Hello,

Looking for some opinions on a noise that 496 BB is making. It has never been a mechanically quiet engine. However, this noise is currently not present on a cold engine at any rpm. At least to my ear. However, once the engine is hot it is audible. No power loss is present.

Not very noticable at idle. Most noticeable at a constant engine speed of 2,000-3,000 rpm. Also on deceleration of engine rpms.

The noise is present in Park or in Gear, no real change to the noise.

Noticed this after a weekend at the drag strip making quite a few passes. Engine oil level is correct. Pressure is 30-40 psi at idle depending on temperature. Oil pressure raises quickly with rpms.

Recently changed to Joe Gibbs Driven 10w40 oil about 1 month ago from Lucas Hot Rod oil 20W50.

I have not drained the engine oil for inspection just yet.

No change to the concern removing one spark plug wire at time.

496BB

Hydraulic Flat tappet .540 lift Dur @ .050 251 Int & 263 Exh
Eagle Crank and Eagle H-Beam rods
Indy SR Aluminum Heads
Timing is set at 34*
727 3800 Turbo ACtion coverter, B&M flexplate

https://www.youtube.com/watch?v=DrtTynp6pHw

https://www.youtube.com/watch?v=zrRS5MOOk48

https://www.youtube.com/watch?v=xDldGUt3lbA

Please see video descriptions

Thanks!

If the oil is clean then look at flex plate to crank bolts.

You won't be making "quite a few" passes with a knocking rod

I'd check the converter bolts first. If those are tight, I'd pull the valve covers and look for a loose rocker and/or lash opening up.

After checking the other mentioned post, I'd drop the pan.

ive heard a sound kinda like that before....counter weights on the crank were hitting the windage tray...but the tick would get faster with rpm...just a thought

Sounds like a rod to me. No oil pressure change? I'd cut the filter before running it any more. Bearing material may have plugged the oil feed in the crank giving a false sense of security as to oil pressure. Why take a chance $$$$$$$$$$$$$$$$$$$$$???????
Doug

Well, I believe I have found the cause of the noise. If not, the engine needs to be removed and serviced by a machine shop anyways.

Take a look at the following pictures of the camshaft bearings. #4 cam bearing seems to be the worst. Excessive wear is present to the top and bottom of the bearings. The bottom is worn worse then the top.

This is the second time this has occurred with this engine block. The first time I found it early on during a camshaft swap, no noise was present at that time. About 1000 miles on the engine at that time. Current mileage since camshaft swap about 4,000 miles.



Note: This engine was lined bored after installation of Pro-gram billet main caps. For three seasons after that no camshaft bearing wear like this was present. The engine was then disassembled to install different pistons for a different engine combo. At that time the machine shop replaced the camshaft beatings with Clevite 77 bearings AND installed a new Cloyes timing chain (which is still in the engine), the new Clevite 77 bearings wore excessively within 1,000 miles but no noise was present. Then the KING camshaft bearings were installed by another machine shop. The King bearings last 4,000 miles and are the bearings that are currently still in the engine.

Note: The camshaft currently in the engine was the one used for 3 seasons without any camshaft bearing failure. So the current camshaft was swapped back in after the first set of cam bearings failured with another camshaft.

Has anyone seen accelerated camshaft bearing wear like this before?

Could the timing chain be too tight? I would think that the #1 cam bearing would be worn worst and its not, its #4 again.

I would think if the line bore was an issue I would have seen it within the first 3 seasons.

Maybe time for engine block swap...


At one time this engine housed a few different solid roller camshafts. The bearings never wore like this but the COMP cams 829-16 lifters failed continuously and I swapped back to a Hydraulic flat tappet.

Who installed the cam bearings and who installed the cam ?

I doubt you have anywhere near enough spring pressure to have the cam move around enough to do that . Mopar cam tunnels are notoriously tight and out of round on seasoned blocks, if the cam bearings weren't clearanced for the cam that was going to be run when the engine was built then it clearanced itself once it was run.

What do you cam lobes look like ?

The machine shop installed the camshaft and bearings. Note: This occurred with two different camshafts and two different sets of bearings.

I agree spring pressure is relatively low. Comp Cams 924 springs.

I used a borescope to take the pictures, from what I can see with the borescope the cam lobes look ok. I dont see any flat, wiped or damaged lobes at this time.

Would the proper repair be to install new camshaft bearings and have each one clearanced for the camshaft being used or is it possible that this block/cam tunnel is too far out of round?

Thanks!

Those pictures don't strike me as "wear", that looks more like damage that could have only occurred at time of install to me. It also doesn't seem like the sort of thing that would cause the noise I heard in the earlier videos.

Do you run a mechanical fuel pump? If so, you might look at the pushrods and arm. Just a thought.....

I also thought of the fuel pump pushrod and arm. It is certainly worth an inspection.

However, I dont think there is much material left on the cam bearings. Therefore, I still need to correct this issue.

Thanks for the response. I'm open to any other thoughts or advice.

One of the machine shops I use to use in Orange County, CA would hone out the out of round and undersize cam journals in my blocks to factory size. I had ask him about align honing them and he said he couldn't do to them all being different I.D.
I ended up buying the tool set needed to install cam bearings in my shop and I install the rear cam bearing first and slide the cam in, if it rotates freely I repeat until all five of them are in. I have had more than block that the new cam bearing wouldn't allow the cam to spin properly do to being to tight and I had to scrape those bearings with a bearing knife repeatedly removing the high spots until it rotates freely
It sounds like your block is one of those needing custom fitted bearings or fixing the block cam journal I.D. :
Let us know what you find this time and decide to do to fix it

There is a lot more bearing material on that cam bearing insert than you think, I doubt that is the source of the noise.

You could pull the engine and go thru it and change the cam bearings if it will make you feel better.

Not to hack this thread, but I'm going though the same elimination route
for my knock.

Plug wire pulling told me nothing too, checked fuel pump push rod...OK
Absolutely NO type of residue after pulling valve covers and in the drain pan when I last changed the oil three weeks ago.

Oil pressure 80 cold, 35 hot with 10/30 VR1, rods and mains were at both at .0025 when buttoned up last year.

Hydraulic FT purple cam, Hughs roller rockers, six pack, Hooker Super Comps.

I guess I'll put the car up and take a peek at the converter bolts.

Pulled all the plugs and they all look rich (idle) noticed oil pooled near a rear intake bolt (above #6) That plug shows a lot of soot.
Time to pull manifold and use some additional sealing. Be able to look at the lobes too.

I'll chime in if I find anything else.

Good luck Nitrofish, Joe

PS I agree that the marks I see on your cam bearings look like an unorthodox installation.

Hello JohnRR,

Thanks for reply.

Not trying to be a wise guy in any way but are you stating from your posts that the cam bearings are not that bad off? Also that the damage/wear that is done isnt going to get any worse? You stated that the cam wore itself into the bearings, which I agree it defiantly did that...

This picture of the back side, bottom portion of the #4 cam bearing LOOKS like there isnt much material left. This was the same on the first failure. However, LOOKS especially when using a borescope can be deceiving..

In the 3rd video, it sure sounds like converter bolts hitting the back of the block. Ask me how I know that sound?

Thanks Dave,

I checked and retorqued all of the converters bolts last night. There was not any signs/witness marks of the bolts contacting anything...

Damn! I was hoping for an easy fix for you. Maybe a stethoscope? Pinpoint the area of the noise? I really can't figure how the cam bearing would make that sound. Sounds like a pretty solid tapping of metal on metal somewhere.

You might as well accept the fact, whatever it is, just the pics there alone says it needs to come out and apart and fixed correctly since this is the same movie 2x.

Unless your comfortable knowing your motor is slowly eating itself.