Home » Public Forums » GMCnet » Differences between motorhome and car engines?
| Differences between motorhome and car engines? [message #240860] |
Sat, 22 February 2014 12:40  |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
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OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience with I'd like to hear from you.
What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure the engine is set up properly for the motorhome?
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: Differences between motorhome and car engines? [message #240864 is a reply to message #240860] |
Sat, 22 February 2014 13:57  |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Agree 455 or more CI - torque is where its at.
Roller cam is better if you can afford it. Not cheap.
Cam should have peak torque close to your cruising RPM. Crane likes wider LSA ~114, Comp likes narrower ~110
Roller rockers may not hold up all that well depending on the brand. If you do run them, you will likely need to space the cover up [2 extra gaskets coated and glued worked on my buddys olds jet boat] cut and reweld your covers or expensive tall covers.
Gotta disagree with the gear drive. A quality double roller chain is fine.
All this is moot for production rebuilds as they usually run what they run. You'll have to ask if they will do custom mods and if it will effect their warrantee.
76 Glenbrook
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| Re: Differences between motorhome and car engines? [message #240867 is a reply to message #240860] |
Sat, 22 February 2014 14:25 |
KB
Messages: 1262
Registered: September 2009
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I would have liked to switch to a 403 (for better mpg's) when we did our replacement, but it was going to be too hard to find all the other stuff (tinwork, manifold, brackets) so we stuck with a 455.
I'd also have loved to go to roller lifters and roller rockers, but the price difference was too much for us (almost doubled the cost). At that point, I'd seriously consider one of JimB's engines instead.
If you talk to S&J and tell them it's for a GMC Motorhome, it'll basically be their heavy truck engine build (Note: the warranty on their heavy vehicle engines is only 12 months, not 5 years like on their car engines).
At a minimum, add a double row roller timing chain; the cost is small (eg Cloyes tru roller or Melling 40409). One of the best GMC engine builders told me privately that oil restrictors are not needed on a hydraulic lifter engine, but strongly suggested a high volume oil pump and pickup (eg Melling EM22FHV and D22FSI). We also went with an RV cam (eg Melling MTO-1, Elgin E-976P, or equivalent), but that's not technically legal on a CA coach that must pass smog tests. I believe Jerry Work went with a standard cam but advanced it 4 degrees.
Sorry, these part numbers are for a 455; I don't know what the 403 equivalents would be.
Hope this helps.
Karen
1973 23'
1975 26'
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| Re: Differences between motorhome and car engines? [message #240870 is a reply to message #240860] |
Sat, 22 February 2014 15:18 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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The Qjet part numbers are MH specific. So is the distributor curve. If Jim K is not doing engines as another thread mentioned, you could call Cinnabar for a price. That would give you a price you could try to be under for reference. They use an 'RV' type cam, oil restrictors and exhaust crossover restrictors so the choke still works. I think the warranty was 18 mos unlimited mileage. I have one as I needed the replacement while in Mi. No problems though I did advance the timing from where they set it it was a real dog and gas hog running too retarded.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Differences between motorhome and car engines? [message #240876 is a reply to message #240867] |
Sat, 22 February 2014 16:03 |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
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| KB wrote on Sat, 22 February 2014 12:25 |
I would have liked to switch to a 403 (for better mpg's) when we did our replacement, but it was going to be too hard to find all the other stuff (tinwork, manifold, brackets) so we stuck with a 455.
I'd also have loved to go to roller lifters and roller rockers, but the price difference was too much for us (almost doubled the cost). At that point, I'd seriously consider one of JimB's engines instead.
If you talk to S&J and tell them it's for a GMC Motorhome, it'll basically be their heavy truck engine build (Note: the warranty on their heavy vehicle engines is only 12 months, not 5 years like on their car engines).
At a minimum, add a double row roller timing chain; the cost is small (eg Cloyes tru roller or Melling 40409). One of the best GMC engine builders told me privately that oil restrictors are not needed on a hydraulic lifter engine, but strongly suggested a high volume oil pump and pickup (eg Melling EM22FHV and D22FSI). We also went with an RV cam (eg Melling MTO-1, Elgin E-976P, or equivalent), but that's not technically legal on a CA coach that must pass smog tests. I believe Jerry Work went with a standard cam but advanced it 4 degrees.
Sorry, these part numbers are for a 455; I don't know what the 403 equivalents would be.
Hope this helps.
Karen
1973 23'
1975 26'
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Karen
Great information, thank you.
I'm very happy with the 403. Even, apparently, on only seven cylinders it ran great and pulled some serious hills without problems on our 2500 mile trip through the Southwest last fall. Gas mileage was down but at the time I figured I was just pushing it a little harder. Thankfully, it didn't self-destruct somewhere in the middle of Utah or Arizona.
Darryl
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240879 is a reply to message #240876] |
Sat, 22 February 2014 16:17 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I do not have a dog in this hunt, but what the heck, it has never stopped
me before. If you were happy with the 403 even on 7 cylinders, you will be
happy with it running on all 8. With stock final drive gearing, the 403
falls on it's face below 50 mph. The 455 will pull quite well at that rpm.
But, at 62 mph, it is a different story. The 403 will run with the 455 at
that rpm and any faster than 65. If you regear the final drive to 3:70 on
the 403, it will hold it's own with the 455 at any speed.
They are two differently performing engines. Both are good. Add headers and
3" exhaust along with a properly timed cam chain and RV cam and EBL EFI to
the 403 and, my oh my. No contest. But they are both durable, high torque
at fairly low rpm engines, both well suited to the task of moving a 12,000
pound motorhome. Your experience may vary, but check with Migel in LA.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sat, Feb 22, 2014 at 2:03 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
>
> KB wrote on Sat, 22 February 2014 12:25
> > I would have liked to switch to a 403 (for better mpg's) when we did our
> replacement, but it was going to be too hard to find all the other stuff
> (tinwork, manifold, brackets) so we stuck with a 455.
> >
> > I'd also have loved to go to roller lifters and roller rockers, but the
> price difference was too much for us (almost doubled the cost). At that
> point, I'd seriously consider one of JimB's engines instead.
> >
> > If you talk to S&J and tell them it's for a GMC Motorhome, it'll
> basically be their heavy truck engine build (Note: the warranty on their
> heavy vehicle engines is only 12 months, not 5 years like on their car
> engines).
> >
> > At a minimum, add a double row roller timing chain; the cost is small
> (eg Cloyes tru roller or Melling 40409). One of the best GMC engine
> builders told me privately that oil restrictors are not needed on a
> hydraulic lifter engine, but strongly suggested a high volume oil pump and
> pickup (eg Melling EM22FHV and D22FSI). We also went with an RV cam (eg
> Melling MTO-1, Elgin E-976P, or equivalent), but that's not technically
> legal on a CA coach that must pass smog tests. I believe Jerry Work went
> with a standard cam but advanced it 4 degrees.
> >
> > Sorry, these part numbers are for a 455; I don't know what the 403
> equivalents would be.
> >
> > Hope this helps.
> >
> >
> > Karen
> > 1973 23'
> > 1975 26'
>
> Karen
>
> Great information, thank you.
>
> I'm very happy with the 403. Even, apparently, on only seven cylinders it
> ran great and pulled some serious hills without problems on our 2500 mile
> trip through the Southwest last fall. Gas mileage was down but at the time
> I figured I was just pushing it a little harder. Thankfully, it didn't
> self-destruct somewhere in the middle of Utah or Arizona.
>
> Darryl
>
>
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240880 is a reply to message #240860] |
Sat, 22 February 2014 16:28 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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People seem to have good luxk with the Drew Koba builds Jim Bounds supplies. You'd have a couple hundred to ship though. Likewise Mondello. I'm watching all of you - mine runs fine at 100K... but when it dies, I'll go get another from whomever seems to have the inside track on building them. Warren Johnsdon is just across the lake, I wonder what he'd get to build one... :) :)
--johnny
'76 23' transmode norris
Braselton, GA.
________________________________
From: Darryl Meyers <hospacctg@att.net>
To: gmclist@temp.gmcnet.org
Sent: Saturday, February 22, 2014 1:40 PM
Subject: [GMCnet] Differences between motorhome and car engines?
OK, I've pretty much made the decision to replace my engine with a "remanufactured" engine. I'll get on the phone Monday to S&J and maybe Motorworks (Thanks Karen and Jerry for your comments). If anyone has any other rebuilders they have had a good experience with I'd like to hear from you.
What is different about the 403/455 engines we use in the motorhome and the same engines in the Toronado and other automotive applications? I understand the cam is different; what is the difference? Anything else? What do I need to ask for to make sure the engine is set up properly for the motorhome?
--
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240882 is a reply to message #240864] |
Sat, 22 February 2014 16:36 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Well, the original build has hauled my lump 100K without problems other than a water pump. If the paperwork is to be believed, the PO had Sirum apply a rebuilt carb. I see no great need to go beyond what GM did to begin with. I'd rather spend the money on an engine builder who is willing to take the time to set everything in it to the same spec GM did to begin with. Another 100K will probably outlast me. My toad has all the fancies stuffed in, and takes advantage of them. I doubt the GMC really needs them.
--johnny
________________________________
From: Chris Tyler <dtyler11@tampabay.rr.com>
To: gmclist@temp.gmcnet.org
Sent: Saturday, February 22, 2014 2:57 PM
Subject: Re: [GMCnet] Differences between motorhome and car engines?
Agree 455 or more CI - torque is where its at.
Roller cam is better if you can afford it. Not cheap.
Cam should have peak torque close to your cruising RPM. Crane likes wider LSA ~114, Comp likes narrower ~110
Roller rockers may not hold up all that well depending on the brand. If you do run them, you will likely need to space the cover up [2 extra gaskets coated and glued worked on my buddys olds jet boat] cut and reweld your covers or expensive tall covers.
Gotta disagree with the gear drive. A quality double roller chain is fine.
All this is moot for production rebuilds as they usually run what they run. You'll have to ask if they will do custom mods and if it will effect their warrantee.
--
76 Glenbrook
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240883 is a reply to message #240881] |
Sat, 22 February 2014 16:52 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Dan, I hope that you have located all the engine mounts and accessory
brackets that work in the Motorhome with the Cadillac engine. You will need
them. The a/c compressor is located where the thermostat housing is on the
403, hoses for the radiator are in a different place, the alternator is on
the passenger side, the distributor is in the front of the engine instead
of the rear, power steering hoses and brackets are different than olds,
Carb is different, exhaust manifolds and exhaust pipes will need some
changing as well. But the swap can and has been done before. Larry Wiedner
and Ken Henderson as well as Jim K. all have them and are good sources of
tech info that you can trust. No B.S. from any of them. The gantry is still
at Jerry Work's place. He is in Mexico right now. When he returns, I will
retrieve it. I have to come to Boston Bar after the route 66 rally to help
Kim Davison install a 1 ton front end. If that is not soon enough we will
make a trip with the gantry.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Feb 22, 2014 2:30 PM, "Dan Borlase" <bord@shaw.ca> wrote:
>
>
> Jim, I am defiantly having a Caddy 500 built for the stretch. (as we
> speak) Do you have any suggestions re the build? I have told the builder
> to maker it stock, and yes, he knows it's for the coach.
> PS...the 403 will go to you...assuming you still want it.
> I'll have to work with you on getting the gantry system for the swap.
> _______________________________________________
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240885 is a reply to message #240879] |
Sat, 22 February 2014 17:11 |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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If you regear the final drive to 3:70 on
the 403, it will hold it's own with the 455 at any speed.
They are two differently performing engines. Both are good. Add headers and
3" exhaust along with a properly timed cam chain and RV cam and EBL EFI to
the 403 and, my oh my. No contest.
Jim
Speaking of the 3:70 I thinking now may be the time to upgrade. Would there be any substantial labor savings in swapping out the drive with the engine R&R now rather than later on its own? If I'm going to spend what I'm going to on the engine I'm not anxious to spend a bunch more on a new FD but if it saves money in the long run I might do it.
Darryl
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240887 is a reply to message #240885] |
Sat, 22 February 2014 17:28 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Darryl, If you have the entire power unit out, and you had been wanting to
re gear the final drive, this would be an excellent time to make the swap.
Also look carefully at your transmission pans and seals for fluid leaks. If
you have not changed it already, replace the transmission vent with an
angled fitting with a hose barb and run an overflow line so that it does
not discharge onto the headers or mufflers. Good prevention. Also inspect
your motor mounts. Replace them when the engine is out is a no brainer.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Feb 22, 2014 3:11 PM, "Darryl Meyers" <hospacctg@att.net> wrote:
>
>
> If you regear the final drive to 3:70 on
> the 403, it will hold it's own with the 455 at any speed.
> They are two differently performing engines. Both are good. Add headers and
> 3" exhaust along with a properly timed cam chain and RV cam and EBL EFI to
> the 403 and, my oh my. No contest.
>
>
> Jim
>
> Speaking of the 3:70 I thinking now may be the time to upgrade. Would
> there be any substantial labor savings in swapping out the drive with the
> engine R&R now rather than later on its own? If I'm going to spend what
> I'm going to on the engine I'm not anxious to spend a bunch more on a new
> FD but if it saves money in the long run I might do it.
>
> Darryl
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240890 is a reply to message #240886] |
Sat, 22 February 2014 17:40 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I have never done a Big Block Chevrolet into a GMC, but it has been done.
Takes a modified engine oil pan. The pictures that I have seen bored two
holes on opposite sides of the pan, inserted a tube that was bigger than
the final drive shaft, and welded it into the holes. There used to be some
guys in Sequim, Wa. that sold a kit for the GMC but I believe they are not
in the GMC engine swap business at present. They raced at Bonneville with a
modified GMC quite a few years ago with Chevrolet Big Block for power.
Chev's are a lot cheaper to rebuild than Olds or Cads.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Feb 22, 2014 3:25 PM, "Bill Dolinsky" <Wildbillnick@yahoo.com> wrote:
>
>
> How much extra work for a BBC?
> --
> Bill Dolinsky
> Edmonton, Alberta, Canada
> 1977 Kingsley TZE167V102169
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| Re: [GMCnet] Differences between motorhome and car engines? [message #240892 is a reply to message #240890] |
Sat, 22 February 2014 17:54 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Jim,
Hal Kading installed a new BBC in his Buskirk Stretch, maybe he'll spot this email and reply.
Jim Rosenberg and Dyno Sources up in Sequim are long gone. Along with BBC's they did 8.1 Vortec installations but unlike Dave Lenzi
they had problems. As I understand it on one customer's engine they couldn't get the OEM EFI to work so they put a carb on the
engine.
MOE was the name of the GMC they raced; it had a BBC with a supercharger on it. It was a gutted motorhome that JimB found for them
down in Florida. http://www.gmccoop.com/land_speed_record.htm If you read this article basically JimR screwed JimB! He never even
gave JimB any credit for helping him!
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: James Hupy
I have never done a Big Block Chevrolet into a GMC, but it has been done.
Takes a modified engine oil pan. The pictures that I have seen bored two
holes on opposite sides of the pan, inserted a tube that was bigger than
the final drive shaft, and welded it into the holes. There used to be some
guys in Sequim, Wa. that sold a kit for the GMC but I believe they are not
in the GMC engine swap business at present. They raced at Bonneville with a
modified GMC quite a few years ago with Chevrolet Big Block for power.
Chev's are a lot cheaper to rebuild than Olds or Cads.
Jim
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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