Home » Public Forums » GMCnet » [GMCnet] 455 Engine On Ebay
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| Re: [GMCnet] 455 Engine On Ebay [message #32016 is a reply to message #32015] |
Sun, 04 January 2009 16:55   |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
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Is there anything specific to the engine itself that would make buying a motorhome-specific engine better than any other 455? And how rare are 455's becoming? And is the block on a 455 interchangeable with any other big block GM, so that if you had a catastrophic engine failure, the choice of suitable replacements would extend beyond merely other GMC motorhomes?
I bet Ken B could find space in his hangar for a nice QEC 455 with trans and final drive on a stand ready to go.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: [GMCnet] 455 Engine On Ebay [message #32021 is a reply to message #32016] |
Sun, 04 January 2009 17:24 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Randy,
The basic 455 is about the same between the passenger cars and the
motorhome. But the intake manifold is common only to the MH and the
Toronado. One of the exhaust manifolds (I don't remember which) is the
same as the Toronado; the other is unique to the MH. ALL old car parts,
and especially our MH parts, are becoming rare. We've probably got a
brief respite from the indiscriminate crushing of our irreplaceable
parts, but when the economy revives, it will start again. Most of the
junkyards have already been emptied in trying to fill the Chinese sinkhole.
NO, other 455's are not interchangeable with the Olds. Not by any
stretch of the imagination. They might bolt to the bell housing, but
the crankshaft/drive axle interference problem might be overwhelming;
certainly there's no direct bolt-in replacement among them. The easiest
alternative is the 66-78 Eldorado engines, since the rest of the
drivetrains are the same; even they are not direct bolt-ins.
Someone needs to save that engine, etc, as well as other unique parts
from the destroyed coach -- like the suspension, and, if still in good
shape, the front frame clip.
JMHO,
Ken Henderson
Americus, GA
www.gmcwipersetc.com
'76 X-Birchaven
Randy wrote:
> Is there anything specific to the engine itself that would make buying a motorhome-specific engine better than any other 455? And how rare are 455's becoming? And is the block on a 455 interchangeable with any other big block GM, so that if you had a catastrophic engine failure, the choice of suitable replacements would extend beyond merely other GMC motorhomes?
>
> I bet Ken B could find space in his hangar for a nice QEC 455 with trans and final drive on a stand ready to go.
>
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| Re: [GMCnet] 455 Engine On Ebay [message #32061 is a reply to message #32016] |
Mon, 05 January 2009 05:41 |
Steven Ferguson
Messages: 3447
Registered: May 2006
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Randy,
If it's an early '73, there's a chance that it is a W30 short block.
Basically, that's a high nickle block with a steel crankshaft. The
pan and intake are unique and shared with the Toro.
The 455's are indeed becoming extinct. They were only built for 6-7
years and used for everything from passenger cars, several different
motorhomes, jet boats, irrigation pumps and perhaps other industrial
applications. It doesn't hurt to pick them up when you find one at a
reasonable price. Just don't leave it outside unless it is tightly
bagged. At least two cylinders will have open valves that invite
water invasion and nothing kills a block quicker than water in a
cylinder. Bag it!
On Sun, Jan 4, 2009 at 3:55 PM, Randy <Acrosport2@hotmail.com> wrote:
>
>
> Is there anything specific to the engine itself that would make buying a motorhome-specific engine better than any other 455? And how rare are 455's becoming? And is the block on a 455 interchangeable with any other big block GM, so that if you had a catastrophic engine failure, the choice of suitable replacements would extend beyond merely other GMC motorhomes?
>
> I bet Ken B could find space in his hangar for a nice QEC 455 with trans and final drive on a stand ready to go.
> --
> Randy
> 1973 26' Painted Desert
> Ahwatukee (Phoenix) AZ
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>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] 455 Engine [message #121671 is a reply to message #32015] |
Wed, 13 April 2011 06:54 |
Gary Casey
Messages: 448
Registered: September 2009
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Well, Jim H. asked for it, so here's an opinion: There a number of factors that
affect the designer's choice of bore and stroke ratio. With a given
displacement a bigger bore:
1. Makes the engine longer - or might require compromises like siamezed
cylinders
2. Has a heavier piston - the weight goes up roughly with the cube of the bore,
while the displacement goes up only by the square.
3. Has a higher octane requirement - a longer flame travel means there is more
time for detonation to occur. So the compression ratio has to be lower
4. Allows largr valve diameters - a very good thing.
5. Longer piston rings lead to potential oil control problems (like on the
early Chevy 502's)
6. Lower piston speeds
7. Increases the crankshaft journal overlap, giving a stronger crank.
8. Increases the hydrocarbon emissions on account of the the highe
surface-to-volume ratio of the combustion chamber.
9. With the same deck height the rod angles are lower, reducing piston side
load and peak accelertion.
All those influence encourage the designer to match over-square engines wtih
more aggressive (longer duration) camshafts leading to a higher-rpm torque
peak. It will have lower compression pressures at low rpm, negating the
derimental effect on octane requirement and takes advantage of the lower piston
speeds by running the engine faster.
But in the case of the Olds 455 we see other influences in the choices they made
- primarily those of capital and tooling cost. Once the base engine was
designed it is very, very expensive to change the bore centers, so that has
stayed the same forever. Changuing deck height is less expensive. So there no
changes in bore centers and one change in deck height. I'm not sure if the
valve diameters have changed at all between the 330, 350, 455 and 403. When the
403 was created as a move to increase fuel economy why did they increase the
bore of the 350 instead of stroke it? I don't know, but I suspect the 403 is
about the same weight as the 350, much lighter than a stroked version with a
taller deck.
was the 403 a good design? I think it could have been better if they had
increased the valve diameters and gotten more aggressive with the camshaft.
They could have had an engine with more power and more fuel economy than the 455
- but at a higher noise level (higher rpm). Oops, that wouldn't have worked
:-).
FWIW,
Gary Casey
Jim, in my personal experience, an engine that has an undersquare design,
stroke being longer than the bore, with the camshaft advanced 4 degrees over
straight up, will produce torque at a lower rpm. An oversquare design like
the 403 Olds, with the bore larger than the stroke, same cam timing, tends
to produce it's max torque at a slightly higer rpm. There are many more
variables than this, like compression ratio, valve sizes and port designs
along with header tubing diameter & length, intake manifold design and carb
venturi sizes & the list goes on. Plusses might include 4 bolt main bearing
caps, forged pistons, stellite valve seats and stainless steel valves,
roller cams and rockers, trueroller timing chain set, this will generate
plenty of opinions + or -.
Jim Hupy
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