Cat 3406 B RPMS / shifting

On a truck without a pyro whatcha gonna do? Many don’t have that from the factory.

remember that golden rule low rpm’s EGT’s go up water temp stays down. High rpm EGT stays in check but water temp rises. So if you got but 1 gauge which way you want to run? I mean if you’re gonna play that card.

You touched on vibration earlier have you ever pulled a mechanical down past 1400? Nothing about it sounds right. Again the C’s were better than the B’s but still not great. Pulling one down that far also causes liner fretting which leads to low liner protrusion. Then you put the rack in full fuel position because it’s trying to pull and that huge boom at low rpm and base timing causes the bottom of the liner to flex wearing the lower bore. The early advances started opening at 1400 to 1450. The later style was 1260. Which put your base timing all the way down to 11 to 9.5. So ya pull em down there then bring em to to a little one bay shop out in the sticks to be fixed.
CAT literature does say you can pull them down to 1200. For very short periods. Like a big incline and it’s loosing faster than you can gain. It also shows above 1500 optimal cruising RPM. Its example shows a 3.90 rear and 4.10 with a 9 over .73 overdrive. I’ll let you figure the rpm’s at the 65mph example given

 

I don't have a pyro on mine, but I do have a boost gauge. When I get concerned about oil and coolant running hotter, I keep the RPM up and my foot out of it.

 

Bingo you hit the nail right on the head.

 

I can’t say I have rebuilt many, many engines. But I have rebuilt a few and I have owned and rebuilt a B model cat. I can tell you 1300 is lugging the #### out of it. 15-1600 cruising. 17-1900 in a pull. Any less and she will heat up if you have any fuel at all to her.

lugging will build EGT heat as well as water temp.

 

1300 in a B model? I couldn't bear to do it even without a pyrometer just on sound alone. but with a pyro....that needle spins clockwise faster than the second hand on a clock