[VAC] Re: Vintage tow vehicle (1972); Which Airstream?

["Harvey Barlow" <harveybarlow@xxxxxxxxxxxxx>]

Jack,

The GVWR figure of 8100 pounds you quoted is for the truck plus carried
weight versus gross combined weight rating which includes the total weight
of the puller as well as the total weight of the trailer.  I don't know if
the domestic light truck manufacturers provided GCWR figures in that era.
My best guess for GCWR would be around 10,000 to 12,000 pounds for adequate
performance.

The old Ford 390 engine was a tough, stroked 352 or 360, I've forgotten
which now.  But  the 390 was built to produce more low engine rpm torque
than a 352 or 360.  I think an F250 Camper Special with 390 engine was
likely to be equipped with the old C-6 automatic transmission which was a
tough transmission.

There are two more bits of information that would be helpful in offering an
opinion as to how much trailer you can tow.  What is the rear axle or
differential ratio?  You should be able to find a code on a tag on the
driver's door frame.  The letter-number code can probably be deciphered by a
Ford dealer and it is probably still the same code in use in '90s era Ford
trucks.  My guess is it is a 3.73:1 but it could be a 4.11:1.  Either will
be good for towing but not for fuel mileage.

The other relevant factor is tire size or, more precisely, diameter.  Those
trucks were originally equipped with the old style bias ply 7.50x16 8 or 10
ply tires.  They were a pretty tall tire which reduces the effective final
drive ratio.

I assume you remember that trucks of the period simply did not produce the
horsepower or torque of modern fuel injected and computer controlled
engines.  Particularly those built after 1970 when the federal government
and the insurance industry forced the manufacturers to begin detuning the
engines.  Beginning in 1971 the manufacturers begin lowering compression
ratios which reduced performance.

Having said all of that, if you want to maintain adequate performance with a
safety and performance margin as you said (and I agree), my recommendation
would be to limit your gross trailer weight (including propane, water,
clothing, food, personal items) to around 6000 pounds.

Airstreams of similar lengths became heavier in each decade.    If you are
seeking a trailer of the same era as your puller, i.e. a '71 to '72 for
example, a 27' Overlander (or smaller) would probably make an excellent
candidate.  An Overlander is a tandem axle, typically rear bath and center
bedroom with either twin beds on each side or a double bed on the curb side.
They have comfortable living room areas with a couch bed across the front.
My daughter had one until recently.  Loaded for travel an Overlander is
probably at or pretty close to 6000 pounds.  Lots of them are still around,
affordable, and some look almost like new.

The old 390 engines were relatively easy and inexpensive to modify slightly
for increased power.  A four barrel carburetor and matching intake manifold
can be pirated from a high performance Ford or Mercury sedan, a dual exhaust
set from manifolds to tailpipes can be bent by any good muffler shop, and a
mild "RV Grind" camshaft can be installed.

Everything I have written here is highly subjective, based on my memory and
opinion.  It is worth exactly what you paid for it.

Good luck with your vintage truck and trailer.

Harvey Barlow
WBCCI # 1171, WDCU, VAC