Increased Rocker Assembly Noise

[kurts100]

My 100 had the engine rebuilt back in '02 and since then I've put no more than 1500 miles on. Last Fall I noticed the rocker assembly making more noice than usual so this Spring I had it rebuilt, as this was not done when the engine was rebuilt. When I put the new shaft on, the previous owner had removed the pedestal studs and used 3/8" BSF bolts all the same length(I assumed these bolts were original). When tightening these bolts, one was very loose and stripped (too short a bolt on the high side of the pedestal). Hoping I still had some thread in the hole and after realizing the bolts were wrong, I ordered the correct studs, but when torqueing to 20lbs it stripped at about 10 or 15lbs. Not a good feeling. I ordered the correct Helicoil and installed and now have the rocker shaft properly mounted. When I started the engine it was still making alot of noice under the valve cover. I happened to check the oil and it was a milky white which is when I realized Anti-freeze had been leaking out of that semi-striped hole and running down the holes for the push rods and into the sump. Changed oil and filter and eliminated the leak but still very noisy.

My question is could this have damaged either the cam, cam bearings, tappets or pushrods which is why I'm getting all the noice from the rocker assembly. I've triple checked my valve clearances but the noice continues. I've run 10W30 since the rebuild but this time I used 10W40.

Thanks,

Kurt (Frustrated)

 

[Keoke]

Hi Kurt my answer to your question is yes !! the cam very well may be damaged more so from the lightness [10/30W]of the oil during the critical break in period [first 1500 Miles] of a freshly rebuilt engine, rather than from the coolant leak. I suggest you take what ever measures are available to you to have the cam checked and refrain from running the engine until the source of the problem is located and cured. Preferably an oil such as Castrol GTX 20/50 weight should have and is recommended for future use.--Fwiw--Keoke

 

[Dave Russell]

Hi Kurt,
Sorry you are having problems. Antifreeze-oil mixture doesn't lubricate very well. The most critical parts to lubricate & the most likely to fail would be the cam & tappets.

10-30 oil is pretty risky, especially on a cam break in. Many of the recent formulations, especially 10-30, have reduced ZDDP content which is vital for reducing flat tappet cam wear. I don't think 10-40 would be much better. There are many past discussions of this topic in the forum archives. I personally would add a pint of General Motors Engine Oil Supplement (E.O.S.) to each oil change & use 20-50 oil. There are other opinions though.

The generally accepted cam break in procedure is to start the engine & bring it to 2,000 to 2,500 rpm for 20 to 40 minutes so that the additional splash lubrication will help the cam break in. Maybe too late though?

With the rocker assembly off, put a dial indicator with magnetic base on each pushrod & measure cam lobe lift. If the lift on all lobes are not the same within about 0.004", the cam may be worn.

If the cam is worn, the tappets are likely damaged also. It's quite a bit more work to get access to them to check though. Visual inspection is the only way.

Also, when installing the rocker assembly, screw the oil feed/banjo bolt in far enough to center the shaft with the rocker stand before you tighten the rocker shaft studs. Pre aligned. If the shaft hole is even slightly off center with the banjo bolt, after the rockers are mounted, the bolt will strip the aluminum stand when you try to tighten it.

Another possibility for noise is grooved/worn rocker arm tips. This would cause valve lash as measured with a feeler gage to be considerably greater than the gage measurement.
D

 

[kurts100]

Keoke and Dave, thanks for the quick reply. Looks like I'll be working on the engine this weekend. Will try the dial indicator and then may take out carbs and exhaust manifold so I can get to the access plate to the tappets and visually inspect them and the cam lobes. Never realized I needed a heavier oil for the cam break in. Did they have this problem when the cars were new or did the factory put a heavier oil in for the break in period?

I'm curious about something, since I am not an engine expert. If the cam lobes are slightly worn, when you adjust the valve clearances wouldn't those differences be eliminated with respect to the rocker arm tips and the valves? That's why I was thinking maybe the cam bearings are bad. Is there a good way to check them while engine is in place? Maybe I can see if there is any movement by just trying to move it side to side.

Thanks again,

Kurt

 

[Keoke]

Hi Kurt, Both US and UK oils back in the day were on the heavier side of the specifications and formulated for the old engines. Current engines and the larger customer base they represent dictated that current oils be lighter. If the tappet tips are worn conventional valve adjustment will mask the wear and the differences will not be compensated for.---Fwiw---Keoke

 

[Dave Russell]

Hi Kurt,
The only real problem in removing the tappet cover is the tachometer drive housing which must also be removed.

The only way to check cam bearing clearance is to remove the cam, measure the cam journal diameters & the cam bearing inner diameters very precisely. I really doubt is this is the problem.

Attached is a pic of two tappets. The LH one has many miles & shows no signs of failure. Some very light circular marks due to the tappet rotating as it works which is desirable. The RH one (same mileage) shows the beginnings of failure, note the start of pitting on the face, & the beginning of failure to rotate.

Flat tappets are designed to rotate which reduces wear considerably. They rotate because 1- The tappet centers are located slightly off center of the cam lobe centers. 2- the cam lobes have a slight taper of about .002" front to back. 3- The Tappet faces are crowned about .0015". If there is enough wear in the parts to disturb this geometry the tappet will stop rotating & wear a trough on it's bottom surface.

This is why variations of .004" with a precise cam lift measurement would show that the above cam lobe taper, & or the tappet crowns have been reduced (worn). This will proceed to serious cam lobe/tappet wear & failure.
D

 

[RonMacPherson]

When you adjust the clearances, If the clearances become larger(i.e a .008 becomes a .012 for example) then the cam lobe, lifter, pushrod tube, rocker arm is wearing, something in that column.

If the clearances tighten up(.008 becomes a .006) then the valve to valve seat clearance is becoming smaller, or the valve stem is stretching, valve seat sinking into the head, valve face flattening, valve stem stretching. Definitely the worse of the two, as indicative that something is going to "grenade" soon.

 

[kurts100]

Thanks for everyones response and thanks for the photo Dave. Guess I'll be tearing into it to check it out. Obviously, not a happy camper with only 1500 miles. So it sounds like the antifreeze may not have been the problem at all, but more like improper cam break in and the wrong oil. Live and Learn!

Thanks alot!

Kurt