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Topic: knock ..knock.....

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knock ..knock..... (1/8)
8/15/18 3:08pm

art-corvette
Former Member
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Joined: 8/16/2005
Posts: 242

looks like the nightmare for every car owner happend to me.... a knocking (tapping, ticking?) sound from the engine.

the car ran fine , oilpressure was still fine but i started to hear a knocking/tapping .

in the beginning i had hopes that is was just a lifter issue .... so i changed oil , put some atf in oil to clean the engine ( only had it run for 5 min and then had it sit overnight and tried engine again .... no change.

i already was able to locate the knock... the rear(4th) cylinder on driverside... i pulled off the valvecover to check the rocker arm to see if a lifter might be "dead" and tried to adjust the valve ... the first few seconds i thought i had solved the problem but then the knock got back..... i also notice that the oilpressure started to fluctuate a bit... normally i have a pressure of 40 on the gauge but pressure started to swing upwards so i turned of the engine right away to prevent further damage.... all in all i start to fear it might be a rod bearing.

tomorrow i will pull off the oilpan and see what i can find there , if nothing special there i gonna pull off the intake manifold to see the hydraulic lifter on that 4th cylinder...and the next step after that might be the camshaft.....

arthur

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Re: knock ..knock..... (2/8)
8/17/18 12:49pm

danascar
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Germansville, PA - USA

Vette(s):
1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. . 1999 C5 Convertible, 6 speed, Atomic orange, Oak interior.

Joined: 1/28/2010
Posts: 858

Don't know what you have or how much mileage but if it's around 74-76 Chevy had soft cams that rounded off. I had that problem. When you pull valve covers check to see if all rockers are working the same, if one or two don't hardly move that might be your problem.

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DanT

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Re: knock ..knock..... (3/8)
8/17/18 1:18pm

nosal1
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 262

Hello Art, I have seen this problem before and you are wise to pull intake and check "lifters".

I had an engine that I could adjust lifter until it stopped "ticking" and run smoother then go back to ticking.

I pulled intake and went to the suspect lifter and pulled the lifter to find the bottom of the lifter was still resting on the cam lobe.I quickly removed said lifter and found it was split clean in the lower part of the lifter with internal spring etc.still intact.

I removed all the lifters and replaced all the lifters.I was lucky as it could have been a "flat mashed'' lobe on the cam,thereby a bigger job/problem.

Before you take off intake start engine and adjust the suspect lifter to see if you can quieten the lifter and have a smooth idle,if not then remove intake.. Good Luck.Sal C nosal1

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Re: knock ..knock..... (4/8)
8/19/18 4:21am

art-corvette
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Joined: 8/16/2005
Posts: 242

nosal1 said:

I had an engine that I could adjust lifter until it stopped "ticking" and run smoother then go back to ticking.

I pulled intake and went to the suspect lifter and pulled the lifter to find the bottom of the lifter was still resting on the cam lobe.I quickly removed said lifter and found it was split clean in the lower part of the lifter with internal spring etc.still intact.

Sal , i had tried to adjust the lifter and for a few seconds the tapping noise stopped but then got back.

i have pulled the oilpan to check the rod-bearings but i couldn't notice anything uncommon there . looking up from beneath (as far as it was possible )i couldn't notice anything on the lobes of the cam . but when i first noticed the tapping i got the idea it came through the distributor , but since that is close the the 7th cylinder and in direct contact with the cam i can imagine the distributor shaft worked as a resonator

but what did you mean with the suspect lifter was split clean in lower part of the lifter with internal spring still instact ?? to me it sounds like the lifter was still fine ? :)

now i will gonna pull the intake and look in there to the suspected lifter.

one worry i have was the i could notice a few tiny spots/flakes of metal in my oilpan..... the positive is that i had cut open the oilfilter but couldn't notice any metal in there.

ohh.. btw... from what i could find out about the past of the car it looks like a previous owner did an engine overhaul , and i think he installed an edelbrock performer cam about 25 years ago.... but i dunno about the quality of the overhaul :)

arthur

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Re: knock ..knock..... (5/8)
8/19/18 4:52am

Art, Please send me an email address and I will send you pictures of the lifter that I found that the bottom was cut off.I have an email I sent my Brother (his engine) that has pictures of said lifter but for some reason can not download to this forum..

I will send the forwarded email with pictures.

Sal C nosal1

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Re: knock ..knock..... (6/8)
8/19/18 12:36pm

art-corvette
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Joined: 8/16/2005
Posts: 242

Today I took off the intake to be able to inspect the suspected lifters on cylinder 7...on the outside I didn't notice anything wrong.. ... So I am still in the dark about what causes that kbo k tapping noise. Arthur

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Re: knock ..knock..... (7/8)
8/20/18 2:12pm

apesa63
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Hillsboro, OR - USA

Vette(s):
1975 L48 4sp. Coupe... Rebuilt Motor

Joined: 7/20/2015
Posts: 49

art-corvette said: Today I took off the intake to be able to inspect the suspected lifters on cylinder 7...on the outside I didn't notice anything wrong.. ... So I am still in the dark about what causes that kbo k tapping noise. Arthur

Art,

A bad rod bearing that is knocking will/should sound different from a mis-adjusted valve that is ticking, at least in my experience. While you've already pulled the intake off, you should look at all the lifters and then re-adjust all the valves. Also check for exhaust gasket leaks especially if you have headers. A blown exhaust gasket and a ticking valve could sound similar. Also, oil pressure will be higher than 40psi if the oil is cold due to higher viscosity. If it dropped below 20psi I would be concerned.

Also, the PO of my vette also installed an Edelbrock cam/lifters and timing chain kit that lasted about 20k miles after I had bought the car. I only found out after one of the lobes was ground down and I could not adjust the valve any farther down on the valve stud. When I pulled the cam and lifters I found out it was an Edelbrock cam/lifter/timing chain kit.

I would expect the bottom end on a chevy sbc to be about as bullet proof as they get when stock and not abused, so I would focus on the valve train first.

some more opinions, hope they help,

Good luck,

Pat

|UPDATED|8/20/2018 11:12:09 AM (AZT)|/UPDATED|

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Re: knock ..knock..... (8/8)
8/20/18 5:50pm

art-corvette
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Joined: 8/16/2005
Posts: 242

apesa63 said:

Art,

Also check for exhaust gasket leaks especially if you have headers. A blown exhaust gasket and a ticking valve could sound similar. Also, oil pressure will be higher than 40psi if the oil is cold due to higher viscosity. If it dropped below 20psi I would be concerned.

Good luck,

Pat

i think i have found the problem... last night i have been searching the internet about causes of an engine noise since to my idea my lifters on problem cylinder #7 looks ok.. not collapsed .. not even a scratch of wear... rod-bearing i couldn't notice any play

several options i found : flywheel , lose bolts/nuts.... and ... exhaust gasket leak

so i started checking this morning and i noticed on the exhaust port on cylinder #7 a leaking gasket

i never knew an exhaust leak could cause such a "problem"

thanks for all the input

arthur

|UPDATED|8/20/2018 2:50:27 PM (AZT)|/UPDATED|

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