CNC Mill Mark Removal in Intake Port

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pittsburghracer said:
I didn’t watch the video but nobody said anything about an as is cast heads. Smoothing and SHAPING goes a long way towards making a port better.
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I know it's not a cnc head but came across the video thought some might be interested in the results.


14:50 is where he shows the flow chart, recap under .500" there's little/no change above to 1.00" 10-25 cfm gains with 60 grit.
 
273 said:
I know it's not a cnc head but came across the video thought some might be interested in the results.


14:50 is where he shows the flow chart, recap under .500" there's little/no change above to 1.00" 10-25 cfm gains with 60 grit.
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That's a good example of how the valve job controls flow below 0.300-0.400 lift and the port doesn't matter all that much until velocity gets high. Those were big changes at high lift.
 
Newbomb Turk said:
That’s the problem with being a reader and not a doer.

Because port surface finish has an impact not only on power but on jet sizing as well.

If you can run 5 sizes smaller jet and make the same (or more) power the car will be quicker.

Darin Morgan already said you can’t make them too rough.

Larry Meaux says the same and he does the exhaust ports and chambers in a rough burr finish. Says he’s making more power the more he does it and the rougher he makes it.

Chad Spierer won’t do a manifold that isn’t burr finished. And some of his intake ports are burr finished.

Once again the claims made by DV and others because he’s not the only one saying it are found to be wanting.

If you don’t test you won’t know it.

Plus, I’ll say with pump gas or any alcohol based fuel today there is power in a burr finish.

You have to test it or you won’t know.
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The problem with the DV Quote-bot, it is not in context, DV was stating that simply smoothing the surface of most as-cast heads results in very little to no gain...flow-wise...not that there is not a desired surface to increase output & decrease BSFC....
And screw the drag stuff, run a circle track or road course & tell Me how much those reduced fuel consumption #'s are worth to You.....
 
The funny thing is, for all of the experience DV has, He acted somewhat puzzled when He gave a NAPCAR team a "super atomizing" carb setup He created for a restrictor plate engine......and it lost like 6mph+ or something on that order. Since I've despised the sanctioning body since the early '80's, I really don't follow the engine developments the way I should, but as another member here pointed out...a restrictor plate engine is running into 8" depression at full speed. The last thing an engine like that needs is vaporized fuel displacing valuable volume needed for the one thing it is starving for.....atmosphere-borne oxygen. And if the intake is experiencing that much depression, certainly it is higher in the cylinders at various points during the intake event. Just a guess, but super even cylinder to cylinder distribution is probably the most critical, not atomization in those things.
 
Killer6 said:
The funny thing is, for all of the experience DV has, He acted somewhat puzzled when He gave a NAPCAR team a "super atomizing" carb setup He created for a restrictor plate engine......and it lost like 6mph+ or something on that order. Since I've despised the sanctioning body since the early '80's, I really don't follow the engine developments the way I should, but as another member here pointed out...a restrictor plate engine is running into 8" depression at full speed. The last thing an engine like that needs is vaporized fuel displacing valuable volume needed for the one thing it is starving for.....atmosphere-borne oxygen. And if the intake is experiencing that much depression, certainly it is higher in the cylinders at various points during the intake event. Just a guess, but super even cylinder to cylinder distribution is probably the most critical, not atomization in those things.
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You think the fuel takes up too much space if its too atomized or converted to a gas?
 
Here let me help you:

Killer6 said:
The last thing an engine like that needs is vaporized fuel displacing valuable volume needed for the one thing it is starving for.....atmosphere-borne oxygen.
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The chemically correct fuel air ratio is: 0.0667/1 by volume. By weight its 14.7 to 1.
 
Hysteric said:
Here let me help you:


The chemically correct fuel air ratio is: 0.0667/1 by volume. By weight its 14.7 to 1.
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Is the volume ratio calculated with the fuel in a liquid state or a gas?
 
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Im stating that a 0.06 percent of the whole is insignificant.

At 12.5 to 1 that 1 is not equal in volume to a 12th.
 
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Hysteric said:
Im stating that a 0.06 percent of the whole is insignificant.

At 12.5 to 1 that 1 is not equal in volume to a 12th.
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So You're stating that wet flowing & dry flowing a carb shows no difference on the bench??
 
Hysteric said:
Im stating that a 0.06 percent of the whole is insignificant.

At 12.5 to 1 that 1 is not equal in volume to a 12th.
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Would some of the gasoline between the carburetor and the cylinder be a vapor?
 
92b said:
Would some of the gasoline between the carburetor and the cylinder be a vapor?
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That's a given.

Do you also think that the super atomization of 0.0667 as a ratio to the air ingested would magically crowd out all the air and would kill power?
 
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Hysteric said:
That's a given.

Do you also think that the super atomization of 0.0667 as a ratio to the air ingested would magically crowd out all the air and would kill power?
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I wonder how much the volume changes for a given weight of gasoline when it changes from a liquid to a vapor?
 
Hysteric said:
That's a given.

Do you also think that the super atomization of 0.0667 as a ratio to the air ingested would magically crowd out all the air and would kill power?
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I suppose first you would have to define " power killer". Attaching a number or range of horsepower or even a measured difference in lap times that would have been considered a power killer at the time this carb was tested in cup racing. Without the details of the results of the testing that was done at that time it would be hard to determine. I'm surprised that if a super atomizing carburetor lead to "super vaporizing" the mixture in a way that displaced area in the intake tract and killing power as a result that Vizard wouldn't have been aware of this possibility. He writes in one of his books in detail about how in an air restricted class of racing that he removed the light ends of the fuel they were using by blowing air into a drum of fuel. The purpose was to prevent the vapors from taking up space that could otherwise be occupied by air. He claimed this was successful and gave them a power advantage. So it would seem that, true or not, Vizard believed at one time it is possible to kill power with too much vapor in the intake tract in a air restricted engine. Speaking for myself I don't know but find it interesting to think about.
 
92b said:
I suppose first you would have to define " power killer". Attaching a number or range of horsepower or even a measured difference in lap times that would have been considered a power killer at the time this carb was tested in cup racing. Without the details of the results of the testing that was done at that time it would be hard to determine. I'm surprised that if a super atomizing carburetor lead to "super vaporizing" the mixture in a way that displaced area in the intake tract and killing power as a result that Vizard wouldn't have been aware of this possibility. He writes in one of his books in detail about how in an air restricted class of racing that he removed the light ends of the fuel they were using by blowing air into a drum of fuel. The purpose was to prevent the vapors from taking up space that could otherwise be occupied by air. He claimed this was successful and gave them a power advantage. So it would seem that, true or not, Vizard believed at one time it is possible to kill power with too much vapor in the intake tract in a air restricted engine. Speaking for myself I don't know but find it interesting to think about.
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It’s funny as I’ve seen it go both ways.

I’ve seen an engine lose power when switching to a cold intake because the carb/booster didn’t atomize the fuel well enough. Seen that a lot.

I’ve also seen where too much heat killed power.

I’m in the camp of cold intakes and very active boosters and let them do the work.
 
So after readin all this, I'm still kornfrooshed. Is there a consensus as to which way is better? Smooth or rough ports? Or is it combination dependent? Or some other magic fairy dust?
 
RustyRatRod said:
So after readin all this, I'm still kornfrooshed. Is there a consensus as to which way is better? Smooth or rough ports? Or is it combination dependent? Or some other magic fairy dust?
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Rough is always better. That’s according to Darin Morgan and Larry Meaux.

The outlier is CNC step over. I’ve seen that so coarse you couldn’t even read the manometers.

I can’t remember what the CFM loss was but it was big.

I’ve never seen a burr finish do that but I would suppose it’s possible to get that too rough.
 
What I don't get about this obsession of atomization, is how far off optimal atomization is the average build?

Is there really a lot of power to be gain in the average built engine, just waiting for the owner to sort it out and can the average builder really do much about it? And if so is it the most cost effective pursuit for power?
 
273 said:
What I don't get about this obsession of atomization, is how far off optimal atomization is the average build?

Is there really a lot of power to be gain in the average built engine, just waiting for the owner to sort it out and can the average builder really do much about it? And if so is it the most cost effective pursuit for power?
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It’s critical.
 
Newbomb Turk said:
It’s critical.
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I get it's critical, but beyond something being severely off, my point/question is the average well tuned engine out there leaving a lot of easiably gain power just laying in wait? Like how well is the average performance engine handling fuel atomization.
 
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