The Stovebolt Site Forums The Shop Area Engine Shop Uneven oil distribution to rocker arms

I adjusted my valves today for the first time (1949 stock 216 with bypass oil filter) and noticed that the back rockers were getting much more oil than the front rockers. The very back rocker (#6 exhaust) has a steady stream of oil coming out the hole, #6 intake has less, and so forth going forward. Only the back 5-6 rockers had noticeable oil coming out the hole. The others didn't look dry, but there was no oil coming out the hole. This was at idle with the engine fully warmed up. Is this normal?

When was the last time you had your rocker arm assembly out for a good clean?

1. The hole in the top of each rocker arm should be cleaned/cleared (an appropriate diameter piece of wire works quite well).

2. The two rocket arm tubes should "ream-cleaned" down the center from end-to end; and, the oil "feed" holes should be cleaned cleared.

Regarding getting good settings for rocker arm gap settings:

3. When you have the rocker arm assembly out, take the assembly apart (keeping the parts in order) and look at the "contact surfaces" - if any surface is worn/cupped, grind it flat (I use a fine-grit belt sander).

Thank you for the quick response. I've never had the engine apart in the 7-1/2 yrs I've owned it, aside from removing the valve cover, and that was just recently. Based on the information I have, it was rebuilt roughly 13,000 miles ago, which I'm guessing based on my ownership was probably at least 15 years ago (or more). There's no visible sludge in the head, so I'd expect the internals to be relatively clean too.

I'll try to clean the holes with wire. I'm thinking I might be able to cover/plug the back holes to force the oil more to the front to help clean out the holes. I guess if that doesn't work it may be time to tear the rocker arm apart.

I rebuilt my 261 and had the rocker arm assembly torn right apart for a rebuild. After everything, my front rocker arms performed in a similar fashion to yours. Yes, they were getting oiled but not as heavily as the rear. I have 1600 miles on the engine so far and no problems. Oil was moving, so I thought it was good enough.

Is there oil leaking from the bottom of any of the rocker arms (especially toward the front)?
This can be caused by badly worn rocker shafts.
If it were mine, I would turn the idle screw in to raise the RPM to about 800 and see if oil shows up on the front rocker holes.
If that doesn't work, I would take the rocker assemblies off and look at the shafts and the inside of the rocker arms for excess wear, and thoroughly clean the inside of the rocker arms.
When I do this, I remove the end plugs to make sure that they are completely clean. The end plugs are just like freeze plugs and come out and go back in without much trouble. Just make sure that they are snug when you put them back in.

No, the only place I see oil emerging from the rocker arm assembly is the holes on the rear rockers. Thanks for the tip on the end plugs. If using a wire in the holes doesn't do the trick, I think I'll next try to remove the front end plug to check things out. I'm assuming I can do that without taking the entire rocker arm assembly out.

I've been told from a few very wise stovebolters the top end neither needs or likes too much oil in the top end. Just needs to be wet and coated. Put a little rpm in that engine with the valve cover off and see if it gets wet, if it does, I wouldnt worry too much about it.

X2

The rocker shafts, rocker arms and rocker spit holes are somewhat notorious for getting gunked up and sometimes clogged with sludgy dirty oil. The fact that the rear rockers are getting oil is a good sign that you are probably generally getting a sufficient supply of oil to them. So if it were me, I would likely pull the rocker assembly off and give it a good thorough cleaning with solvent, including each individual rocker and running a pipe cleaner with solvent through each spit hole, and making sure the oil groove inside the rocker is clear and clean. Scrub the shaft clean clean clean. Make sure you keep track of the rockers, they must go back in the same exact order. Also, do not mix and match the push rods. Make sure they either remain in place or if you are removing them, keep track of where they go.

Finally, look at the ball on each of the rocker adjusters. The lack of oil may have messed them up. They are supposed to be round. If they are oblong or pointy, you will need to source a set of adjusters. That can be a bit of a challange but they turn up on ebay every once in a while.

Doesn't a stovebolt engine have a slight tilt toward the firewall? A 216 running at hot idle has virtually no oil pressure, so I'm surprised you're seeing any oil at all to the head because the oil distributor is routing most of the oil pump output to the lower end of the engine. Raise the idle speed to about 1,000 or more and I'm pretty sure the problem will go away. Unless there's at least 15 pounds of oil pressure in the bottom of the engine, the oil distributor isn't supposed to allow more than a trickle to the rockers.
Jerry

Sure does - as you know - and I too thought that could be the reason. But I just got a chance to look at the rocker assembly a little closer and discovered a couple things. First thing I noticed is that I can stick a wire down the weep hole in the back rockers, but not the front rockers. The problem is not that they're plugged with crud, the holes in the rockers don't line up with the holes in the shaft/tube, assuming they're there somewhere. After I stopped the engine and looked down the weep holes of the front rockers I could see the shiny looking metal thru the hole. Seems like maybe an assembly problem?? Obviously I'm going to need to disassemble to fix it, but curious if anyone has seen this and might have an idea what the problem is?

Second thing I noticed, which isn't related to the oil distribution problem, has to do with a couple of the pushrods. One of back ones isn't perfectly straight. I didn't remove it to check it, but I can see as it rotates that it's slightly bent. Maybe a 1/32 - 1/16 of an inch. I'm assuming that pushrod is at risk of completely bending and doing more damage?

Another of the pushrods looks completely different than the others and I'm assuming has been replaced. It has a weird mushroom shape at the top. Does this look like an appropriate pushrod for a 216? Any suggestions on whether I should replace this one at the same time I replace the bent one?

Definitely replace that bent pushrod. It's not going to get straighter.

As far as the weep holes in the rockers, I don't believe you should be able to push a wire down thru them without hitting the top of the rocker shaft. The oil supply holes on my rocker shafts were on the bottom of the shaft, with the weep holes on top (of course), so the oil gets supplied to the bottom of the rocker pivot point, works its way up to the top and out the weep hole. If the oil supply holes are on top, then the oil is going to just spurt out of the weep holes continuously (unless the weep hole doesn't line up with the supply hole at some point in the rocker travel) and supply to the bottom of the rocker, where the pressure is, will be compromised.

I really think your rear rocker shaft is assembled upside down if the weep holes line up with the oil supply holes in the shaft.

Someone will correct me if I'm wrong, but I don't think I am.

The circled pushrod in the pic is original equipment. The tubular ones in the photo are replacements. Either one will work as long as they're the right length. Pushrods can be straightened, using a small arbor press and a dial indicator. Use a set of V blocks to support the pushrod, find the high spot with the indicator as you rotate it, and use the press to straighten it. I roll pushrods across a piece of plate glass cut to a length that allows the bulged ends to hang off the sides to check for high spots. Use a bright light to back-light the rod as you roll it across the glass.

The holes in the rocker shafts should point down. Later model rockers intended to be used with pressurized rocker shafts have lubrication grooves offset from the lube holes to prevent oil from squirting out of the rocker weep holes.
Jerry

Thank you guys so much for your guidance.

I have no idea who rebuilt my engine - many years ago - but I'm now a little worried there might be other misassembled parts. It makes complete sense how you've described the rocker shaft oiling should work. What I'm seeing is a steady stream of oil out the back rocker because the holes in the shaft and rocker are completely lined up and the oil can flow freely out the hole. Unfortunately it will be a while before I have time to do this because of traveling, but it will definitely be at the top of my truck work items. I will also try to straighten that push rod in my press. Worst case I have to replace it. Might as well try to fix it first.

My truck has been worked on by guys that have a pipe wrench, a BFH, that “git-er-dun” attitude and have the nerve to call themself’s mechanic’s.

Here is a LINK for the Rocker Arm Assembly in the 48-51 Chevy Truck Manual. This should help.

Thanks for the link. I just read thru that section and I don't see it stated clearly anywhere which way the shaft holes are supposed to face. If anything, Fig 16 would make me think the holes should be facing up. Makes me wonder how many other trucks out there have a misassembled valve train, with it not being clearly specified.

The holes in the shaft are located on the bottom. It sounds like the rear rocker shaft needs to be rotated so the holes face down. The holes in the shaft and rocker are not supposed to line up. The rockers have a groove that lines up with both holes, so oil supplied to the bottom travels to the top where the weep holes are on the rocker, helping the oil spread evenly.

Yes, the holes, grooves, and weep holes DO line up on early model rocker assemblies that have the open tube at the oil connector that vents excess oil. Later heads had rocker shafts that ran full oil pressure, had a pinched-off oil connector vent, and had grooves in the rockers thast did not line up with the weep holes. The oil holes in the shafts face downward toward the head in all the applications. Decades of mixing and matching parts can result in all kinds of mismatched assemblies.
Jerry

The holes you can see in the shaft in that figure are for the attaching bolts. They go completely thru the shafts, of course, otherwise it would be hard to get the bolts thru. You'll notice that there are only 3 of them, corresponding to the three bolts on either front or rear shaft. I had to look at that figure for a while to be sure of what those three holes were for. There are 6 smaller holes on the bottom, so a total of 9 holes on the bottom of the shaft.

Just to clarify, It is my understanding that the holes do align with the groove in the rocker but do not align with each other. In other words, you can’t stick a wire in the rocker weep hole straight into the rocker shaft. The rocker hole is on top and the shaft hole faces down, so the oil travels thru the shaft, out the bottom hole into the internal groove and exits out the weep hole in the rocker.

Please give me a sanity check!

You got it Phil!