New Feller

[Heavy Duty]

Hello, I just bought my first squarebody. Its a 1976 GMC K25 High Sierra with a 400sbc and a th350, 91,000 miles which I believe to be the original miles. The first two owners were hobby farmers so it has stayed in good condition. Everything works except the AM radio and hazards. I am new to this era of vehicles and carburetors in general, so I am sure many of my questions will seem stupid. I do have a two questions at the moment, Firstly I was told by my mechanic after I bought the truck that when you start driving these trucks around that their motors will blow, is that true? And if not how reliable is a stock 400sbc? Secondly my trucks bed has the fuel doors, were those available in 1976?

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[RustyPile]

Nice old truck..Welcome to our zoo..

Did "your mechanic" elaborate as to why the engine will blow?? Did he find some problem areas?? Was he trying to sell you another engine?? 91K is a lot of miles, but depending on how the miles were applied and the care given the truck, that's certainly no reason for the engine to give up.. Probably, he was just cautioning you against hauling ass off road with a 40 year old vehicle without doing some preparatory work first. That would apply to the whole truck, not just the engine..

Starting in 1973, GM removed the gas tank from behind the seat and mounted it to the frame and placed access doors on the bed sides.

 

[Heavy Duty]

The only problem that we came across is that when idling the oil pressure drops, he said its probably the engine starting to go out. I have also heard that it is just what they do.

 

[Honky Kong jr]

Welcome. What oil is in it and are you relying on the factory dash gauge? When was the oil changed last?

 

[CSFJ]

The bed on yours may have been swapped with a later model one. Iirc, the fuel fillers got doors over them around '78 or so. Prior to that the fill cap was right at the outer sheet metal.

 

[Heavy Duty]

Welcome. What oil is in it and are you relying on the factory dash gauge? When was the oil changed last?

I am relying on the factory gauge, I am not sure what oil it has, or when the oil was changed but judging by the way the oil looked it had been recently changed.

 

[74 Shortbed]

Welcome to the site, clean truck.

 

[Heavy Duty]

The bed on yours may have been swapped with a later model one. Iirc, the fuel fillers got doors over them around '78 or so. Prior to that the fill cap was right at the outer sheet metal.

Thats what I thought. Thanks for the clearing that up, I had been arguing with people about it. lol

 

[78C10BigTen]

The bed on yours may have been swapped with a later model one. Iirc, the fuel fillers got doors over them around '78 or so. Prior to that the fill cap was right at the outer sheet metal.

My 78 has just caps no doors. Nice truck and welcome and theres no such thing as stupid questions. U never know till you ask. And i wouldnt trust factory oil gauges, ive never had one correct.

 

[Heavy Duty]

Welcome to the site, clean truck.

Thanks, I will get some more picture of it.

 

[Honky Kong jr]

I am relying on the factory gauge, I am not sure what oil it has, or when the oil was changed but judging by the way the oil looked it had been recently changed.

I'd blob a manual gauge to it those OEM gauges can be flakey. I'd also do an oil and filter change using 15-40 and an AC filter and see if that doesn't change things.

 

[RustyPile]

I am relying on the factory gauge, I am not sure what oil it has, or when the oil was changed but judging by the way the oil looked it had been recently changed.

Instead of relying on what mechanics, POs and others have told you about your truck, I suggest you take a day or 2 and put your truck on jack stands.. change the engine oil and filter, same for the transmission, diffs, and transfer case.. Remove the tires and inspect the brakes.. While you're there, pack the wheel bearings.. It doesn't have to be a permanent install, but hook up a manual oil pressure gauge and check the oil pressure.. When you're finished with the inspection and service, all your data and information will be first hand and accurate.. BTW, stop stressing over gas filler doors and just drive the damn thing..

 

[1973c10]

Welcome aboard

 

[Heavy Duty]

Instead of relying on what mechanics, POs and others have told you about your truck, I suggest you take a day or 2 and put your truck on jack stands.. change the engine oil and filter, same for the transmission, diffs, and transfer case.. Remove the tires and inspect the brakes.. While you're there, pack the wheel bearings.. It doesn't have to be a permanent install, but hook up a manual oil pressure gauge and check the oil pressure.. When you're finished with the inspection and service, all your data and information will be first hand and accurate.. BTW, stop stressing over gas filler doors and just drive the damn thing.. [/

Your right, I shouldn't get worked up over stupid fuel doors when I have more important things to tend to on it.

I am planing on going through everything but just haven't had the time. I’ll look into hooking up a manual gauge.

 

[Heavy Duty]

Here are some more pictures. I also forgot to add that the transmission was rebuilt about 2,000 miles ago by the previous owner.

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