First off let me confess. I never did work at the Corvette St Louis Assembly Plants. I'll wager in the 1950s-60s-70s those fine GM union assembly line workers were typical Blue collar folk. And I do find it somewhat remarkable that any of those folk on the line would have any knowledge of the Rubber Manufacturers Association. Or their manner and means of identifying extruded & molded rubber product. Those raised or recessed identification marks were not pertinent to their job of hooking up the 63-67 expansion tank hose criss-crossing at the requisite angle.
I read a former worker said this or that, but a 50+ year old memory without further material support is a rather weak line of reasoning. When I think back 50 years to my 3 MGBs & 1 XKE of which I don't have a single photo & cannot even recall their colors. The argument regarding alligator skin or cross hatch is as hackneyed as they come. I cannot believe this is still being debated as if it was a definitive design feature, not unintended consequences like over spray or 16 shades of Black & blackout. There is no polite manner stating this: referring to hose that must or must not exhibit those feature displays a lack of knowledge of how cloth inserted hoses are manufactured as well as dismissing the effects of rubber aging.
Most all 53-82 Corvette automotive hoses are reinforced by a fabric mesh within the hose. It made by extruding the rubber mix first through a die, then wrapping it in a criss-cross fabric mesh; followed by a second run through another extruder to place another layer of rubber on top of the fabric mesh. This is called double extruded hose: heater, fuel, radiator, etc.
Any guesses at what can happen over 50 years of aging? (63-68 AC Freon hose had two separated layers of mesh; therefore it is triple extruded.) Referring to approved heater hose suppliers on GM blueprints there were domestic (Gates, HKPorter, Goodyear, American Biltrite, Electric Hose & Swan) & 2 Canadian approved suppliers (Gates Canada, Uniroyal) for heater hose. Each has its own small cross section to show their assigned RMA rib patterns as well as a verbal pyramid plateau description. Without a Bill of Lading I'm not convinced which supplied, or if anyone else supplied the St Louis plant exclusively. It sure would be easier to recognize that GM had their own rubber extrusion facility if one could discern its location - like Flint, MI engines, Muncie, IN trans or Rochester NY FI. But none have yet been revealed & I'm not holding my breath waiting.
A Google search say GM had 99 assembly plants in 1963. In order to produce millions of feet of hose, many different extruders with many specific extrusion dies were humming along with looms fabric wrapping hose & running them thru the second extruder & finally a vulcanizer. Followed by an offset printer if printed with BlaBlaBla. No inkjet or laser printing back then. 63-67: about 116,000 units required heater hose; more than 812,000 feet.
Blueprint says: material to be furnished in approx. 50 foot rolls. Tag roll with number of feet included. Each AIM part number shows a specific length, which on the blueprint appears such as 35 inch +.50/-.25 Looks like it was chopped up to length at the plants. No rational person could believe that only one heater hose extruder, with one extrusion die produced every foot used in the St Louis Corvette plant. Those extrusion dies were made on milling machines by tool & die makers.
The precision of EDM did not have a real start until after 1967 when Russia produced a machine. But I don't think St Louis had one. It is not rocket science to state that rubber shrink & hardens with age, as the more volatile components continually evaporate. Any wrinkles become more pronounced above the fabric layer. As it shrinks the surface gets taut, hard & shiny. You cant have it both ways.
I am amazed that an over the counter sold heater installation kit was accepted as definitive proof of yada yada but other references to non assembly line installed GM service listings was po pooed. You cant have it both ways. Whats good for the Goose, is good for the Gander. It is remarkable that the rigid framework for the correctness of some items, is in remarkable contrast to generally accepted multiplicity assigned to other similar generic auto parts like WB, TR, RBW, A and ad nauseam to every other alphabetic acronym from BS to FOS.
Lastly have you ever seen the period photo of a 67 427 with the GM logo on the hose? Its from a Road Test comparison to a Rustang conducted in 1967 & printed in the March 1967 Motor Trend - not later 1977, 1987 or 1997, etc. Its amazing that logo is so prominent in this old Black & White photo, particularly if the reported size of 5/16 high. In this photo it does appears they are larger than the above size. Hmmmm.
The reports from the recent club events, as well as the new type of non stock Corvette vehicles being evaluated seems to illustrate that the ever increased parsing & bifurcating of this item, or that items cosmetic acceptable appearance is increasing the number of acolytes that will struggle & may never be able to attain that highest honor of a Blue Bow. It will certainly ensure that fewer will endure the arduous task to repeatedly update their pride & joy to the newest $75.00 ncrs final authority. Or at least final for that edition of the manual.
Also, help me out: upon what parameters does one judge a Corvette with a blower & wheelie bars? Are we having FONTS yet? You do know that this hieroglyphic stuff often changes with each new run of parts. http://www.docrebuild.com/curr-evnt/currentevents-138.html
Never say never. No 63 escaped with 2 bar KOs. No 63 ZO-6 tank could be ordered in a convertible. No L88s were made in 1966. NCRS manual contain their best guess amateur assumptions, subject to replay & further review. Forgive me, but my cognitive ability is slipping. When I first drove my Aunt Sil new 63 fuelie, while home from college in June? of 1964 all I can remember is was wicked fast. The hoses? The fonts? The shades of Black? I'll yield to those with their 50+ year remarkable memories of their hoses. Too bad they don't have any old photos. All I saved were photos of old girl friends, which my wife tried to throw away. Same thing probably happened to their heater hose photos.
But I do remember the first repros offered for some items. The 53-60 Aluminum grill teeth; the heavy 58 trunk irons, the shallow 56-57 Waffle inserts and the logo heater hose. Hand stamped - plain heater hose was all that was available. All those 30+ year old repros were plain hose. Call me jaded, but that is possibly what some will actually see today. Looks old: must be good. The only way to get any of the ribbed hoses shown on the GM blueprints was to order it special 5,000 ft was our minimum from Swan. You cant find ribbed heater hose at AZ, CQ, NAPA, etc.