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

[deerefan]

It's interesting how a 42 year old dump truck can generate as much or more interest than a brand new truck! It's always fun to buy something old and put it in good running condition and much cheaper than a new one.

Reminds us all of better times. The fact you can actually wrench on it is something.

 

[crashz]

It's a classic piece that is still very viable. I think it's great, and I'd gladly trade my 87 1 ton dump for an older truck like that.

 

[Grumpy Old Man]

It's a classic piece that is still very viable. I think it's great, and I'd gladly trade my 87 1 ton dump for an older truck like that.

Some of us grew up or started working driving these old trucks(which were new top of the line back then ) So to some of us they are whats left of a time when we did not have a care in the world ! You could have your kids run the countryside with no qualms about it , teenagers showed respect and A man who worked with his hands was not looked down on because he did not drive the NEWEST LATEST MODEL ! you gained respect for what you could build with your hands and not because you lived in a $400,000.00 house and drive a brand new dump witch are both probably financed to death ! That truck needs a tach bolted to the dash like I need another Project .Most old guys can tell you if it's running 1,000 rpm or 4,000 ! just because it's old does not mean you have to trash it to make it work ! Chevrolet was putting tachs in cars way before 1970 did you ever think they just thought whoever would be driving it just did not need one ?:thumbsup:

 

[deerefan]

Some of us grew up or started working driving these old trucks(which were new top of the line back then ) So to some of us they are whats left of a time when we did not have a care in the world ! You could have your kids run the countryside with no qualms about it , teenagers showed respect and A man who worked with his hands was not looked down on because he did not drive the NEWEST LATEST MODEL ! you gained respect for what you could build with your hands and not because you lived in a $400,000.00 house and drive a brand new dump witch are both probably financed to death ! That truck needs a tach bolted to the dash like I need another Project .Most old guys can tell you if it's running 1,000 rpm or 4,000 ! just because it's old does not mean you have to trash it to make it work ! Chevrolet was putting tachs in cars way before 1970 did you ever think they just thought whoever would be driving it just did not need one ?:thumbsup:

I can see we have some similar thoughts. I hate to see older vehicles get butchered too far beyond originality. As for a tach, I like to have one. It is a great tool to monitor engine behavior. Being around engines basically my whole life, I can tell rpm pretty well but still like a tach to confirm. The 305 is a 4k rpm motor max. Anything over that and power decreases greatly.

 

[downslope]

Distributor is definitely an HEI unit. No points in that one. I think they started coming out around '73. I know that I had a '74 Pontiac with it.
The spark plug number for sure rings a bell in many of the engines I tinkered with and/or swapped out of the '76 K20 & '78 K10 Chevys and '79 K15 GMC that I owned in the 80's and 90's.
Your option sticker shows a 4.57 rear, so if it's really a 4.10 now there's been a change along the way. Never messed with the heavier trucks so I couldn't tell you about the shocks. I know that the half ton 2WD's of that era had rear coils with shocks.
I see that it was originally dark green. Brings back memories of my very first vehicle. 1969 C10 with 250 CI six banger, 3 on the tree and factory wood floor in the bed. Also dark green.

I still own a 1973 C30 long wheelbase stake that I bought new in spring of 74. It is a 350 4-barrel with 4.11 rear and has a points distributor, not HEI. I think what may be confusing here is that the HEi might have been used in light duty trucks and the ones over 6000 or 6200 GVW stayed with the points ignition a while longer, or else someone swapped in a later year 305. The HD 350 4-barrels were not that bad on gas at all. I would average around 14mpg, half fully loaded/half empty, as long as you don't push the truck much over 55 mph. Many times a 4 barrel will get better mileage than a 2-barrel of the same size, again as long as you don't run at high speed.

I also owned a 71 half-ton 6-cyl 250 until two years ago. Those could be had with either leaf springs in the rear or an X-type frame with coils. Either one worked OK but the X-frames tended to rust out.

 

[stingray1]

You got a super deal,simple to work on.Congrats.

 

[downslope]

Re: Picked up a 1970 GMC C3500 --Transmission Question

Not to hijack this thread, but it seems we have some knowledgeable people here about these old GM trucks.

Do any of you know if the 4-speed with granny low in my 1973 C30 350 V8 can be replaced with a later 5-speed with overdrive and how much work it would be?
Bellhousing? input shaft? drive shaft? cross member mounting, what year(s) would work, etc?

Or if another forum where they talk about this kind of stuff?

Thanks.

 

[deerefan]

Not to hijack this thread, but it seems we have some knowledgeable people here about these old GM trucks.

Do any of you know if the 4-speed with granny low in my 1973 C30 350 V8 can be replaced with a later 5-speed with overdrive and how much work it would be?
Bellhousing? input shaft? drive shaft? cross member mounting, what year(s) would work, etc?

Or if another forum where they talk about this kind of stuff?

Thanks.

Yes it will. Its been done before. However, the 5spd is not as stout. There will be some machining necessary and you will need to pick up an adapter (possibly) to mate the motor to the trans. How about a full swap, a motor/trans out of a donor truck? The motor mounts should line up but the driveshaft may have to be modified. We had a 90 chevy 3/4 ton 350 5spd at work a while back that was in good shape, we sold it for 3k.

 

[Gem99ultra]

I think you 've made a GREAT buy!

I'll chip in with my 2 cents too, just for things to consider.

From the looks of the plugs, I strongly suspect oil blow-by, i.e. rings are pretty worn. Not much you can do about that short of an engine rebuild. And I doubt that's in the plan. So - a set of hotter range plugs every once in a while should do you good enough.

Missing two bolts in the carb will definetly let it run lean, and not have much power at low rpm's. Replace those.

Please - get some mounts welded for the shocks. You don't need shocks 'till you need them. But then - you NEED them.

I'd stay with the 305 as long as it's running to suit you. Sure - a 350 is better. But then, you're probably not wanting a race truck or show truck. If you need more power though, switching the intake and carb for a 4bbl setup would be the cheapest and simplest; think 'junk yard' stuff.

With the parts that you've already bought and are installing, you're probably close to having a very good farm truck. And for a steal of a price

 

[pclausen]

Appreciate the feedback. I'm monitoring oil consumption and will pull a few of the new plugs once I get some miles on them to see what they look like and then go hotter as needed.

I actually had a set of carb studs laying around, but when I went to screw them into the empty holes, there was what appears to be stripped bolts already in the intake threads, so I'll need to pull the carb to see what's going on. If it looks real bad, that might be the excuse I need to find a 4bbl setup.

The main issue right now is that it will hesitate/stall if applying anything more than very modest gas pedal pressure until fully warmed up, but it otherwise ruins great and fires right up after a few pumps. I got to get the rear wire harness fixed up and throw the FARM USE tag on it and take it for a 10 mile drive to the dump with a bunch of junk. That will be my first "real" trip.