Best thermostat

J

jerry burt

New member
Feb 13, 2016
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What is the current best thermostat to put in our 73 - 455?
I was looking for a Robert Shaw based on what I have read on the forum. The only place I found them was at Summit and Speedway. NAPA has the
re-branded Mr. Gasket. All are now made in China.
I was reading a couple of Vette forums and it seems the Chinese thermostats' quality has fallen off.
Any suggestions?

While on the T'stat subject, the bolts on the t'stat housing are metric. Is this correct for 73? They are the only metric bolts I've run across so
far.
Thanks.
--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
Photos - http://jburt.smugmug.com/GMC-Motorhome
Lots of upgrades but lots to do to make it ours.
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
 
I got my Robert shaw clone from summit it is the same thermostat for most GM and some other mfgs of the era. I am pretty sure all 73 to 78 are SAE and
not metric in the original thermostat housing bolts.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
> I got my Robert shaw clone from summit it is the same thermostat for most GM and some other mfgs of the era. I am pretty sure all 73 to 78 are SAE
> and not metric in the original thermostat housing bolts.

I'm still trying to decipher what I have here. The base color (original??) on the intake looks like Case Tractor (competition) gloss orange and was
repainted gloss black. The numbers on the oil fill tube show it is a '73 but there is no VIN number on the front left side of the block. According to
several Olds forums that is an indication of a replacement block.

Applied GMC has a couple of heads they are sending me.
I've decided to redo the top end based on the compression test, no carbon build up, and the fact there is no ridge in the cylinders. What I thought
was a crack in the block turned out not to be. Where I have the coach stored does not lend itself to pulling the engine. When I get it running, if the
lower-end is bad, at least I can get it to someplace I can pull the engine and do a short block. Bassackwards I know but I need to build up my
discretionary funds before I do the Paterson/Manny combo.

--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
Photos - http://jburt.smugmug.com/GMC-Motorhome
Quad bags w/disc brakes - Alcoas w/ Michelins lots of interior updates.
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
 
I had a factory replacement 455 block I thought the casting number was on the rear of te block and yes it is a totally different number. Other then
that the block is identical to the original.The thermostat mounting holes are on the intake manifold not the block. If the intake is aftermarket I
suppose it could be metric but why would they do that?
--
Roy Keen
Minden,NV
76 X Glenbrook
 
The mechanicals seem to be a Frankenstenian combination of parts. I'm not interested in doing a numbers matching build. I'm just trying to get some
sense of what I've got. The intake is cast iron with the proper casting numbers. I will re-thread the t-stat bolt holes to Am/std. Could this be off
of an industrial engine?

The later blocks (Fa) did have the casting numbers in the back. The casting number on my block is on the front,center next to the oil fill tube and is
an F block cast in 72. The engine serial number is on the oil fill tube as it should be according to the GMC manual. This shows it is a 73. Since the
tube can be re-installed on a different block, it doesn't help with whether the block is original or not. On cars, the vehicle VIN is supposed to be
stamped on the front, left side of the block. I was wondering if that was the case with our coaches.

> I had a factory replacement 455 block I thought the casting number was on the rear of the block and yes it is a totally different number. Other
> then that the block is identical to the original.The thermostat mounting holes are on the intake manifold not the block. If the intake is
> aftermarket I suppose it could be metric but why would they do that? I believe all the Motorhome engines were GM blue but some earlier car engines
> were also red I believe like an earlier 425?

--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
Photos - http://jburt.smugmug.com/GMC-Motorhome
Quad bags w/disc brakes - Alcoas w/ Michelins lots of interior updates.
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
 
This thing is not an all matching numbers concours show quality vehicle. It
is more akin to a manure spreader. A useful vehicle to be sure, but, it is
still a pig no matter how much lipstick you put on it. It is assembled from
parts scrounged from other vehicle assembly lines, at the lowest cost
possible. For the most part, they used Oldsmobile pieces. Some were
modified in later years as they proved not to be robust enough for the
weight and forces applied to them by motor home use.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> The mechanicals seem to be a Frankenstenian combination of parts. I'm not
> interested in doing a numbers matching build. I'm just trying to get some
> sense of what I've got. The intake is cast iron with the proper casting
> numbers. I will re-thread the t-stat bolt holes to Am/std. Could this be off
> of an industrial engine?
>
> The later blocks (Fa) did have the casting numbers in the back. The
> casting number on my block is on the front,center next to the oil fill tube
> and is
> an F block cast in 72. The engine serial number is on the oil fill tube as
> it should be according to the GMC manual. This shows it is a 73. Since the
> tube can be re-installed on a different block, it doesn't help with
> whether the block is original or not. On cars, the vehicle VIN is supposed
> to be
> stamped on the front, left side of the block. I was wondering if that was
> the case with our coaches.
>

> > I had a factory replacement 455 block I thought the casting number was
> on the rear of the block and yes it is a totally different number. Other
> > then that the block is identical to the original.The thermostat mounting
> holes are on the intake manifold not the block. If the intake is
> > aftermarket I suppose it could be metric but why would they do that? I
> believe all the Motorhome engines were GM blue but some earlier car engines
> > were also red I believe like an earlier 425?
>
>
> --
> Patti & Jerry Burt
> 73 Gmc 26' Canyon Lands -
> Photos - http://jburt.smugmug.com/GMC-Motorhome
> Quad bags w/disc brakes - Alcoas w/ Michelins lots of interior updates.
> Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Why mess with the bolts? If it works now with metric bolts and has no leaks, leave it that way. It is not like these bolts are something you will be
playing with frequently.

Note: those holes go all the way into the coolant passage. If re-threaded coolant could migrate up the threads and leak.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thanks Roy and Jim. I'll just wait for the heads from JimK and put it together. Off gto do more cleaning.
--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
Photos - http://jburt.smugmug.com/GMC-Motorhome
Quad bags w/disc brakes - Alcoas w/ Michelins lots of interior updates.
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
 
I would be willing to bet that they are metric because they were rethreaded
to be metric at some point, for reasons lost to history.

In any case, I stud these fasteners instead of using bolts. That way, I
know how much depth of thread is in the manifold, and I don't have to break
the seal on those threads to replace the thermostat. Granted, I started
doing this when I switched to the Rockwell aluminum manifold, where these
holes are not drilled and threaded all the way into the water jacket, and I
wanted to make use of every single thread available to avoid stripping
them. But it's a good idea for the iron manifold, too, and it means you can
use a robust sealer on those threads without fear of being unable to
extract them in the future.

Rick "who would leave them metric and paint the bolt heads or nuts blue as
GM once did with metric fasteners" Denney

> The mechanicals seem to be a Frankenstenian combination of parts. I'm not
> interested in doing a numbers matching build. I'm just trying to get some
> sense of what I've got. The intake is cast iron with the proper casting
> numbers. I will re-thread the t-stat bolt holes to Am/std. Could this be off
> of an industrial engine?
>
> The later blocks (Fa) did have the casting numbers in the back. The
> casting number on my block is on the front,center next to the oil fill tube
> and is
> an F block cast in 72. The engine serial number is on the oil fill tube as
> it should be according to the GMC manual. This shows it is a 73. Since the
> tube can be re-installed on a different block, it doesn't help with
> whether the block is original or not. On cars, the vehicle VIN is supposed
> to be
> stamped on the front, left side of the block. I was wondering if that was
> the case with our coaches.
>

> > I had a factory replacement 455 block I thought the casting number was
> on the rear of the block and yes it is a totally different number. Other
> > then that the block is identical to the original.The thermostat mounting
> holes are on the intake manifold not the block. If the intake is
> > aftermarket I suppose it could be metric but why would they do that? I
> believe all the Motorhome engines were GM blue but some earlier car engines
> > were also red I believe like an earlier 425?
>
>
> --
> Patti & Jerry Burt
> 73 Gmc 26' Canyon Lands -
> Photos - http://jburt.smugmug.com/GMC-Motorhome
> Quad bags w/disc brakes - Alcoas w/ Michelins lots of interior updates.
> Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
'73 230 "Jaws"
Northern Virginia
 
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