Mike,
These engine adapters have been available for years in the back of
car magazines like Hot Rod or Car Craft. One pattern looks like an
upside-down "W". That's referred to the "BOP" (Buick, Olds, Pontiac)
pattern. Cadillac uses that one too. The other looks like an
upside-down "V" and is Chevy only. The only difference is the placement
of the top two bolt holes.
The difficult thing about the Chevy swap would be the custom motor
mounts required. The GMC uses the Toronado/Eldorado style front motor
mount. The only two engines this mounting system was Cadillac and
Oldsmobile. To do the swap with factory parts entails merely getting
the 66-76 Eldorado front mount and bolting it in. I've done a few
engine swaps over the years. Anyone can use a swap kit with fabricated
adapters and parts. I always try to use an engine/vehicle combination
that allows me to use as many factory parts as possible. I look at it
as a challenge.
I see David's point about the 455 putting more power to the
ground than the front tires can use. The power must be used
appropriately. Once your coach is moving down the road, the extra power
can be put to good use for passing or maintaining a decent rate of speed
up mountain roads. At high altitudes, the volumetric efficiency of your
engine drops. So does power output. It has been my experience that
with a larger displacement engine, the power drop will be less of a
problem due to a larger reserve in the first place.
Patrick brought up the issue of transmission durability. The turbo
425 transaxle in the GMC is based on the turbo 400, which has been used
in some pretty heavy GVWR medium trucks as the turbo 475. I don't think
durability would suffer noticeably as long as you keep the fluid
temperature down to normal levels.
A large transmission cooler would do the trick. As always, plumb
the aftermarket cooler so the fluid passes through it before it goes
through the factory cooler. That way the excessive heat is dissipated
into the air instead of your engine coolant. In addition, during cold
weather operation, the radiator transmission cooler would warm and
stabilize the transmission fluid temperature.
Scott Woodworth
These engine adapters have been available for years in the back of
car magazines like Hot Rod or Car Craft. One pattern looks like an
upside-down "W". That's referred to the "BOP" (Buick, Olds, Pontiac)
pattern. Cadillac uses that one too. The other looks like an
upside-down "V" and is Chevy only. The only difference is the placement
of the top two bolt holes.
The difficult thing about the Chevy swap would be the custom motor
mounts required. The GMC uses the Toronado/Eldorado style front motor
mount. The only two engines this mounting system was Cadillac and
Oldsmobile. To do the swap with factory parts entails merely getting
the 66-76 Eldorado front mount and bolting it in. I've done a few
engine swaps over the years. Anyone can use a swap kit with fabricated
adapters and parts. I always try to use an engine/vehicle combination
that allows me to use as many factory parts as possible. I look at it
as a challenge.
I see David's point about the 455 putting more power to the
ground than the front tires can use. The power must be used
appropriately. Once your coach is moving down the road, the extra power
can be put to good use for passing or maintaining a decent rate of speed
up mountain roads. At high altitudes, the volumetric efficiency of your
engine drops. So does power output. It has been my experience that
with a larger displacement engine, the power drop will be less of a
problem due to a larger reserve in the first place.
Patrick brought up the issue of transmission durability. The turbo
425 transaxle in the GMC is based on the turbo 400, which has been used
in some pretty heavy GVWR medium trucks as the turbo 475. I don't think
durability would suffer noticeably as long as you keep the fluid
temperature down to normal levels.
A large transmission cooler would do the trick. As always, plumb
the aftermarket cooler so the fluid passes through it before it goes
through the factory cooler. That way the excessive heat is dissipated
into the air instead of your engine coolant. In addition, during cold
weather operation, the radiator transmission cooler would warm and
stabilize the transmission fluid temperature.
Scott Woodworth
atri63
