how should a 4g63 ported head look exhaust side for a holset turbo?

[dsm-onster]

Good thing it's a theory.... useful for carbureted engines and not EFI. Dynos proved that an extremely rough surface actually increases Hp on carbureted engines. It's thought to increase fuel atomization. No dyno charts ever proved that a rough surface is beneficial with EFI, which already atomizes fuel 100-1000X over carbs.

The dimples in the golfball create resistance and turbulence, but due to the backspin it acts as an airfoil and also gives you hangtime.

The air/fuel mixture is the same air that will be "sticking" to the rough surface, which is nothing more than a thick (slow-moving) boundary layer on a rough surface, and a thin (fast-moving) layer on a mirror surface.

By roughing the port walls, in effect, now you have a smaller port, because the slow moving particles in the boundry layer take up space. It makes a new surface that is super slick, but if you can make the actual port surface superslick, then there's no need for you to have the air do it. Since the port has a certain roughness, smoothing it out and polishing it takes away or minimizes the boundry layer that wa created inthe first place and now you have more "effective" port volume. Is this correct?

 

[pj91gsx]

Do you mean these humps? I'm porting my head and I'm not sure what to do with these. . .

Im thinking maybe you made those humps from porting that area before it.

 

[dsm-onster]

No they are on my other unported head (I have a spare in case I really screw up ).

 

[pj91gsx]

No they are on my other unported head (I have a spare in case I really screw up ).

1 spare is always good, I have 4 heads, so I have 4 tries to get one the way I want it. I never noticed those bumps for the whole time I have been porting and working on head for the last 6 months. It look like I took them out. The first head, I went all out on the exhaust, I copied all motor mike so I will definately need to finish it up and sell it to a NA owner. Your head can use a good port match. Look at the difference in my heads and yours for the match.

 

[dsm-onster]

I know. . . I just spend an hour or so port matching. Still need to polish it up:

 

[dsm-onster]

Also, I noticed that the evo3 exhaust manifold and 1g exhaust manifod have a "hill" in their ports where they butt up to the head. Portmatching th head makes the transition gradually fall then more quickly rise as you start to get into the exhaust runner. If you grab a spare you will se what I mean. I plan on oprting that "hill" to a more gradual rise. If it IS meant to increase velocity, then I'm sure the more gradual change will be beneficial as a well build intake manifold has runners that more gradually shrink in diameter.

 

[Freerevving]

By roughing the port walls, in effect, now you have a smaller port, because the slow moving particles in the boundry layer take up space. It makes a new surface that is super slick, but if you can make the actual port surface superslick, then there's no need for you to have the air do it. Since the port has a certain roughness, smoothing it out and polishing it takes away or minimizes the boundry layer that wa created inthe first place and now you have more "effective" port volume. Is this correct?

correct in my book.

The problem with aero and hydrodynamics is that a lot of it is theory and not completely understood to this day... some people will embellish the theories until they don't hold true to their principles.

It is more likely that the rough surface creates a thicker boundary layer that also affects the surrounding flow... much like a golfball affects the surrounding flow, to create lift, when backspinning. They have proved this in wind tunnels where the smoothest surfaces had the smallest drag coefficient. This would also be the reason that an extremely rough surface would better atomize the fuel with a carbureter.

I once knew of an owner of a CNC aircraft machining company (excellent work) who races as a hobby. He was the first one to point out to me that rough ports were only useful with carburetion. He showed small power increases across the whole band, with smoother intake ports... even when done with primitive fuel injection.
Just remembered the name of his "hobby" company... "Scooter Racing". He would port a head for you at an unbelievable price (very inexpensive)... but there used to be a 3 month wait.
Just informed he retired from engine building, that sucks

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well now that I work in a CNC machine/fabrication shop (used to be manual), maybe I can figure out some of his techniques... He might even have time to talk on the phone if I can find a number. I think his first name is Brad... maybe Gary

 

[pj91gsx]

I know. . . I just spend an hour or so port matching. Still need to polish it up:

nicely done. Did you narrow the dividers a little as well?

 

[dsm-onster]

Thanx. I did a VERY little narrowing of the port dividers. Looks like you've done a good job too. Of course, I jsut used the 'cut and feel' technique .

Thanx too Freerevving. This is reassuring for my intake work. I was unsure about what to do with the intake ports. Now I'm pretty solid.

 

[pj91gsx]

Thanx. I did a VERY little narrowing of the port dividers. Looks like you've done a good job too. Of course, I jsut used the 'cut and feel' technique .

Thanx too Freerevving. This is reassuring for my intake work. I was unsure about what to do with the intake ports. Now I'm pretty solid.

Are you taking out the humps in after the guides?

 

[dsm-onster]

I don't know. Id rather make that portion appear like an airplane cockpit. The valve stem and guid being the beginning of the cockpit, then have that hump let the air smoothly come back together. I don't want a dead or turbulent spot there behind the valve stem. . . . But you have the rest of the length of the valve stem in the middle of the port any way. So I havn't decided. I do see all the race prepped heads have the guides and humps groud down smooth.

 

[Freerevving]

I don't know. Id rather make that portion appear like an airplane cockpit. The valve stem and guid being the beginning of the cockpit, then have that hump let the air smoothly come back together. I don't want a dead or turbulent spot there behind the valve stem. . . . But you have the rest of the length of the valve stem in the middle of the port any way. So I havn't decided. I do see all the race prepped heads have the guides and humps groud down smooth.

I just get rid of the aluminum around the guides on the exhaust side... in terms of turbulence, the pluses outwiegh the minuses

 

[viprez586]

Interesting information, I do have a spare head laying around. I'm curious I just took away these humps and/or obvious imperfections and just mainly focused on getting a nice smooth finish without drastically changing the size if i would yield effective results from the labor....or is it just not worth it?

 

[dsm-onster]

Well, I will be putting my car back together EXACTLY as it was before the motor blew. The compression was factory with the logs I have at 20 psi and the h1c. This time it will be 20 psi with the h1c but with the port work done. It won't be back to back. But I'll be running a 2g maf so we can see the hertz changes throught the rpm range which is a volume flow number. No climate changes affect it. If the volume flow goes up, then this porting helped. How much it goes up will determine the value of the effort, I guess. I started this on a rainy day during a nor-easter. That's why it was worth it to me no matter what.

 

[mach4g63t]

I saw a few of the pics of the work you've started in your profile, but I'm assuming there will be a full before and after montage of pics when you're all done too?

 

[dsm-onster]

I'm working on it. More importantly, there will be before and after LOGS for this head porting. Identical mods. Identical boost and elevation. . .

 

[buddahboost]

Hey guys, any updates and pics?

 

[e85_4g63]

Updates?

 

[96eclipseawd]

any updates on this? I'm pulling my 7-bolt, and I am planning on porting and am very interested in the logs before and after porting.

 

[pj91gsx]

i have some updates for this. Im sorry it took so long. I visited two machine shops that port cylinder heads and got the information that I needed to port my own cylinder head. in conclusion to what i have seen pictures of, I would say that porting down the humps, cutting down the guides and the humps on the sides of the ports make a big difference. But i saw the ported head from the Sexy Grandma Build and that head was ported very big and different from the way i have scene the 4g63 heads ported. But new things are always experimented and improved. I like they way i ported mine, because one thing is for certain, hot air rises. So I ported the roof of the head for the most part. For the curve starting at the valve seat, it is supposed to be ported so its rounded. Imagine water flowing threw the head, air will flow the same way. You dont want any spots for the air or water to be trapped so try to make the port straight as well, but dont change the shape of the port. ill work on getting pics soon

 

[pj91gsx]

heres the beauty i put on my car. i went to some local machine shops that port heads and got the info i wanted. I could have ported it more on the middle divider, but i just wanted something thats better than stock and not overkill incase i were to hit a coolant jacket.

pictures.

 

[joe sobo]

it looks good, but in the last pic, i can see where you cut the guides down, and right behind them they have a lip. will this cause a "drag" spot?

 

[pj91gsx]

Im just glad im done with porting that head. It should flow well.

 

[joe sobo]

so, austin, when are you ready to do the head sitting at my house? so i can put it on when i do the 16g and fmic setup on my car?

 

[JEFFREYCASTGSX]

That port job is, um.... well beautiful. Who did it, you or the shop?