Picked up a 1970 GMC C3500 dump truck that needs some TLC

[murphy1244]

Thanks murphy! I'm surprised the original L6 engine was replaced after only a few years, but it might have been worked hard when new. So you think that distributor is circa 1974 as well?

What Sims said, check by the dizzy hole .maybe a 73 or so. 72 was last year for points. Then in the late 70s the engines went corporate and were all painted blue. That truck is going to drink gas like a drunk on a binge. The great thing about a Chevy small block is they made more of them than McDonalds made hamburgers. Parts galore at any salvage yard. Clean that engine up, get those spark plug wires off the brake line. Buy new filters gas, oil, pcv valve, air, new cap rotor and wires.

 

[pclausen]

If you can get the casting number off of the block that will give you the answer as to what is it. (check the driver's side of the block where the bell housing bolts up).

I was able to clean up that area and stick my cell phone in there to take this pic:

So the casting number is 355909, which appears to be the following:

305 cu. in. made from 1976-79 w/ 2 bolt mains.

So not the 350 I had hoped, but for my use, I'm sure the 305 will be fine.

 

[pclausen]

For the hesitation, with the engine off, work the throttle while looking in the carburator. It should squirt gas.

It does.

On the front of the carb where the gas line connects to it there should be a fuel filter behind the big nut. Make sure to use two wrenches, the big nut always comes loose first and twists the gas line!
Also check the distributor vaccuum advance for blown diaphragm or sticking linkage.

Thanks, I'll be sure to check those items!

 

[pclausen]

Clean that engine up, get those spark plug wires off the brake line. Buy new filters gas, oil, pcv valve, air, new cap rotor and wires.

Thanks. Got those items on my list now for a trip to the auto parts store in the morning.

 

[murphy1244]

It does.


Thanks, I'll be sure to check those items!

Pete, 305s suck. Start looking for a 350 there should be plenty out there or the inline 6 that was in there.

 

[pclausen]

I'll keep an eye out for a 350. I built up one of those back in high school and dropped it into a Firebird that had the crossfire v6 in it originally. Talk about a real sleeper!

Here's a shot of the main gauge panel. The red light the yellow arrow is pointing to is always on when the battery is connected. Any idea what this indicator is for?

And there are working oil temp and pressure gauges:

 

[Bob77064]

Great deal, the rear tires must be worth that much.

 

[JJZ 109]

The red light your arrow is pointing at is the high beam indicator if I remember correctly. I was 16 when I owned a truck of that vintage and I'll be 50 in a couple of weeks, so it's been a while!
I assume this truck probably isn't going to be a daily driver and will only see limited use. With that in mind I'd see how it's going to run when tuned up. If it's running good and not sucking oil, I'd stick with it instead of looking around for a 350. I once rebuilt a 305 just because a buddy had it laying around and gave it to me when I needed a motor for a '76 K20 plow truck. It did whatever I needed it to do.

 

[Stimw]

On the PTO, check the linkage, they will get slop/wear and it makes them iffy to get in gear.
Also check the mechanical advance for sticking/stuck. (rotate rotor button, make sure it is free) Another hesitation/power problem.

 

[woodlandfarms]

As for engine oil, its your call. It is an expensive choice to go full syn but not a bad one. Won't hurt anything. I guess to save a few bucks if I owned it I would just use cheap dino. You won't be driving it more than a 1000 miles a year probably. Change the oil every winter and that should be that.

One more thing. If i had your truck, I would dump a quart of ATF or engine flush and run it a bit before changing the oil. Get the engine nice and warm with the stuff and hopefully knock some crud out of the engine.

Carl