318 Detroit

I drove many 318s over the years and I always thought that you didn't run it under about 1600 rpm or the bottom end wouldn't last long. An overhaul was done in the 300,000 to 400,000 mile range but they were cheap and easy to do.

 

A 318 will fall flat on it's face at anything under 1800 RPM. The power only starts coming in at 2100. I ran mine between 1900 on the low end and 2400 on the high. With gutted mufflers these things really start to sing around 2200. A good 318 will average about 700 miles to a gallon of oil in OTR applications. Less in local. If you happen to park overnight on a sideways incline and idle the truck, don't be suprised to see oil running out from under the truck. They are made that way. If idling all night, try to park on level ground, or facing uphill. This will keep oil from gathering in the air box, as the drain with the check valves is at the rear of the engine.

4.5 MPG is about average. You will need a 4.33 rear or lower in dump truck operation. I can guarantee you will have a strong right arm and left leg before long, as you will get plenty of workout changing gears. Also, don't try to keep the engine full of oil, it will blow it out. Most people ran them 1/2 to 1 gallon low, and added oil when the oil gauge started to jump around.

In the day you didn't have to worry much about a full DOT inspection. No one wanted to crawl around under the oil soaked engine, trans, and everything else under the truck. They did help keep parts from rusting though.

A hot 250 Cummins will out pull a 318.

 

Good choice.

 

In my rookie years I drove a 6-71 10spd daycab and a 318 13spd with 4:33's, they would switch me back and forth but the talk of the shop was a 12V-71 13spd with 4:70's, they all were GMC's. But after I drove my first 350 cummins, I was in heaven and didnt need ear plugs any more and could hear the cb and music in the juke box. But the downfall was the Hendrick Suspension, the roughest ride to date I've ever had on a 160 inch wheelbase.

 

I dont know what your doing with it. But if you run a dump truck 10+ hrs a day. You will see a need for a 80,000 dollar dump truck. They take a beating.

I haul out of a quarry everyday do around 200miles a day. An old truck like your talking will never hold up. But if your using it once a week or something like that then you should be fine.

 

Once again, you drive a 318, the same as any other engine between 1200 and 1550.
If it is set up properly, they will do the job perfectly, The torque is full on at 1200. People keep blabbering about high RPM as if it was some saving grace. At one time they had about 50% of the market. They would start when it was cold, you could work it when it was cold, and unlike a Cummins of the day would not break cranks.

 

The full 318, which was actually rated at 289 HP and 758 ft lbs torque, would fall flat on it's face at anything below 1800 RPM. I owned one, drove several, and tried it. The torque is rated on this paticular version of the 8V71N at 1600 RPM, which to me is a ridiculious statement. This is with the 65 injectors. The max HP is also rated at 2100 RPM, with my experience showing a dramatic increase above this. The torque is such a low rating, the HP at the higher RPMs far outweighs the lower RPM torque, which is totally opposite of today's engines.

What the books state, and reality, was totally different with these engines. This was 1979 specs I quoted, which by that time all manufacturers were aiming for lower RPM's. I would be curious as to what the specs from the 60's were.

If the 8V71N engines had any low end power, they would have not have had rear axle ratios ranging from 4.44 to 4.11 as the standard.

 

I read that the 8V71 produced 318 hp at sea level and 60 degrees ambient temperature. The other manufacturers rated their engines at 500 ft. and 70 degrees. If dynoed like the other engines, the 318 was actually a 304. By the way, my first job was driving a new Crackerbox with a 6-71 and N55 injectors producing 190 hp.