Cam problem?

Gear Case (cams, idlers, cam cover)
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doc308
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Cam problem?

#1

Post by doc308 »

I just adjusted the tappets on my '48 FL ( solid tappets/aluminum, solid pushrods). Here's what I've detected: On the front intake tappet, after adjustment at the lowest point, when I turn the engine past the lowest point, the adjustment loosens for a short duration before it tightens. Is this a sign of a cam lobe problem? I don't notice this with any of the other tappets.

If I need a new cam, what is a good source to find a stock , bolt-in cam for my engine, which is stock ?
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Re: Cam problem?

#2

Post by mbskeam »

the cam should be set to the lowest point....
reset the pushrod at the lower/loose point....

for shits and grins you could pull the front lifter block out and take a look see....
doc308
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Re: Cam problem?

#3

Post by doc308 »

I did do the adjustment at the lowest point ( ie-- when the respective,opposite cylinder intake/exhaust tappet is at its highest point). When I turn the engine, the pushrod loosens for a brief time, before it begins to tighten as the tappet begins to rise. On all of the other tappets, the the pushrods become progressively tighter as the tappets rise , as they should. I'm guessing that this indicates a flat spot on the cam lobe(?). I should mention that the tappet blocks and tappets are brand new. Any other possible causes for this phenomenon?
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Re: Cam problem?

#4

Post by LittleAl »

Alright, I'm no expert here but using the position of another pushrod is no way to positively know EXACTLY what position the pushrod you want to adjust is in. the pushrod your adjusting MUST be at the base circle of it's cam lobe.

find that spot where the pushrod is a little loose and then readjust, you should be fine
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Re: Cam problem?

#5

Post by Hauula Pan »

If you're SURE that the cam lobe was on the HEEL (Lowest Point) when you set the push rods & one got loose as you turned the engine then it is very possible you have a worn spot on your cam. Try holding all of the covers up with some wire and once you've set them, slowly turn the engine and check what each does as far as getting tight or loose is concerned. They definitely should not be getting looser! If one is, then it is time to pull the lifter block & check out the lifter and the cam, you have a problem and need to figure out if its the cam or the lifter that is causing it. Could be either one or both.
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Re: Cam problem?

#6

Post by Hauula Pan »

If you're SURE that the cam lobe was on the HEEL (Lowest Point) when you set the push rods & one got loose as you turned the engine then it is very possible you have a worn spot on your cam. Try holding all of the covers up with some wire and once you've set them, slowly turn the engine and check what each does as far as getting tight or loose is concerned. They definitely should not be getting looser! If one is, then it is time to pull the lifter block & check out the lifter and the cam, you have a problem and need to figure out if its the cam or the lifter that is causing it. Could be either one or both. Just because they're new does not mean they're good, but I'd suspect the old cam before the new lifters.
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Re: Cam problem?

#7

Post by awander »

If it gets looser when you rotate the engine, then you DIDN'T set it at the lowest point. From your description you set it at what you thought SHOULD be the lowest point.
doc308
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Re: Cam problem?

#8

Post by doc308 »

Re: the lowest point, I set the tappets after observing the one I'm adjusting drops to it's seemingly lowest point. Then I continue to turn the engine until the corresponding tappet in the opposite cylinder is at its high point. Should I adjust at that point or before the corresponding tappet begins to rise? Anyway, I adjusted all of the tappets in the same way and only one ( the front intake tappet) is exhibiting this problem. Thanks for all of the input so far--this site is great!
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Re: Cam problem?

#9

Post by steinauge »

Adjust at the low point.IE when the front intake valve is fully open you adjust the rear intake.after adjustment rotate the engine a few times and recheck the adjustments.If you are doing it this way and have the problem you describe then in all probability you have a worn cam lobe.I have had this happen on several occasions when the cam looked OK.Just proves you need to measure everything.HTH
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Re: Cam problem?

#10

Post by awander »

steinauge:

If he does have a worn cam lobe, then what is the sloution?

Will he have to replace teh cam?

or just time it at the lowest point? (ie the REAL lowest point, not "when same pushrod for other cylinder is highest")
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Re: Cam problem?

#11

Post by steinauge »

Replacing the cam is certainly the way to go.I have repaired cam lobes on 2 occasions when there was simply no other choice and will NEVER voluntarily do so again! Cams for these engines are cheap,buy a new one! If no stock cam is available the Andrews J will (IMO) do.
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Re: Cam problem?

#12

Post by 65 Eric »

Doc38,
could a (worn) cam bushing in the cover be the problem?

65Eric
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Re: Cam problem?

#13

Post by mbskeam »

I get that if the rear intake is open then do the front intake ...
but that is just making it harder to do...
this is the way I do mine.....
look at a lifter and when it hits the bottom of the stroke/lift
rotate a few more degree's and set the pushrod lash, by doing the xtra bit of rotation this will ensure that you are at the lowest point of the cam....

disclamer......
this is the way I do it, other may do it diffrent, but if it works, cool......

and then ....if the cam/liter setting still does not seam right, pull it apart.
in less than 1hr you will see whats up.....only if for piece of mind.....
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Re: Cam problem?

#14

Post by NightShift »

Dear Everybody,

Watching the opposite valve will get you in trouble with a catalog cam.

Real respectful when its easy.
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Re: Cam problem?

#15

Post by Panacea »

I'm with you mb, that's how I've always done it and have no problems...Mike
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