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Why is this camshaft going flat?????

 
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clay
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1972 Chevrolet Nova

PostPosted: Wed May 12, 2010 10:37 pm    Post subject: Why is this camshaft going flat????? Reply with quote

When I tore my wounded engine down, I noticed the cam had 2 lobes starting to go flat and I was wondering why.




I broke cam in without inner springs and ran through the 20 min. routine of around 2000 - 2500 several times before I put the inners back in. After that, I ran the break in another time or two at 2000 - 2500. Used GM E.O.S. and diesel oil - I can't remember which brand on that one. After that, I ran Delo 400 diesel oil with 1/4 bottle of Lucas cam break in additive. There are no stand pipes in the lifter valley to stop oil drainback. Spring pressures are 130 seat and about 320 over the nose. Valve lash hadn't changed yet and they had always been very consistent - I would check them every few months and might have to tweak 2 out of 16 no more than 0.002". Cam is Howards brand and lifters are labeled as made in U.S.A. Any ideas?????? Clay

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Blown65
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1965 Chevrolet Malibu

PostPosted: Wed May 12, 2010 10:56 pm    Post subject: Cam Problems Reply with quote

At first glance it looks like the lifter was running off the lobe. Or at least no running in the middle.

Could be glare of the pic, but the wear pattern looks weird.


Corey

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Blown65
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1965 Chevrolet Malibu

PostPosted: Wed May 12, 2010 10:58 pm    Post subject: Cam Problems Reply with quote

Second look, looks like the wear pattern in the lifter is not in the center. Looks offset some. Again "weird"

Corey

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clay
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1972 Chevrolet Nova

PostPosted: Thu May 13, 2010 12:59 am    Post subject: Reply with quote

I see what you are saying about the lifter - that is weird. Both lifters have a concave shape on the bottom. Right now I'm thinking maybe the lifter gave up and then that wore the cam lobe? Make sense? Clay
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squeeezer
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PostPosted: Thu May 13, 2010 12:14 pm    Post subject: Reply with quote

is the cam sprocket and crank sprocket in perfect alignment?
i realize the taper of the lobes pulls the cam backwards
but
is the crank pulling the cam forward?

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squeeezer
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PostPosted: Thu May 13, 2010 12:17 pm    Post subject: Reply with quote

the pic of your lifters
is it the pic or is the wear patters eccenteric?
and in the foreground
do all the lobes look off-center?

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Blown65
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PostPosted: Thu May 13, 2010 1:16 pm    Post subject: Cam problems Reply with quote

What were you using to keep the cam in place eg Cam button etc. It looks like the cam was walking in the block.

Corey

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clay
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1972 Chevrolet Nova

PostPosted: Thu May 13, 2010 1:47 pm    Post subject: Reply with quote

Quote:
is the cam sprocket and crank sprocket in perfect alignment?

Can't tell you right now. I just finished washing the block for reassembly. I hope to be able to get the crank back in this weekend and I can tell you then.
Quote:
is it the pic or is the wear patters eccenteric?

Yes the wear pattern is eccentric. However on one lifter there is a circle in the center of the wear pattern that is concentric with the o.d.
Quote:
What were you using to keep the cam in place eg Cam button etc.

I didn't have anything locating the cam.
Clay

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Blown65
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1965 Chevrolet Malibu

PostPosted: Thu May 13, 2010 2:15 pm    Post subject: Cam problem Reply with quote

I should have asked this at the beginning, what lobes were going away? It doesn't look like fronts or rears but somewhere in between.

Are the rest of the lobe & lifter patterns in the center and good? Or they off a bit as well?

Corey

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af2
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PostPosted: Thu May 13, 2010 6:02 pm    Post subject: Reply with quote

On a flat tappet cam it is hard to go by the lifter wear pattern because the cam is ground on a taper so to speak. The lifter on the right has a circle that looks centered inside where it was cupping.

If I ever use another flat tappet cam I will use the EDM lifters.

I think back to 1985 when my 431 cam went flat. I ran a file over a good lobe and it cut it like butter. Did the same on a lifter and you had to force it to cut.
You might give that a shot for the hell of it. I bet $.02 the cam is soft.

Brings me back to my GM dealer wrench days in 1982 when we were changing cams weekly under warranty. Shocked Laughing
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Paul P
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PostPosted: Thu May 13, 2010 6:19 pm    Post subject: Reply with quote

Indexing and bushing the lifter bores would not hurt. Also line bore of the cam center line to make sure everything is where it should be.

Oh yeah roller cam.....

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Blown65
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PostPosted: Thu May 13, 2010 7:52 pm    Post subject: Lifter Problems Reply with quote

Hell ,why we're spending money, why not just put a set of Jesel keyway lifters in it and be done. Twisted Evil Laughing

Corey

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87IrocTim
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PostPosted: Sat Aug 28, 2010 11:34 pm    Post subject: Reply with quote

im pretty sure that flat tappet cam lobes are supposed to be a little off center to the lifter so that it constantly keeps the lifter slowly spinning as the lobe hits it, which promotes even lifter and cam wear. that explains why old lifters get a perfect dish shape and not just a concave straight wear spot. i forgot what you said your valvespring specs are, but for a mild flat tappet i would run 100-120 seat pressute and 280-300 open, but even 300 seems to be pushing it for under 7000 rpm. its just wierd how only those two lobes are wearing fast. i would remove the spring, and make sure the valves slide freely, along with the lifters. also, if its hydraulic, do only a quarter turn in for valve lash.
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87IrocTim
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PostPosted: Sat Aug 28, 2010 11:36 pm    Post subject: Reply with quote

one more quick thing, i doubt that crappy lifters is the issue, because it is 2 lifters that happen to be side by side. i just see it being some other issue like how well oil is getting there, maybe something with the block itself, or maybe even a rocker arm or valvestem issue.
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