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1970 GMC Jimmy - Grandfathers Unfinished Business

Dan_P

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Hey Guys,

My wife's grandfather passed away unexpectedly and nobody wanted his 1970 GMC Jimmy, so we ended up with it. He bought the 4x4 Jimmy in 1970 (original owner) and drove it for years (80K original miles). He was in process of restoring it but didn't get a chance to finish it before he passed. It was registered non-op but I was able to get the engine running in ~15 minutes...not super smooth.

My intent is to get it to reasonable driving condition, not intending to wheel it, not a daily driver. Reliable enough to enjoy it regularly. Because I got it cheap I'm fine putting decent money into it and I plan to do a fair amount of work myself if possible. I'm not a car guy, but have had some success with a much much newer cars (mostly my 4Runner), although internet research/parts have been pretty easy for newer cars. I have decent friend support if I have direction.

So...I'm hoping to get some general direction.

- It has the original drum brakes. This is probably the first item to get it drive-able. They are squishy and non functional. I've done some reading on disc conversions. Wondering if there is a strong opinion here? I've read a lot about rear disc conversion...but this isn't intuitive to me, I'd think the front disc conversion would be the more immediate path. Do you guys have guidance?
- The engine is a crazy story and I don't have the details, which you'll see is a major area of uncertainty. It shipped with the original V8 350. The engine must have died...because it now has a boat engine in it. Grandpa owned a boat company and I suspect when the V8 died, he had a comparable boat engine that he was able to swap out cheap. I don't know much more than that but will update the post when I do. I'm hoping to leave this in for now assuming everything works/runs. If a new engine is required I'm willing to do the swap (not sure to what).
- I know I'll need new tires...his have been sitting for years.
- The interior/exterior restoration looks pretty good (see the pics).

The big unknown generic questions: (I realize these are vague, but I don't know up from down right now)...
- Do you guys have advice of how to tackle this?
- What should I be looking for early on to figure out how to proceed?
- Are there known mods that should absolutely be on my list?
- What should I be looking for, and what do I need to learn about the car to do a proper assessment? (Tranny, engine, gearing, etc.)

I admit this post is super bit early...there is so much I don't know. But I'm hoping that some collective knowledge can help point me in the right direction so I can figure out the must do's and the sequence of events. I only have some exterior/interior pics now, but will post more when I get the chance.

Thanks in advance.

Cheers,
Dan

PS - I am ready and willing to be shammed a little bit...so don't hesitate to give the honest truth and point me back to the forum for more reading if that's the deserved response :)

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brut4s

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What a pile! Just send it to me!! LOL! Personally I'd rebuild the original engine and brakes then enjoy it. What a time capsule!!
 

ktmoutfront

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Those brakes will be fine for a weekend warrior vehicle. Put a ne master cylinder, wheel cylinders, soft lines and shoes on it. Flush the rigid brake lines. If the drums are smooth, run them.

Clean the fuel tank, flush the lines.

Pull the carb and clean it. If it has sat after running ethanol fuel, the jets will be plugged and it will never run right.

That is a really nice truck. Congratulations on being the caretaker of such a nice rig.
 

6872xtc

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It looks awesome to me!
I wonder if your Grandpa put a different engine in to get a little more power. If you can get some good gas into it and get the engine running good, I would leave it. If your Grandpa installed that engine, it's part of the history. The original engine would be great for the purist, but it doesn't sound like you are concerned about it being 100% original, and that is just fine! I personally don't leave too many vehicles alone. I gotta play with stuff.

You can rebuild the stock brakes and be ok, but I would put disc on the front, then rebuild the rear brakes. I don't know if the caliper mounts are available new anywhere. You should be able to get some used ones and then new calipers, pads and hoses. But before looking for any parts, make sure that it has an open knuckle front axle. I don't know for sure when that changed on the 1/2 ton axles. If it is a closed knuckle axle, there is a ball and socket like piece that completely covers the axle shaft and universal joint. If it is a closed knuckle, you would be better off to find a newer axle. And that requires finding or building one with the correct ratio to match the rear.

The factory started using disc brakes in the front in '71, so finding the parts to put on yours is somewhat easier by using parts for a '72.

Plan on changing the oil in everything as a matter of maintenance and to make sure that you don't have any water in anything from condensation. This should also give you an idea of what you need to do to it.

Oh, and the brakes on these trucks aren't going to feel the same as most of the newer vehicles, and if the front brakes aren't adjusted up properly, they will feel soft faster because of it. Maybe try to check things out and go from there.
 

Bent77

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That is a nice starting point!
 

diesel4me

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It looks sweet--like a time capsule !..GMC Jimmy's are rarer than Chevy K5's too,that adds some value..
You almost never see a truck of that vintage here in "good original condition" unless someone hauled it here from another part of the country where rust doesn't destroy them in 10 years..

The boat engine may have a hotter camshaft,boats are usually run at higher rpms and have a different grind than a street duty engine,that may be why it doesn't idle smoothly...but it probably will need a fuel system cleaning,tank to carb after sitting..
 

ekajkrats

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Welcome! Very nice rig!

I agree just to do the general maintenance to it and drive it first. If you get the brakes adjusted, make sure there is no air in the line and the vacuum booster is good, the drum brake might suit you. At most I'd just do the disk swap in the front and upgrade the vacuum booster. That should get you stopping really well.

P.s., I'm up in Novato, not sure how close you are.
 

Dan_P

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This has been an awesome. Thanks for for the input, it gives me a plan of attack.

Yes, the GWC is because those were his initials. I was able to keep the custom plate too which is cool.
 

70jimmy

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Very Nice rig. I agree with start with general maintenance, change all fluids, belts hoses etc. Rebuild the drum brakes. Mine had them, I would look at body mounts and replace if needed it was a huge improvement when mine was stock.

Start with basics, go, stop, steer, heat / air, etc. You inherited an awesome piece!!
 

CK5

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Wow, I can't believe nobody else wanted the Jimmy, lucky for you, beautiful looking ride, enjoy it!
 

Dan_P

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Welcome! Very nice rig!

I agree just to do the general maintenance to it and drive it first. If you get the brakes adjusted, make sure there is no air in the line and the vacuum booster is good, the drum brake might suit you. At most I'd just do the disk swap in the front and upgrade the vacuum booster. That should get you stopping really well.

P.s., I'm up in Novato, not sure how close you are.
I love Novato...hope to end up in the North Bay at some point. Currently down in South Bay (Los Gatos). If you end up down this way I'd love to exchange beers for some knowledge!
 

K85 Octane

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That is a nice starting point!

Or as a lot of us would consider finishing point. Gezz that's nice and nobody wanted it. That's so sad grandpa didn't have anyone in the family to talk trucks with. And such a beautiful truck he had. That's how these things get crushed or sent around the Ebay circuit.

That is a beautiful rig. Enjoy it!

Yeah. Enjoy it for the nice weekend driver it is. I would keep the GWC on the hood too, forever.
I probably speak for most of us here when I say "I'd give my left nut for that thing". It's always the left.
I'm sure it was a smoking penny you paid for that thing, probably have no idea the deal you got LOL. Welcome to the club. I hope the truck grows on you. If not at first, take the top off and it will. :D
 
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