heater/AC box to firewall nuts

http://www.megapartsusa.com/proddetail.asp?prod=MP%2DBMN8162AC

Do these attach the blower motor to the heater box (engineside) as the name suggests or the heater/AC box to the firewall? To me they look like the one's that attach the box to the firewall, not the blower. Trying to figure out why there are 6 for an A/C car, as the heater A/C box is attached using 5 studs....

what was original finish on both the nuts that bolt the blower motor to heater box as well as the heater/AC box to firewall? my original nuts that hold the box to the firewall look just like these but have a gray plated finish on them and are not gold CAD-like as these are?

trying to figure if the appearance of the finish on mine is as it looked new or as it looks after 42 years...

also in a case like this do you go with what is on your car if you think it has been there possibly its whole life as opposed to something that is a repop?

Thanks

First off, Mega parts is a fine vendor. However, they and most everybody else like Roger Gibson, etc. are re-selling fasteners from amkproducts.com. What AMK sells is often either exactly correct for Mopar, or it is labeled "similar". Plus a full description is given, such as on page 52 of their online .pdf catalog, "1/4-20 7/16 AF .62 OD .29 OAH, B-12829 6 pcs S36 for $3.00". Mega Parts doesn't say what size these nuts are.

Three of these nuts above fit the 1/4" studs on the base of my A body blower motor, and the S36 is code for zinc plated plus dipped in yellow-rainbow dichromate solution. Sometimes you can spot the yellow-rainbow coating on the backside of the old washer, but it is almost always gone from the topside of nuts that were exposed to the atmosphere and the elements for 45 years. In other words, you usually won't see the yellow-rainbow chromate any more, and the nut will look dark gray or rusted. To be precise, my factory nuts are "peri" type, meaning the bottom of the washer has pointy snag places, but this AMK nut does not. But the peri part is invisible once installed.

My A body A/C evaporator box has four studs 5/16-18 that penetrate the firewall. The exactly correct nuts for this are AMK page 53, part B10448, also peri and also S36 or zinc dichromate yellow-rainbow.

In both cases, the blower motor studs and the evap box studs are S2 phosphated.

If you are restoring your own fasteners, you can have have them re-zinc plated, as long as they were originally zinc plated and aren't badly rust pitted. The correct procedure is (1) electro-zinc plate, (2) dip in yellow-rainbow dichromate. This should be cheaper than buying new nuts, as long as you meet the plater's minimum order.

Correction, my blower moor studs are S8 clear zinc plated, and the A/C evap box studs are S2 phosphated.

S8 is code for electro-zinc plate followed by dipping in blue chromate, which is almost invisible with just a hint of blue. If you look carefully at new zinc plated faasteners at the hardware store, you can see the slight hint of blue.

Wow great info

The ones on my '68 road runner that held the heater-A/C to the firewall were a gold color and LARGER than the gray color smaller nuts that held the fan in the firewall. I don't know if they are correct or not but here they are for comparison?

MikeR

Every A body heater box I've seen ( and I'll admit it's not been that many ) has been 1/4-20
Also, the A-bodies I've worked on the heater box fasteners have been black phosphate
I have one each A/C and non A/C A-body boxes on hand, I'll ck the sizes in the AM. Both the boxes I have are post 1970 boxes.


B-bodies are all 5/16-18 thread
B-body with A/C takes quantity of 5 of the 5/16-18 nuts with a 1"( in most cases) captive serrated washer

Blower motor on an B-body a/c car uses 3 yellow zinc di-chromate 1/4-20 nuts to hold the blower motor itself.

E-bodies the heater box nuts are 1/4-20 and ( typically) clear zinc.

Thanks a bunch Guys. Very very helpful....

on that note weren't all the blower motor (engine side) black?

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on that note weren't all the blower motor (engine side) black?

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This one had no signs of black paint on it anywhere, neither does the spare A/C box I have on the shelf.