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#1
04-24-2006, 10:02 AM
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Signs of a wiped cam lobe?
Without having to remove the intake and push rod cover what are some of the indications of a possible cam lobe problem?
The engine has less than 1500mi. on a total rebuild (400 + Eagle stroker). The cam is a Crower solid flat tappet 240/248 with their lifters. I'm finding silver glitter in the oil filter and I have a stumble/hesitation when I stab the throttle (have gone through the distributor and carb with great detail-both OK). Prior to winter storage I reset valve lash and found a couple of rockers that were .04+ where the cam card spec was hot .022/.024. I just took the car out of storage this weekend and did not get a chance to recheck the lashes. Could the excessive lash be from a wiped out lobe? If so, does the lash keep increasing each time I reset or once it is reset on a wiped lobe it usually stays put? Thank you for any feedback. |
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#2
04-24-2006, 10:07 AM
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Recommend You pull the covers to verify. Set lash first. Pull all the spark plugs (will spin faster) and have someone crank the engine over. Watch for the same movement up & down in all the rockers.
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#3
04-24-2006, 10:29 AM
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P-Dude,
So if there is little no no movement on any give rocker (after setting the lash) during cranking is it safe to assume there is a good chance a lobe is wiped? |
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#4
04-24-2006, 11:22 AM
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I have always noticed the popping back through the intake or exhaust first and a rattling rocker arm.... By this time though the lobes were way gone....
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#5
04-24-2006, 12:43 PM
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Does anyone have a pic of a wiped lobe?
I want to make sure I know what I'm looking at should I decide to remove the pushrod cover. |
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#6
04-24-2006, 02:19 PM
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http://www.visualmktg.biz/transam78/...s/IMG_0921.jpg
http://www.visualmktg.biz/transam78/...s/IMG_0919.jpg http://www.visualmktg.biz/transam78/...May_16_05.html I made a valve cover where I could adjust while running. I would tighten this rocker and right after tightening it would start making noise - IE it was eating as fast as I would tighten. If that's your case tear the WHOLE thing apart. It will be in all your bearings and in the cylinder walls. Rehone - rebearing etc. I went with a roller cam as I was scared to have to do it all again. No probs yet (cross fingers!).
__________________
http://www.christransam78.com/ |
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#7
04-24-2006, 10:51 PM
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Start up the engine with the valve covers off. If you've got a bad lobe, you will notice one, maybe two, rockers that are not moving much. Those are the wiped out lobes. Pull the intake and valley cover, the bad lobes will be easy to spot in contract to the rest. You can't miss them! I know - I blew out a lifter and lobe after only 1,000 miles. The engine is coming completely apart so I can thoroughly clean all the passages. Ouch!!!!!!
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#8
04-24-2006, 11:59 PM
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If you are at the early stages of wiping a lobe, you will find the lash getting loose each time you check it. Lobe wear has to be pretty bad before you can visually see the rockers moving less.
If you can get a dial indicator, a good way to confirm lobe wear with solid lifters is to remove the valve covers and check the lift on the pushrod end of each rocker. They should all be close to the cam spec. |
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#9
04-25-2006, 08:33 AM
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Chris, thanks for the pics, it gives me a visual of what to possibly expect.
Malky, I was thinking the same thing, how am I suppose to keep a watchfull eye on 16 rapidly moving rockers with hot oil squirting everywhere. I like your dial indicator suggestion. I will start with that first. This engine has already had a thrust bearing failure (at 100miles) and when the engine builder finally agreed to repair the damages he never replaced the cam or lifters even though the bearing material was embedding in the cam lobes, I seen it. I guess he was trying to be cost effeicient and instead he had the cam "parkarized", (not sure if thats how you spell it). Can someone explain what that is exactly? |
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#10
04-25-2006, 08:39 AM
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Cams come parkerized.
And I would like to know where he had THAT done with a used cam? |
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#11
04-25-2006, 08:40 AM
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Quote:
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#12
04-25-2006, 01:25 PM
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P.Dude,
Maybe he shoved it up his arse and then said 'here you go, its all parkerized'. Every time I try and put the bad experience I had with this engine builder, BAM theres another reminder. |
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#13
05-01-2006, 09:04 AM
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I used a vernier to measure the spring height to determine the exh. and int. lift heights (I know its not the best method but its all I had). Here are the cam card specs:
Exh. Lobe lift x rocker arm - exh. lash = 0.524 Int. Lobe lift x rocker arm - int. lash = 0.500" The actual lift specs range from: Exh. .491 to .508" Int. .506 to .525" My question is how much lift is lost when a cam lobe gets wiped out? Thank you. |
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#14
05-01-2006, 11:44 AM
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Quote:
__________________
"For some reason a glaze passes over people's faces when you say "Canada". Maybe we should invade South Dakota or something." 
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#15
05-01-2006, 12:01 PM
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I have a fairly basic question - if the engine / cam was already broken in, what would cause a wiped cam ? I know about the critical stages of break in, but what precautions should be taken during normal operations ?
Glen. |
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#16
05-01-2006, 01:05 PM
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So how do my lift numbers look?
Any potential for a wiped lobe or should I be focusing elsewhere for the cause of the glitter in the oil? |
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#17
05-01-2006, 03:04 PM
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A wiped lobe's pushrod will not be spinning, which is easy enough to see with a valve cover off.
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#18
05-01-2006, 08:33 PM
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When I examined my bad camshaft, I'd estimate the lobe lost about 0.20 to 0.21 inches of lobe lift. As the the question regarding what causes this, in my case I'd say the use of engine oil without enough zine phosphate. I broke the cam in correctly as stated by the manufacturer, with plenty of cam lube. Once the engine was broken in, I changed the oil to standard 10w30 and drove the car about 1,000 miles over the course of 6 months, before I noticed the lifter tapping.
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#19
05-02-2006, 08:31 AM
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T/A,
Just to confirm thats 0.20" and not 0.020"? ie. if the actual lift prior to damage of your cam was .500" your damaged lobe would now be 0.300" or 0.480"? |
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#20
05-02-2006, 12:22 PM
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Quote:
Sorry, couldn't resist... ;-)
__________________
-- Sam Agnew Where you come from is gone; where you thought you were going to, weren't never there; and where you are ain't no good unless you can get away from it. Ministry - Jesus Built My Hotrod |
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