OST-013: Massaging a virgin ;)

[oldeskewltoy]

Project D Wrote:port matching with the exhaust gasket, clean the mismatched seat and removed all the casting I presume

Look carefully... is it gasket matched? If it is, why is there not a perfect match???

Part of what is difficult to see (I tried) is deep in the port, just before the bowl, the port wall has been tapered. The taper is begun back in the bowl, and is brought forward into the port.

In the left view/bottom, if you look below the guide(roof of port), you see no shadow lines, now look at the right hand view same area. This is a key area because the flow is already in transition from vertical flow to horizontal flow when it "hits" the intruding port wall and is forced to merge with the gasses coming from the 2nd valve(out of view). By tapering the port to the bowl, the merge is far smoother, the actual merge point is larger, and occurs mostly AFTER the transition point from vertical to horizontal flow.

[Project D]

Well, when I said it match with the gasket i'm talking about the concentricity.
On your picture, the left side of the port look like further of the gasket than the right side.
But after a bit of reflection I believe it's more about the angle of the picture

I will hijack a little bit your thread.
This is my own head that I'm working on and I want to know what you think about it


Remember that the valve guides will be replaced by Supertech (200000 km on the clock so not really like brand new ^^)

[oldeskewltoy]

Project D Wrote:I will hijack a little bit your thread.
This is my own head that I'm working on and I want to know what you think about it



Remember that the valve guides will be replaced by Supertech (200000 km on the clock so not really like brand new ^^)

imho.... I'd recommend a bit of taper where the port meets the bowl - I believe I see some dark shadows back there.

I like what you did to the port floors....


(Loynings exhaust port for my engine)

[oldeskewltoy]

from the proverbially other forum Wrote:It's as gasket matched as i'd feel comfortable doing.

fair enough... there can be flaws in the gasket, anything in the airstream will reduce power SUBSTANTIALLY, infact it would be far better for performance to leave the port untouched, then have a gasket interfere in the flow.

A point to all to remember, when this head, or any other porting job is mounted, the exhaust gasket is most often installed with the engine in the car. This means unless you have a small amount of foil acting as a dowel pin (to center the gasket on the studs/bolt holes) the gasket will hang a bit. A gasket match to the edge on the port will assuredly hang and intrude on the airflow. And of course.... the gasket will then interfere @ the port roof, where the highest flow occurs


Btw... the header flange in the airstream is just as bad... and it should be checked and ported if need be to make sure the flow is smooth

[oldeskewltoy]

Since we are off thread some....



Above is the exhaust ports to OST-007. Apologies for some blurry views The reason the far right view is possible is because the client had a lower timing pulley problem, and he decided to do a complete inspection and so the head was removed.

[Project D]

Thanks for the advise :wink:
When you say taper, you mean this ?

Tec Art's 230hp head (I have the full article if you want, but it's in Japanese)

Personally i go to 35mm for the exhaust port but I will use larger exhaust gasket (38mm) and the flange of my Cusco header is 37mm so no problem I believe

[oldeskewltoy]

Project D Wrote:Thanks for the advise :wink:
When you say taper, you mean this ?

I blend these walls out(blue arrows) that is where I'm saying taper. taper the outer walls of the port, to the outer walls of the bowl.

[oldeskewltoy]

oldeskewltoy Wrote:Time to work the exhaust side....



2 down... 2 to go....

Any guesses as to which are which

Exhaust ports now complete




Next stop Loynings - for a 3 angle, and matching the valves to the seats

[oldeskewltoy]

Project D Wrote:When you say taper, you mean this ?


Tec Art's 230hp head

Does anyone have an idea why I don't mean that?

What does a 200+hp head have that none of my heads has?

Why is the above taper not as effective in one of my heads??

(one answer covers all questions)

[Project D]

Quote:Does anyone have an idea why I don't mean that?

What does a 200+hp head have that none of my heads has?

Why is the above taper not as effective in one of my heads??

(one answer covers all questions)

Basically not the same goal (?)
if it's not the right answer I hope you will enlighten us with the right one (cause I want to know )

I have another question for you (or loynings)
Why many tuner do this on guide bosses?

(This one is made by Toda)

PS: If this is to much off topic tell me :wink: