Lifter failure cause determined!
02-11-2010, 01:25 AM
#1
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Lifter failure cause determined! After 500 miles on my rebuild I ended up with 3 turned lifters and several flared ended lifters. I've finally determined the cause. It's not an issue with the lifters, rods, rockers, pre-load, or any of the things I was suspecting.
What I noticed was that on all of the flared lifters one edge of the side of the end of them appeared nicked. I figured this was the result of the flaring, but I also noticed that they didn't appear to be rolling dead center on the cam lobes. The edges of the lifters were dangerously close to the adjacent lobe. I then took a screw driver and tried to slide the cam side to side. It moved!
I determined that the cam can move towards the back of the engine (but NOT past the correct location towards front). I'm not an expert but what this says to me is that the cam thrust plate is in place (cam can't move to the front), but whatever holds the cam from going to the back isn't doing it's job. I assume that he bolted on cam gear keeps the cam from going towards the back. When I reinstalled the cam gear I torqued to spec with red locktite, could the bolts have walked out? I don't want to start tearing into the front of the engine until I figure out the possible causes.
What I noticed was that on all of the flared lifters one edge of the side of the end of them appeared nicked. I figured this was the result of the flaring, but I also noticed that they didn't appear to be rolling dead center on the cam lobes. The edges of the lifters were dangerously close to the adjacent lobe. I then took a screw driver and tried to slide the cam side to side. It moved!
I determined that the cam can move towards the back of the engine (but NOT past the correct location towards front). I'm not an expert but what this says to me is that the cam thrust plate is in place (cam can't move to the front), but whatever holds the cam from going to the back isn't doing it's job. I assume that he bolted on cam gear keeps the cam from going towards the back. When I reinstalled the cam gear I torqued to spec with red locktite, could the bolts have walked out? I don't want to start tearing into the front of the engine until I figure out the possible causes.
02-11-2010, 06:35 AM
#2
The only thing that would let the cam move is if the cam retainer plate is loose or missing. There is no place for it to go out the back. Even if the sprocket and chain are off, the cam will not move like that, they have no effect of cam retention.
02-11-2010, 06:38 AM
#3
Sure sounds like an issue with the cam gear/retainer plate. There have been cases where the cam wasn't cut correctly and it wouldn't spin when installed because the cam gear was squeezing it hard on the back side of the retainer plate. Unfortunately, it sure sounds like those components are very suspect and you need to check them. The actual cam motion allowance is very small, don't have my service manual with me right now though. I assume the motion you are describing is small (1/8" or so).
Just thought of something, what timing set are you running? Reason for asking is if you installed a set with a Torrington bearing but left the bearing out.
Just thought of something, what timing set are you running? Reason for asking is if you installed a set with a Torrington bearing but left the bearing out.
