Cross-over pipe question - preheat or not preheat, bus

[BellePlaine]

What is the difference between pipe J and pipe H? My fuel injected aircleaner has an open port that looks like it should have a hose attached to it; is that what pipe H is for?

I'm attempting to set up a stock muffler on my fuel injected 1974 engine with 1976 heater boxes in my 1975 bus.

[vwlover77]

That extra piece on pipe H is an intake air pre-heater that was present in the early FI models and dropped in the later versions. If your air filter box has a large open port around 2 inches in diameter, that's probably what it's for.

[Amskeptic]

That extra piece on pipe H is an intake air pre-heater that was present in the early FI models and dropped in the later versions. If your air filter box has a large open port around 2 inches in diameter, that's probably what it's for.

It was insane complexity for no good reason. One day, the engineers woke up, slapped each other, "HANS! No need for intake preheating with injecktion!" And that's the truth.
Colin

[BellePlaine]

That's what I thought; that the H-pipe was related to the downward port on the air filter box. I just checked my spare (seized) engine and it still has the proper engine tin attached with the holes for the preheat hose. If Busted Bus has the H-pipe, and it's not killer expensive, I'm tempted to use it.

[BellePlaine]

I gather that it's not necessary to use that preheat pipe for fuel injection, but it makes me wonder why the engineers designed it in the first place. Did they think that if it was good for carburation it would still be good for fuel injection? Any chance that using the preheater would make the engine run hotter? Do you think this is why they removed it?

[Amskeptic]

Any chance that using the preheater would make the engine run hotter? Do you think this is why they removed it?

No, like every other preheater system, it shuts off via thermostatic valve in the air filter. It was only to keep fuel vaporized in the intake air stream. Injection does NOT REQUIRE such things with injectors adding fuel right at the intake valve!
Colin