SM Head Modifications on a budget

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Newbomb Turk said:
That’s because it was beat into the head of every potential head porter that if you even look at a short turn wrong the casting is junk and you should never try again.

I didn’t get the fear gene.

Guys that are motivated by fear (or I suppose unmotivated by fear too) will never make a go of it no matter what.

I **** on all those authors and talking head bastards who spent the 1960’s and onward telling guys what not to do rather than what to do.

And when they did do some articles no porting they bought some sorry assed paper roll kit and maybe a couple of burrs and they say just remove the casting flash but don’t move any metal and never touch the short turn unless Ernie Elliott or Smokey Yunick are standing there, holding your hand.

You’ll never learn to port unless you do it. If you live in fear of killing a short turn or poking a hole in something you’re in the same boat.

To learn to port the guy MUST learn to pick his own tools and such so that HE can make the shapes HE wants.

No two guys see things the exact same so it takes different guys different tools to make the same shape.

There isn’t one way to port. What matters is the end result.

I’ve always said if someone chopped a short turn down to almost hitting water and you went out and set a national record with them, as soon as it was spread about what you did every swinging dick with a grinder would be chopping down their short turns, not considering as to WHY it was done in the first place.

Eventually you have to stop copying what other people do and learn for yourself.
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Pretty much the approach hughes took on there "bigmouth" porting on the edelbrock head. Just murdered the short turn, looks like there approach was "volume at any cost."
 
The guy who gave me some guidance when I was first getting started was a big proponent of going after the SSR, so that was instilled in me early on.
I remember telling him how Mopar warned against touching the SSR.
He had already ported a few sets of BBM factory heads that worked pretty well, and his response was basically, without reworking SSR on those heads, they’ll never flow very much.
 
Earlie A said:
What was the valve size? Interesting that the tube protrusion didn’t create problems.
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2.08...the tube pulls air to that side of the bowl. If you want it there. I really don't think much of my advice will work with your valve job. But I do think laying back the chamber wall should get you some but maybe not until you move the ST belly back some and blend the VJ on that side.
 
I’m going to tell you guys two things that will probably make you either doubt me or laugh.

1. I’ve never watched a video on porting a Mopar head. I’ve shared a lot of Darren Morgan’s stuff but never watched one.

2. I’ve probably watched 10 videos on porting LS heads. Not so much to see what to do, but to see what not to do.
 
pittsburghracer said:
I’m going to tell you guys two things that will probably make you either doubt me or laugh.

1. I’ve never watched a video on porting a Mopar head. I’ve shared a lot of Darren Morgan’s stuff but never watched one.

2. I’ve probably watched 10 videos on porting LS heads. Not so much to see what to do, but to see what not to do.
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Only person laughing would be the guy that's never picked up a grinder and gave it a go. I've learned from the most unassuming people at times!
 
Brian Hafliger said:
Only person laughing would be the guy that's never picked up a grinder and gave it a go. I've learned from the most unassuming people at times!
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Before Photobucket got greedy there was a fantastic posting area on Yellowbullet where guys posted tons of pictures of their porting work. I learned more looking and studying those pictures than I did anything. If you didn’t pay photobuckets high ransom they blurred out your pictures. One of many tech post’s ruined. Without pictures tech is almost useless.
 
Earlie A said:
Here's my last test of the day and my last test until we get more direction from PBR. I went ahead and worked the short side blend a little more as can be seen in the pictures below. This was done with a 1" diameter 60 grit roll and took 1-2 minutes. I basically removed the 70 degree purple line area and blended smoothly back to the SSR. This is still very easy work to do, requires little skill and is not getting near the valve seat itself. This increased the throat to 1.826 wide x 1.851 deep which is now 89.5%. The first two flow test papers show the incremental improvement over the previous test.

Here's an opinion on throat size. I would love to hear other people's opinions. I do not believe that this latest improvement was because the throat size increased. I believe it is because the shape of the short turn got better. The 91% throat was the result of the modifications, not the goal of the modification. It is my opinion that if we could keep this short side shape and reduce the throat size to 88% that flow would improve. The only way to do that is if there was more metal to work with on the long side. We could then extend some angles, blend in a different way and direct the high speed air on the long side in a different manner. This in effect is an offset throat, i.e. the throat is not concentric with the valve, it is shifted toward the short side.

I thought it would be good to show progress so far, so the last two papers compare the very first flow test of the stock port vs the improvements to date.

I'm done for the day. What's next PBR?

View attachment 1716265822
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Went back and corrected this post that contained some bad math. In this post I used by beloved 1" sanding roll to blend a small ridge of 70 degree undercut into the short side radius. I originally stated that the throat size increased to 91%. That is an incorrect number that came from dividing by a valve size of 2.02" instead of the correct valve size of 2.055". Post has been corrected to the actual 89.5% throat size. So, in reality, only a few thousandths of an inch were removed. So @pittsburghracer, may I have permission to continue using my 1" roll?
 
Earlie A said:
Went back and corrected this post that contained some bad math. In this post I used by beloved 1" sanding roll to blend a small ridge of 70 degree undercut into the short side radius. I originally stated that the throat size increased to 91%. That is an incorrect number that came from dividing by a valve size of 2.02" instead of the correct valve size of 2.055". Post has been corrected to the actual 89.5% throat size. So, in reality, only a few thousandths of an inch were removed. So @pittsburghracer, may I have permission to continue using my 1" roll?
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Hey you are the one doing the porting. I explained why I stay away from larger sized porting tools. Each head Porter chooses his weapon.
 
Here's what the port mold revealed. Mold was cut in 3 locations, with location number 1 being in the center of the head bolt bulge which is also the apex of the short turn. Area at this port section is 2.04 in². Area at cut 2 is 2.42 in² and area at cut 3 is 2.80 in². Port length distance from the apex of the short turn to cut section 3 is less than 2 in. So in a distance of less than 2 inches, the port area increases by 37%. No wonder we have flow separation at high speeds. It's impossible not to. The paper labeled 'Port Mold Section 3' shows a circle of 1.88 diameter which is 2.80 in², the area of that section. If average port velocity is constant from section 1 to section 3, only the upper 2.04 in² of the area is needed. The bottom 0.76 in² marked in pink are not needed for flow and is the area where flow separation occurs. Obviously this is an oversimplification, but the point is evident.

We have established that there are SSR issues with this head. It also appears that area at the apex is a huge problem. I have included a flow graph of the port being discussed in this post (port 3/6) and a flow graph of another port in this same head that I've been working on for quite some time (port 4/5). Port 4/5 has had significant porting and widening of the apex along with chamber and PRP mods. It has had some minor SSR work. Port 3/6 has had no SSR work and no apex area work. Port 4/5 is peaking close to 300 cfm on a SSR that has been widened and laid back but not lowered.

The port being worked in this post (3/6) is stuck around 260 cfm. I believe the biggest issue is lack of area at the apex and too much expansion immediately thereafter. The SSR controls the instability at 0.500" lift and up and probably reduces peak flow a little.

This leads into another topic about the purpose for large bowls. One theory says that a large bowl slows the air down to help it get around a turn. In this case that seems like hogwash. If the air is in the turn already, it's too late to slow it down. At high speeds the large bowl just promotes separation.

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PRH said:
EA, do you know the area of the heavily modded port at the “cut #1” point?
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This mold was cut into 5 sections. Section 1 should be roughly the area of the head bolt pinch.

Note to anyone else: These pictures are not the port being testing throughout this post/thread. This is a different port on the same head.

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You could change the thread title to "The Scientific Approach to Head Porting"
 
PRH said:
Big difference.

Where would you say most of the gain in area came from?
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Head bolt bulge taken all the way to the brass tube. Roof raised (too far actually) and clayed back up. Cyl center wall pushed out (too far again) then clayed/epoxied back. Corners squared up. No intentional floor lowering other than when necessary to square the corners out. Squared up means 1/4" radius from 1/2" tooling.
 
Probably, but can't swear to that. I do remember making a port mold with clay in the port and I was surprised it worked fine.
 
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