I'm about to do some light PP work on a set of 243 heads. They are currently at the machine shop getting shaved. 025 and receiving a valve job.

My question is in regards to the SSR...short side radius. Is there anything to be gained by easing it down? Or is it better left alone?

After an evening of online searching, I'm having trouble finding a consensus. It seems there aren't very many posts or articles on the subject in real terms of "its been proven that....."

Anyone have anything on this subject?

 

Welcome to the forums.

And you will find a lot of differing opinions on what works and what doesn't. I have read on this site that you can ease it down, as you said in reference to the SSR, and it usually increases flow.

Here is a link to a similar discussion on this site. It has a lot of useful links on post #7:
https://ls1tech.com/forums/generatio...guys-come.html

Hope this helps.

 

Thanks for responding.

I think I've read about every thread that might contain any glimmer of hope on the subject. It seems there isn't a clear cut, black and white answer. Only opinions.

Does anyone have clear cut facts?

 

Given that most people doing any sort of porting at home do not have access to flowbenches, most DIY port jobs are not going to have clear cut results. Plus, every flowbench is different, people use different settings on the same model, the results vary and are almost useless when comparing against the results of a different flowbench... much like dyno's, the flowbench mainly just gives the individual user/porter/tuner a datum to compare his/her individual work against. So finding clear cut facts on DIY porting will be difficult unless one of the professionals that have tested just about everything decide to chime in with an answer for you.

Read as much as you can and make a decision based on the information you have available. When dealing with information presented on a forum, you have to either pick someone's opinion based on how they lay out their information, or you count opinions for/against what you want to do and choose the popular majority opinion.

You might be able to call and ask someone who professionally ports heads and get their opinion on what to do and what not to do, but most of they time they are very busy and are not very willing to freely give up the secrets of their craft.

I am in no way trying to discourage you from home porting your heads, but what is wrong with running stock ports with a nice valve job on shaved heads? Run them like that until you have enough money to get them CNC ported. Gotta love the port-to-port consistency of CNC porting.

 

The short side radius is one of the more critical areas of the port. If you're comfortable porting heads, by all means yes, lay it down, widen it, maybe even put a little more bias into it.

 

but realize that a mistake on the short side can give you heads that will flow worse than stock.

 

Thanks for all the input.

I've been practicing on a spare 241 head.
I'm not exactly clear what constitutes "messing it up" or what would be considered beneficial.

The approach I've taken in practice is to start at the "peak" of the radius. Ive lowered the peak, then feathered the radius both towards the runner and towards bowl/seat. I have done this while staying off the straight and curved walls, maintaining the original width so to speak. I then took a long strip of sand paper, maybe 3/4 wide and pulled it back and forth along the radius to contour it.

I haven't gotten very agressive at all. At most I removed .030 from the "peak". Maybe just a tad more.
Does this sound like a reasonable approach? Any input and those who are experience would be greatly appreciated. This is my first go with LS heads.

 

It sounds like you're on the right track. Basically, you're wanting to make a more gradual turn into the valve job. You're going to end up moving that "peak" back into the port a little bit. You can look at a cut away and get a good idea of what needs to be done.



Don't be afraid to widen the SSR either, but be careful not to make the corner radii too tight.

 

That's the clearest cut out I've seen. Thank you.

I think I'm going to have the machine shop to a base line flow on my 243's. When I go pick them up I'll take this 241 that I've worked along and get his opinion. The guys I'm using are one of the top sprint/late model builders in the country. They should have solid insight. After I do the 243's I'll get a follow up test. Since I'm not removing large amounts of material, an increase on the bench should equal success????

 

After spending most of my Labor day experimenting on my sacrificial 241, one thing became clear to me. Replication of modifications to the SSR are going to be nearly impossible for me to accurately accomplish across 8 ports.

I think ill stick with areas that are easily matched port to port. Those areas being the rocker bolt hump, the ramp, valve guide boss, and bowl to valve seat blending.

Thanks to all who offered advice

 

The consistency of CNC porting is its greatest advantage in my opinion. That is why I was saying that perhaps you should run stock ports with a nice valve job on shaved heads until you can afford to have them CNC ported.

I commend you for trying, though. I do not have the ***** to try hand porting a GM head. Ford heads, oh yeah, all day... there's no way to make them worse.

 

Solid advice. In the event my high mileage short block goes south, I may very well do that.
A few days ago I actually decided to start checking with a few of the major LS CNC head porters. None was willing to discount the milling or valve work thats already been done. So that's what has really steered me into a home port.

 

maybe find someone who has a proven set of CNC'd heads and make some templates to guide you.

 

I'd love to. Nobody I know of nearby has a set on the shelf. I wouldn't know how to template it anyhow.

 

Since the SSR is off the table. Where to proceed next?
I'm sure I read a thread or two about someone who tested after taking out the rocker bolt hump only, and lost mid list CFM.
The swirl ramp is also a matter of debate.
What about a simple bowl/seat blend and guide boss reshape? Any danger or grey area here?

 

Any advice from those with experience would be monumentally appreciated.

 

Have a valve job done, open the venturi up to ~90% of the valve diameter, and then blend it all in. I used to use snap gauges to measure the venturi.

 

It looks like you worked it till just shy of where the valve contacts the seat?

 

It was actually below the bottom cut. The thin line is the seat cut, it's about .040" wide.

 

Here's another picture with it all done and blended in.