Shopline - Engine Builder Magazine


I have experienced some problems with piston failures on DDC 12.7L engines with iron pistons. Are you aware of any updates?

The AERA Technical Com-mittee offers the following information regarding Series 60 iron piston failures on DDC 12.7L engines. DDC has made an improvement by adding piston cooling nozzle machining to all Series 60 cylinder blocks with unit number 6R-408505 on or about 3/2/1998. This change occurred just before the introduction of the steel piston to the Premium engines on or about 3/16/1998. All 12.7L standard rated units continued using iron pistons until or about 6/1/1999.

Engines with serial number 6R-408505 and higher were machined to accept the steel pistons and piston cooling nozzles. It is recommended that steel pistons be used if you encounter an iron piston or saddle strut failure on the effective serial number blocks. Note that you will need additional parts to be compatible with the new steel pistons. Reuse the original cooling nozzle plug bolts for the cooling nozzles. In the event that only one iron piston fails, the remaining 5 cylinders should also receive the steel pistons.

This is not a formal DDC modification program, but considered an upgrade. It is also important to note that during May 2001 the crankshaft was re-designed and it will only accept the newer steel piston assembly. The iron piston pin bolts will interfere with the new “lightweight” crankshaft design as mentioned in a previous AERA technical bulletin.

How do you properly break-in a flat-tappet camshaft?

The AERA Technical Committee offers the following information regarding flat tappet camshaft break-in. The information in this bulletin should be considered for any engine that uses a flat tappet design and should be referenced before initial engine start-up.

The current engine oils used by engine manufacturers in new car production are not appropriate for initial flat tappet camshaft break-in. Those oils are less desirable than older formulations that have better wear additives than the current SM category oils. With the advent of roller lifters/cams as well as roller rockers, the need for those expensive elements has diminished.

There have been numerous reports of premature flat tappet camshaft failure. This has been an issue of late and not just with one brand or type of camshaft. In almost every case, the hardness or the taper of the cam lobe is suspected, yet in most cases that is not the problem. This growing trend is due to factors that are unrelated to camshaft manufacturing or quality. Changes in today’s oil products and “advanced” internal engine design have contributed to a harsher environment for the camshaft, which may lead to failure during break-in. But there are several things you can do to turn the tide on this discouraging trend.

Chart 1
shows a list of oils with higher levels of wear preventive additives that may be more desirable during flat tappet camshaft break-in. All of the oils have flashpoints above 400° F.

All cam manufacturers offer cam assembly lube. Using liberal amounts of this lube during assembly on all moving or rotating points will offer a front line defense as soon as the engine is rotated.

*Total Base Number (TBN) is the measurement of a lubricant’s reserve alkalinity. The higher a motor oil’s TBN, the more effective it is in handling contaminants and reducing the corrosive effects of acids for an extended period of time.

To receive all of AERA’s regular monthly technical bulletins and other association services and benefits, call toll free 888-326-2372 or email: [email protected]

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