1975 GMC Palm Beach Restomod

[Mike Perez]

This is going to be the build thread for my 1975 GMC Motorhome restoration/modernization.

The general scope of my plans are as follows:
Rebuilt 455 running modern GM engine management including drive by wire, coil near plug ignition, and multi-port fuel injection
Rebuilt Manny Tranny (ordered one the day I heard he was retiring)
Modern wiring, both 12v and 110v
Modern instrumentation for both dashboard and coach systems
Completely modernized interior with rear twins, dry bath, modern appliances, inverter/charger, etc...
New holding tanks with macerator
High capacity battery bank
and on and on and on.....

Before I purchased this, I considered buying a extended high roof Sprinter or ProMaster and then building it out. Ultimately, the narrow interior width just bothered me too much. Also, if I was going to spend $30-40,000 on a cargo van, and then have to do everything anyway; I figured why not restore a GMC for the same or less and have a way cooler platform to start with.

 

[Mike Perez]

This is my plan for the outside and a rough color palette for the inside.

 

[Mike Perez]

First, it was taken down to the structure

 

[Mike Perez]

Started working on some custom engine management adapted from a Chevy LS

 

[Mike Perez]

Pulled entire subframe out.

 

[Mike Perez]

Rebuilt Manny Trans, rebuilt engine, aluminum heads and intake, roller cam, roller rockers, individual coil packs, drive by wire throttle body and serpentine brackets.

 

[Mike Perez]

CTS-V 850 watt brushless fan mounted to custom shroud on Griffen GMC aluminum radiator.

 

[Mike Perez]

That pretty much catches up today.. I left out a lot of details that I had posted on Facebook, and I'll fill in the gaps little by little.

 

[gmc260]

sure is impressive so far.. that engine work youre doing is cutting edge. really cool!

 

[Mike Perez]

Thank you.

 

[6cuda6]

Great work Mike!!

 

[Mike_H]

Awesome work, Mike

 

[Mike Perez]

Box for Vintage Air Gen IV Magnum.

 

[Bad Carp]

Beautiful work. Seriously jealous over that power plant.

 

[pvfjr]

Wow, I did not know you could pull the subframe out like that. I can't wait to see this finished! Thanks for sharing all the pics, I enjoy getting to see the guts.

 

[Justin Brady]

That engine is looking sexy as all hell.
One of these days I'll pull out my front subframe and do a a similar (though likely less intense) overhaul.
Mine runs great with no issues but I hate lifting the hatch because the rest of my coach is beautiful and the engine still looks like a ratty 70's hotrod lol.

 

[Mike Perez]

That engine is looking sexy as all hell.
One of these days I'll pull out my front subframe and do a a similar (though likely less intense) overhaul.
Mine runs great with no issues but I hate lifting the hatch because the rest of my coach is beautiful and the engine still looks like a ratty 70's hotrod lol.

Pulling it out the front wasn't as bad as I thought it would be.

 

[Mike Perez]

The box is mocked-up now for the air conditioner. Unfortunately, just like the original, if there has to be any service to the unit other than maybe just adding refrigerant, you’re gonna have to drop the box completely out which will require removing the radiator. My plan is to use some bulkhead fittings on the left side for both the heater hoses and refrigerant lines. There should really not be a reason to ever open up the box unless it needs major service.

I still have to cut a hole out of the back where the “max vent” is. That is now going to be the intake.

 

[gmc260]

First, it was taken down to the structure

hey Mike, I just noticed in this shot that there is no bath module. I guess youve decided to change it out completely? I removed the rear hatch on my '76, wasnt too big of a deal but I did find they used a minimal amount of hot glue to secure it so I made up some 2x4 bracing and used a scissors jack for persuasion. worked like a charm and didnt crack anything. I'll post more info on that when I catch up on my thread.

 

[Mike Perez]

hey Mike, I just noticed in this shot that there is no bath module. I guess youve decided to change it out completely? I removed the rear hatch on my '76, wasnt too big of a deal but I did find they used a minimal amount of hot glue to secure it so I made up some 2x4 bracing and used a scissors jack for persuasion. worked like a charm and didnt crack anything. I'll post more info on that when I catch up on my thread.

Yeah, the bath module is gone. I wish I could have saved it for someone, but I was unfortunately under the gun for time and it wasn't part of my design so it was removed in pieces.

I personally don't like the majority of the floorplans from the original coaches for a few reason. First, I'm not a fan of wet baths. Mine will have a dry bath. Second, I don't need that much seating. 99% of the time it will just be me, the wife, and the dogs. I think my original floorpan had seating for 13 people. 2 in the drivers seats, 3 on the couch, 4 in the dinette, and 4 in the back. That is insane. Mine will seat no more than 6. Also, I'm not a fan of the bed at the rear being across the coach. The problem with that is that if the person in the back has to get up to use the bathroom in the middle of the night, then they have to crawl over the other person. I'm not a fan of that. So for me, I think rear twins with a connected area around the shoulders is the great design. A couple pictures for reference. You get the idea. Rear twins still allows for the generator and propane compartments in the back. Also, since you don't need the area above your feet to be very high and it is forward of the window, you can have a closet cabinet start above your feet if you want.