Author Topic: CB550 home porting attempt (Read 11130 times)

Scott S · « **on:** November 28, 2011, 06:55:56 AM »

After reading many, many threads on the subject, studying lots of pics and conferring with a couple of head porters, we decided to give it a shot at home.
My Dad knows a guy that has ported heads for years, primarily V8 stuff. He agreed to take a look at the info we had on the SOHC CB550 and "supervise". Well, while waiting to catch up with him, my Dad rolled up his sleeves and dug right in. "Here goes nothin'...", right?
To his credit, my Pop was a hot rodder way back in the day and has fooled around with similar stuff before, albeit many years ago. (He used to hop up Cushman scooters and go pick on the Harley guys!).

Anyway, let's begin at the beginning....
I started with a really nice head. It had very little of the casting flaws and marks that I've seen in other pics. There was almost no ledge at the seat, etc.

Looking from the combustion chamber side. Almost no ledge at the seat.

Just a little bit of 'slag' from the casting process around the intake boss.

Scott S · « **Reply #1 on:** November 28, 2011, 07:00:50 AM »

Using my Dremel tool, he removed the casting marks from around the "football".

...ran a hone through the intake manifolds...

[b...and port matched the manifolds....[/b]

Scott S · « **Reply #2 on:** November 28, 2011, 07:03:34 AM »

Here's the #1 cylinder with the manifold attached. It's the only one that he's smoothed out, so far.

And from the combustion chamber side.

Scott S · « **Reply #3 on:** November 28, 2011, 07:09:51 AM »

The exhaust side of this head was really, nice to begin with, too. We cleaned out the carbon and hit a few casting marks on the combustion chamber side.

The outlet side doesn't really need anything....right? This is 'as cast'.

Scott S · « **Reply #4 on:** November 28, 2011, 07:13:50 AM »

This is all "in progress" stuff. We're having a hard time finding some of the correct flap wheels, etc., to get in the tight spots. He's also a little unsure about attacking the "football" until we get some guidance from our friend. Removing material from it will alow easier access for more smoothing and "finish" work, but we don't want to make a mistake and take off material where we shouldn't.

The goal here is a nice running street bike. I will have a CB650 cam and I want to keep power in the mid-range and usable. No race stuff or super-high RPM's. Thoughts so far?
(Constructive criticism is appreciated. Others....well, keep it to yerself!

)

ekpent · « **Reply #5 on:** November 28, 2011, 07:14:14 AM »

No expert here but it does sound like a nice Father/Son bonding project. Hope all goes well,wish my Ole' Man was still around,passed away around 6 years ago

Scott S · « **Reply #6 on:** November 28, 2011, 07:23:30 AM »

Thanks, ekpent. We butt heads from time to time, but we've been working on stuff together for the last ~17 years or so, starting with VW's and moving on into motorcycles.

For comparison, some before/after of the one intake that's had the most work, so far.

Before:

After:

Before:

After:

(Note: I don't think the above pics are of the same cylinder, but just to give you an idea of what we're doing....)

octagon · « **Reply #7 on:** November 28, 2011, 11:32:40 AM »

really interesting - please keep us posted.

nancy · « **Reply #8 on:** November 28, 2011, 12:06:46 PM »

Look forward to hearing from you on the outcome Scott....interesting stuff.

Regards
Mark
PS: Yep my old man fell from his perch too - 8 years back and I wish he could get involved with this stuff now. Never asked him to when he was upright.

Bluegreen · « **Reply #9 on:** November 28, 2011, 06:10:33 PM »

I'd like to follow this.

Doctorlumen · « **Reply #10 on:** November 28, 2011, 06:55:50 PM »

Thanks for putting this up, Scott.

Its great to see the before and after stuff...so often the discussion on porting these old heads is...well, a bit heady. I'm really looking forward to seeing the results so I can go to work on mine!

Grabcon · « **Reply #11 on:** November 28, 2011, 07:07:34 PM »

I also have been contemplating a port and polish job and then I read articles like the one in the link below. Now I have communicated many times with Mike via e-mail and he is very sharp so I respect his opinion. Take the read for what it is worth.

http://www.motorcycleproject.com/motorcycle/text/cows-porting.html

ataylor136 · « **Reply #12 on:** November 28, 2011, 08:10:42 PM »

Grabcon,
Good link.

ekpent · « **Reply #13 on:** November 28, 2011, 08:21:20 PM »

I have read that before once and it is quite a sobering link. Looks like experience working on a lot of these doing that specific mod would be priceless.

Xnavylfr · « **Reply #14 on:** November 28, 2011, 08:32:29 PM »

REMEMBER ! if you make it too SMOOTH you won't get the atomization and mixxing needed for the combustion chamber!!!

Xnavylfr(CHUCK)

Greggo · « **Reply #15 on:** November 28, 2011, 11:24:31 PM »

Very cool Scott! I've got an extra head to clean up, and was thinking of giving it a go. This is definitely inspirational.

camelman · « **Reply #16 on:** November 29, 2011, 01:17:06 PM »

I'm no expert on porting, but I tried my hand at it a while back on my 350F. If you look for my posts on it then you will find the flow bench I put together to compare flow between intake and exhaust ports (I made it from a tupperware container and a shopvac... don't judge).

Anyway, I found that a deep pocket (I took out 2-3mm) below the valve guide shown in your first pic made a big difference. I blended that into the rest of the port and opened up the port on either side of the valve guide. Once I was done with the intake ports, I blended the intake manifolds into the intake ports and also blended the sync screws to the profile of the intake ports. I only did major work on the intake valves, but I did find that one of the exhaust ports had about 20% less flow area than the other three. I blended it out until my flow bench showed even flows across the exhaust ports. I did the same for the intakes.

My end result was dramatic. Before the head work I had to downshift to 4th to maintain speed on an uphill on highway 101 with only me on the bike. Afterwards, I could stay in 5th gear with a passenger and maintain speed on the same hill at the same speed.

The whole reason I'm saying this is to recommend the homemade flowbench I used. It seemed to give consistant results.

Caveat: results may vary. ;-)

Camelman

Grabcon · « **Reply #17 on:** November 29, 2011, 01:32:55 PM »

Your home made flow bench sounds very interesting. Do you have pics that you can share, or a diagram of how you set this up. I think one thing in particular that you stated is key. That is one port had a 20% less flow rate then the others.

So my approach would be to do a baseline of all ports prior to any work and record that info in a spread sheet. If possible a current dyno run would really be of benefit. It will be difficult to get all intake or all exhaust identical in flow but if they are within a couple of percent that would be better than the 20%.

If this was just a port and valve job then once back together a comparison dyno should be run to see the plus or minus benefits.

singedebile · « **Reply #18 on:** November 29, 2011, 01:55:49 PM »

i really like how this thread is developing,

a perfect example of why i love this forum

Scott S · « **Reply #19 on:** November 29, 2011, 02:25:49 PM »

Quote from: camelman on November 29, 2011, 01:17:06 PM

If you look for my posts on it then you will find the flow bench I put together to compare flow between intake and exhaust ports (I made it from a tupperware container and a shopvac... don't judge).

Anyway, I found that a deep pocket (I took out 2-3mm) below the valve guide shown in your first pic made a big difference. I blended that into the rest of the port and opened up the port on either side of the valve guide. Camelman

I think this is the thread you're talking about, right?
http://forums.sohc4.net/index.php?topic=67722.msg749158#msg749158

The pocket below the valve guide...you mean on the combustion chamber side?

Grabcon · « **Reply #20 on:** November 29, 2011, 02:53:53 PM »

That link provides a very ingenious setup for the home mechanic. I like it simple but functional.

seanbarney41 · « **Reply #21 on:** November 29, 2011, 03:00:15 PM »

Quote from: camelman on November 29, 2011, 01:17:06 PM

I'm no expert on porting, but I tried my hand at it a while back on my 350F. If you look for my posts on it then you will find the flow bench I put together to compare flow between intake and exhaust ports (I made it from a tupperware container and a shopvac... don't judge).

Anyway, I found that a deep pocket (I took out 2-3mm) below the valve guide shown in your first pic made a big difference. I blended that into the rest of the port and opened up the port on either side of the valve guide. Once I was done with the intake ports, I blended the intake manifolds into the intake ports and also blended the sync screws to the profile of the intake ports. I only did major work on the intake valves, but I did find that one of the exhaust ports had about 20% less flow area than the other three. I blended it out until my flow bench showed even flows across the exhaust ports. I did the same for the intakes.

My end result was dramatic. Before the head work I had to downshift to 4th to maintain speed on an uphill on highway 101 with only me on the bike. Afterwards, I could stay in 5th gear with a passenger and maintain speed on the same hill at the same speed.

The whole reason I'm saying this is to recommend the homemade flowbench I used. It seemed to give consistant results.

Caveat: results may vary. ;-)

Camelman

...I have an old (late 70's/early 80's) issue of Car Craft magazine that contains complete plans to build your own flowbench with plywood, tubing, and stuff, using a shopvac...it would probably take me several hours just to find it but I know the info is out there...

Scott S · « **Reply #22 on:** December 04, 2011, 12:00:24 PM »

Here are a few shots of the finished intake ports. We left some height on the "football" in order to keep some of the low/mid-range power. We could've taken more off, but that just adds gains in the upper RPM range. This suits our needs.
The boss was narrowed at the back and the valley's were shaped and contoured.

Scott S · « **Reply #23 on:** December 04, 2011, 12:05:06 PM »

Here are the exhaust ports. We really didn't do anything here except remove the casting marks and seams. It looks rough, but you can't feel it with your fingers. At least, no rougher than the rest of the (stock) port casting.
The ledges at the seats all looked good, though the #3 cylinder had a slight bulge on the combustion chamber side that we removed so that it matched the others.

Greggo · « **Reply #24 on:** December 04, 2011, 12:07:39 PM »

Looks Great! Did you end up making a flow bench?

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Author Topic: CB550 home porting attempt (Read 11130 times)