>Many years ago I had a '69 bus, whose original heat exchangers were
>wonderful. On a zero-degree Colorado night, fire the bus up, get on the
>freeway, and ten minutes later you could take off your jacket and drive
>in shirtsleeves.
>
>Finally one heat exchanger developed an exhaust leak, so I replaced both
>with inexpensive replacements, aftermarket types I guess. (Not J-tubes).
>The heat output of the new ones was only a fraction of the old ones-- I was
>_very_ disappointed. I don't know what the differences were, but they had
>to be significant. Unfortunately, I also don't know what to look for when
>shopping for them now, which I have to do for my recently-purchased '71 bus.
>I'm considering J-tubes and a gas heater, just to avoid a recurrence of the 
>past disappointment.
>
>The moral of the story is, if you buy new heat exchangers, make sure
>(somehow...?) that they are identical to the originals, in airflow, metal
>composition, number of internal fins, etc.
>
>Good luck!
>
>-Steve Maher         smaher@ball.com         '71 Transporter

You didn't get the "race" exchangers by chance?  They look like the real
thing, but have no exchanger core, they are sold as "lightweights."  They
provide little or no heat.

Sincerely,
Eugene

PS, now I feel really bad about those manifolds, I shoulda tried harder.