Truck Shop
Senior Member
Below are some photos of a early Big Cam IV Cummins I've had for some time, basically ended up with it for free.
Finally decided to tear it down and find out what was wrong with it. It's a weird pile of pieces, should have been a
BC III style block with standard liners-No it's a NT88 block with lower press fit liners and 3/4" main bolts. Pistons
were Cummins TriTech 3 ring 15.3:1 compression with standard .250 deep valve reliefs-Should have had 4 ring 14.1
compression with .340 deep valve reliefs. This engine is a Early 400 BCIV CPL 676 which used a high lift cam {on
exhaust lobe only} which also used the early .140 valve protrusion cylinder head which requires a piston that has
.340 valve reliefs. In few later versions Cummins used a flush valve to head deck and used a piston with .250 reliefs.
When I removed the pan I found part of a push tube {follower end}. Which caused caution. The main bearings were
in excellent shape but rod bearings {top shell} not so good. Rod bushings worked over. Removed upper end and heads. It was a boxing match.
Who ever assembled this mess was drunk. Note where exhaust valves beat into piston valve reliefs-things really got tight
when the jake was flipped on.
If anyone on here has any plans on rebuilding any older Cummins engines especially anything after 1984 look it over
from top to bottom and make sure all parts match CPL.
Finally decided to tear it down and find out what was wrong with it. It's a weird pile of pieces, should have been a
BC III style block with standard liners-No it's a NT88 block with lower press fit liners and 3/4" main bolts. Pistons
were Cummins TriTech 3 ring 15.3:1 compression with standard .250 deep valve reliefs-Should have had 4 ring 14.1
compression with .340 deep valve reliefs. This engine is a Early 400 BCIV CPL 676 which used a high lift cam {on
exhaust lobe only} which also used the early .140 valve protrusion cylinder head which requires a piston that has
.340 valve reliefs. In few later versions Cummins used a flush valve to head deck and used a piston with .250 reliefs.
When I removed the pan I found part of a push tube {follower end}. Which caused caution. The main bearings were
in excellent shape but rod bearings {top shell} not so good. Rod bushings worked over. Removed upper end and heads. It was a boxing match.
Who ever assembled this mess was drunk. Note where exhaust valves beat into piston valve reliefs-things really got tight
when the jake was flipped on.
If anyone on here has any plans on rebuilding any older Cummins engines especially anything after 1984 look it over
from top to bottom and make sure all parts match CPL.
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