On /12/2010, Dave Addison in New Zeland wrote:
"About the two pressed steel retaining plates which hold, respectively, the rubber dust excluder for the brake and clutch pedals on the driver's side and the rubber blanking plate on the passenger side, do these go flange up, or flange down"?

This should be a simple point of trivia, but it seems a lot of people are heavily opinionated and like to turn this into a religious war. So after repeated questions, it becomes a web page.

Point 1.) All versions of the factory issued Workshop Manual and Service Parts Lists show flange up. There are a few errors in factory publications, but I don't this this is an error. Let me know if anyone wants to present evidence that the factory documentation is wrong in this case. This could be end of the discussion (until some religious zealot says you can't prove that the books are correct).

Point 2.) When someone at a car show claims that flange up or flange down is correct, they are blind sided by a vested interest in not having points deducted in judging on that day. Take such a vested interest with a grain of salt, and resume the discussion later outside of the show environment. If the car owner is interested in originality and concours judging, he should be much more receptive to discussion on discovering the truth, so he may get it right and not have points deducted in the next concours show. When you can produce official factory documentation (Workshop Manual and SPL) showing flange up, the odds are heavily in your favor for concours judging (even if it might ultimately be proven to be wrong). Concours judging is (or should be) done on the basis of best evidence of originality. Therefore, whatever appears to be correct by preponderance of the evidence will be absolutely correct for concours judging.

Point 3.) On drivers side of the car the bolts holding the retaining plate also secure mounting of the pedal assembly to the heater shelf and other brackets, ultimately including the master cylinder mounting, These bolts must be quite tight to keep pedals and master cylinder from moving. Look closely at the "Plate assembly, box base", Item 31 in the 1500/1600 SPL (item 18 for the Twin Cam). You should notice in the location of the bolts securing the retaining ring there are raised (washers) welded to the plate assembly to serve as vertical spacers. There are also large cut-outs in the flange of the rubber pedal excluder to fit around these spacers. This allows the bolts to be drawn up tight without excessively crushing the "gasket" or distorting the retaining ring. Those welded washers will be slightly thinner that the rubber part to allow for nominal compression of the "gasket" without excessively distorting the retaining ring.

Point 4.) On the passenger side (where you find the flat rubber blanking plate) there is no intermediate "Plate Assembly", only the rubber blanking plate and retaining ring. Therefore the bolts here must be tightened more gently to avoid excessively smashing the rubber "gasket" and distorting the retaining ring. If you install the retaining ring with flange down, then when bolts are tightened it will still distort the retaining ring to some extent. Pull it down enough and the flange of the retaining ring will ultimately contact the heater shelf and damage the paint.

Point 5.) It is my casual observation that the retaining rings will not function properly if installed with flange down, because the flange is taller than thickness of the "gasket". The gasket in this case is either the rubber pedal excluder or the rubber blanking plate. With flange down the edge of the flange would hit the painted heater shelf and interfere with compression and sealing of the "gasket". When bolts are tightened this would also chip the paint and distort the flange, and the "gasket" may not seal. For this to work with flange down the height of the flange would have to be less than thickness of the "gasket" when compressed. The rubber blanking plate can be compressed a lot when the bolts are tightened, finishing quite thin in the area of the bolts, so flange on the retaining ring would have to be very short to avoid biting into paint on the heater shelf. This flange is actually relatively tall to serve as a stiffener for the retaining ring (allowing the ring to be made of thinner material to reduce weight and production cost).

Point 6.) Form follows function. If you invert the retaining ring in the interest of appearance and end up with a gasket leak and chipped paint, you defeat the intended function of the part. For those people who insist that flange down is correct, you might offer to pour a cup of water onto the rubber blanking plate to see if it might leak through onto their carpet.