RoadWarrior
10-23-2008, 09:28 PM
Hi folks,
Some of you may have noticed I've not been on here as much. Well Marvin took a hissy fit, and munched on his tranny, a few days worth of cleaning and rebuilding the valve body and making sure the governor was free confirmed that it wasn't anything "easy" and the oil pump was likely shot. The finger of impending doom in the form of the wrath of the city is pointing towards Wile-E 'coz his sticker is expired, and finding and picking up a tranny on the cheap for Marvin being slightly unpossible with begged rides, means I turned my attention to Wile-E....
So the head was off and stripped down and got it to a machinist, wanted as much as possible off it, which turned out to only be 30 thou. Whereupon the clean cut metal revealed some secrets.... this head had been messed with before. Looked like it had dropped the valve seats at some point, munched on them some, and had to be welded up. Probably had a few thou shaved then. Bugger, would have preferred a factory spec head to be messing with, but welds were very cleanly done and I was gonna have trouble getting out to find a decent used head anyway, so pressed on with this one...
First thing was to heavily tape the freshly cut deck so I didn't score it up. Then cleaned the chambers out a bit more to see what I was dealing with. Hum yup, welding was little more obvious now 'cos the chamber shape was a little lumpy in 2 of 'em and they were all a bit pitted up.
Got to work on the chambers first, working with 1/2" sanding rolls and various grindstones. Took out a slight ridge between the valves, then laid back the chamber edge a bit away from the valves on either side, blending into the squish pad without taking too much out of it. This is a D shape crossflow hemi chamber. Try to resurface as delicately as possible with the sanding rolls, and do minimal blending and de-shrouding 'coz I don't want to lose much compression. Cut a single groove in each squish pad, U cross section, and a kind of ski-jump or cutoff J longitudinal section. Used the grinders again to round everything off, grooves, squishpad, chamber edges. Then went onto 150-220-360-400 grit hand polishing followed by steel wool, followed by kitchen cream cleanser, followed by metal polish... yes I wanted them shiny! The mirror finish is somewhat spoiled by some pitting that I couldn't get out without removing farrrr too much metal, but I'm fairly happy with it. Also during this phase I rounded in the top of the valve seats a bit, being real careful not to catch the normal second cut seating face. The intakes are a bugger 'coz they're inset a bit, could really only take the edge off them and hope.
I had intended at this point to use a bright finish anodising process I had come across, to put a thick, hard, durable clear gloss coating on the chambers... however, with limited transportation the chemicals and supplies I needed proved hard to get hold of, so I had to scratch that idea. The plan was that this would cut thermal heat transfer by a factor of 10, while preserving the high shine for radiant heat rejection. I've got a nice finish on them, so hopefully this will stop carbon sticking and the radiant heat rejection will work for a good while. Hopefully this step will get done to Marvin's spare heads which I should theoretically not be under such time pressure for and have transport to gofer this and that.
Next up I attacked the exhaust ports... The seat to bowl transition was awful as was the SSR out of the seat so those were radiused with a hand file and grinders. Tackling the boss area was difficult, didn't have quite enough reach with my grinder from chamber or port side, so all I could do really was feather out a casting seam and bulge on one side, and knock off a couple of edges. The floor and roof were mostly left alone. The seats were given a bottom blend/cut from the 3rd angle, this along with the top blend/cut more or less "5 angles" them. I cleaned up the walls a bit as far as I could reach in with the sanding roll, exhaust ports should be smooth. There was room in the casting to modify the roof, but this is not a top end motor with high lift cam so there is no point. The ports could use being smaller. I did an edge round and turbulation groove bias on 2 sides of the exits of the ports to trip the air a bit in the direction the stock exhaust manifold turns. This wasn't too much of a bias and reshape, I'm hoping to find a GT header for it eventually.
Intake ports, again the major work was transitioning the seat into the bowl. These are swirl ports with a sort of spiral staircase cast alongside the boss, filling one side of it as you look down the port. Now I wanted to keep swirl so I didn't want to mess with these much. Ideally I would have liked to have hogged out some room for the air to swoop around the outside of the boss there a little better, but the casting is maybe 2mm thick there, so there's no room without major restructuring. Also was at the limit of tool reach there so couldn't mess with much. Added turbulation trip grooves along the bottom turn in around the valve boss to get the air turning into the "spiral staircase" better. Mostly the intake shaping work was about the blend into the seat which was 'orrible. The outer ports were speckled with casting flash, which was a PITA. I had to get that off with a sanding roll first, because although texture is good, I wanted my own texture on there.
Texturing was achieved by chucking a 4" piece of round wood rasp into a drill and dragging it round the port. This achieved fine grooving, suitable for boundary layer energisation, and variable boundary layer effect and providing scores thin enough to spread fuel droplets by capilliary action. One drop of alcohol in the middle of the outer port spreads half way up the walls! By using the rasp in reverse wrt to airflow I have hopefully achieved a texture with a cross section approximating |\|\|\|\|\ where airflow is right to left, which should provide more resistance to reverse flow that forward flow, and may encourage reflection of any reverse pulses back towards source. Also note, the turbulation grooves on the side of the boss area will not work in reverse flow situations.
The final touch to the intakes was using a 1/16 drill bit to put some shallow pits in the top of the port near the entrance. These should function as Helmholtz resonators in the ultrasonic range when high speed airflow is across them. This should in theory help break up large fuel droplets at large throttle openings. As the top of the port is at the SSR of the intake piping, I was hoping also to put some in the bottom of the port where air would initially be moving faster, but the angle of the port made it unpossible for me to get the holes in at anything close to the 90* angle they need to work right.
On the to do list:
Clean valves, groove top of intakes, bottom of exhausts, (15% more flow) and polish and de-edge, round out face cut a little.
Copper plate intake ports (might need texture touching up again if it plates heavy)
Make SS port plates for exhaust, to round turn out of valve and restrict port to keep velocity higher, also add AR benefits.
...
...
...
Reassemble, install
There's another deep magic strange physics trick I'll be working in in the middle there, which if it works insanely well, may become proprietary, but most likely is just worth a couple of percent, so when the pudding is proved, I'll tell you about it, or leave you going insane trying to figure how I am getting 150mpg while I attempt to get some dough in my pocket for it. :D
When it's running I need an e-test pretty much straight away, but support mods, including a fuel heater will be going on the car to bring the full potential out after that.
Road Warrior
Some of you may have noticed I've not been on here as much. Well Marvin took a hissy fit, and munched on his tranny, a few days worth of cleaning and rebuilding the valve body and making sure the governor was free confirmed that it wasn't anything "easy" and the oil pump was likely shot. The finger of impending doom in the form of the wrath of the city is pointing towards Wile-E 'coz his sticker is expired, and finding and picking up a tranny on the cheap for Marvin being slightly unpossible with begged rides, means I turned my attention to Wile-E....
So the head was off and stripped down and got it to a machinist, wanted as much as possible off it, which turned out to only be 30 thou. Whereupon the clean cut metal revealed some secrets.... this head had been messed with before. Looked like it had dropped the valve seats at some point, munched on them some, and had to be welded up. Probably had a few thou shaved then. Bugger, would have preferred a factory spec head to be messing with, but welds were very cleanly done and I was gonna have trouble getting out to find a decent used head anyway, so pressed on with this one...
First thing was to heavily tape the freshly cut deck so I didn't score it up. Then cleaned the chambers out a bit more to see what I was dealing with. Hum yup, welding was little more obvious now 'cos the chamber shape was a little lumpy in 2 of 'em and they were all a bit pitted up.
Got to work on the chambers first, working with 1/2" sanding rolls and various grindstones. Took out a slight ridge between the valves, then laid back the chamber edge a bit away from the valves on either side, blending into the squish pad without taking too much out of it. This is a D shape crossflow hemi chamber. Try to resurface as delicately as possible with the sanding rolls, and do minimal blending and de-shrouding 'coz I don't want to lose much compression. Cut a single groove in each squish pad, U cross section, and a kind of ski-jump or cutoff J longitudinal section. Used the grinders again to round everything off, grooves, squishpad, chamber edges. Then went onto 150-220-360-400 grit hand polishing followed by steel wool, followed by kitchen cream cleanser, followed by metal polish... yes I wanted them shiny! The mirror finish is somewhat spoiled by some pitting that I couldn't get out without removing farrrr too much metal, but I'm fairly happy with it. Also during this phase I rounded in the top of the valve seats a bit, being real careful not to catch the normal second cut seating face. The intakes are a bugger 'coz they're inset a bit, could really only take the edge off them and hope.
I had intended at this point to use a bright finish anodising process I had come across, to put a thick, hard, durable clear gloss coating on the chambers... however, with limited transportation the chemicals and supplies I needed proved hard to get hold of, so I had to scratch that idea. The plan was that this would cut thermal heat transfer by a factor of 10, while preserving the high shine for radiant heat rejection. I've got a nice finish on them, so hopefully this will stop carbon sticking and the radiant heat rejection will work for a good while. Hopefully this step will get done to Marvin's spare heads which I should theoretically not be under such time pressure for and have transport to gofer this and that.
Next up I attacked the exhaust ports... The seat to bowl transition was awful as was the SSR out of the seat so those were radiused with a hand file and grinders. Tackling the boss area was difficult, didn't have quite enough reach with my grinder from chamber or port side, so all I could do really was feather out a casting seam and bulge on one side, and knock off a couple of edges. The floor and roof were mostly left alone. The seats were given a bottom blend/cut from the 3rd angle, this along with the top blend/cut more or less "5 angles" them. I cleaned up the walls a bit as far as I could reach in with the sanding roll, exhaust ports should be smooth. There was room in the casting to modify the roof, but this is not a top end motor with high lift cam so there is no point. The ports could use being smaller. I did an edge round and turbulation groove bias on 2 sides of the exits of the ports to trip the air a bit in the direction the stock exhaust manifold turns. This wasn't too much of a bias and reshape, I'm hoping to find a GT header for it eventually.
Intake ports, again the major work was transitioning the seat into the bowl. These are swirl ports with a sort of spiral staircase cast alongside the boss, filling one side of it as you look down the port. Now I wanted to keep swirl so I didn't want to mess with these much. Ideally I would have liked to have hogged out some room for the air to swoop around the outside of the boss there a little better, but the casting is maybe 2mm thick there, so there's no room without major restructuring. Also was at the limit of tool reach there so couldn't mess with much. Added turbulation trip grooves along the bottom turn in around the valve boss to get the air turning into the "spiral staircase" better. Mostly the intake shaping work was about the blend into the seat which was 'orrible. The outer ports were speckled with casting flash, which was a PITA. I had to get that off with a sanding roll first, because although texture is good, I wanted my own texture on there.
Texturing was achieved by chucking a 4" piece of round wood rasp into a drill and dragging it round the port. This achieved fine grooving, suitable for boundary layer energisation, and variable boundary layer effect and providing scores thin enough to spread fuel droplets by capilliary action. One drop of alcohol in the middle of the outer port spreads half way up the walls! By using the rasp in reverse wrt to airflow I have hopefully achieved a texture with a cross section approximating |\|\|\|\|\ where airflow is right to left, which should provide more resistance to reverse flow that forward flow, and may encourage reflection of any reverse pulses back towards source. Also note, the turbulation grooves on the side of the boss area will not work in reverse flow situations.
The final touch to the intakes was using a 1/16 drill bit to put some shallow pits in the top of the port near the entrance. These should function as Helmholtz resonators in the ultrasonic range when high speed airflow is across them. This should in theory help break up large fuel droplets at large throttle openings. As the top of the port is at the SSR of the intake piping, I was hoping also to put some in the bottom of the port where air would initially be moving faster, but the angle of the port made it unpossible for me to get the holes in at anything close to the 90* angle they need to work right.
On the to do list:
Clean valves, groove top of intakes, bottom of exhausts, (15% more flow) and polish and de-edge, round out face cut a little.
Copper plate intake ports (might need texture touching up again if it plates heavy)
Make SS port plates for exhaust, to round turn out of valve and restrict port to keep velocity higher, also add AR benefits.
...
...
...
Reassemble, install
There's another deep magic strange physics trick I'll be working in in the middle there, which if it works insanely well, may become proprietary, but most likely is just worth a couple of percent, so when the pudding is proved, I'll tell you about it, or leave you going insane trying to figure how I am getting 150mpg while I attempt to get some dough in my pocket for it. :D
When it's running I need an e-test pretty much straight away, but support mods, including a fuel heater will be going on the car to bring the full potential out after that.
Road Warrior