More than you ever wanted to know about early VW 1500 heater tubes

I recently bought an NOS early left side heater muffler (311 255 355 B). The seller has a number of them available, but only for the left side. I bought one in the hope that a right side one will eventually turn up somewhere. Hey, it worked for the sun visors, so why not roll the dice again?



This insulated duct (referred to by VW as a "muffler") fits between the left heat exchanger on the engine and the left heater junction box on the body under the car. It was introduced in January 1963 (chassis no. 0 141 008) and first appears in the parts book with supplement 11, superseding a simple metal flex tube. It will fit all VW 1500s from 1961 through the first few months of the 1964 model year. Even though it's not a part that my Ghia would have originally had when new, it was introduced just a few months after my car was built as an improvement on the original part, so I think it's an acceptable upgrade. I never did like the metal flex tubes, since they have a tendency to unravel themselves.



I had always assumed that the insulation in these mufflers was asbestos, but it actually appears to be industrial felt much like what was used to insulate the engine lid. Though since it was made in the 1960s it's more than likely the felt includes asbestos fibers. I may try to keep my heater use to a minimum.

I remembered a discussion about these heater mufflers on the Type 34 Registry mailing list a few years ago. The list archives seem not to be available online anymore, but luckily I never throw anything away, including old e-mail, so I was able to find it on my computer. Larry Edson did a pretty good job of documenting the confusing yet strangely compelling history of early 1500 heater tubes and ducts:

My earliest book, which I know to be really early because it still lists the 32 PHN carb instead of the 32 PHN-1) shows that the early cars had metal flex pipes with these part numbers -- left 311 255 357 A, right 311 255 358 A. But then my next oldest book with updates to 13/63 no longer shows the flex pipes and have mufflers in their place and are listed thus: left 311 255 355 B, right 311 255 356 B. The next book with update 1/64 tells the next part of the story: To chassis no. 0 221 974 -- same as previous book. From chassis nos. 0 221 975 to 0 280 370 gets a 60mm flex pipe (the same as the early cars) -- left 311 255 357 A, right 311 255 358 A. Update 1/64 gets this entry: From chassis no. 0 280 371 gets a 65mm flex pipe -- left 311 255 357 D, right 311 255 358 D. The latest parts book seems to have cobbled all of this together and botched it (just like the publisher botched the speedometer part numbers in the Type 34 parts book). This book mistakenly lists the mufflers up to chassis no. 0 280 371. This is the reason I have so many books. You just can't trust the publisher to keep the numbers straight over years of changes.

So true. This note in the VW Workshop Manual helps explain and leads to more confusion at the same time:



So either beginning with the 1964 model year at chassis no. 0 221 975 or at no. 0 238 920 (take your pick) the mufflers were discontinued and the metal flex tubes used in earlier years were reintroduced, but with an additional insulated jacket. This Workshop Manual note hints at why the muffler design might have been dropped (restorers please take note):



That's right: within a few weeks of introducing the muffler they realized the plastic and/or insulation would burn unless an insulating ring was added at the connection with the heat exchanger.

At no. 0 280 371, not long after switching back to the metal flex tubes, the heat exchangers were redesigned requiring a larger diameter tube (65 mm vs. 60 mm). This design change keeps the 311 255 355 B and 356 B mufflers from fitting any cars built after chassis no. 0 280 370 (September 1963). Alles klar? Long story short, if you have an early car with a later engine or newer heat exchangers you might have some trouble finding the right combination of parts to make the heater connections, as some have found out the hard way.

Anyway, if anyone knows of where I can find an NOS or good used right side muffler (311 255 356 B) please let me know!