Hi, neat questions! Right up my alley... I swapped a 396 into one of
my 59 1/2 tons over 20 years ago. I had the stock 3 speed in it for a
week, then a Saginaw 4 speed for about 6 months, then an automatic.
Here's what you're looking at:
The SM420 will bolt right up to the 55-72 pickup V-8 bellhousing (also,
the same bellhousing was used on 64-72 6 cyl trucks). But, beware that
they used two different bellhousings starting in about 1968, the bell
for the SM465 has a larger center hole...so measure yours (or ask me to
measure one) before you buy a bellhousing, you need the correct center
hole size. The correct truck bellhousing will let you bolt the 402 to
the tranny you have, and will bolt to the crossmember also. There will
be a problem here, though...the exhaust on the 402 will hit the steering
box. Stock manifolds will almost fit, if you get the correct ones (the
ones on the truck should be them), but there will be intereference, even
if you grind the manifold down. Instead, you can use Hedman 68-86 truck
big block headers, and whack them a bit to clear. It will be tight, but
probably acceptable. For front mounts, you'll probably want to install
an aftermarket tube crossmember to use the side mounts on the V-8,
instead of the original old truck front engine mounts. Keep the engine
at the same angle as the 6 cyl, which is about 4 degrees up in front.
The clutch should not be a problem...I'd suggest a 12" truck unit, as
used in most Chevy trucks with the 4 speed during the 70s. The flywheel
for a 402 is the same as for a 1986 or older 350, so they are easy to
find. Make sure you get the 14" diameter flywheel, not the small one.
The tranny and transfer case will not like the added strain, but if you
drive carefully, they will live for quite awhile. If you drive like a
teenager, don't expect them to last!
The throttle linkage from a 59 V-8 truck should work ok, if you can find
one. The stock radiator seems to work just fine with a 402, although it
could be marginal with a 454. You'll want to find a V-8 keyswitch, with
the "start" position, although you can just add a pushbutton starter on
the dash instead. THe stock battery box is fine. You can run a
generator on a big block (I've done it), but it's a lot easier to
convert to an alternator, with a built in regulator.
It looks like you have a pretty good idea of what's involved. Don't
expect it to all go smoothly unless you really do your homework, but
it's not that hard of a swap...I did the above mentioned swap in two
long days of work, at age 17....
Jim
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Kevin wrote:
I've recently been
given the opportunity to purchase a reasonably priced "in the truck and
daily running 402 BB.
Beatrice (My '59 Chevy Apache 38 NAPCO 1-Ton) is equipped with a 235
with an
SM-420 4-Speed, and a Spicer Model 23 Transfer case with 1.87 to 1
reduction.
Bell housing alignment problems?
Clutch issues?
Motor Mounts?
Transmission/T-Case will or will not take the strain?
Throttle linkage hook ups?
Foot starter or ignition conversion?
Cooling troubles?
Generator to alternator difficulties?
Battery box repositioning cures?
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