66glide Posted June 11, 2014 Share Posted June 11, 2014 This '08 came in with a complaint of popping underhood and no power. IDS showed a bad cylinder contribution on #8, and slight drop on #3 and #6. #6 and #8 both showed 3% drop and 6% drop respectively on relative compression tests. Here is the #8 exhaust rocker: Oddly the #8 INTAKE pushrod was bent also. My plan is to replace rocker arms, bridges, pushrods, fuel supply tubes etc., But I began wondering about lifter condition, and the cause of the bent intake pushrod. First I used an elastic band around the lower cover bolts to hold the top of the pushrods "up" toward the center of the engine. I then barred over until both pushrods were "down" (lifters sitting on the base circle of the cam. Then I took a rough measurement from the top of the pushrod to the lower cover lip...both were about 2.623". This was a rough measurement because of space limitations, but hopefully enough to tell me there is no terrible lifter/cam wear. I then installed a dial indicator with the tip on top of each pushrod, zeroed it with the lifter on the base circle, then barred the engine over and watched the lift as the pushrods came up. Both intake and exhaust showed about .220" lift on each pushrod. Based on these measurements, I'm thinking the lifters/lobes are ok. (or they are both worn almost exactly equally...unlikely). I'd appreciate your educated opinions! Is there something I'm overlooking? Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted June 11, 2014 Share Posted June 11, 2014 Looks good, I like the testing and results. Not sure of the mileage or how long this unit sits, but every bent push rod in my bay was the result of a valve that did not open when asked. Quote Link to comment Share on other sites More sharing options...
66glide Posted June 11, 2014 Author Share Posted June 11, 2014 Looks good, I like the testing and results. Not sure of the mileage or how long this unit sits, but every bent push rod in my bay was the result of a valve that did not open when asked. Brad, can you elaborate? Valve not opening due to carbon? Quote Link to comment Share on other sites More sharing options...
66glide Posted June 11, 2014 Author Share Posted June 11, 2014 I gotta ask...I don't know how much wear is common, but the fulcrum tips of ALL the rocker arms (where they contact the valve bridges), are badly worn and spalled...so bad that one is missing the little metal clip that holds the tip in. (I can't find it, so it's somewhere in the engine). I'm gonna report it to the customer...could cause bad things to happen in the future yes? Quote Link to comment Share on other sites More sharing options...
tonybullitt Posted June 11, 2014 Share Posted June 11, 2014 Worn out rocker arms are normal on 6.4s. Seems like evey one I have valve cover off of are worn out. I agree with Brad see if valves move. We had a truck come thru dealer that broke rocker arm valve stuck and seen in warranty history that the other head was just replaced for same concern the month prior like 1500 miles before. Quote Link to comment Share on other sites More sharing options...
tonybullitt Posted June 11, 2014 Share Posted June 11, 2014 I think the worn rocker tips cause the bridge to push valves to the side and wears the guide abnormally. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted June 11, 2014 Share Posted June 11, 2014 Although the measurements look good, the last one I had with the pushtube bent and the rocker arm broken, ended up having the corresponding roller MIA on on the lifter, scalding the cam lobe nicely. Quote Link to comment Share on other sites More sharing options...
Aaron Posted June 11, 2014 Share Posted June 11, 2014 Typically that (roller gone) shows up in a BIG way on the oil pan drain plug magnet. Quote Link to comment Share on other sites More sharing options...
Matt Saunoras Posted June 11, 2014 Share Posted June 11, 2014 Here is the result of the last 2 broken rockers and bent pushrods I had. The rollers were intact still but not for long Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted June 12, 2014 Share Posted June 12, 2014 Interesting lifter failures. It seems that well cycled, high mileage engines are bending push rods due to lifters, as opposed to low mileage not driven vehicles that used to exhibit stuck valves. So the next step would be to look down in there at the tops of lifters and drain the oil to look at the magnet? Quote Link to comment Share on other sites More sharing options...
Matt Saunoras Posted June 13, 2014 Share Posted June 13, 2014 I don't know what happened there. Cause or effect? Did the lifters fail causing the rockers to break or did they fail as a result of the rockers breaking? Quote Link to comment Share on other sites More sharing options...
Alex Bruene Posted June 13, 2014 Share Posted June 13, 2014 The majority of broken rocker arms that I've seen (with the rocker tips entact) have been due to a lifter/cam failure. Quote Link to comment Share on other sites More sharing options...
djmiller Posted June 16, 2014 Share Posted June 16, 2014 2 of the many 6.4s I've seen have catastrophic failure I found that lifter spring clip wedged into the pressure relief valve of the oil pump. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted July 4, 2014 Share Posted July 4, 2014 IIRC there is a spec for allowable "loss of lift". Sadly , every popping under the hood complaint I ever got involved camshafts Quote Link to comment Share on other sites More sharing options...
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