How to mod a 12A OMP to pump 2-cycle oil
07-02-05, 01:57 AM
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Rotary Freak
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How to mod a 12A OMP to pump 2-cycle oil
This procedure is for those wishing to modify their stock 12A metering pump to receive and deliver cleaner-burning 2-stroke oil to the apex seals rather than dirtier, detergent-laden 4-stroke oil from the rotary engine's oil pan. But first, for those new to rotaries, a little history to bring you up to speed:
Most of us are aware that the 4-cycle engine oil used in the rotary engine is ideal for lubricating bearings and cooling the rotors, but not the best choice for metering into the intake system for the purpose of lubricating the apex seals. The best oil for this purpose is 2-cycle oil, preferrably a TCw3 or equivalent.
2-cycle oil adheres to metal serfaces better than 4-cycle oil does due to its less viscous penetrating qualities and more importantly, its much cleaner burning characteristics when burned with the air/ fuel mixture in the combustion chambers. This leaves fewer carbon deposits behind to clog seals, decrease compression and shorten engine life.
But Mazda did not go this route because it was thought that many owners would not like the idea and/or fail to follow proper rotary engine care and feeding practices. This was a compromise, but one that seemed to make the most sense to those in charge at Mazda.
The racing community has known this since the earliest Mazda rotaries were produced, and typically they discard the metering pumps on their rotaries and instead install block-off plates over the original metering pump mounting surface on the front cover. 2-cycle oil is then pre-mixed with the fuel at a fuel-to-oil ratio of about 100:1. This practice has also been adopted by private owners who take rotary maintenance procedures seriously, with favourable results.
Another method of delivering 2-cycle oil to the intakes is to bolt a metering pump adapter between the oil metering pump (OMP) and the mounting surface. This adapter acts as a block-off plate to stop the flow of 4-cycle oil from the oil pan to the omp, and also has an orfice to admit 2-cycle oil into the metering pump from a separate reservior. A shaft inside the adapter links the metering pump to the drive unit located inside the front cover allowing the omp to deliver 2-cycle oil in the same manner as it previously metered engine oil.
I have used one of these adapters for over two years, and when my metering pump failed recently (a problem not related to the adapter but rather, caused by a worn metering cam inside the metering pump) the adapter was found to be in excellent condition with no detectible wear.
Another member on the RX7 forum had previously suggested that rather than using an adapter, the best route would be to modify the stock metering pump to receive 2-cycle oil from a reservior and then place a thin block-off plate between two stock omp gaskets. I decided to try this, with very good results. Many thanks to the forum member (whose name I can't recall) that originally suggested this mod.
This procedure renders all metering pump adapters obsolete, but represents a non-reversible mod to the stock omp. If you wish to keep your car all original you'll need to pick up a spare stock omp to swap back in for future car shows, appraisals or whenever you wish to sell the car.
Materials and tools required for this modification:
1. Two stock 12A metering pump gaskets from Mazda at approx. $3 each.
2. One 3" by 2" piece of thin (ie: 0.020") aluminum, or an empty beer can.
3. A tube of silicone sealant.
4. A small jar of Vaseline.
5. A tube of red Loctite.
6. "JB Weld" (or equivalent) 2-part adhesive/ sealant.
7. An electric drill.
8. Drill bits: 1/16", 1/8" and 1/4"
9. A flashlight, preferrably a "Snake-light" or equivalent.
10. A small shallow container, ex: used soft-plastic butter container (for solvent).
11. Solvent, ie: varsol or gasoline.
12. 4 to 6 very small hose clamps. sufficient to clamp onto standard 1/4" internal diameter fuel hose.
13. A 3-ft length of neoprene fuel hose. (Neoprene is impervious to oil).
14. A brass 90-degree elbow fitting to link the fuel hose to the home-made fitting.
15. A suitable impervious to oil reservior complete with mounting bracket and bolts, ie: small power steering fluid reservior from a Nissan or equivalent. Do not use plastic washer fluid reserviors --- oil eats them.
16. A short length of hose and adapter fitting to match reservior outlet to fuel hose.
17. Depending on reservior, a suitable-diameter short length of neoprene hose, bolt and clamp to make a plug for the (former) power steering fluid reservior inlet port.
18. A 3/4" hole saw.
19. Various tools, ie: pliers, wrenches, sockets, ratchet, extensions, multi-point screwdriver, tin snips, hacksaw, utility knife, shop rags, dental pick for o-rings.
The following is a step-by-step procedure for performing this modification:
1. Remove the air filter housing and air pump to better access the metering pump. Then remove the metering pump from the engine. It's held on by two bolts that require a 10mm wrench to remove, two metering lines and a cotter pin that attaches a control rod to a lever on the rear side of the pump.
2. Dis-assemble the omp down to the last part, including all o-rings. These o-rings will have to be replaced with Viton 0-rings. Unlike stock neoprene o-rings, Viton is a material that seals well and stands up to heat for a long period of time without becoming brittle and prone to leaking. If your metering pump was seeping oil before, it will absolutely gush once you switch to 2-cycle oil unless you change these seals. They're not expensive, btw --- somewhere on the order of pennies apiece.
You'll need four of them: two 13/16" outside diameter ones that are 1/16" in cross-section (ie: the thickness of the actual seal material), and two o-rings that are a metric size that's very slightly larger than 1/4" in outside diameter with an approximately 1/16" cross-section.
The two larger seals go under the end caps. The grooves in which they sit are actually a round-edged diamond shape, but these seals will conform to that shape quite easily. The two smaller seals go beside each other in the same 1/8" wide groove on in the metering adjustment lever cam located near the rear of the metering pump.
Note: Some metering pumps have one 1/4" O.D. seal on the metering cam rather than two o-rings. But this one seal is twice as wide, ie: 1/8" wide with cupped edges. I believe it's a Mazda-specific part, but it can be replaced by two Viton o-rings of 1/16" cross-section each.
3. Thoroughly clean all components in solvent, and then carefully inspect each component for evidence of wear. Pay particular atention to the metering cam on which the two smaller o-rings are installed. The cam, when rotated by a rod connected to the lever on one end of the shaft, adjusts oil flow. when the throttle is opened, this rod is pulled upward, rotating the cam to a position where it moves a pin inside the pump to a new position that allows more oil to flow. If this cam is worn, oil flow will be minimal (or not at all), and the apex seals will be receiving insufficient lubrication.
4. Having acquired the necessary replacement seals and confirmed that all components are in good working order, you can now begin making the necessary changes to the metering pump so that it can receive and deliver 2-cycle oil. This mod should be done while the metering pump is still dis-assembled.
5. First, it is necessary to drill a 1/16" access hole into the EDGE of the approximately 1/4" thick mounting flange on the pump body. This hole must start at the front lower portion of the pump body and extend through the flange to the inside surface of the original oil inlet hole into the pump, where the engine oil used to enter the pump after being fed there from inside the front cover.
This hole must be drilled so that it will be PARALLEL to the mounting surface on the front cover when the omp is in its installed position, and so that it angles Upward at about 45 degrees to intercept the original oil inlet orfice. The distance (depth) of this new hole is approximately one inch.
The reason for starting near the bottom of the flange and angling upward to the inlet hole is two-fold: First, this will allow clearance for the drill bit and chuck to clear the front of the omp on the way in and second, to allow the fitting (that you are going to make and thread into the hole) to clear the bottom of the pump and angle under and to the forward right-hand side of the pump, ie: in the general direction of the front right-hand headlight. In this position it is easy to clamp the oil delivery line from the reservior onto the end of the fitting.
DO NOT drill this hole any larger than about 1/16" in diameter. If you do, the mounting flange will be weakened to the point where it will break off when you attempt to tighten the omp mounting bolts. (ask me how I know this).
6. Next, it will be necessary to counter-bore this new hole to a depth of no more than 1/4". Drilling this counter-bore any deeper will weaken the flange too much. The diameter of this counter-bore depends on the INSIDE diameter of the threads that you will be cutting on the OUTSIDE diameter of the small piece of steel tube that you will be using to make a fitting out of.
You may want to re-read the above paragraph a few times for it to make sense. First, the internal diameter of the fitting should be about 1/16". But the thickness of the flange is only 1/4". This means that the ideal outside diameter of the steel tube (that will soon be a home-made fitting) is around 3/16". But do not drill the counter-bore out to this larger dimension or you will have no material inside the counter-bore in which to cut threads. This means that the best diameter to drill the 1/4" deep counter-bore is about 1/8". This leaves enough material to thread the 3/16" diameter fitting into the counterbore.
7. Go to an auto wrecking yard with a hack saw and locate an approximately two inch length of steel emission control tubing, the type usually found on carburator-equipped cars. Most of this tubing will be too large in diameter, on the order of 1/4", but there are smaller-diameter pieces available. Ideally you'd want a piece that has a bead (ie: a "ridge") at one end so that the hose you clamp onto it will be more likely to stay clamped on. File and de-burr the end of this 2" length of steel tubing.
8. Next, *very carefully* bend the tubing at the center to about 10 degrees. Do not bend beyond this or the tube may kink. The purpose of the bend is to allow the tubing to point in the proper direction once it's threaded into the omp body. This position allows the oil delivery hose to be easily clamped into position with your screwdriver in the most efficient position.
9. Now you can cut the external threads into the first 1/4" of the outside diameter of the tubing and then the internal threads into the first 1/4" of the hole you drilled into the omp body. The actual pitch (# of threads per inch) of the threads cut isn't important (although finer threads are best for this), but you'll need to make sure that the size and pitch of the internal threads cut into the hole match those of the external threads cut into the tubing.
10. Remove all swarf (metal shavings) from inside the pump body. Then put red Loctite onto the outside of the external threads of the fitting. Carefully thread the fitting into the hole. You'll want its final position to be pointing out toward the front right-hand corner of the car and from under the omp.
If the threads begin to tighten up before it's in this ideal position, DO NOT try to tighten it to position --- the fitting will break right at the threads. (Again, ask me how I know this). Instead, back off the threads to the position you want. The Loctite and JB Weld will do the rest.
11. Mix up a small batch of JB Weld. Thoroughly clean the outside of the omp body once more with solvent and then gob the JB Weld onto the base of the fitting where it threads into the omp body. You'll want to use enough JB Weld to provide as much structural rigidity to the fitting as possible while protecting against leaks.
12. Use Vaseline to lubricate all internal metering pump components except the larger o-rings. Re-assemble the metering pump. When you get to the larger o-rings that live under the end caps, smear them with Silicone sealant to aid in sealing and to help them conform to the diamond shape of their grooves as you screw the caps back on over them. Do not over-do it with the silicone. You don't want a large gob of it to cure, break off and then plug up your metering pump. Be sure that the seals haven't slipped out of their grooves as you tighten them down.
13. You need to make a block-off plate in the shape of the gaskets (minus the oil feed hole of course) out of thin aluminum. Cut out an approximately 2" by 3" piece of aluminum from a beer can.
Next, use the 3/4" hole saw in the drill to cut out a 3/4" diameter hole in the middle of the aluminum. Now place the mounting omp over this hole so that the omp's drive key (on the mounting surface side of the pump) is inserted into the 3/4" hole.
Now trace a line on the aluminum around the outside of the omp mounting flange. Use the snips to cut out this shape, de-burr, and then once again place this shim over the drive key. Use the 1/4" drill bit to drill out the mounting bolt holes in the block-off plate.
14. *Very sparingly*, coat one side of one of the gaskets with silicone and then place it into position on the omp. Make sure no silicone is allowed to enter the original oil inlet hole on the omp. Then apply another very thin coat of silicone to the other side of the gasket, and then lay the block-off plate into position over it.
Apply another very thin layer of silicone to the other side of the block-off plate, and then place the second gasket into position over it. Now apply a final layer of silicone on the other side of the second gasket.
15. Wipe the mounting surface on the engine's front cover clean and then re-install the metering pump onto the engine. Hook up both oil lines and re-connect the control rod, making sure you put the cotter pin through the second hole from the bottom of the rod. Hint: It will be easier to connect this rod and cotter pin it if you do this BEFORE maneuvering the omp into position and bolting it down. (You really don't have to ask me how I know this, do you?)
16. Mount the reservior high up on the forward portion of the right-hand strut tower, opposite the washer fluid reservior. This will insure proper gravity feed. If you do not wish to mutilate your prized stock RX7 by drilling holes in the strut tower to mount this reservior, another option would be to fabricate a bracket that allows you to use two of the upper strut attach nuts to secure the reservior.
17. Cut the fuel hose to length and clamp it onto the bottom outlet of the reservior. Fabricate and install an adapter to match the fitting to the hose if necessary. Install the brass 90-degree elbow onto the omp end of the fuel hose. Then cut a 2" length of fuel hose and install it between the other side of the elbow and the home-made fitting on the omp. Use hose clamps to secure.
18. If necessary, install a plug in the other inlet port on the reservior, ie: if this reservior used to be a power steering fluid reservior it will have an extra port to seal off.
19. Fill the reservior with TCw3 or equivalent 2-cycle oil. Dump another 8 oz of this oil into the fuel tank to insure proper lube until the oil is being pumped into the engine by the omp. Wipe up any oil spills in the vicinity of the omp so that new leaks, if any, will be more visible.
20. Start the car and watch as the lines re-fill with green 2-cycle oil. This may take up to twenty minutes before they are full. Watch for leaks. If all checks out you are almost done.
21. Re-install the air pump and air filter housing. You're now done. Congratulations.
Keep a close watch on the nylon feeder lines from the omp to the carb for the first few weeks. Check oil level in the reservior at every fuel fill-up and note how much it takes to top off the reservior. It's also a good idea to keep a couple liters of TCw3 2-cycle oil in the car at all times. Walmart sells this stuff for the best price --- $2 to $3 per liter for their in-house "Tech 2000" brand vs. up to $7 per liter at service stations. The service station brands are really no better considering the purpose.
Most of us are aware that the 4-cycle engine oil used in the rotary engine is ideal for lubricating bearings and cooling the rotors, but not the best choice for metering into the intake system for the purpose of lubricating the apex seals. The best oil for this purpose is 2-cycle oil, preferrably a TCw3 or equivalent.
2-cycle oil adheres to metal serfaces better than 4-cycle oil does due to its less viscous penetrating qualities and more importantly, its much cleaner burning characteristics when burned with the air/ fuel mixture in the combustion chambers. This leaves fewer carbon deposits behind to clog seals, decrease compression and shorten engine life.
But Mazda did not go this route because it was thought that many owners would not like the idea and/or fail to follow proper rotary engine care and feeding practices. This was a compromise, but one that seemed to make the most sense to those in charge at Mazda.
The racing community has known this since the earliest Mazda rotaries were produced, and typically they discard the metering pumps on their rotaries and instead install block-off plates over the original metering pump mounting surface on the front cover. 2-cycle oil is then pre-mixed with the fuel at a fuel-to-oil ratio of about 100:1. This practice has also been adopted by private owners who take rotary maintenance procedures seriously, with favourable results.
Another method of delivering 2-cycle oil to the intakes is to bolt a metering pump adapter between the oil metering pump (OMP) and the mounting surface. This adapter acts as a block-off plate to stop the flow of 4-cycle oil from the oil pan to the omp, and also has an orfice to admit 2-cycle oil into the metering pump from a separate reservior. A shaft inside the adapter links the metering pump to the drive unit located inside the front cover allowing the omp to deliver 2-cycle oil in the same manner as it previously metered engine oil.
I have used one of these adapters for over two years, and when my metering pump failed recently (a problem not related to the adapter but rather, caused by a worn metering cam inside the metering pump) the adapter was found to be in excellent condition with no detectible wear.
Another member on the RX7 forum had previously suggested that rather than using an adapter, the best route would be to modify the stock metering pump to receive 2-cycle oil from a reservior and then place a thin block-off plate between two stock omp gaskets. I decided to try this, with very good results. Many thanks to the forum member (whose name I can't recall) that originally suggested this mod.
This procedure renders all metering pump adapters obsolete, but represents a non-reversible mod to the stock omp. If you wish to keep your car all original you'll need to pick up a spare stock omp to swap back in for future car shows, appraisals or whenever you wish to sell the car.
Materials and tools required for this modification:
1. Two stock 12A metering pump gaskets from Mazda at approx. $3 each.
2. One 3" by 2" piece of thin (ie: 0.020") aluminum, or an empty beer can.
3. A tube of silicone sealant.
4. A small jar of Vaseline.
5. A tube of red Loctite.
6. "JB Weld" (or equivalent) 2-part adhesive/ sealant.
7. An electric drill.
8. Drill bits: 1/16", 1/8" and 1/4"
9. A flashlight, preferrably a "Snake-light" or equivalent.
10. A small shallow container, ex: used soft-plastic butter container (for solvent).
11. Solvent, ie: varsol or gasoline.
12. 4 to 6 very small hose clamps. sufficient to clamp onto standard 1/4" internal diameter fuel hose.
13. A 3-ft length of neoprene fuel hose. (Neoprene is impervious to oil).
14. A brass 90-degree elbow fitting to link the fuel hose to the home-made fitting.
15. A suitable impervious to oil reservior complete with mounting bracket and bolts, ie: small power steering fluid reservior from a Nissan or equivalent. Do not use plastic washer fluid reserviors --- oil eats them.
16. A short length of hose and adapter fitting to match reservior outlet to fuel hose.
17. Depending on reservior, a suitable-diameter short length of neoprene hose, bolt and clamp to make a plug for the (former) power steering fluid reservior inlet port.
18. A 3/4" hole saw.
19. Various tools, ie: pliers, wrenches, sockets, ratchet, extensions, multi-point screwdriver, tin snips, hacksaw, utility knife, shop rags, dental pick for o-rings.
The following is a step-by-step procedure for performing this modification:
1. Remove the air filter housing and air pump to better access the metering pump. Then remove the metering pump from the engine. It's held on by two bolts that require a 10mm wrench to remove, two metering lines and a cotter pin that attaches a control rod to a lever on the rear side of the pump.
2. Dis-assemble the omp down to the last part, including all o-rings. These o-rings will have to be replaced with Viton 0-rings. Unlike stock neoprene o-rings, Viton is a material that seals well and stands up to heat for a long period of time without becoming brittle and prone to leaking. If your metering pump was seeping oil before, it will absolutely gush once you switch to 2-cycle oil unless you change these seals. They're not expensive, btw --- somewhere on the order of pennies apiece.
You'll need four of them: two 13/16" outside diameter ones that are 1/16" in cross-section (ie: the thickness of the actual seal material), and two o-rings that are a metric size that's very slightly larger than 1/4" in outside diameter with an approximately 1/16" cross-section.
The two larger seals go under the end caps. The grooves in which they sit are actually a round-edged diamond shape, but these seals will conform to that shape quite easily. The two smaller seals go beside each other in the same 1/8" wide groove on in the metering adjustment lever cam located near the rear of the metering pump.
Note: Some metering pumps have one 1/4" O.D. seal on the metering cam rather than two o-rings. But this one seal is twice as wide, ie: 1/8" wide with cupped edges. I believe it's a Mazda-specific part, but it can be replaced by two Viton o-rings of 1/16" cross-section each.
3. Thoroughly clean all components in solvent, and then carefully inspect each component for evidence of wear. Pay particular atention to the metering cam on which the two smaller o-rings are installed. The cam, when rotated by a rod connected to the lever on one end of the shaft, adjusts oil flow. when the throttle is opened, this rod is pulled upward, rotating the cam to a position where it moves a pin inside the pump to a new position that allows more oil to flow. If this cam is worn, oil flow will be minimal (or not at all), and the apex seals will be receiving insufficient lubrication.
4. Having acquired the necessary replacement seals and confirmed that all components are in good working order, you can now begin making the necessary changes to the metering pump so that it can receive and deliver 2-cycle oil. This mod should be done while the metering pump is still dis-assembled.
5. First, it is necessary to drill a 1/16" access hole into the EDGE of the approximately 1/4" thick mounting flange on the pump body. This hole must start at the front lower portion of the pump body and extend through the flange to the inside surface of the original oil inlet hole into the pump, where the engine oil used to enter the pump after being fed there from inside the front cover.
This hole must be drilled so that it will be PARALLEL to the mounting surface on the front cover when the omp is in its installed position, and so that it angles Upward at about 45 degrees to intercept the original oil inlet orfice. The distance (depth) of this new hole is approximately one inch.
The reason for starting near the bottom of the flange and angling upward to the inlet hole is two-fold: First, this will allow clearance for the drill bit and chuck to clear the front of the omp on the way in and second, to allow the fitting (that you are going to make and thread into the hole) to clear the bottom of the pump and angle under and to the forward right-hand side of the pump, ie: in the general direction of the front right-hand headlight. In this position it is easy to clamp the oil delivery line from the reservior onto the end of the fitting.
DO NOT drill this hole any larger than about 1/16" in diameter. If you do, the mounting flange will be weakened to the point where it will break off when you attempt to tighten the omp mounting bolts. (ask me how I know this).
6. Next, it will be necessary to counter-bore this new hole to a depth of no more than 1/4". Drilling this counter-bore any deeper will weaken the flange too much. The diameter of this counter-bore depends on the INSIDE diameter of the threads that you will be cutting on the OUTSIDE diameter of the small piece of steel tube that you will be using to make a fitting out of.
You may want to re-read the above paragraph a few times for it to make sense. First, the internal diameter of the fitting should be about 1/16". But the thickness of the flange is only 1/4". This means that the ideal outside diameter of the steel tube (that will soon be a home-made fitting) is around 3/16". But do not drill the counter-bore out to this larger dimension or you will have no material inside the counter-bore in which to cut threads. This means that the best diameter to drill the 1/4" deep counter-bore is about 1/8". This leaves enough material to thread the 3/16" diameter fitting into the counterbore.
7. Go to an auto wrecking yard with a hack saw and locate an approximately two inch length of steel emission control tubing, the type usually found on carburator-equipped cars. Most of this tubing will be too large in diameter, on the order of 1/4", but there are smaller-diameter pieces available. Ideally you'd want a piece that has a bead (ie: a "ridge") at one end so that the hose you clamp onto it will be more likely to stay clamped on. File and de-burr the end of this 2" length of steel tubing.
8. Next, *very carefully* bend the tubing at the center to about 10 degrees. Do not bend beyond this or the tube may kink. The purpose of the bend is to allow the tubing to point in the proper direction once it's threaded into the omp body. This position allows the oil delivery hose to be easily clamped into position with your screwdriver in the most efficient position.
9. Now you can cut the external threads into the first 1/4" of the outside diameter of the tubing and then the internal threads into the first 1/4" of the hole you drilled into the omp body. The actual pitch (# of threads per inch) of the threads cut isn't important (although finer threads are best for this), but you'll need to make sure that the size and pitch of the internal threads cut into the hole match those of the external threads cut into the tubing.
10. Remove all swarf (metal shavings) from inside the pump body. Then put red Loctite onto the outside of the external threads of the fitting. Carefully thread the fitting into the hole. You'll want its final position to be pointing out toward the front right-hand corner of the car and from under the omp.
If the threads begin to tighten up before it's in this ideal position, DO NOT try to tighten it to position --- the fitting will break right at the threads. (Again, ask me how I know this). Instead, back off the threads to the position you want. The Loctite and JB Weld will do the rest.
11. Mix up a small batch of JB Weld. Thoroughly clean the outside of the omp body once more with solvent and then gob the JB Weld onto the base of the fitting where it threads into the omp body. You'll want to use enough JB Weld to provide as much structural rigidity to the fitting as possible while protecting against leaks.
12. Use Vaseline to lubricate all internal metering pump components except the larger o-rings. Re-assemble the metering pump. When you get to the larger o-rings that live under the end caps, smear them with Silicone sealant to aid in sealing and to help them conform to the diamond shape of their grooves as you screw the caps back on over them. Do not over-do it with the silicone. You don't want a large gob of it to cure, break off and then plug up your metering pump. Be sure that the seals haven't slipped out of their grooves as you tighten them down.
13. You need to make a block-off plate in the shape of the gaskets (minus the oil feed hole of course) out of thin aluminum. Cut out an approximately 2" by 3" piece of aluminum from a beer can.
Next, use the 3/4" hole saw in the drill to cut out a 3/4" diameter hole in the middle of the aluminum. Now place the mounting omp over this hole so that the omp's drive key (on the mounting surface side of the pump) is inserted into the 3/4" hole.
Now trace a line on the aluminum around the outside of the omp mounting flange. Use the snips to cut out this shape, de-burr, and then once again place this shim over the drive key. Use the 1/4" drill bit to drill out the mounting bolt holes in the block-off plate.
14. *Very sparingly*, coat one side of one of the gaskets with silicone and then place it into position on the omp. Make sure no silicone is allowed to enter the original oil inlet hole on the omp. Then apply another very thin coat of silicone to the other side of the gasket, and then lay the block-off plate into position over it.
Apply another very thin layer of silicone to the other side of the block-off plate, and then place the second gasket into position over it. Now apply a final layer of silicone on the other side of the second gasket.
15. Wipe the mounting surface on the engine's front cover clean and then re-install the metering pump onto the engine. Hook up both oil lines and re-connect the control rod, making sure you put the cotter pin through the second hole from the bottom of the rod. Hint: It will be easier to connect this rod and cotter pin it if you do this BEFORE maneuvering the omp into position and bolting it down. (You really don't have to ask me how I know this, do you?)
16. Mount the reservior high up on the forward portion of the right-hand strut tower, opposite the washer fluid reservior. This will insure proper gravity feed. If you do not wish to mutilate your prized stock RX7 by drilling holes in the strut tower to mount this reservior, another option would be to fabricate a bracket that allows you to use two of the upper strut attach nuts to secure the reservior.
17. Cut the fuel hose to length and clamp it onto the bottom outlet of the reservior. Fabricate and install an adapter to match the fitting to the hose if necessary. Install the brass 90-degree elbow onto the omp end of the fuel hose. Then cut a 2" length of fuel hose and install it between the other side of the elbow and the home-made fitting on the omp. Use hose clamps to secure.
18. If necessary, install a plug in the other inlet port on the reservior, ie: if this reservior used to be a power steering fluid reservior it will have an extra port to seal off.
19. Fill the reservior with TCw3 or equivalent 2-cycle oil. Dump another 8 oz of this oil into the fuel tank to insure proper lube until the oil is being pumped into the engine by the omp. Wipe up any oil spills in the vicinity of the omp so that new leaks, if any, will be more visible.
20. Start the car and watch as the lines re-fill with green 2-cycle oil. This may take up to twenty minutes before they are full. Watch for leaks. If all checks out you are almost done.
21. Re-install the air pump and air filter housing. You're now done. Congratulations.
Keep a close watch on the nylon feeder lines from the omp to the carb for the first few weeks. Check oil level in the reservior at every fuel fill-up and note how much it takes to top off the reservior. It's also a good idea to keep a couple liters of TCw3 2-cycle oil in the car at all times. Walmart sells this stuff for the best price --- $2 to $3 per liter for their in-house "Tech 2000" brand vs. up to $7 per liter at service stations. The service station brands are really no better considering the purpose.
07-02-05, 02:23 AM
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Thanks Aviator; I've been wondering if there was a cheaper way to do this than the $100 "aviation" version. Sounds great: I'll try this when/if I get the time...
Seriously, I've been pondering how to connect my old OMP to my Edelbrock ever since I've installed it. Getting damn tired of calculating premix and over-mixing to allow for unforseen WFO (Wide Full Open) events. If I find a way to get it connected to said 1405 I'll write it up also.
Note to webmaster: this should be a sticky thread.
Sanspistons for Life
Seriously, I've been pondering how to connect my old OMP to my Edelbrock ever since I've installed it. Getting damn tired of calculating premix and over-mixing to allow for unforseen WFO (Wide Full Open) events. If I find a way to get it connected to said 1405 I'll write it up also.
Note to webmaster: this should be a sticky thread.
Sanspistons for Life
07-02-05, 02:26 AM
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Originally Posted by txredneckmedic
can we do pics for those that cant follow directions very well?
)I don't have a digicam, and while I used to know how to post photos via Photobucket (albiet, conventional photos that were scanned into my computer), since they changed the format of this forum several months back I haven't figured out the new procedure for this. On top of that, my scanner has crapped out.
If I can find someone local with the proper set-up and know-how I'll try to arrange for some visuals but at this time I can't promise.
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07-02-05, 02:36 AM
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Originally Posted by TurboSE
^^^x2 and also would this work or can it be done on a 13B
Also, later 13B engines (S-5 models, 1989 and up) used an electric metering pump that goes into limp mode if oil isn't being delivered. Since I know nothing about those I can't say for sure if they'd work if modified in this manner. PCV Technologies does make an adapter for these electric metering pumps, so it stands to reason that it should still be modable without causing it to go into limp mode.
07-02-05, 11:49 AM
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heres another one with pics from the performance section https://www.rx7club.com/rotary-car-performance-77/diy-2-stroke-mop-write-up-pics-372329/
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