4age bigport head: port & polish

[BenR]

I would not be tempted to follow the N2 specifications, they are out dated and old theory. On the bigport heads i high advise NOT touching the port dimentions at the mouth of the port, it is already too large by a long way. Concentrate on the area from the valve seat to 0.5" infront of the valve guide..........THIS is where you will gain all your flow, anywhere infront of that will make no difference.

If you want to make them smaller then you will have to experiement with liquid aluminium since welding like i do is a very very expensive thing to do, there are many parts to do before you can use a head that has been welded. But also, you will have to spend alot of time on the flow bench and on the dyno to test the effects of making a port smaller. My advice would be to leave the port dimentions alone, you will see no gains by trying to make things smaller or bigger..........you will only cause yourself trouble in the long run.

And because you are running ITB's, you can run much wilder cam, i would be looking at 275-280 at least or you will be wasting the RPM potential of the 4age.

For the savenging, its all about exhuast header design. This depends on the head flow rates, valve sizes, port lengths and dimentions, cam specs aswell as installed cam timing, compression ratios, induction methods etc. Then you can calculate the exhaust header primarcy and secondary lengths, bore sizes, stepdowns etc etc. It is complex to get right, so most people will settle for a design that will work nicely, rather than perfectly. I would buy one of the already available manifolds unless you have £600-1000 to play with for headers.

Do not run a cat, run a de-cat pipe.

Os7213 Wrote:Haha nice thank alot!
Lol sorry for the maths think it was late when my math have been done

For rod stretch since im using OE con-rod from a Ae11 blacktop i think ill be good cause my engine will not rev 12000 so

For the splitter in front of valve guide you are totally right...my bad...havent think about the round diameter of the valve guide ive just see something in the port!!! Thank for the advise

I think the head will be perfect, im using the 4agze since i want "middle" power what the blue-top head cant provide... The only thing i need to think about is the perfect dimension of the port for "middle" power and high rpm almost near 9000rpm or more since my cam peak power is near 7500. Do you think this kind of combinason is possible!?Ive also think about a 264deg ext cam since im running itbs who good on high rpm. Ill trying to check the port size by begin with the N2 port size specs..I already know they are too big for my application so i need to make them smaller but how can i have the best port dimension?! Ill find something between the dimension of the stock port and the N2 specs I think it can work! Since i dont have to change port configuration i have all my time to check these meusures.If you have tips dont hesitate!!

For the scavenging effect i have only begin to read about it... The only thing i know is the exhaust manifold have a restricted volume but in fact that help!! The thing you need to check is for too much rapid restriction if i have understand right...Dont you think a simple porting or the headers can help a lot? I only know the cat-bak intern desing play an important role so a test pipe its not the way to go and since i dont want to "reshape" the interior of a cat i think i will just install one..Where im lost is the part of the exhaust line leight im not sure wich type of headers i can use, i suppose a nice smooth curved one no high rise... And the total leight of the exhaust im not sure i dont find proper infos about it...
Thank a lot to help a guy who want to lear and have poor english skills

Thank a lot in advance
Ugo

[Os7213]

Thank a lot for all you advises everyones!

BenR im now on the porting of my blue-top head(Since i have a blue-top for tests and a red-top to run the setup). What im gonna do its a porting match for the mounth of the port and ill do nice ports from the valve seat to the valve guide and reshape the splitter. That gonna be my test and ill post up some pics of the work!

For the cams 272deg 9mm that i already have i think they could work pretty well with the red-top head ive chosse them for a nice and smooth powerband following the stock one but at higher rpms...And since i dont have money to spend on others cams ill keep them! But yeah the 280deg 9mm lift are very interessting. The idea of putting a 264deg cam was only to push the limit of the powerband to higher rpm but i really want to keep my middle power!

And for the cat pipe ill take you advise and put it on dyno to compare!

Thank
Ugo

[BenR]

No problem.

Remember, port matching isnt everything. If the manifold is smaller than the port onthe inlet side, then its typically fine, it doesnt have to be a perfect match as too big.....as they say.....is too big.

Have fun

[Os7213]

Hi guys just to continue the thread and for more advise during the job i post some pics of some parts during the work. Today i have complete the shape and ill post pics when the finish will be okay. Oh almost forgot just for info someone told me to use a 400 grade sandpaper for the finish but im affraid that become too shinny someone have an advise?









Note these pics are during the work but I think the final result is pretty good Ill post pics in no time but since its my first porting job please be smart guys Oh btw this is my blue-top head not the red-one.

Thank
Ugo

[BenR]

The basics are looking good! you will notice a difference there, just make sure it had a good valve job now.

80 grit finish is all you need......400 is a waste of time.

[Os7213]

Hi guys.
Thank for the advises BenR
Here the final result of the shape before the finish:







Oh btw if the port doesn't look simetrical i think its the finish who give this effect!
So if i use a 80 grid paper everything sould be ok!I was affraid of a too shinny finish. Nice
The valves should arrive soon and Ill make a 3angles valves job.

Now i just need to do the 3 others inlets ports and the exhaust one

Thank a lot
Ugo

[BenR]

oh, you've gone too far........it was better in the first set of pics.

The ports are nor meant to be symmetrical.

80 grit is all you need.

[Os7213]

Ah! unfortunately I have made a mistake but now i see the error!
I was trying to put the deck height more low and leave room for air but i hope that gonna be okay. I will not repeat the mistake!

Thank
Ugo

[BenR]

the deck height?

The first pic sets had a nice shape and not too much done..........remember, a good flow specialist gains maximum flow with minimum material removal.

[Os7213]

Yes im sorry ive call it a deck since im not very good in english i mean the entry just before the 2 ports is too low! I now see the error like a 45ft truck hitting me... That was my second question is it true you only need small material removing lol Yes cause the new ports ive made take me almost no time to do and i clearly see the difference now The port are more open ,with less material removal,and have a round shape only the valve seat need to be matched and material remove on wall and splitter, i think i have now a perfect idea of the shape of the ports thank a lot!

Im not sure ill be able to use the head with a port like that.. but that what it cost to learn!

Btw is this normal sometimes the valves seat are already bigger than the head..i mean to match them up cause on 2 valves seat on the head i cant remove any material to match up cause some material miss near the valve seat and create a little gap...

But anyway ill just learn with this one, just for fun prepare it like this, blot it on the engine and see what it does! Because im really not sure i can use a port like this. For this one i have made a test from a Honda engine who have like i did big open ports with the bottom of the ports very low...since i know nothing and need to experiement its my first try but today i have work on the second port and i now understand!

When i will finish ill send you a pic to show if i understand the thing!

Thank a lot
Ugo