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| [GMCnet] 403 engine, rebuild or replace with ? [message #97172] |
Wed, 25 August 2010 12:19  |
larry erd
Messages: 132
Registered: August 2010
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Senior Member |
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the gmc i just bought ('77 kingsley) has the engine ,trans,front susp. out.
it has a 403 , is that a good engine to rebuild
or should i replace it with a 455 or ?? is the trans a stock toronado one,
i've read there is a mod. for better
shift points. before i start the rebuild i want to know what the best
options are.
thanks for the advise,
larry erd
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97179 is a reply to message #97172] |
Wed, 25 August 2010 13:22  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Most owners that I've talked to, indicate that there is not much performance difference between the 455 and 403. This is based on their owning several different years of GMC manufacture. 403 is lighter and should provide better gas mileage, 455 puts out more torque. Better gas mileage is in the eye of the beholder.
Have the transmission done by Manny. He works magic. Can ship you a re-built one anywhere in the country. Return your core to him.
Tom Phipps,
without a Manny rebuild
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97181 is a reply to message #97172] |
Wed, 25 August 2010 13:32 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| larry erd wrote on Wed, 25 August 2010 11:19 |
the gmc i just bought ('77 kingsley) has the engine ,trans,front susp. out.
it has a 403 , is that a good engine to rebuild
or should i replace it with a 455 or ?? is the trans a stock toronado one,
i've read there is a mod. for better
shift points. before i start the rebuild i want to know what the best
options are.
thanks for the advise,
larry erd
_______________________________________________
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You will get a lot of opinions on the engine, but I have a 403 and so far it's bullet proof. My neighbor has a 455 and we can't tell the difference either way. 403 parts are relatively plentiful and if you have one already, you might as well stick with all of the related harware, hoses, brackets, wiring, etc. They are similar, but not identical.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97183 is a reply to message #97179] |
Wed, 25 August 2010 13:45 |
larry erd
Messages: 132
Registered: August 2010
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thanks tom, do you know how to reach Manny? i'm new to GMC's so i don't know
all the players yet,
i've always wanted one for the last 30 years.so i've bought a basket case,
i guess i'd rather put it together myself.
larry
On Wed, Aug 25, 2010 at 2:22 PM, Thomas Phipps <tph1pp5@yahoo.com> wrote:
>
>
> Most owners that I've talked to, indicate that there is not much
> performance difference between the 455 and 403. This is based on their
> owning several different years of GMC manufacture. 403 is lighter and should
> provide better gas mileage, 455 puts out more torque. Better gas mileage is
> in the eye of the beholder.
> Have the transmission done by Manny. He works magic. Can ship you a
> re-built one anywhere in the country. Return your core to him.
>
> Tom Phipps,
> without a Manny rebuild
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97184 is a reply to message #97172] |
Wed, 25 August 2010 13:50 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Larry, The 403 is a large bore/short stroke engine and develops its maximum
torque at a higher RPM than the 455 does. The 455 is a smaller bore than a
403 but with a longer stroke, so it develops its maximum torque at a lower
RPM. There is a lot of variables in the set up of your coach. If you tow,
the 455 likes 3:50 gears and the 403 likes 3:70. The two engines are within
14 foot pounds of torque of each other at max torque. Longevity seems to be
about equal and most owners report slightly better fuel economy with the
403. I have run both engines and I prefer the 403 because it seems to like
running at the speed I prefer to drive which is 65 to 70, and the 455 sounds
like it is working hard at that speed. It is r eally 6 of one and a half
dozen of another. If you ask 20 different GMC owners, you are likely to have
their preferences equally split up. One important difference is that any
engine manufactured after the introduction of unleaded fuels will have
hardened valve seats in the heads, and some of them have valve rotators
also. These are preferable if you are rebuilding an engine. If you have more
specific questions about the engines, Dick Patterson and Joe Mondello are
good sources of factual information as are several other GMCers.
Jim Hupy
Salem, Or
78 Royale 403
On Wed, Aug 25, 2010 at 10:19 AM, larry erd <1ljerd@gmail.com> wrote:
> the gmc i just bought ('77 kingsley) has the engine ,trans,front susp. out.
> it has a 403 , is that a good engine to rebuild
> or should i replace it with a 455 or ?? is the trans a stock toronado one,
> i've read there is a mod. for better
> shift points. before i start the rebuild i want to know what the best
> options are.
>
> thanks for the advise,
> larry erd
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97185 is a reply to message #97181] |
Wed, 25 August 2010 13:51 |
larry erd
Messages: 132
Registered: August 2010
Karma: 0
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Senior Member |
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thanks bob, do you know if these 403 's have the 3 main bearing web like the
car engines have
or (hopfully)do they have the solid web around the main bearing? i read
about 403's years ago
and the hot roders loved the solid web ones.
larry erd
On Wed, Aug 25, 2010 at 2:32 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>
> larry erd wrote on Wed, 25 August 2010 11:19
> > the gmc i just bought ('77 kingsley) has the engine ,trans,front susp.
> out.
> > it has a 403 , is that a good engine to rebuild
> > or should i replace it with a 455 or ?? is the trans a stock toronado
> one,
> > i've read there is a mod. for better
> > shift points. before i start the rebuild i want to know what the best
> > options are.
> >
> > thanks for the advise,
> > larry erd
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
>
> You will get a lot of opinions on the engine, but I have a 403 and so far
> it's bullet proof. My neighbor has a 455 and we can't tell the difference
> either way. 403 parts are relatively plentiful and if you have one already,
> you might as well stick with all of the related harware, hoses, brackets,
> wiring, etc. They are similar, but not identical.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
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List Information and Subscription Options:
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97188 is a reply to message #97183] |
Wed, 25 August 2010 14:20 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| larry erd wrote on Wed, 25 August 2010 13:45 |
thanks tom, do you know how to reach Manny? i'm new to GMC's so i don't know
all the players yet,
i've always wanted one for the last 30 years.so i've bought a basket case,
i guess i'd rather put it together myself.
larry
|
From:
http://www.bdub.net/GMCSupplierLinks.html
Manny Trovao - Transmissions (including Switch Pitch) built specifically for our motorhomes. 3.50:1 Power Drive chain and sprockets.
San Jose, CA 408-937-1583 mtrovao@hughes.net
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97189 is a reply to message #97185] |
Wed, 25 August 2010 14:17 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Most of the ones I have seen are the windowed style. At the horsepower and
torque levels that most of us run in these coaches, those webs are very
strong and are trouble free. If you are spinning the engine above 5000 rpm
like some jet boats and racing applications do, try to find a Crusader
marine block, or there were some industrial engines that were used in
irrigation and power plant applications that had solid main bearing webs.
There is a cam plug in the rear of the cam gallery just in front of the
distributor drive gear on the 403 MH that has a small orfice in it to
provide lube to the distributor drive gear. Some engines do not have that
drilled plug. It can be accessed under the large welch (freeze) plug in the
bell housing and flywheel area. If you rebuild this engine yourself, do not
neglect removing all gallery plugs and cleaning all of these passages with
rifle bore brushes. All of these oil galleries will collect worn metal parts
and sludge and the best hot tank in the world won't clean them out. Do the
same thing with all the drilled passages in the crankshaft, and if you turn
the crank, have it nitride coated after it has been turned. If the crank
grinder doesn't know about the coating, shop around for a machine shop that
does. There are several more important requirements in the Olds engines, and
unless the shop that works on them is familiar with olds engines, it can
have bad results. Expect to pay $3000.00 to $4000.00 to have one
remanufactured. Good work isn't cheap and cheap work is usually not worth
what you pay for it.
Jim Hupy
Salem, OR
78 Royale 403
On Wed, Aug 25, 2010 at 11:51 AM, larry erd <1ljerd@gmail.com> wrote:
> thanks bob, do you know if these 403 's have the 3 main bearing web like
> the
> car engines have
> or (hopfully)do they have the solid web around the main bearing? i read
> about 403's years ago
> and the hot roders loved the solid web ones.
>
> larry erd
>
> On Wed, Aug 25, 2010 at 2:32 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
> >
> >
> > larry erd wrote on Wed, 25 August 2010 11:19
> > > the gmc i just bought ('77 kingsley) has the engine ,trans,front susp.
> > out.
> > > it has a 403 , is that a good engine to rebuild
> > > or should i replace it with a 455 or ?? is the trans a stock toronado
> > one,
> > > i've read there is a mod. for better
> > > shift points. before i start the rebuild i want to know what the best
> > > options are.
> > >
> > > thanks for the advise,
> > > larry erd
> > > _______________________________________________
> > > GMCnet mailing list
> > > List Information and Subscription Options:
> > > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> >
> > You will get a lot of opinions on the engine, but I have a 403 and so far
> > it's bullet proof. My neighbor has a 455 and we can't tell the difference
> > either way. 403 parts are relatively plentiful and if you have one
> already,
> > you might as well stick with all of the related harware, hoses, brackets,
> > wiring, etc. They are similar, but not identical.
> > --
> > Bob de Kruyff
> > 78 Eleganza
> > Chandler, AZ
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
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http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97197 is a reply to message #97188] |
Wed, 25 August 2010 15:59 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Larry,
No one has directly addressed your question of whether the TH-425 in the GMC
is the same as the Toronado. No, it is not. Nor is that in the Eldorado.
Nor are all years the same, with the later years being less desirable
because of plastic parts they include. In view of all that, everyone's
suggestion to let Manny build you a transmission is well founded. Some of
the parts he uses are not even available elsewhere. Even if you have AT
rebuilding experience, I would recommend Manny.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Wed, Aug 25, 2010 at 3:20 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
> larry erd wrote on Wed, 25 August 2010 13:45
> > thanks tom, do you know how to reach Manny? i'm new to GMC's so i don't
> know
> > all the players yet,
> > i've always wanted one for the last 30 years.so i've bought a basket
> case,
> > i guess i'd rather put it together myself.
> > larry
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97203 is a reply to message #97172] |
Wed, 25 August 2010 17:11 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| larry erd wrote on Wed, 25 August 2010 10:19 |
the gmc i just bought ('77 kingsley) has the engine ,trans,front susp. out.
it has a 403 , is that a good engine to rebuild
or should i replace it with a 455
|
I have only had 455s. I have a friend with a 403. I find the 403 to be a tight tidy engine. Perhaps it is the shorter stroke but it sounds perky. We spoke with Miguel Mendez (MGM GMC in Southern California) and he is a big fan of the 403.
I have read that the 403 can only be bored .040in (with .020 max recommended) because the cylinders are siamesed (no water between cylinders) so that might make a difference. Of course you can always have it sleeved.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97207 is a reply to message #97172] |
Wed, 25 August 2010 17:30 |
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I'm suprised no one mentioned this option, so I will! Go all in and drop in a Caddy 500 CID! These coaches need hill climbing torque and next to something with a deathrattler, the Caddy will deliver! If you need a caddy motor to build I may be able to supply you one depending on where in the country you are...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] 403 engine, rebuild or replace with ? [message #97222 is a reply to message #97214] |
Wed, 25 August 2010 19:38 |
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Gene, if your only making 395ft with a caddy 500, your not doing something right, you should be putting out 500+ ft lbs by 2k rpm with a good build....
| Mr ERFisher wrote on Wed, 25 August 2010 18:39 |
>
> I'm surprised no one mentioned this option, so I will! Go all in and drop
> in a Caddy 500 CID! These coaches need hill climbing torque and next to
> something with a deathrattler, the Caddy will deliver! If you need a caddy
> motor to build I may be able to supply you one depending on where in the
> country you are...
>
not a dime's difference in any of them,
read here
http://www.gmcmotorhome.info/engine.html#403_VS_455
and
------------------------------
--------------------------------
*Dyno tests*
----------------------------------------------------------
I was digging through some old GM test data and thought I would share the
following:
*Olds 455* test data with an uncertain pedigree (Toro or not? Test
conditions?) and it showed a torque at 2800 and below of about *398*. No
data below 2000, but other tests implied a peak torque at 1200 to 1600 rpm.
Peak hp was 234 at 3600.
*Cadillac 500 EFI* - peak torque *395* at 1200 and 1600 rpm. Peak hp 225 at
3600. The engine was knock limited and spark was retarded about 10 degrees
from MBT at most rpms. Both of these are consistent with other big GM
engines built at the time(except for the knock-limited part). Max
torquewas always below 2000 rpm and peak hp was never above 4000.
That's not
counting performance engines like the Chevy 427 or the Chrysler Hemi, of
course.
so now you can do what you want to do,
just because you can
gene
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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