What will cause valve/lifter/pushrod failer?
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What will cause valve/lifter/pushrod failer?
So for the past month i have been working bugs out of my truck. I got most of then out and was getting ready to start driving it and it started to get a constant exhaust backfire and a carb backfire. It was happening on the same two cylinders every time. Then i noticed i had a louder than usually tick coming from the top end. So i pulled the valve covers and pulled some of the pushrods to see if i had bent one. I then noticed at the metal shavings in my oil. Im thinking i might have had a lifter seize up and bend a valve. i haven't pulled the intake yet though to look at them. Any pointers?
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From: Ottawa, Ontario
What year is your truck? If it's got a flat tappet motor the cam has probably eaten a lobe or two.. these things need a ZDDP additive in the oil now because the oil companies have completely eliminated zinc from modern oils as all newer motors use roller cams.
Hotshot
Joined: May 2003
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From: south louisiana
You've got a wiped cam lobe (or two). If it's a fairly new cam, then poorly machined lifters are the primary cause of this. A poorly machined lifter bottom will prevent the cam lobe from setting the lifter in motion (rotating the lifter in it's bore), this in turn will drastically shorten the lifte of both the lobe and lifter, in as little as the 20 minutes it takes to break-in the cam. Lack of ZDDP can shorten the life of the cam and lifters, but this will happen over a long period of time and to all the lobes and lifters, not just one or two.
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um no. from the engines ive built and the ones we have had in the shop pushrods are not suppost to spin, which means either your cam/lifters are loosing metal, or your pushrod length is too short, or your valve lash is incorrect, or if your lifters are hydraulic lifters then they may be collapsed and will need to be replaced.
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Hotshot
Joined: May 2003
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From: south louisiana
X2, the motion of the lifter sets the pushrods into rotataing as well. Roller cammed engine's pushrods do not spin, flat tappet pushrods do.
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Joined: May 2003
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From: south louisiana
If it was a bad lifter, the only thing you did "wrong" was fail to inspect all of the lifters before dropping them in their bores. Also should have made sure they rotated freely in the bores azs you dropped them in. Worn lifter bores can also prevent the lifter from rotating. You're not the Lone Ranger here, I've had two cam failures that each had a single lobe/lifter fail. You're just one of many, many victims of failures of the past ten years, so don't beat yourself up. One was a Crane cam, the other a Comp cams. I'm 90% certain both may have been bad lifters with poorly machined bottoms. Too much moly lube on one lifter's sides could also have done the deal, the other could have been the cold temps at startup (low 30's, & thick 30 weight oil) If that lifter has worn to the point where the lifter has a new oiling hole in it's bottom, the cam lobe is toast and the whole cam will need to be replaced. You could drop a good lifter in there and rotate the crank and compare the lift it generates now to decide on whether the cam s toast, chances are it is.