Trouble Shooter Electronic controls are designed to protect engines from internal damage due to operator error. But a driver with an overabun- dance of misdirected energy still can wreak havoc…maybe.

The Rite of Spring(s) resulting bent pushrods on one bank. Most were Last month, I wrote about a 2003 Dodge Ram equipped with manual transmissions, some with 4x4 truck with 100,000 miles on the odometer aftermarket power chips or engine programmers. and a 5.7L engine that had experienced an en- Either way, the end result was the same: engine gine failure. At least four of the intake valves overspeed and bent pushrods. Karl and pushrods were bent and the engine would We normally assume that an engine manage- Seyfert not start. The timing chain was inspected and ment’s built-in will protect the engine valve timing was correct. Further examination from damage. Perhaps you’ve even put a rev lim- [email protected] of the engine revealed no obvious cause for iter to the test by holding the accelerator to the the damage. floor with the engine in Neutral. When it works After exploring several possible causes in that as designed, the rev limiter will keep engine rpm column (incorrect oil viscosity, faulty valve seats, below a certain level by cutting the ignition or weak valve springs or a combination of all three), fuel, or both. As the cutoff rpm is reached, en- I concluded by asking if MOTOR readers might gine rpm will drop quickly as the rev limiter acti- have additional insights. I was gratified by the re- vates. If you hold your foot on the accelerator, sponses and will share a few of them here. engine rpm will cycle up and down as the rev The owner’s son was driving the truck when limiter activates repeatedly. Add-on power chips the damage occurred. Although the teen has or engine programmers may either override the claimed ignorance, the shop owner (Pat rev limiter or raise the engine rpm necessary for Leonard) believes he was abusing the engine in it to engage. Perhaps the driver was free-revving some fashion. Many of your responses picked up the engine to impress his friends. that thread. Even when it’s functioning properly, there are Chris Ewald, service manager at a Ford, some situations when a rev limiter can’t protect Dodge, Chrysler & Jeep dealer, reports seeing the engine. Several readers asked if the truck was several engines that had been overrevved, with equipped with a manual transmission. If so, it would be possible to overrev the engine through mechanical means. Driving along at highway speed in 5th gear, the driver could have acciden- tally downshifted from 5th into 2nd gear, instead of 4th. Selecting 2nd gear at that speed, the Performance en- truck’s rear wheels would have the inertia neces- gine builders go to sary to force the engine rpm well past . great lengths to The rev limiter would have no way of preventing make certain the this and the engine would continue at this dam- valves, rocker aging rpm until either the driver stepped on the arms, pushrods clutch to disengage the transmission or vehicle and road speed decreased. remain in contact What happens when an engine is overrevved? with each other at all times. Hefty You’ve probably heard the term valve float, but valves springs what does this mean? In a normally operating en- guarantee valves gine, the valves open and close the correct open and close amount and at the right time, based on the me- when commanded, chanical action of the camshaft, pushrods and and only by the rocker arms. Engines with hydraulic lifters main-

desired amounts. Mavrigian Mike Photo: tain proper clearances between these moving

6 May 2009 Trouble Shooter

parts and eliminate the need for period- ic valve clearance adjustments. Editor & Publisher Each time the camshaft rotates to John Lypen 248-312-2700 the base circle on one of its lobes, the corresponding valve spring is responsi- Executive Editor ble for closing the valve and keeping it Karl Seyfert, CMAT, LI, AF-SAE closed until the lobe begins to re- Managing Editor open the valve. Valve springs are de- Paul M. Eckstein signed to a compromise. If they’re very Art Director strong, they can cause wear in other Harold A. Perry parts of the as those parts Senior Writers are forced to work against the resis- Bob Cerullo, AF-SAE tance of the springs. If the springs are Mike Dale, SAE too weak, they won’t be able to keep Dan Marinucci, AF-SAE, L1 the valves closed when they should be Mike Mavrigian Mark Warren, AF-SAE, CMAT, L1 closed, or allow them to open smoothly when they should be open. Contributing Writers The valve spring design compromise Sam Bell Bob O’Connor means they’re strong enough to do the Paul Weissler job, within the engine operating rpm defined by the manufacturer. If the en- Production Manager Veronica Knight gine is revved beyond the safe operating 248-312-2712 range (past redline), all bets are off. Above redline, the valve springs may Associate Production Manager Jennifer Herrmann not be strong enough to close the valves when they should be closed. The cam Circulation Coordinator lobes kick them open and the valves Andrea Maione 516-227-1401 “float” and never close properly. In a worst case, an overburdened Classified Advertising Manager valve spring could compress completely Michael Padalino 800-858-3137 and allow the corresponding valve to travel much farther then it normally Regional Sales Manager would. This overextended valve could Chris Cardinal 610-253-2463 be struck by the as the piston traveled upward in the . The en- Associate Publisher ergy would bend the valve and possibly Dave Marlowe 248-312-2720 transfer to the pushrod and bend it as well. We mentioned last time that this engine had some early valve spring PUBLISHED BY problems. It’s not known if they were HEARST BUSINESS PUBLISHING, INC., replaced, and even if they were, they A UNIT OF THE HEARST CORPORATION may have weakened after 100,000 miles Frank A. Bennack, Jr. of service. Vice Chairman & Chief Executive Officer Brad Graham in Albuquerque, George R. Hearst, Jr. NM, had a similar situation with a Chairman 5.7L HEMI in a 2005 Ram 2500. The Richard P. Malloch was slightly swollen and mis- President & Group Head, Hearst Business Media shapen and the oil pressure relief valve Steven A. Hobbs was clogged with deposits. At high en- Executive Vice President & Deputy Group Head, Hearst Business Media gine speed, the oil pressure was not re- lieved and kept the lifters “pumped up” Robert D. Wilbanks Vice President & Group Controller, like solid lifters. Cleaning the relief Hearst Business Media valve and flushing the cor- Kevin F. Carr rected the problem, and the truck has President, Motor Information Systems had no further problems with bent pushrods. If this was the cause of the 1301 W. Long Lake Road, Suite 300, engine failure at Pat’s shop, the teen Troy, MI 48098 driver could be blameless! Circle #6

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