Noise/Tick After Engine Rebuild

[Chubbs878]

I know most of you guys drive diesel engine Discos over there, but regardless one of you may have come across this. He rebuilt his 4.0 V8 almost entirely and everything is new. Did have a couple of issues with a loose bolt in a cylinder and another with the oil pump. He replaced rod, bearing and piston on that one, replaced front cover and pump gears entirely on the other. Checked Piston and valve clearance after rebuilding from the accident, all bolts torqued to spec, replaced cylinder heads, etc. Compression is upper 190's - lower 200's on all cylinders. He ended up with a pretty loud tick that has come and gone a couple of times. Its loud and the noise does not go away when the leads are removed cylinder to cylinder. Please check the video clip and post suggestions.


https://www.youtube.com/watch?v=cwJSKvdtnyo&feature=youtu.be

[justinc]

Faulty/ collapsed cam follower, rocker arm pushrod insert/s worn, were the followers replaced with genuine ones or generic GM ones? The other issue that can arrise after machining deck heights and cylinder heads is that lifter clearances become too tight . Have a read https://www.google.com.au/url'sa=t&source=web&rct=j&url=http://cranecams.com.au/pdfs/pp1110c.pdf&ved=0ahUKEwjYgsia1cXMAhVKz2MKHZe8CdkQFggvMAQ&usg=AFQjCNFOYbLkA957DBJuPYaouXjAdTVfTw&sig2=uZd--IoI97D6vqVO8gixkQ

[Chubbs878]

Faulty/ collapsed cam follower, rocker arm pushrod insert/s worn, were the followers replaced with genuine ones or generic GM ones? The other issue that can arrise after machining deck heights and cylinder heads is that lifter clearances become too tight . Have a read https://www.google.com.au/url'sa=t&source=web&rct=j&url=http://cranecams.com.au/pdfs/pp1110c.pdf&ved=0ahUKEwjYgsia1cXMAhVKz2MKHZe8CdkQFggvMAQ&usg=AFQjCNFOYbLkA957DBJuPYaouXjAdTVfTw&sig2=uZd--IoI97D6vqVO8gixkQ


thank you! I will relay the info and wait for a response.

[Chubbs878]

Faulty/ collapsed cam follower, rocker arm pushrod insert/s worn, were the followers replaced with genuine ones or generic GM ones? The other issue that can arrise after machining deck heights and cylinder heads is that lifter clearances become too tight . Have a read https://www.google.com.au/url'sa=t&source=web&rct=j&url=http://cranecams.com.au/pdfs/pp1110c.pdf&ved=0ahUKEwjYgsia1cXMAhVKz2MKHZe8CdkQFggvMAQ&usg=AFQjCNFOYbLkA957DBJuPYaouXjAdTVfTw&sig2=uZd--IoI97D6vqVO8gixkQ







since the Disco doesn't have adjustable lifters, were you thinking that the clearances are too far off with the upgraded cam? I didn't mention that. he isn't using a stock camshaft. but the springs and rocker assembly, pushrods, lifters are all OEM I believe. Since it is non-adjustable, how would one go about searching for the issue in the valvetrain, and the fix, if found?

[justinc]

With an increase in lobe lift then DEFINITELY have to check lifter preloads!!! There are shim kits available to fit under the rocker shaft pedastals.

Jc

[Pedro_The_Swift]

Justin! did you notice the top rad hose?? :confused:

[lewy]

there are lots better ears listening to this than mine,but i think if it was in the tappets the noise would be there all the time,and a lifter it comes and goes depending on the oil supply.

[justinc]

Justin! did you notice the top rad hose?? :confused:




Thermostat???

😮

Jc

[PhilipA]

I wonder if there is a combination of too much lift on the cam maybe tied with not much preload gap causing the collets on one valves or more to hit the valve guide.

Regards Philip A

[Jazzman]

It might help with diagnosis to know if the tapping gets faster with engine revs or not.

It could be something as simple as changing to a different oil thickness or oil pressure.

Or as serious as the piston that was replaced probably came with new rings? If the bore wear had a lip it is possible the new ring broke after making contact with the lip. You might still measure good compression if only the top ring was damaged slightly. (Granted this is less likely as the noise comes and goes)

I'm not a pro but it would be helpful to know if the tapping frequency increases and decreases with RPM.

[peter51]

Justinc is on the money. It is lifter preload.

You need to search this forum on how to measure that and then buy or make shims to lift the rocker pedestals. It is done with a digital micrometer.

Just a tip - Be very careful torqueing down the pedestals. If you set your torque wrench incorrectly - say set the Nm value on your imperial foot pound torque wrench then the pedestals will crack as the engine reaches operating temperature, and you will lose oil pressure. This is what happened to me when I was rushing one evening plus distracted by other household matters. Lucky I have an oil pressure gauge and saw it go whilst idling in the garage.