Fred I recommended the engine builders recomended by hot rodders etc not for
their ability to build engines with lots of power, but rather for their
expertise in engine building period. There is a wide range of expertise when
it comes to machine shops. It is a common misconception that builders of
high RPM, mega HP engines are not capable of building ones for a RV. I do
not think this is true. A machine shop that can build engines to these
specs can build one for us. In the case of the 455 used in the GMC
motorhome, its low speed torque is largely due to the RV cam. We want an
engine that pulls hard at low RPM and is built for the long haul. For me
reliability is the number one concern.
And another thing, very few repair shops or dealerships build their own
engines, contrary to what they may advertise. Ask any of the big GMC
motorhome dealers (Golby, Buskirk, Cinnabar etc) if they rebuild their own
engines and they will tell you no. They simply do not have the volume to
justify the large outlay in equipment, tools, training, and personnel. If a
dealership does rebuild an engine, they do only the basics, bearings, rings,
valves, oil pump etc, and not the goodies that really make the 455 run and
live a long time. Same is true for our transmissions.
I have found a good shop here in New York and spent several hours talking to
the owner about building me an engine for my coach. His main business is
building for car restorations with a healthy market in NASCAR racing. He is
not only very knoweledgeable but has the equipment (dyno, clean room, best
tools) to do the job right. He will build to my specs and at much less than
dealers.
For example he quoted me a price of $1300 for rebuilding my 455 with forged
pistons, special rings, bronze valve guide inserts, stainless steel valves,
RV cam, high volume oil pump, complete magnamfluxing and dyno check. He
does extensive work on cyoinder heads where we can really see a marked
difference in HP and Torque. There is some other things that I would want
to do that will probably add to the price, but still very acceptable.
All of us would do well to get all of the specs together we need and than
write a standard spec sheet for the GMC motorhome 455 and 403 so that any
owner could hand the sheet to a good machine shop that builds engines and be
assured that he would get an engine that does the job at the right price.
Only my opinion.
>
>I recommend caution in using engine rebuilders who have a bias for hot rod
>engines unless they comfortably relate to the need to build an engine for long
>life, high torque and relatively slow engine speeds.
>
>High performance engine people often build large CID vehicle engines for peak
>power at much higher RPM for peak torque and power than is preferred for the
>GMC MH. The optimum engine for the GMC MH develops peak torque at less than
>3000 RPM and full power at about 3400-3600 RPM. This is designed to match the
>vehicle requirements taking into account vehicle mass, body drag coefficients,
>gearing, desired acceleration rates, cruise/top speed, engine life, etc.
>
>The 403 CID engine in my Royale gets the job done but it has to compensate for
>its 11.5 % smaller displacement by working harder than the 455 CID engine. It
>probably will not live as long as a 455 would have lived. But economics and
>environmental polititics drove GM to use the 403 beginning mid - '77 rather
>than engineering.
>
>My $0.02.
>
>Fred Hudspeth
>'78 Royale
>
>
their ability to build engines with lots of power, but rather for their
expertise in engine building period. There is a wide range of expertise when
it comes to machine shops. It is a common misconception that builders of
high RPM, mega HP engines are not capable of building ones for a RV. I do
not think this is true. A machine shop that can build engines to these
specs can build one for us. In the case of the 455 used in the GMC
motorhome, its low speed torque is largely due to the RV cam. We want an
engine that pulls hard at low RPM and is built for the long haul. For me
reliability is the number one concern.
And another thing, very few repair shops or dealerships build their own
engines, contrary to what they may advertise. Ask any of the big GMC
motorhome dealers (Golby, Buskirk, Cinnabar etc) if they rebuild their own
engines and they will tell you no. They simply do not have the volume to
justify the large outlay in equipment, tools, training, and personnel. If a
dealership does rebuild an engine, they do only the basics, bearings, rings,
valves, oil pump etc, and not the goodies that really make the 455 run and
live a long time. Same is true for our transmissions.
I have found a good shop here in New York and spent several hours talking to
the owner about building me an engine for my coach. His main business is
building for car restorations with a healthy market in NASCAR racing. He is
not only very knoweledgeable but has the equipment (dyno, clean room, best
tools) to do the job right. He will build to my specs and at much less than
dealers.
For example he quoted me a price of $1300 for rebuilding my 455 with forged
pistons, special rings, bronze valve guide inserts, stainless steel valves,
RV cam, high volume oil pump, complete magnamfluxing and dyno check. He
does extensive work on cyoinder heads where we can really see a marked
difference in HP and Torque. There is some other things that I would want
to do that will probably add to the price, but still very acceptable.
All of us would do well to get all of the specs together we need and than
write a standard spec sheet for the GMC motorhome 455 and 403 so that any
owner could hand the sheet to a good machine shop that builds engines and be
assured that he would get an engine that does the job at the right price.
Only my opinion.
>
>I recommend caution in using engine rebuilders who have a bias for hot rod
>engines unless they comfortably relate to the need to build an engine for long
>life, high torque and relatively slow engine speeds.
>
>High performance engine people often build large CID vehicle engines for peak
>power at much higher RPM for peak torque and power than is preferred for the
>GMC MH. The optimum engine for the GMC MH develops peak torque at less than
>3000 RPM and full power at about 3400-3600 RPM. This is designed to match the
>vehicle requirements taking into account vehicle mass, body drag coefficients,
>gearing, desired acceleration rates, cruise/top speed, engine life, etc.
>
>The 403 CID engine in my Royale gets the job done but it has to compensate for
>its 11.5 % smaller displacement by working harder than the 455 CID engine. It
>probably will not live as long as a 455 would have lived. But economics and
>environmental polititics drove GM to use the 403 beginning mid - '77 rather
>than engineering.
>
>My $0.02.
>
>Fred Hudspeth
>'78 Royale
>
>
