AG burr finish

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I don’t...... it was a while ago that I read it.
About when Larry seemed to start advocating for the burr finish.

There is a 64 page thread about it on ST...... if you need to get really deep into it.

Edit- Frankly, I’m glad that there are more discussions about how a textured port finish is superior to the sand roll finish.
As I said previously, not sand rolling the ports is a time saver for me.
If the sanding of the ports is really of no benefit........ then it’s just a waste of time.

It would be interesting to do the back to back dyno test between sanded and then rough heads/intake ....... but I don’t know if I want to know the answer bad enough to fund that test myself.
 
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I have my stuff tested, I don’t have a bench. The comments have been “ why didn’t you finish them” and then “better than it looks”. Generally I’m somewhere a little smoother than PRH on the intakes, smooth on the exhaust where blown down really doesn’t care and the carbon doesn’t build up, and smooth in the chamber just because I’ve always felt thats the most consistent surface for the flame kernel to expand over. But that’s just me. And no I do t think it’s a big difference in overall performance. Not as compared to overall shape and localized speed.
 
Just out of curiosity for myself, what makes the rougher burr finish port better than the smoother sanded port? I would think the dimples would create more turbulent air, but then again thats just my best uneducated guess.
 
RammerJammer75 said:
Just out of curiosity for myself, what makes the rougher burr finish port better than the smoother sanded port? I would think the dimples would create more turbulent air, but then again thats just my best uneducated guess.
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Probably the same thing that makes a dimpled golf ball fly further than a smooth one. Something to do with boundary layer, I think?
 
RammerJammer75 said:
Just out of curiosity for myself, what makes the rougher burr finish port better than the smoother sanded port? I would think the dimples would create more turbulent air, but then again thats just my best uneducated guess.
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There is a 64 page thread discussing just that over on SpeedTalk.
 
gzig5 said:
Probably the same thing that makes a dimpled golf ball fly further than a smooth one. Something to do with boundary layer, I think?
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It helps it fly through the air better, something to do with the spinning of the ball. It may be applicable to this as well, I don't know.
 
I wonder if these will end up being the last set of heads I did that got the sanded finish(on the intake ports at least).......

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For us regular guys not deeply involved in this type work, There are countless articles on this topic, from The old Vizard book of 1980, Performance With Economy and some words and pictures about shape vs. finish. Always read If you’re paying for a port job you like shine and polish, probably would feel gyp’d if you got back your heads and things were rough and patchy. Can’t resist the urge to polish but I always rough things up with 40 grit at least. Wonder if there’s a burr of some sort that could re create a cnc rippled effect, or a device that could dimple surfaces....

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I'm not sure if it's worth worrying about too much unless we could dyno test back to back. If a 500hp engine loses/gains about 8-10hp from a change in the port finish that same change can be the difference in the effect the weather has on a tune up from one day to the next. I actually would be surprised to find anything more than that but I could be wrong. I had a set of heads I did for a buddy some 15 years ago here recently , they had bad seals but here is a pic of what my port finish looks like.


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I was hindered by the tulip valves/sunken seats on the intakes and previous bad port work lol but I managed to get 252/190 @.500 and 255/197 @.550 out of them, they are 596s with my favorite exhaust port. Even though they have a hole in them at least they actually have a short turn unlike x/j heads..

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A set of chevy heads I was doing about 8 years ago, bad pic but similar finish. For some reason I don't have any newer pics, guess no time for fun.
 
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lead69 said:
I'm not sure if it's worth worrying about too much unless we could dyno test back to back. If a 500hp engine loses/gains about 8-10hp from a change in the port finish that same change can be the difference in the effect the weather has on a tune up from one day to the next. I actually would be surprised to find anything more than that but I could be wrong. I had a set of heads I did for a buddy some 15 years ago here recently , they had bad seals but here is a pic of what my port finish looks like.


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That almost looks like a “hammered” texture!
 
12many said:
That almost looks like a “hammered” texture!
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That's just "as finished" with my makita wide open, YR thinks I'm nuts but it woks for me. To me it's kind of close to Meaux's finish.
 
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RammerJammer75 said:
I have heard that the rougher port will help atomize fuel, but I have always felt like if the fuel isn't being atomized correctly from the carb/injectors, the rougher port has been the solution for this. But then again, just my thoughts, and I always like to learn more about engines.
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This is a misconception. Everyone discussing this should take the time to view the webinar that yellow rose posted in another thread, if you have not already done so.
Morgan actually talked about this. If I understand correctly, the air makes a turn better than the heavier fuel. So even if the mixture was perfectly emulsified, the heavier fuel keeps going and partially separates from the lighter air that makes the turns through the intake ports. The rougher texture apparently helps to re-introduce the fuel into the airstream. There is more to it and I may have butchered the description, so give the webinar a view.

Understanding the Characteristics of Flow in Induction Systems | Production Engine Remanufacturers Association
 
I think the golf ball analogy is a decent one, but it tends to overlook a few factors I suspect are at play.

1) The dimples are all the same with respect to one another
2) The dimples are of a depth and size that you can bet is not accidental
3) The golf ball is a sphere
4) The dimples, while dimply, are very smooth nonetheless. I bet a golf ball that was roughened by sandblasting wouldn't fly as well.

I think port roughness probably helps on cold engines and at lower port velocities, and that's a valid contribution. But at 7,000RPM on a hot engine, I doubt there's much time for the fuel to get any more or less separated from the air.

On my engine I'm putting together, I'll run it on a carb to get it worked out. But then, I'll switch to injection and the injectors are positioned to spray fuel at the valve and into the chamber. I hope it won't matter how rough the ports are. That said, I think a secondary issue will be that the injectors of today don't produce that great of a fog....more like a spray.
 
Don’t make a mountain out of a molehill. What worked for many many years will continue to work. Sometimes we tend to overthink things like this.
 
gregcon said:
I think the golf ball analogy is a decent one, but it tends to overlook a few factors I suspect are at play.

1) The dimples are all the same with respect to one another
2) The dimples are of a depth and size that you can bet is not accidental
3) The golf ball is a sphere
4) The dimples, while dimply, are very smooth nonetheless. I bet a golf ball that was roughened by sandblasting wouldn't fly as well.

I think port roughness probably helps on cold engines and at lower port velocities, and that's a valid contribution. But at 7,000RPM on a hot engine, I doubt there's much time for the fuel to get any more or less separated from the air.

On my engine I'm putting together, I'll run it on a carb to get it worked out. But then, I'll switch to injection and the injectors are positioned to spray fuel at the valve and into the chamber. I hope it won't matter how rough the ports are. That said, I think a secondary issue will be that the injectors of today don't produce that great of a fog....more like a spray.
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You need to listen to the Morgan webinar. He says rough 3 inches above the injector to the valve with a burr, and rougher is better.

There is so much fuel blowing around in an intake plenum and runners it’s crazy. You have wall flow no matter what you do, and getting that fuel back into the air, even some of it is a good thing.
 
Bobzilla said:
..If I understand correctly, the air makes a turn better than the heavier fuel. So even if the mixture was perfectly emulsified, the heavier fuel keeps going and partially separates from the lighter air that makes the turns through the intake ports. The rougher texture apparently helps to re-introduce the fuel into the airstream. There is more to it and I may have butchered the description, so give the webinar a view.

Understanding the Characteristics of Flow in Induction Systems | Production Engine Remanufacturers Association
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That's why dry intakes with the injector close to the valve or at a line of sight can be so strange looking from what we consider a "straight runner" performance intake. ie. the 5.0 intake that has the air make a 180 turn from the intake ram to the swept runners. Try that on a carbed motor and the fuel will just hit the wall and condense on the cold intake wall there. VW guys put heaters on their intakes to keep them warm as its a long way to the valves from that bug spray zenith carb on top.
 
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