Ok...I've been playing with the idle on my 258 cid and noticed a tapping sound coming from the valve train. From what I have read it seems that 258's are notorious for valve train noise but this is a fairly loud tapping sound. I took the valve cover off and grabbed all the push rods and found the two on the last cylinder to be somewhat loose. The others were all fairly tight. I'm not sure if depending on what stroke you are on if they ever loosen that much. I put the valve cover back on and ran some motor flush through it and then changed the oil again. The sound is still there. When I take off the oil add cap and watch the rockers from above it's almost the tapping is matching the movement of the rocker arms which makes me think I have a faulty lifter. Does this sound correct and how hard would be it to change the lifters. I know this motor doesn't have the plates on the side (like the older models) which allows access to the lifters without pulling the head so I am assuming that I need to pull the head off - fish out the lifters and check them/replace. Any comments would be appreciated. Thanks...
Guest
G
G
...depending on the age, mileage and routine matainance schedule of the vehicle i would not change just the lifters. It sound to me that the cam/lifter combo is actually worn. On a lifter it is a cast piece of metal machined to exacting tolerances to be fitted inside the block. Once you go past the surface that is riding on the cam lobes, which is hardened at the factory, the lifter will actually dimple or concave the face of the lifter. This is only attributed to either high miles or poorly machined tolerances. When this happenes the 'wear' pattern on the cam changes, The lifter in the bore of the block actually stops turning(yes the lifters-pushrods-rings and valves actually do spin in there specific areas) and the overall wear down time for the life of the vavletrain deteriates faster. So in all certainty you should actually change both the cam and the lifters, in a non-adjustable valvetrain like a Chevy you do not have the luxury(...only one...HAHA..)of tightening those rockers. If you replace the lifters and the cam is off you will be back at square one. This is the time to get the cam that would work best with your wheel size/gear/weight and overall driving range.
Mark (OIIIIO) Langmotorsports(business)
1977/CJ7/Glasstub/460ciFord/C6Auto/NP205/4"LIFT/33'S
Mark (OIIIIO) Langmotorsports(business)
1977/CJ7/Glasstub/460ciFord/C6Auto/NP205/4"LIFT/33'S
I agree withMark, if your get deep into it, than your going to have to repalce your lifters and you might as well do they all and replace the camshaft too, there is no sense in replacing one without replacing the other. Weather you do some moderate off-roading or whatever you should check out http://www.compcams.com or another great sourse is http://www.cranecams.com they have some great stuff to help you figure out what you need.
Chad
84 & 76 CJ-7's Give me a striaght six cummins diesel anyday.
Chad
84 & 76 CJ-7's Give me a striaght six cummins diesel anyday.
Yes it could be bad lifters/cam, but the 258 is notorious for the alum. rocker fulcrum wearing out. This is the piece that the rocker arm pivits on. I've had to replace them on MANY amc cars over the years. Check this first, as it is alot easier to fix.(if thats the problem)
http://home1.gte.net/rythem/davescj7.htm
rythem@gte.net
http://home1.gte.net/rythem/davescj7.htm
rythem@gte.net
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