Porting

[larrycavan]

Hello Suzuki Fans,

A friend of mine has been asking me to post pictures of port work over on this fourm for a while now. So I took some pics of a head I finished up yesterday. Sorry this one isn't a GS head but I don't have one in at the moment...

GS heads end up mid 90's on street cut ports. That 2mm larger valve they run gives them an advantage.







Anyway, there's some pictures of the work I do on Kawasaki heads. I didn't take any pics of the last Suzuki head I did or I would have posted them instead...

Larry C

[49er]

Porting - Indeed!!

Thanks for the pics Larry.

Interesting to see that the flow rate doesn't improve greatly when the lift increases from 0.300" to 0.400". Bigger inlet valves, flush cut guides and some more pocket work, would improve those figures for street use.

One thing that the flow bench doesn't account for though, is the fuel atomisation abilities of ports. I don't polish my inlets as smoothly as yours,after viewing a video of what happens to fuel when travelling along highly polished ports. There were big droplets of fuel forming on the port walls, just the opposite of what we are trying to achieve for improved performance.

[BadBillyB]

GS heads end up mid 90's on street cut ports. That 2mm larger valve they run gives them an advantage.

Yeah, I used to make beer money putting Suzuki valves in Kawasaki heads back in the day. They were a little too big for the seats but i had a valve grinding machine and cut them back to 37.5's ......I had a source for brand new Suzuki valves for like 3 dollars a piece....The Suzuki valves were if I remember right, a little shorter, and this was good as the valves had to be sunk a lot to get enough valve to valve clearance......Nice port pics and flow chart you shared with us.....Thanks ......Billy

[Big Jay]

So who is this newby that pops in here and trys to pass himself off as a head porter?

[larrycavan]

Thanks for the pics Larry.

Interesting to see that the flow rate doesn't improve greatly when the lift increases from 0.300" to 0.400". Bigger inlet valves, flush cut guides and some more pocket work, would improve those figures for street use.

One thing that the flow bench doesn't account for though, is the fuel atomisation abilities of ports. I don't polish my inlets as smoothly as yours,after viewing a video of what happens to fuel when travelling along highly polished ports. There were big droplets of fuel forming on the port walls, just the opposite of what we are trying to achieve for improved performance.

You won't see a huge increase from .300" - .400" because you're passing the convergance point at just past .350"
The bowls are left small intentionaly as were the throats.

I could have pushed more air through it but the motor doesn't require it.

Surface finish is 80G.
I generally flow at 28 but the guys in the motorcycle world are accustomed to seeing 10" numbers.

Here you go.... Cavanaugh Racing Heads http://www.flowbenchtech.com/porting/CRH/index.htm

[larrycavan]

So who is this newby that pops in here and trys to pass himself off as a head porter?

Hi Jay.... How's things? I've been swamped. I see you grew over here [BigJay]

Larry

[rapidray]

One thing that the flow bench doesn't account for though, is the fuel atomisation abilities of ports. I don't polish my inlets as smoothly as yours,after viewing a video of what happens to fuel when travelling along highly polished ports. There were big droplets of fuel forming on the port walls, just the opposite of what we are trying to achieve for improved performance.

This is the reason I finish all of the heads I do with 40 grit cartridge rolls on the intake side. Ray.

[49er]

This is the reason I finish all of the heads I do with 40 grit cartridge rolls on the intake side. Ray.

Unless you're doing major hogging, I've found that the 2 valve casting surfaces only require minor finishing, on the inlet ports. The pockets are a different story though, as the machining/casting quality varies significantly from head to head.

[larrycavan]

This is the reason I finish all of the heads I do with 40 grit cartridge rolls on the intake side. Ray.

I'll just say this. If fuel is clinging to the walls of the ports, in a port without serious bends, there are issues but they are not surface finish related.

One thing is for certain. 10" of test pressure testing leaves many things hidden. Crank up the test pressure

[rapidray]

That's why I test @ 28 inches! It is MUCH more accurate & I have found that the rougher the intake port finish, the better the atomization. Almost every street head gets the biggest gain in flow correction in the bowls. Ray.

[larrycavan]

What are you guys using for benches? Pitot or orifice?

[Pete Logan]

I have found that the rougher the intake port finish, the better the atomization. Ray.

On a historical note, Rover engineers trying to get the ex-Buick 215 to go better actually inserted a washer-like thingy between the carbs and the intake manifold to disrupt the air/fuel flow and get a more even mix. Was kind of like a washer but with big saw-teeth on the inside sticking into the intake mouth.

All the Harley porters I have seen recommend leaving the intake ports as rough as you like for better mixing.

[larrycavan]

Why is it that motorcycle people have to always play " Well I know this" when it comes to porting threads? Never did understand that

Car guys are always a lot friendlier and have much more to contribute to such topics.

Everyone in the motorcycle world seem to think they're got some big secret or something......jeesh

[GregT]

There are no secrets now Larry.... Thanks for posting what you have, it's very interesting.
As for the Rover problems - all this points up is how poor the SU carb is at atomising fuel - nothing new there.

Larry, thoughts on gas speed ? In my experience guys who know what they're doing on car heads are looking for a relatively high gas speed. This is of course desirable for their application - maybe 4 speeds and a high vehicle weight
I've found that the same guys tend to produce bike heads which are flow limited because they're aiming for too high a gas speed in this application.
This gives great response and midrange but the top end suffers.
This was brought home to me recently when I had a set of 1098 Ducati heads here - not a lot to do to them really, least of all make them bigger
they're absolutely HUGE.
Ray's heavy texturing of the port walls is of course not needed here because the injectors do all the atomising of the fuel - just as well too.

Greg T

[Big Jay]

The rough wall atomizing deal was important with carb and with cold motors ( drag racing ) Not such an issue with motors that get up to operating temp.

Also as mentioned in the above post, fuel injection now handles all the atomization.