Home ported 241 heads - 45 pics
Curious to see what kind of gains you got guiltboy. Those look like they came out well in a lot of areas. I like your port job over the "polish jobs" I've seen on here. 
You want to polish combustion chambers as to reflect more heat back into the cylinders. You DO NOT WANT TO POLISH INTAKE RUNNERS. You want to leave a rougher surface on them as a rougher surface allows MORE airflow through the ports.
We're trying to flow air through a port that's not aerodynamically designed for best flow. It's mostly designed arount a fuctional goal- letting air enter the motor in short spurts from the intake into the cylinder. It's not a straight shot, but this is what we have to work with. So, air has to flow around a valve-guide and though the radii of the ports. As the air flows it will form eddies as it can't hug the walls at high port velocity. This phenomenon is what causes airflow to decrease, it's called "flow seperation". Now we don't want this to happen. We want the air/fuel mixture to flow though our ports making use off all available cross-sectional area. So, we need the air to "stick" to the walls. How do we do this? We increase the relative surface roughness of the port walls. This will give us more flow resistance, but it also gives us better flow adhesion to the port walls yielding more airflow than if the ports were polished smooth. Another direct application of this is the dimples on golf *****. Do a search on google. Dimpled golf ***** fly 20% farther than smooth golf ***** for a reason.
So back to porting heads, how much surface roughness is desired? Well, I've heard it said that the finish a CNC cutter leaves is a desirable one. On my heads I'd like to see a rougher CNC type finish than a polish job on the runners.
Chambers and exhaust ports? Polish those until they shine. We don't want carbon buildup in the exhaust ports and we want nice reflective ports that send heat into the cylinders not into the radiator. The first law of thermo, heat = work.
Ben T.
(Engineer, May '07)
Originally Posted by 87Fake
Mine are polished. Not like glass, but cleaned up.
I smoothed the entire intake runner, couldn't tell you if it makes a huge difference. Seems most porters try to get them as smooth as possible.
I smoothed the entire intake runner, couldn't tell you if it makes a huge difference. Seems most porters try to get them as smooth as possible.
We're trying to flow air through a port that's not aerodynamically designed for best flow. It's mostly designed arount a fuctional goal- letting air enter the motor in short spurts from the intake into the cylinder. It's not a straight shot, but this is what we have to work with. So, air has to flow around a valve-guide and though the radii of the ports. As the air flows it will form eddies as it can't hug the walls at high port velocity. This phenomenon is what causes airflow to decrease, it's called "flow seperation". Now we don't want this to happen. We want the air/fuel mixture to flow though our ports making use off all available cross-sectional area. So, we need the air to "stick" to the walls. How do we do this? We increase the relative surface roughness of the port walls. This will give us more flow resistance, but it also gives us better flow adhesion to the port walls yielding more airflow than if the ports were polished smooth. Another direct application of this is the dimples on golf *****. Do a search on google. Dimpled golf ***** fly 20% farther than smooth golf ***** for a reason.
So back to porting heads, how much surface roughness is desired? Well, I've heard it said that the finish a CNC cutter leaves is a desirable one. On my heads I'd like to see a rougher CNC type finish than a polish job on the runners.
Chambers and exhaust ports? Polish those until they shine. We don't want carbon buildup in the exhaust ports and we want nice reflective ports that send heat into the cylinders not into the radiator. The first law of thermo, heat = work.
Ben T.
(Engineer, May '07)
I spent many hours porting my heads. They look kinda similar only I broke into the bosses for intake rocker bolt but I took care of that. I would polish the chamber and mill to get the compression back. And probably take off the angles on the spark plug boss. I believe that it restricts the intake flow a little bit. Looks very good.
Thread Starter
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I did smooth out those ports, polish the runners and the combustion chambers, followed by milling .040 for 10.85 compression with MLS .060 gaskets. Sadly I was in a rush to get these on the car so I dont have any finished pictures, but suffice it to say they came out looking very clean at the end.
As for the results? I dont want to give out the exact numbers, but lets just say that I was 2 HP shy of a 5# supercharged LS1. I also pulled 52 more HP than a cam only f-13 car, granted he was running a little rich from a nitrous tune. And finally I pulled 34 more HP than an LS6 motor with a TR 232 cam. All this was through 4.10 gears and a stock crank pulley. Out of 20+ cars that made dyno day, I was the second strongest n/a car there. Im EXTREMELY pleased with the results.
My mods are in sig.
As for the results? I dont want to give out the exact numbers, but lets just say that I was 2 HP shy of a 5# supercharged LS1. I also pulled 52 more HP than a cam only f-13 car, granted he was running a little rich from a nitrous tune. And finally I pulled 34 more HP than an LS6 motor with a TR 232 cam. All this was through 4.10 gears and a stock crank pulley. Out of 20+ cars that made dyno day, I was the second strongest n/a car there. Im EXTREMELY pleased with the results.
My mods are in sig.
