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Bad lifter or something else?

k20

k20

3/4 ton status
Joined
Sep 9, 2001
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Location
Mineral Springs, NC
Hey all, trying to figure out a problem with my 496. It has a crane hydraulic roller cam, crane roller lifters, crane gold race rockers. Anyway, there is this annoying tap from the valve train. Lets back track 8 months ago, I broke a guideplate, bent a pushrod, and chewed up a rocker, on exhaust valve of #8. Put in new parts, runs like a top. About.....3 weeks ago, I noticed a light ticking sound, pulled the valve cover and noticed that one of the rockers was a touch loose. Tightened it up, no more noise. Then approximately 2 weeks ago, I noticed it was back, pulled the valve cover, nothing seemed loose, so I re-adjusted all of the rockers. It didnt make a change. The noise is still there and its just driving me nuts.

It doesnt tick when its cold, or if it does it is very mild and I cant hear it over the exhaust. Its only once the oil gets good and hot that it does it. It lightly does it at idle, but just off idle it gets louder up until 2000rpm or so, then I cant tell if it quits or I cant hear it because of exhaust. The noise seems to be loudest on a coast down. Like if you are cruising at 50, and let off for a redlight up ahead, as the revs comes down, that is its loudest point. If you shut the truck down hot, let it sit 5 or 10 mins and fire it back up the noise is there from the second it fires.

Now today, I had it running with the valve covers off (making a nice mess btw), with a piece of 3/8" fuel hose stuck in my ear, I noticed that the noise seems to be coming from #6 exhaust valve. I tightened it and then loosened it, and it didnt make any change in the noise. So I pulled the 2 rockers for #6, the noise went away, then I swapped rockers to eliminate a bad rocker, and the noise stayed on the exhaust valve.

Now for the question, I was talking to a friend of mine and he mentioned it could also be a worn valve guide. The guides were replaced....25000 miles ago when the motor was rebuilt, of course so were the lifters. Does this sound more like a lifter problem, or more of a valve guide problem?

Thanks for the help guys.
Chris
 
My non-expert opinion that it's going to be the lifter.

Reason I say that is because the valve guide is fixed, and (ideally) the valve movement is just up and down, with no other "failure" points unlike a hydraulic lifter. If there was any undue friction between the guide and valve, I'd expect it to clearance itself out pretty quick, or to bend something.
 
im dealing with the same issue with my big block right now,

I have a guide plate that is out of place and a rocker arm off of a push rod on #8..


ill be watching this thread! mine cant have more than a few thousand miles on it yet..
 
Yeh when mine did it on #8, it was a freak, only thing I figure is that the rocker loosened up, maybe the polylock went bad, the pushrod jumped out of its seat, and bad things happened from there.

I just dont wanna throw a lifter at this thing, a lifter is $89, so Im tryin to make sure I dont miss anything stupid
 
valves adjusted correctly? not tryin to make you seem stupid but just incased you missed it ya know.

edit: didnt read the whole thing whoops
 
I am not real up on BBC... But Did you use better rocker studs than stock? Dont think stock will work with performance cams. Also what about push rods.? Are they made for your cam?
 
Yeh its got the upgraded screw in studs, 1 piece pushrods, etc etc. Its worked for 25k miles, Im thinking its the lifter....argh....
 
i would say its a lifter. I have heard from several engine builders that vehicles that are not daily drivers often develop lifter problems. Had one bad in my BBC at about 20k after replacing them.
 
Well I did a compression check, so atleast the valve aint got a hole in it lol. Anyway, I think Im gonna go with the bad lifter, mine is a daily driver, but its in spurts, its daily driven for 6 months, then I break something and its down for 2 months lol.
 
I put off replacing a bad lifter, and it wore the lifter bore out of round............ruined the block! :mad:
 
Well gents, started tearing it down and it aint good. One of the crossbars on the roller lifters broke, the lifter spun sideways, and ground itself into oblivion on the cam, speaking of the cam, I need a new one......time to upgrade.....atleast some good will come of it.
 
lol lopey cams arent always the best for 4 wheeling and im sure you know that. I have a buddy that pulled the 347 out of his fox body and put it in his yj and it sucked then he went to a rv cam and that thing is nasty now, espcially since its running on pane.
 
iwaxmyjimmy said:
lol lopey cams arent always the best for 4 wheeling and im sure you know that. I have a buddy that pulled the 347 out of his fox body and put it in his yj and it sucked then he went to a rv cam and that thing is nasty now, espcially since its running on pane.
Click to expand...

The only fourwheeling that truck does is over at Bojangles on the curb ;)
 
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