by Ron Salmon
"It looks like the [Federal] "49 states" 1979 exhaust could be adapted to 75-78 vehicles, using 72-74 heat exchangers -- either straight, or with a modification in the crossover tube. But I have never seen one of these. Are they, uhm, less than abundant?"
...I think the exhaust ports for the '79 HE/heads are more square than the earlier ports, if I remember right, so they have to match as a set. I could be mistaken.
I put '72 heat exchangers and exhaust on my '77 FI engine...the later exhaust is very expensive and difficult to find parts for.
In "real world" use, the shape of the exhaust ports on '72-79 heads is close enough that any heat exchanger can be made to work with any head, provided that you use the appropriate copper gaskets to permit a tight seal. Basically, the difference in shape is small enough that with some fiddling, you will find that the copper gaskets will fill in the difference and create a tight seal regardless of what heads and heat exchangers you are mating. This gives you a lot of flexibility concerning exhaust options.
'72-74 heat exchangers and '79 heat exchangers are identical in the way that they hook up to both the heads and the exhaust. That is, both have trapezoidal outputs to the exhaust. What this means to you is that if you have a '79 bus that needs heat exchangers, you can get away with buying the less-expensive '72-74 heat exchangers, and still use your original exhaust. (These heat exchangers run about $80-100 less than the true '79 ones.) Or conversely, a '72-74 exhaust system is a direct bolt-on onto '79-83 heat exchangers. (More on this below.)
'75-78 heat exchangers have a triangular output flange, and require a whole network of no-longer-available piping to go to the heads (as opposed to the '72-74 heat exchangers, which are fully self-contained). Furthermore, an original quality (stock) exhaust system is no longer available for the '75-78 heat exchangers, leaving you with the $79 Pacesetter system as your best option for these years, if you want to use your stock heat exchangers. The Pacesetter is better than almost any other aftermarket exhaust system I know of, but certainly not comparable in quality to a stock system.
Therefore, there is little reason, in my opinion, to stick with the '75-78 heat exchangers. They require ancilliary parts that can't be found new, and limit you to aftermarket exhaust systems. Better to put '72-74 heat exchangers on your '75-78. This will eliminate those unavailable u-pipes, and allow you to install either a catalyst or non-catalyst stock exhaust system, which is likely to outlast the aftermarket systems by a sizeable margin. In fact, in most of the rest of the world, this is what VW did; these triangular port '75-78 jobs are pretty much a U.S. only setup from what I've seen. I'm not suggesting that anyone run out and buy '72-74 heat exhangers and exhaust if your present '75-78 system is just fine, but the changeover is worth considering if you are in need of heat exchangers and/or exhaust anyway.
If you want '72-74 heat exchangers, I do have a small quantity of genuine N.O.S. German Volkswagen right side heat exchangers for $149.95, which is an absolute bargain for these extremely heavy duty units that have long been unavailable. You would have to buy a Danish left side for $189.95, but even one German side will give you better heat than if you had put Danish on both sides.
For exhaust systems that will mate up to the '72-74 (or '79-83) heat exchangers, your best option (albeit without provision for a cat or egr valve) is the stock '72-74 system, which was actually used in Europe thru '83. This is a heavy duty system, and very simple in design. Basically a big muffler that connects right to the heat exchangers, with a tailpipe on one end. Normally I sell a Danish made system for $159.95. However, on the list of bargains that I will be posting within a day, consisting of the parts I just received from Europe, you will find a similar system including a Stainless Steel German muffler for only $30 or $40 more. This was a closeout deal I found in Germany and is well worth grabbing, as mufflers of this quality have not been imported to the U.S. before at any price. Your second option, should you require a catalytic converter and egr valve port, is a stock '79-83 49-state setup, complete with crossover pipe, etc. This system runs $299.95, plus $99.95 additional for the cat. Since cat's were legally required from '79 on (and from '76 on in California), that would be the main reason for buying this setup, as it offers no performance or reliability advantage over the '72-74 setup and costs twice as much.
The Bus Depot, Inc.
[posted to Type2 on 10/6/99 -- prices and
availability subject to change]