455 to 403 coach swap issues?

[Matt Colie]

At the lunch bunch yesterday Greg Breem mentioned that the engine in his 78 Buzkick-Royale is in trouble but he has access to a fully rebuilt 455
coach engine that he can get at a reasonable price. From what I remember looking at the 403 here, there are more than a few changes. I do have zero
first hand experience with this swap.

Does anyone have better information if this is a realistic thing to expect to do and not end up with something that is a mess?
Greg is not a mechanic and would have to trust someone to do the job right.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[XPlorID]

Tell Greg to make me an offer for the roller cam 403 in my garage in Boise. Just put it back up on the Swap Meet page a few days ago. I know a shop
in Warren that could facilitate , and I am really anxious to get the engine out of my garage and running in someone's coach.

Jeff
in Toledo at the moment visiting my folks.
--
1973/94 GMCII Manny 6.5 TD AL radiator 1 ton front 4 bags back, Huber TBs

 

[Ken B]

Not a whole lot to change. We did it on Roger Blacks coach at least 12 years ago (maybe longer). The biggest difference that I remember was the oil
cooler lines are different. Also I believe the radiator hoses and some vacuum line routing were different. I'm working on a 403 right now trying to
get it going. I haven't noticed much difference other than there is more room to get to things.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[john r. lebetski]

I think if the new engine has all the accessory brackets intact you will be miles ahead. IIRC it is different. Also are the exhaust pipes to mufflers
different from BB to SB? I would think so. Waiting for answers.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Ken B]

|I forgot about the exhaust but I do not remember us having a problem with them. I was not there the whole time so maybe Roger took care of that when
I wasn't around.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[kosier]

If the exhaust pipe lacks clearance under the crossmember, just cut it and
add an inch. The 403 has a nicer mount for the alternator, but
because the head is now higher, it will probably touch the engine lid. I
just ground a little clearance where it touched. IIRC, there's two
pieces to the PS pump that don't touch now, but a longer bolt and a tubing
spacer took care of that. The increased torque means the
tires spin more easily, but the will still last a long time.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "Ken Burton"
Sent: Monday, October 23, 2017 10:23 AM
To:
Subject: Re: [GMCnet] 455 to 403 coach swap issues?

> |I forgot about the exhaust but I do not remember us having a problem with
> them. I was not there the whole time so maybe Roger took care of that
> when
> I wasn't around.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
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[hal stclair]

You are right on the exhaust, the 455 is about 2" wider and the Y pipe will need to be modified. The exhaust manifolds are different between the two
also. The 455's right side won't fit the 403.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM

 

[charles boyd]

The oil filter adapter is different also. The one piece oil cooler lines should work.
--
C. Boyd
76 Crestmont
East Tennessee

 

[Jim Hupy]

The 403 engine oil cooler lines work on the 455. Not the other way around.
The oil filter adapter is surrounded by the exhaust manifold on the
passenger side. The a/c brackets and fuel lines in the vicinity of the
mechanical pump are different also. The late (77 & 78) coaches are hampered
by the front body mount support brackets. But, the 455 bolts up to the
cross member and transmission the same as the 403. Power steering pump is
the same, but spacers and brackets are different. So is the alternator
support brackets. Best to have all the brackets from a 455 to do the swap.
Watch for misalignment on the drive pulleys. Exhaust pipes will need some
work, too. Just my observations, yours might vary a bit.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> The oil filter adapter is different also. The one piece oil cooler lines
> should work.
> --
> C. Boyd
> 76 Crestmont
> East Tennessee
>
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