Small cam Cummins engine serial #

If the numbers @pup looked up say NTA370 on the Quickserv then that is what it is. I’ve never known Quickserv to be wrong. Lots of NTA’s were externally converted over to standard NTC’s and still timed like an NTA. Got away from the smoke and harder cold starting. Made for a good combo. Ntc parts were more common. The parts for nta’s were hard to get back then and are not around anymore. The waterpumps are rare. Nta had 13.8:1 compression when most Ntc’s had 14.2 to 14.5. Made a difference.

 

On the rh side of the block around were the starter is there may be a date code cast into the block. This will also give a clue as to when the engine was cast. Cummins was known to cast blocks and let them sit and “cure” for a while before they built them. It wouldn’t be uncommon to find a block that is a year or two older than the truck it orginally went into. That is why Cummins started warranty on day the truck was first used even if it was sitting for a couple years on lot. If engine is cast newer than the year of truck you obviously know its a swing in replacement. If reman from Cummins it would have another number hand stamped on it sometimes by the original on lh side or sometimes on rh block behind turbo oil return hose on one of the machined bosses.

 

My 350 has 4-74 (apr 74) for 74 that was field installed in truck later in ‘75 because of an engine shortage going on at the time of order. My 250 has 10-71 (oct. 71) for a 72. I have a ‘51 220 that has date code on lh side behind pump that is 2-51.

On the ‘74 my uncle ordered 3 new 359’s from Marvin Rush with cpl 160 350’s. Cummins was going through a major shortage of engines due to big orders and strikes. Cat had the same problem but not as bad.
Marvin told my uncle to get them with 8v71 Detroit's temporary so they can be built and delivered and then they would swap them later when the Cummins came in. One as a joke Rush had ordered with a 12v71 and didn’t charge extra for it or the ext hood. The other two with 8v71’s and standard hoods. Almost a year later the 350’s came in and my uncle decided to keep the 12v 71 in the one and put a wrecker body on it a few years later. Marvin was hoping to be able to keep the 12v 71 to put in a demo truck. Lol!
After they swapped the 350’s in a Cummins field engineer came in and tested and checked everything out to sign it off and start the warranty. He then hand stamped a number on the rh sides to denote that. One of those 350’s has been in my ‘67 since 1992. That truck was totaled in late 80’s and parted out. The other two trucks were sold off by 2003.

 

The Nta’s had the fuel pressure higher than normal from the factory that is why they slowed timing and lowered compression. You have to be careful leaning on them. They will get hot. That is why they had a bigger flow waterpump off to the side.

 

Don’t know. They could’ve set it and the whole engine to 350 or 400 or left it the same. The hand wriitten pump code tag and a pump test stand at a pump rebuild shop is the only way to know for sure. When it fires up cold and doesn’t smoke white and gallop a bit like a gas engine with a cam till it warms up and then settle into a smoother idle when warm than it is no longer timed like a Nta anymore and most likely has been overhauled with the higher compression ntc pistons. The Nta 420 almost always needed the Cummins installed ether system to start when cold. Too many years have gone by for people to tinker with it and do just about anything to it.