jimmeh
07-03-2006, 11:56 AM
reference:http://www.theoldone.com/articles/b16a%5Fhead/
B-16 Cylinder Head Mods (Part I)
This is an semi-complete view of cylinder head modifications for the B-16 Honda engines. It's meant to be a guide of sorts to some of the folks who have decided to do the porting modifications themselves.
First, I need to say that the B-16 cylinder head is a pretty good piece from the factory. The port volume is generous right out of the box, and unless the head's intended for some very "special" use, enlarging the ports isn't recommended.
There seems to be considerable core shift in all the castings we've worked with, so there's a good chance that doing your porting correctly will mean that the porting won't necessarily be cosmetically beautiful, so don't count on seeing shiny surfaces everywhere.
I'm starting out with a picture of "Old Trusty" and the bits that are used for the B-16 job.
http://www.theoldone.com/articles/b16a%5Fhead/The%20Grinder.jpg
I've inserted a D16 piston to provide a point of reference in this photo. Note that the grinder is not small. The reason is simple: It's darned near impossible to properly control a die grinder properly without leverage. With one hand on the snout and the other on the handle, it's possible to maintain enough mechanical advantage over the cutter (or polisher) to impart the shapes you desire. You can't port cylinder heads without your every move being deliberate and precise.
Note the speed control for rpm reduction. Most pros run the speed as low as the control will permit. These Dumore grinders will go pretty darned slow and still provide sufficient torque for the job. Under the handle is a trigger that is also used as a throttle (or another rpm control). You learn quickly to regulate rpm and cutter speed by continuously switching the grinders off and on. The switches do require replacement after every 20 sets of heads, but they're more than worth the price.
Note that the cutter in the picture is a .5" diameter oval shaped "alumicut" with coarse (very few) cutting edges. These cutters are capable of removing material pretty quickly and they also leave a descent finish that's easily polished to texture. The cartridge roll is a 60 grit .5" long by 1.5" length. Note the rounded nose on the roll. We shape the square noses by working the cartridge rolls on cinder blocks next to the grinding benches. A couple seconds will shape a new roll to "perfection". The split rod has 40 grit paper attached. This works good on intake ports, while 80 grit does a good job for chambers and exhaust ports.
I suspect that the length of the shanks on the various tools might have attracted some attention. It should, because the length is the key to doing good porting. It's a necessity to stay far enough away from the work to see what's going on and that's impossible when the cutters have a 3" shank. Every tool we use on cylinder heads is long for this reason and the additional reach also allows one to complete grinding a radius that's "hidden" over the crest in the ports. This way, you're not working from two different directions, attempting to connect two radii at the crest, which is inevitably the most critical part of the port. Now that you see the length of these particular tools, the necessity for low rpm operation should be apparent, since high rpm can make the shanks "whip" and cause major damage.
Now, I have some pictures of some B-16 exhaust ports to show what you start with and what you'll want to see when the grinding's finished.
http://www.theoldone.com/articles/b16a%5Fhead/Cyl%20Head%201.jpg
This is the exit view of a stock B-16 exhaust port. Note that the divider isn't centered in the port. This particular port is #2 and it angles to the right (if you're looking at the head in plan view with the intakes nearest for reference). The port should not be reworked to remove the angle. The crests of the short turn radius are reasonably high (good) and the shape is ovaled, which is good for low lift flow and great for moderate street performance. Also note the reasonably deep indentions on the long side of the bowls at the casting's parting lines.
This is a picture of the same cylinder number's exhaust port which has been roughed out.
http://www.theoldone.com/articles/b16a%5Fhead/Cyl%20Head%202%20.jpg
B-16 Cylinder Head Mods (Part I)
This is an semi-complete view of cylinder head modifications for the B-16 Honda engines. It's meant to be a guide of sorts to some of the folks who have decided to do the porting modifications themselves.
First, I need to say that the B-16 cylinder head is a pretty good piece from the factory. The port volume is generous right out of the box, and unless the head's intended for some very "special" use, enlarging the ports isn't recommended.
There seems to be considerable core shift in all the castings we've worked with, so there's a good chance that doing your porting correctly will mean that the porting won't necessarily be cosmetically beautiful, so don't count on seeing shiny surfaces everywhere.
I'm starting out with a picture of "Old Trusty" and the bits that are used for the B-16 job.
http://www.theoldone.com/articles/b16a%5Fhead/The%20Grinder.jpg
I've inserted a D16 piston to provide a point of reference in this photo. Note that the grinder is not small. The reason is simple: It's darned near impossible to properly control a die grinder properly without leverage. With one hand on the snout and the other on the handle, it's possible to maintain enough mechanical advantage over the cutter (or polisher) to impart the shapes you desire. You can't port cylinder heads without your every move being deliberate and precise.
Note the speed control for rpm reduction. Most pros run the speed as low as the control will permit. These Dumore grinders will go pretty darned slow and still provide sufficient torque for the job. Under the handle is a trigger that is also used as a throttle (or another rpm control). You learn quickly to regulate rpm and cutter speed by continuously switching the grinders off and on. The switches do require replacement after every 20 sets of heads, but they're more than worth the price.
Note that the cutter in the picture is a .5" diameter oval shaped "alumicut" with coarse (very few) cutting edges. These cutters are capable of removing material pretty quickly and they also leave a descent finish that's easily polished to texture. The cartridge roll is a 60 grit .5" long by 1.5" length. Note the rounded nose on the roll. We shape the square noses by working the cartridge rolls on cinder blocks next to the grinding benches. A couple seconds will shape a new roll to "perfection". The split rod has 40 grit paper attached. This works good on intake ports, while 80 grit does a good job for chambers and exhaust ports.
I suspect that the length of the shanks on the various tools might have attracted some attention. It should, because the length is the key to doing good porting. It's a necessity to stay far enough away from the work to see what's going on and that's impossible when the cutters have a 3" shank. Every tool we use on cylinder heads is long for this reason and the additional reach also allows one to complete grinding a radius that's "hidden" over the crest in the ports. This way, you're not working from two different directions, attempting to connect two radii at the crest, which is inevitably the most critical part of the port. Now that you see the length of these particular tools, the necessity for low rpm operation should be apparent, since high rpm can make the shanks "whip" and cause major damage.
Now, I have some pictures of some B-16 exhaust ports to show what you start with and what you'll want to see when the grinding's finished.
http://www.theoldone.com/articles/b16a%5Fhead/Cyl%20Head%201.jpg
This is the exit view of a stock B-16 exhaust port. Note that the divider isn't centered in the port. This particular port is #2 and it angles to the right (if you're looking at the head in plan view with the intakes nearest for reference). The port should not be reworked to remove the angle. The crests of the short turn radius are reasonably high (good) and the shape is ovaled, which is good for low lift flow and great for moderate street performance. Also note the reasonably deep indentions on the long side of the bowls at the casting's parting lines.
This is a picture of the same cylinder number's exhaust port which has been roughed out.
http://www.theoldone.com/articles/b16a%5Fhead/Cyl%20Head%202%20.jpg