OST Cylinder Head Porting Services

[oldeskewltoy]

OST-050: the Black Limited head half way through....

[flymat88]

Hello Oldeskewltoy,
I have read many threads all around the 4A-GE- engine and there are only a few people, spreading "good information" and you are definately one of them.
Thanks for sharing information and pictures about the head-work. I am doing it right now on my 16V bigport and I have some questions.

The most spreaded opinion in forums is, that the exhaust port is not optimal designed. The inner radius is to narrow or the turn is too sharp!?
Is there a benefit to widen up the sharp bend, to make it more smooth and widing up the port diameter in that area?
My feeling would say YES, because the pressure and velocity of the gases just leaving the cylinder, is hight?! So at the exhaust side BIGGER is BETTER?
(Different story at the intake-port, where you want to have velocity, achieving it by reducing the diameter...).
Do you have some advice here and maybe some numbers?

All this thoughts in respect to the these engine specs:
252 - 262 EX cams
8.5 - 9 mm lift
free-flow exhaust and custom header

Thanks for your reply!

[oldeskewltoy]

Hello Oldeskewltoy,
I have read many threads all around the 4A-GE- engine and there are only a few people, spreading "good information" and you are definately one of them.
Thanks for sharing information and pictures about the head-work. I am doing it right now on my 16V bigport and I have some questions.

The most spreaded opinion in forums is, that the exhaust port is not optimal designed. The inner radius is to narrow or the turn is too sharp!?
Is there a benefit to widen up the sharp bend, to make it more smooth and widing up the port diameter in that area?
My feeling would say YES, because the pressure and velocity of the gases just leaving the cylinder, is hight?! So at the exhaust side BIGGER is BETTER?
(Different story at the intake-port, where you want to have velocity, achieving it by reducing the diameter...).
Do you have some advice here and maybe some numbers?

All this thoughts in respect to the these engine specs:
252 - 262 EX cams
8.5 - 9 mm lift
free-flow exhaust and custom header

Thanks for your reply!

As to the exhaust side.....


negative space.....

It just doesn't get any simpler - view the exhaust port on the left as it goes from beastly to beauty........

positive space....





not opinion... flowbench tested many times now....




on to intake... while "velocity" is important, the velocity of WHAT is more important. Currently the velocity @ the valve seat is high because the valve is significantly larger then the seat opening. But because the opening is small, it doesn't create a great deal of bowl, or port velocity, as say a hole that would be larger. The current accepted "performance" ratio range is 85%-90% of the valves diameter is the throat of the seat. The 4AG seat sits @ about 83% - some room to grow. By carefully blending the seats, short radius, and the bowls into the port, more volume and more velocity can be generated.

[oldeskewltoy]

most recently a complete restoration/rebuild....




more to come....

[oldeskewltoy]

Largeport intake "under construction"

[flymat88]

That looks absolutely fantastic!

I am not sure about the way to go...
At the moment, I would like to do the following:
I did cylinder head porting and combustion chamber deburring on my Bigport-head. Finally measured the chamber volume - all equal now.
I want to install some CatCams with IN 267° / OUT 262° or Poncams.
Full standalone ECU with Rev-Limit around 8.000-8.200 RPM, no turbo.

And here come my doubts:
I need new valves. I considered oversize valves, for example IN +1,5mm / Ex +2,0mm AND
I would love to have the Silvertop, or Blacktop ITB´s.
But with my Bigport-Head and bigger valves, I am not sure if the performance is even worse as with the standard valves, T-VIS and plenum...
I can´t image how the alterations may affect the mid-range performance...any suggestions for the way to go??
I guess the small-port head would be better?

Thank you in advance for your thoughts!
Have a nice week.

[oldeskewltoy]

That looks absolutely fantastic!

I am not sure about the way to go...
At the moment, I would like to do the following:
I did cylinder head porting and combustion chamber deburring on my Bigport-head. Finally measured the chamber volume - all equal now.
I want to install some CatCams with IN 267° / OUT 262° or Poncams.
Full standalone ECU with Rev-Limit around 8.000-8.200 RPM, no turbo.

And here come my doubts:
I need new valves. I considered oversize valves, for example IN +1,5mm / Ex +2,0mm AND
I would love to have the Silvertop, or Blacktop ITB´s.
But with my Bigport-Head and bigger valves, I am not sure if the performance is even worse as with the standard valves, T-VIS and plenum...
I can´t image how the alterations may affect the mid-range performance...any suggestions for the way to go??
I guess the small-port head would be better?

Thank you in advance for your thoughts
Have a nice week.

apologies for not getting back in touch sooner......

Hmmmm, those Cat cams should twist a bit higher then 8200, their (Cat cams) 252 will peak there (8200), so their 267/262 is likely to twist to about 8700-9000 depending on cam timing settings....

Why do you need new valves?? Are the margins too thin? Stems too thin? Bent? For a 1.6 4 valve head the 4AG valves are decently sized - I'm still using them, and I'm making 140 whp. The 32/27.5 valve combination is best suited for either a race 1.6, a stroked 1.6(5AGE) OR a 1.8 (7AGE).

While the bigport head isn't ideal, the bigger problem for making power is with the TVIS manifold. The TVIS manifold seems to be a problem as you approach 150-160hp (135-140whp), so if you are building something over 160hp, you will want ITBs. My recommendation would be Silvertop throttles - slightly smaller "helps" with intake velocity.



What is the rest of your build like? Pistons? Rods? Assume crank is stock unit?


What are the plans for this build? Drifter? Track car? Mountain carver?

[oldeskewltoy]

I do other heads too... this one, a 99-01 Miata 1.8




and then showing that port finished....





as always... more to come.......

[oldeskewltoy]

just an update.....

[oldeskewltoy]

Big valve heads too

[Ita Racer]

Looking to buy a 1600 4AG head
Do you know of one for sale?

[oldeskewltoy]

Looking to buy a 1600 4AG head
Do you know of one for sale?

I have a few 4age heads. send me an email and I'll be happy to discuss it.

oldeskewltoy@yahoo.com - title it "ita racer"

[oldeskewltoy]

Some recent doings........ 3 different heads... top is a silvertop 20V, middle in a 3TC intake manifold, and bottom is a 1GGE








Tis the season... being March, now's the time to get in touch about getting your head done...... contact me.