Big port head flow tuning

[Diskovod]

Hello.
I'm having a '84 JDM Celica AA63 (coupe) with big port MAP-sensored 4AGE.
It has miled 160k kms and now it's time to have a good rebuild and free some horses. I want to find some hidden horses in my head, so please, help me
Port enlargement is defo not what the big port head needs. Did anybody have ported or flow tuned the big port head? What have you done there, except removing some marks of factory castings and meeting parts to each other?
I know that polishing itself doesn't get any result except the fuel flows on the walls and the result is lean mixture and crappy power.

[oldeskewltoy]

A few weeks back I did a bit of porting... MILD porting!. Here is the work I just did....

Raw, unworked ports on left........................................................ blended ports on the right








Now besides cleaning and blending around the valve seat, the exhaust ports are usually rather rough. Here again, blending is the call.
This time finished ports are below raw ones




Finally, for a street port, blending and doing mild shaping to the exhaust port as it approaches the manifold. Not BIGGER, but shped to allow the flow out as easy a path as possible


The above photos are of one exhaust port, each view focuses on one valve.

*IF* you are unsure of what to do... doing nothing is superior to a bad porting job

[eight-six]

OST - I have basically done the same as your self with a spare head, mainly just for the sake of experience more than anything else. Would post some photo's but I am struggling taking them with my Iphone.

I have focused on the bowls and cleaned up / smoothed the various lips etc. I have also run down the ports cleaned up the casting marks and applied the appropriate finish to the ports.

Out of interested have you noticed depressed areas in the ports just before the valve (seems to be more prominent on the intake side)? Just wondering if this has an effect or if removing the various sharp edges and excess material and smoothing the bowl out will be suffcient and aid flow?

[oldeskewltoy]

eight-six Wrote:Out of interested have you noticed depressed areas in the ports just before the valve (seems to be more prominent on the intake side)?

Just wondering if this has an effect or if removing the various sharp edges and excess material and smoothing the bowl out will be suffcient and aid flow?

Actually what I believe you are talking about is a ridge that is created because the valve seat isn't perfectly centered. The valve seat needs to be ground so the seat and port wall do not have a ridge.

When doing streetport work... remember flow direction, some ugly things need more work than others

[totta Crolla]

Some nice work there OST, could you tell me what tools you used to do the grinding ?

[oldeskewltoy]

totta Crolla Wrote:Some nice work there OST, could you tell me what tools you used to do the grinding ?

Give away my secrets





Dremel, and flex shaft






1) alum oxide grinding stones for removal of material(coarse),



2) Sanding bands for lighter removal, and 1st, and 2nd step smoothing after stone use. Available in coarse, medium, and fine grit(60, 120, 240) I don't use the 240,



3) Abrasive "puffs" no not POOFS, puffs. I prefer medium grit, but medium is only available with a fine.


HOURS of knowing what I can do... and what I cant. Knowing that I can seriously screw-up if not done correctly. I'm talking MORE than hitting a cooling jacket...

[oldeskewltoy]

These photos are all thanks to our Aussie friends down unda!

[totta Crolla]

*IF* you are unsure of what to do... doing nothing is superior to a bad porting job

Thanks Dan, duly noted :wink:

[oldeskewltoy]

Hopefully this explains it all

example #1) this is an intake port. As such the red area is the REALLY bad area because it restricts flow into the cylinder. The yellow area isn't as significant, but a proper streetport blends the entire area.

example #2) this is now an exhaust port as such the yellow area is the really bad area, because it restricts flow out of the cylinder. the red area isn't as significant, but a proper streetport blends the entire area

[Diskovod]

Yeah, man! Thanks for points!

I'm thinking about removing these boundaries also as there are no ones on Formula Atlantic heads...


and then slice some mms from the bottom of the head to have 11:1 compression...