How to determine which engine I have

[mike]

I'm trying to find tune up parts for my 1978 Royale. Looking through the Parts Book, it shows two different engine assemblies for 1978. One of them,
561032, reads, ENGINE ASSY - type 403 CID V-8 gas code RA (STD) (eff w/ 1978). The other, 561033, reads, "ENGINE ASSY - type 403 CID V-8 gas (RPO
NB4) (eff w/ 1978)

How do I know if I have a standard or RPO engine? Its not listed on the VIN tag as an option so should I assume that its the 561032 assembly? I ask
as they have different distributor caps...
--
Mike and Jessica
West Michigan (Just north of Grand Rapids)
1978 Royale Twin bed, Dry Bath

 

[JSanford]

Look at the options sticker in your glovebox, NB4 will be listed on there.
--
Jeremy Sanford
Sacramento, CA

 

[richard h staples]

Mike,
RPO NB4 is the California emission system engine, so you may already know whether or not this applies to you. I'm not cursed with this option, but
one quick way to tell might be checking your evaporative canister down behind the right front wheel. IIRC, the California coaches had two canisters,
the rest of us one. There are several other unique "features" on CA engines, notably the "throttle pusher" diaphragm and control valves on the left
side of the carburetor which hold the throttle open slightly under certain conditions.

HTH,
Rick Staples
--
Rick Staples, '75 Eleganza, Johnstown, CO

"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien

 

[mike]

So, If that RPO code is not there, I have the "standard" engine?

http://www.gmcmhphotos.com/photos/data/500/medium/VIN_Small_.jpg
--
Mike and Jessica
West Michigan (Just north of Grand Rapids)
1978 Royale Twin bed, Dry Bath

 

[jim kanomata1]

On the block on both sides it cas a large casting mark 403

On Sun, Sep 29, 2019 at 2:49 PM Mike via Gmclist
wrote:

> So, If that RPO code is not there, I have the "standard" engine?
>
> http://www.gmcmhphotos.com/photos/data/500/medium/VIN_Small_.jpg
> --
> Mike and Jessica
> West Michigan (Just north of Grand Rapids)
> 1978 Royale Twin bed, Dry Bath
>
>
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[mike]

> Mike,
> RPO NB4 is the California emission system engine, so you may already know whether or not this applies to you. I'm not cursed with this option,
> but one quick way to tell might be checking your evaporative canister down behind the right front wheel. IIRC, the California coaches had two
> canisters, the rest of us one. There are several other unique "features" on CA engines, notably the "throttle pusher" diaphragm and control valves
> on the left side of the carburetor which hold the throttle open slightly under certain conditions.
>
> HTH,
> Rick Staples

DING DING! Rick, you are the lucky winner. I missed your post earlier, and figured out the California emissions thing with a little more research.
Thanks for replying!
--
Mike and Jessica
West Michigan (Just north of Grand Rapids)
1978 Royale Twin bed, Dry Bath

 

[steve southworth]

> DING DING! Rick, you are the lucky winner. I missed your post earlier, and figured out the California emissions thing with a little more
> research. Mine was delivered in Indiana, so I should be safe from the Commifornia emissions.

Don't count on it. Mine was delivered in MS and had the CA option.

Fortunately mine is a '74 so that only included the double canisters and fuel tank heat shields on the exhaust.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

 

[johnny]

Quick n dirty - Look behind the pax side front wheel and count the round vapor cannister(s). If there's one, you have a 49 states setup. If there's
two, congratulations, you have a California setup. The two will also have different numbers for the Quadrajet, and the California one will have
slightly different vacuum setups and as someone noted, a throttle 'slow to idle' diaphragm on the linkage. California runs the vacuum advance off
ported vacuum, not sure about the 49 state. On my two coaches, both initially California spec, didn't seem to make a lot of difference except for the
extra hose on the vapor cannisters. Replaced on both and got much better idle performance. Overall, I think the Cal setup is more to make the CARB
happy than any great difference in performance - or emissions.

--johnny
--
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