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Drilling holes for Injectors in older Cylinders without a Boss

L

lr172

Well Known Member
I am working on converting my O-320 to Fuel Injection. One of my cylinders has a cast in Boss for the Injector hole, the other three do not (old cylinders). I could probably get the hole in the correct place by using the dimensions off the one cylinder with a boss. My concern is that the castings without the boss seem to be quite a bit thinner. It appears that the boss adds a decent amount of extra aluminum in that area.

Has anyone done this? Is there enough meat in the wall to provide enough threads after tapping the hole?

Thanks for any assistance you can provide.

Larry
 
Airflow Performance use to sell (and I believe still does) injectors that can be installed in the primer ports.

I remember looking into installing fuel injection 20-years ago before my RV-6 was flying. Their 'Flash" website shows system available for 320 and 360 with injectors in primer port or cyl head.
 
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RV6_flyer said:
Airflow Performance use to sell (and I believe still does) injectors that can be installed in the primer ports.

I remember looking into installing fuel injection 20-years ago before my RV-6 was flying. Their 'Flash" website shows system available for 320 and 360 with injectors in primer port or cyl head.
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I was aware of those, but I am looking at a setup that has the standard injectors and supply tubes. I will have to buy new injectors and make new lines if I use the Primer ports. Not the end of the world, but would like to use the standard locations if I can.

Larry
 
I have an HIO-360 on one of my project airplanes and it used the injectors in the lower position for the helicopter application. These were the same injectors as the standard aircraft units. They are the same physical size (1/8 NPT), and the discharge angle at the valve is much better than in the upper location. Are the early cylinder "primer ports" different from the late model "lower" ports?

As for lines Larry, unless you have a new set of the standard aircraft configuration laying around (and you know their history), I'd suggest buying a new set. They are typically replaced only on condition, and the failure mode is to break at the nipple due to fatigue. A used set may have 10,000 hours on them, look perfect, and be 1 hour away from failure.
 
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Toobuilder said:
I have an HIO-360 on one of my project airplanes and it used the injectors in the lower position for the helicopter application. These were the same injectors as the standard aircraft units. They are the same physical size (1/8 NPT), and the discharge angle at the valve is much better than in the upper location. Are the early cylinder "primer ports" different from the late model "lower" ports?

As for lines Larry, unless you have a new set of the standard aircraft configuration laying around (and you know their history), I'd suggest buying a new set. They are typically replaced only on condition, and the failure mode is to break at the nipple due to fatigue. A used set may have 10,000 hours on them, look perfect, and be 1 hour away from failure.
Click to expand...

I believe that both ports are 1/8" NPT.

Once I get the setup in the next week or so, I'll see what I have and what brand of injectors they are. From my research, Don at AF makes a special injector for the primer ports. It has something to do with the venting method that he uses that requires special treatment in the horizontal orientation. That may not apply to injectors made by Bendix or others and I may be ok. Do you know the part # of the injectors on your setup? I would like to do some research to see if they are different than the injectors supplied for top mounting.

I do know the history, but if I use the primer ports, I'll have to make new lines. Are these typically flared or ends brazed on?

Larry
 
In operation it makes no difference if a standard injector nozzle, (mine, Bendix or Precision) is installed in the normal top of cylinder head location or the primer port location. The possible problem comes at shut down. Since the injector nozzle is of the air bled design there is a vent hole in the body of the nozzle to introduce air into the fuel stream to atomize the fuel. With the nozzle installed in the primer port location the discharge end of the nozzle is higher than the vent hole in the body. So there is a possibility that fuel could drip out the vent after shut down or during the prime cycle before starting. Since the exhaust system in in the vicinity of the injector nozzles this would introduce a fire hazard. To protect this from happening, we install turbo nozzles in the primer ports. The turbo nozzles have a shroud that is O-ringed to the body. The shroud is connected to an air rail (stainless steel) and the nozzles from each side are vented together with a #6 hose running overboard or to protected air.

Injector lines have a cone type fitting silver soldered to the nozzle line material. We make custom length nozzle lines.


Don
 
Don at Airflow said:
In operation it makes no difference if a standard injector nozzle, (mine, Bendix or Precision) is installed in the normal top of cylinder head location or the primer port location. The possible problem comes at shut down. Since the injector nozzle is of the air bled design there is a vent hole in the body of the nozzle to introduce air into the fuel stream to atomize the fuel. With the nozzle installed in the primer port location the discharge end of the nozzle is higher than the vent hole in the body. So there is a possibility that fuel could drip out the vent after shut down or during the prime cycle before starting. Since the exhaust system in in the vicinity of the injector nozzles this would introduce a fire hazard. To protect this from happening, we install turbo nozzles in the primer ports. The turbo nozzles have a shroud that is O-ringed to the body. The shroud is connected to an air rail (stainless steel) and the nozzles from each side are vented together with a #6 hose running overboard or to protected air.

Injector lines have a cone type fitting silver soldered to the nozzle line material. We make custom length nozzle lines.


Don
Click to expand...

Thanks for the reply Don. Do you sell the ends and SS tubing for me to make my own Lines? Assuming this is preferred over removing the ends and re-installing on new lines. I have some experience brazing. Also, what becomes the recommended source for MAP when using the Primer ports for Injectors?

Larry
 
You can purchase nozzle line material and cones to make your own lines. I suppose the old cones could be used but from our experience the time spent getting the cone fitting clean and then not knowing if it takes the solder correctly is not worth the time or risk. Same goes for using old nozzle line tubing. We just use new material so when the part is cleaned and pressure tested we have no rejects. You would be looking at around $150 to $180 for a set of custom made nozzle lines. To do your own; nozzle line material is $9.50 /ft. Cones are $5.00 each.

The new MAP connection must be installed somewhere after the throttle plate. Could be in the throttle body flange, cable bracket adapter, an intake manifold pipe etc.


Don
 
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