48. Duct, duct, goose!

Radiator exit duct:

Before I could install my radiator exit duct (for good), I had to clean up the wiring in the radiator box.  There’s a surprising amount of copper running back and forth through here!

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Front end wires and harnesses cleaned up.
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Radiator exit air duct installed.
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Another view showing the honeycomb grill cover.

I used McMaster PN 92725T42 which is made from aluminum and has a 79% open area.  I thought this would be enough so the exiting air wouldn’t be restricted due to the presence of the grill.  The main purpose of the grill is to keep debris from falling into the box and collecting at the bottom (there’s a gap to allow water to drain but it’s not big enough for leaves).

I can’t say I’m a big fan of this material.

It’s relatively inexpensive but the very thin aluminum doesn’t have much strength – so it’s pretty easy to distort.  McMaster PN 92725T22 has the exact same hole dimensions but is made from steel.  It might have been smarter to go with this in lieu of the lighter aluminum.  I’ll run this piece for a while and see how it holds up though it’s likely I’ll be looking for a different grill covering in the near future.  The silver reflective material lining the duct is Second Skin Thermal Block; it’s actually a thin sheet of aluminum meant to deflect radiant heat.  Other than the sun, the duct shouldn’t be getting much radiant heating so it’s not all that necessary.  I’ll likely paint the interior black at some point in the future.

Oil cooler duct:

I needed to fabricate a similar duct for my oil cooler.  The cooler is positioned just behind the driver side intake.  Once air enters the interior bodywork it kind of just flows everywhere, it’s unlikely very much will actually flow THROUGH the oil cooler without some assistance.

When I initially positioned and mounted my oil cooler I had done so without the body in place.  I took some rough measurements of the spider while it was on the ground and SWAG’d at some dimensions on the frame.  When I eventually remounted my spider I discovered I had 2 issues:

  • The oil cooler was not centered vertically with my revised intake opening.
  • The oil cooler was positioned too far rearward and came dangerously close to the rear wheel.

Complicating things further on the re-do was my fuel system was set and I couldn’t move the oil cooler forward much because it would mean moving my fuel pumps!

Rock and a hard place.

So I tweaked the oil cooler angle slightly and centered it vertically.  Better, but not great.  This also mucked with my oil cooler plumbing so that’s not ideal either … a few more items to the “future to-do list”.

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View from above; air coming into the inlet is more likely to flow above, below, and around the cooler than it is to go through it!  Therefore a duct to force 100% of the incoming air through the cooler is needed.  There’s just enough room to install a sheet metal wheel liner in front of the wheel.

The following photo shows it well; any air coming in this intake is going to flow above, below, and around the oil cooler instead of going through it – not so good for cooler efficiency!

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This is an Earl’s 25-row oil cooler.  I’ve used Earl’s oil coolers on other applications and they’ve always performed exceptionally.  With a duct to control airflow I don’t think cooling will be an issue but there’s now plenty of vertical space to stuff a larger cooler if it’s deemed necessary.  Thanks again to HJones for posting his how-to on doing this mod.

More fiberglass work …

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As I did with the radiator exit duct, I mocked up an approximation of what I needed using foam core poster board.
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The duct is too bulky to install so I sectioned it into two halves.  Inserting each half then assembling the duct once it’s inside the bodywork will make installation possible.
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I then applied packing tape to one half of the duct.  The intent is to create an overlapping feature that I’ll run some screws through to keep the two halves together.  The overlap will also act as a sort of seal to prevent air from leaking through the joint.
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I then added more fiberglass to build an overlapping strip.
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Some cleaning up, cutting, and weld nuts bonded to the duct and it’s ready for a test fit.
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Two halves joined.
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Installed; I left a gap between the duct and oil cooler so the duct wouldn’t rub through/damage the cooler.  I plan to add some type of weatherstripping here but figured I would run it as-is.  If the cooler efficiency isn’t high enough I’ll take steps to seal it better.
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Looking into the side intake.  The duct continues to curve, following the contour of the intake along the interior surface.
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A little bit of paint to hide the blemishes.  The rear wheel liner has been installed – there’s not much room between it and the cooler!
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Mesh grill covering installed.

The to-do list is shrinking!

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