any ideas of combustion chamber size?

 

Thanks

[camerondownunder88]

Hi,

Out of interest what would happen if you ran a big port manifold on a small port head?

 

Cameron

[Taz_Rx]

what happens if you drive a truck down a drive way that starts 3m wide and ends up 2m wide!! :lol:

 

On a more serious note, you'd end up with a pocket of turbulent air at the end of the runners. :cool:

[camerondownunder88]

I figured it would make turbulent air. But this can't be to bad right mix the fuel better?

 

As I was more thinking the space of exposed cylinder head where the big port manifold would not meet up properly when bolted up fuel could pool there and when you jump off the accelerator it would get sucked in and your motor would run away for a second? Does this happen?

 

Cheers

Cameron

[irokin]

what happens if you drive a truck down a drive way that starts 3m wide and ends up 2m wide!! :lol:

 

On a more serious note, you'd end up with a pocket of turbulent air at the end of the runners. :cool:

 

Truck != air and you cannot compare the two as such.

 

 

I have run a bigport manifold on a small port head. Made no difference. Definitely no engine runaways!

[camerondownunder88]

HI,

No run aways that is good. As I have a twin carby big port mani on a 5K small port now not running yet so it just occurred to me AHAHA it might stuff up. But I will see how it goes I guess.

 

Cheers

Cameron

[old corolla bloke]

Truck != air and you cannot compare the two as such.

I have run a bigport manifold on a small port head. Made no difference. Definitely no engine runaways!

 

but could it have been better if you had port matched it.?

 

whilst in your case it felt as though there was no difference , it should be noted there is an adavantage in port matching all production engines.

 

it will contribute to smoother running and in some cases improved engine performanec.

 

yes you can do it...will you notice a decrease in perfomance. most likely not however in many cases you will notice the engine does not run as smoothly and there is a flat spot on acceleration from light throttle cruising

 

a case in point is to put a single DCOE onto a manifold that was designed around a ke20 head{usually bigport} and then put it all on a 4k.std head. it will run like a dog until port matched then in 99% of cases be ok.

 

the engine will not run away

 

brian

[camerondownunder88]

Hi,

Well performance if it is minor i will give it ago I guess. I have 2 big port heads at home but they will de-compress the 5K in my sprinter so I wont use them yet...

 

But I will try using my big port twin carby mani and let you know how it goes. if it goes bad I will use my twin carby small port one instead.

 

Thanks for info fellas.

 

Cameron

Edited September 2, 2007 by camerondownunder88