Engine with A Heartbeat! Rare 903 Rebuild

Preventive maintenance avoids a whole lotta heartbreak on this rare 903 Cummins, that thumps like a heartbeat when it's in trouble. Thankfully the owner brought it in for TLC from veteran Mechanic Lane Harper, a.k.a. The Diesel Doctor, with over 60 years of experience. This rare engine came off a Staeger Farm tractor, but it's more commonly scene in US military trucks.
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[@richardjamieson2007]

They are well respected and loved in Australia. They changed road transport forever in that country.

[@robertarrol4374]

They certainly did.

[@billsmith1770]

they reminded me of the sound a 1950 ford car w/flathead v8 and dual exhaust makes when going thru the gears , or just going down the road . always loved that sound .

[@maplemanz]

M2 Bradley fighting vehicles are still powered by these,rated 600HP.

[@jamesfinn4547]

I have a VT504 (VT190) in my International and I like that little engine

[@camshaftP16]

The TV show "Movin On" Kenworth had a 903 engine in it.

[@Djtherock70]

Those engines do very well in Bradley’s

[@hoost3056]

Cummins V8s, Mack 998s, Cat 3408s always had a thump and cackle to them with the Mack sounding like a locomotive. Scanias do the same thing.

[@georgerenton965]

The early naturally aspirated engines were far less problematic than the later turbocharged engines. I worked on many of these. They where a
valve train nightmare, that and oil pumps falling into the oil pan. Don’t miss muscling those cylinder heads over the steering tire and up onto the
the block. We didn’t have shop cranes over the truck bays back in the day.

[@RomeKG471]

Built by Cummins not cummings.

[@edwardkeck2464]

I put a turbo on a 903, but did not change the cam key, is this a problem

[@georgerenton965]

Yes, they use an offset key to advance the timing. Also the early blocks didn’t have internal ventilation. It would cause oil starvation. The block
not vented internally the oil would build up into one rocker cover ( bank ) and not return to the sump. The remedy was to remove the engine
barring gear that was integral the compressor mounting cover. You tapped and threaded bore hole the barring gear-shafts passed through
and installed a hose mounting nipple with a hose that ran to the rocker box.

[@georgerenton965]

Let me ask you something, was this engine an early build, and was originally naturally aspirated? It’s when Cummins added turbo’s that the
problems began. The naturally aspirated engines had an issue where oil leaking down the intake valve guides was “ coking “ on the intake
valve heads, and clogging up the port. As the build up of this baked oil restricted the engines ability to breath it developed smoking problems.
Cummins decided they would initiate a program to deal with this as what the described as a “ social acceptability problem “ and added a turbo.
That is when the trouble started. Boost pressure was causing the intake valves to float open at maximum boost pressure, so the they added
more spring tension. They then had trouble with the valve seats, and valves dropping. The hardened the valve keepers, and beefed up the rockers.
Then the pockets in the cam followers pounded out, so they addressed that, and the tips of the push tubes. The next weakest link was the bronze
cam follower pine that carries the cam follower rollers. We were the distributor for Cummins products for Ontario Canada. We had some ( for that
era of time ) large truck leasing fleets that had a lot of these engines engines, and they where blowing up left right and center while we where
trying to catch up and retrofit these components into the engines as they where towed in. The first thing you did was get a antifreeze basin and
position in under the oil pan drain plug to catch the coolant when you removed the plug. The dropped valve would smash the hell out of the head,
and the injector and the copper injector tube. The coolant would down flood the cylinder, and as you know you cannot compress a liquid according
Pascals theory, but it didn’t stop the piston from trying too once. So lots of towed trucks, and late deliveries of cement to the batch plants and
hurt feelings all round it may have contributed to the failure of that up and coming truck leasing company. Some said the got too big to fast,
but there may have been more too it. Meanwhile… the older naturally aspirated engines kept pounding up and down the road puffing out its
smoky haze till the cast iron webbed oil pump that weighed what felt like 25 lbs or more dropped into the oil pan, and that was the end for that
engine. You only have to get hit in the face once while laying on a creeper dropping the oil pan to “ No gonnie do that again, gonnie no ! “
The construction version of the same engine known to us as a “ 265 “ there where two versions of this engine, so don’t get confused here if
your that old, but the one with the same rocker covers as the 903 but didn’t have 903 cast into them, they where mostly found in construction
machinery like cranes, and large rubber tired loaders where all natural aspirated models. Turbocharged marine engines were capable of 420 hp.

[@waltchapman3659]

I need that turbo part number!! Please!

[@georgerenton965]

Possibly an ST 50.

[@dtbellamy]

Truckers called them nine O nothings!!

[@sandasturner9529]

Because of lack of power??