Check this out, cause of a knock? - Team Camaro Tech
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post #1 of 14 (permalink) Old Apr 8th, 11, 09:18 PM Thread Starter
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Kelly
 
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Check this out, cause of a knock?

A while back I started a thread about my engine knocking and was seeking some insight. Well, here's an update. The engine (396 bbc) is out of the car and during disassembly I noticed that a lifter was almost stuck in it's bore. It would come out about a quarter of an inch then get jammed. It took some vise grips and a lot of umph to get it out. This lifter (as well as a few others) did not sit completely on the cam lobe, it was a little bit off center. The bottom of this particular lifter as well as the cam lobe was badly chewed up.

http://www.flickr.com/photos/[email protected]/5601616889/
http://www.flickr.com/photos/[email protected]/5601616385/
http://www.flickr.com/photos/[email protected]/5602200894/
http://www.flickr.com/photos/[email protected]/5602200218/

I propose this, the cam lobe pushed this lifter up into the bore and got partially jammed. The lifter would not smoothly ride down the backside of the lobe because of the jam up, instead the valve spring pressure would eventually "pop" the lifter loose where it would crash back down onto the lobe causing the "knock".

What do you think?

If this is the case (or close to it) what could cause it? Over torqued rocker arm? Why would a lifter not sit squarely on a cam lob? Why would the lifter jam?

P.s. I tested another lifter in the bore and it came in and out smoothly as advertised. It's as if the damaged lifter "expanded".
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post #2 of 14 (permalink) Old Apr 8th, 11, 09:47 PM
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Brian
 
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Re: Check this out, cause of a knock?

My guess is the lifter was stuck in the bore because the end of the lifter got mushroomed out. They have removed most of the zinc from motor oils and there are alot of flat tappet cams getting chewed up. There are zinc additives out there for flat tappet cams, as well as a few oils that have enough zinc in them. Was this a new engine?

Experience...... It's what you get when you didn't get what you wanted.
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post #3 of 14 (permalink) Old Apr 8th, 11, 10:22 PM
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Steps
 
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Re: Check this out, cause of a knock?

Quote:
My guess is the lifter was stuck in the bore because the end of the lifter got mushroomed out.
Which is not uncommon on high milage engines anyway.

So dont jump to conclusions yet..
What are the cylinder bores like? measured the piston skirts?

My Spelling is not incorrect...it is creative

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post #4 of 14 (permalink) Old Apr 9th, 11, 03:44 AM
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darrell
 
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Re: Check this out, cause of a knock?

i agree with all that and check your springs
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post #5 of 14 (permalink) Old Apr 9th, 11, 05:07 AM Thread Starter
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Kelly
 
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Re: Check this out, cause of a knock?

Haven't got that far just yet. Should gave the pistons and crank out today. The wife keeps me pretty busy round the house when I'm not on the road for work!
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post #6 of 14 (permalink) Old Apr 9th, 11, 02:29 PM
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Steps
 
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Re: Check this out, cause of a knock?

U realy think u need to pull the crank , looking for a knock?
If was in thr crank would have picked up real quick with a mechanics sthoscope, about the only thing that is hard/to impossible is often a collasped piston skirt..or a gudgen.

My Spelling is not incorrect...it is creative

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post #7 of 14 (permalink) Old Apr 9th, 11, 04:40 PM
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John
 
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Re: Check this out, cause of a knock?

Kelly, fighting that lifter out of the block, you may have ruined the lifter bore in the block
they can be built, bored and sleeved, if you left marks in the lifter bore get it checked.
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post #8 of 14 (permalink) Old Apr 9th, 11, 05:02 PM
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george
 
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Re: Check this out, cause of a knock?

What a mess.After viewing your supplied pictures of the carnage..no way would I compromize the lifter bore, strong arming trashed mushroomed lifters upward and out the top.Better to hold them up while rotating the cam out of the block and then drop them down for recovery.
This is not high mileage wear..its total lobe interface failure.

With this much trash circulated..not much will be saved.Forget about the filter trapping this stuff..when the spinning cam and crank throws get first dibs and the metal particules inbed in the piston skirts and get behind the rings.

Total rebuild is reqd here with that level of failure.Right down to the bare block and scrubbing all the oil galleys.Anything less is a crap shoot.

George
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post #9 of 14 (permalink) Old Apr 9th, 11, 06:51 PM
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jeff
 
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Re: Check this out, cause of a knock?

Perfect time to build that 468.
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post #10 of 14 (permalink) Old Apr 10th, 11, 11:10 AM Thread Starter
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Kelly
 
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Re: Check this out, cause of a knock?

A total rebuild is in the works. All the lifter and cylinder bores are smooth with no signs of scoring. All of the bearings (main, rod, cam) look barely used with most if the original "sheen" still present.

I DID find small chunks of black plastic in the oil pump pickup. What could that be? Also, what would cause that much lobe/lifter damage on just one lobe?
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post #11 of 14 (permalink) Old Apr 10th, 11, 04:02 PM
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Re: Check this out, cause of a knock?

Quote:
Originally Posted by Steptoe View Post
U realy think u need to pull the crank , looking for a knock?
If was in thr crank would have picked up real quick with a mechanics sthoscope, about the only thing that is hard/to impossible is often a collasped piston skirt..or a gudgen.
gudgen?

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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post #12 of 14 (permalink) Old Apr 10th, 11, 06:55 PM
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Re: Check this out, cause of a knock?

Quote:
Originally Posted by novaderrik View Post
gudgen?
Gudgeon pin = wrist pin.

JohnZ
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post #13 of 14 (permalink) Old Apr 10th, 11, 07:00 PM
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darrell
 
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Re: Check this out, cause of a knock?

black plastic--you sure its plastic and not silicon--maybe the sleeve that goes around the oil pump shaft
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post #14 of 14 (permalink) Old Apr 10th, 11, 07:06 PM
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darrell
 
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Re: Check this out, cause of a knock?

not sure why--better chck the valve guide to that lifter
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