I have 1000 miles on a new 383 with a Crane hydraulic roller (.509/.522 222/230), Crane hydraulic retrofit roller lifters, Crane recommended pushrods, Edelbrock RPM heads, 1.52 CC magnum roller rockers (OK, I read the threads on how useless roller tip rockers are, but I had an uninstalled new set from a few years ago and decided to use them until I buy full rollers). Again, all parts are new. The block is a seasoned 4 bolt main that has no core shift. It was decked. The machine shop went through the heads and made sure the surfaces are flat and the valve job is complete (They had to mill .009 off the bottom of each head to make the surface flat).

At 500 miles the entire valve train started rattling on start up every time. After the engine warmed to between 150 and 180 degrees, the noise went away and the engine ran as smooth as possible with no noise. That took around three to five minutes. At that point all the rocker studs were taken out and retorqued to the exact specs (none of them were loose in the first place), the stock rocker nuts were replaced with polylocks, and the oil was changed (Quaker State 30 weight). Settings are zero lash plus a half turn.

That solved the problem until now, 500 miles later. The last three times it has been started, it's back to the entire valve train rattling as loud as before. When it warms up to between 150 and 180 degrees the noise goes away, the engine smooths out and it runs fine. Any ideas on what might be wrong?

By the way the car ('77 Vette) stays in the garage when home. The valves were set when the temperature in the garage was 65 degrees and it never gets below 60 degrees overnight. Oil pressure is fine.

 

I wonder what your open spring pressure is with that cam at full lift. You can only load those rockers up so much. Check with Comp's web site and see if the pressures are too high for those rockers.

Just something to check.

Are you sure it isn't piston slap? Not usualy an issue with cast or hypereutectic pistions but more common with forgings.

Is it definately valvetrain?

-Mark.

 

sounds like Lifters bleeding down over night. Are you sure about the spec on adjustment on those lifters (zero lash + half turn) half turn will be different depending on the rocker stud threads in your heads. Just a suggestion

 

Thanks for the suggestion stingr69. I have hyperutectic pistons. I had piston slap in my old L82 with forged pistons, it's a different sound. You can hear it with a stethoscope all around the valve covers, but it is quiet around the block.

I will check the CC site for max pressure with roller tip rockers. That sounds like a good possibility. It seems like it would have to be something wearing or stretching. I have tenatively eliminated wear because the magnet in the oil drain plug has had virtually nothing on it when I check. If something was wearing that fast there should be some metal on the magnet.

 

Thanks for the suggestion Sixfooter. I don't think it is bleeddown and I must emphasize "think". The motor has great oil pressure and it takes too long for the noise to go away. Additionally, it takes nearly 500 miles for the problem to begin.

 

So why did the noise stop when you worked on the engine after the first 500 miles ? You say you changed oil after 500 miles, at that time you re-torqued the rocker arm studs (which were not loose) and you replaced the rocker arm nuts.

It is unlikely that re-torquing the rocker arm studs solved the problem since they were not loose to begin with...
It is unlikely that the new rocker arm nuts helped if the old nuts were tight....

Change the oil again and see if the noise goes away...

 

BINGO! RedBad1979. I have determined those were not the problem. Now my question is, "What is the problem?" I plan to change the oil asap, but if there is something that someone might think of that would have to be changed, I would like to do it before I change the oil.

 

No idea what's causing it but you did something that made the noise disappear for 500miles..... like I said it's probably not the new nuts or re-toquing the studs, the only thing left is the oil... unless you did something else that you have not mentioned.

 

Do you have any oil restrictors in the car? I ask because your oil pressure reading comes from near the filter. The pressure at the lifter may be completely different. I can't figure out why, but the scenario at start up sounds exactly like a lifter pumping up. It can take a long time to pump up a lifter that is empty. The only thing I can think of is that when you changed your oil, you also changed your filter. A new filter could affect the oil pressure/flow. Maybe you should open up the filter and see if there is anything in it. Just a thought.

Ken

 

RedBad1979. I have to admit, I did not check the adjusting nuts before they were removed at 500 miles. My bad. The nuts were the ones that take a 5/8" socket to adjust and that size socket was very difficult to work with inside the magnum roller rockers, i.e. not enough clearance. My first thought was that they were either backing off or misset originally. The polylocks seemed to be a permanent fix if there was a problem. In retrospect I should have checked the 500 mile setting and not assumed the original nuts were the problem. It sure would be a valuable piece of information to have right now. On the other hand, it seemed like the correct analysis when I installed the polylocks and the problem went away. Little did I know it was going to be a temporary fix. This time I will see how many turns, if any, the nuts are off from the original setting. This will be much easier with the polylocks.

BB69.You, RedBad1979, Sixfooter, and the machinist who built the engine (he just returned my call) seem to be saying the same thing. It sounds like bleed down. I'll change the oil and filter again and see what happens (It sure would be nice if that is all that is wrong). The next step is to readjust the polylocks (and add a half turn to the setting per machinist suggestion).

By the way the maximum open spring pressure for the magnum roller tip rockers is 350 pounds. I don't know what open spring pressure my setup has. The machinist thinks it may be pushing that number, but cannot be sure without testing. If the two steps mentioned above do not fix the problem for the long haul, I'll put on full roller rockers.

Thanks to everyone who responded. I don't know exactly what is wrong, but I do have a plan.

 

Neverfinished,
I don't understand how changing the rockers will affect the problem. The spring pressure is the same with any rocker arm as long as the ratios are the same. The only thing I can figure is it has to be related to the oil or filter somehow. It's that, or we are missing a piece of information.

You said it was 500 miles before this happened each time. However, was it the same amount of down time on the car? In other words, did the engine sit for the same amount of time? Something just doesn't seem to add up.

Ken

 

I have been driving the car to and from work (8 miles one way) and to lunch. Last weekend I drove it nearly a hundred miles around town. The valve train noise happens when the engine is started after being allowed to cool down to room temperature. It has been warm in Austin for the last two months. The engine does not cool down completely between ariving at work and going to lunch. It does cool to room temperature overnight while sitting in the garage. Room temp is 60 degrees in the garage.

The only reason to change the rockers is if the current ones are failing due to too much open spring pressure. The machinist seems to think that is a possibility but not likely. The bleed down issue seems to be the most likely cause.

I hope an oil and filter change makes a difference. It is sure worth a try. If not, I'll adjust the valves again, but first determine if the setting has backed off from the original zero lash plus 1/2 turn. If the setting has not changed the machinist suggested an additional 1/2 turn might solve the problem. If the setting has changed, i.e. looser than the 500 mile setting, it is possible that the problem is the magnum roller rockers. That is when I would replace them.

Maybe I should have asked if a few minutes of valve train rattling is that much of a problem in the first place? It sounds horrible.

 

If it's only 8 miles one way, the engine barely gets to operating temperature. The water will be hot, however the oil will still be relatively cold.
It's possible that you have a lot of water (condensation) in the oil - how's your crankcase ventilation ???

One other thing you could try before you take the valve covers off: get some MarvelMystery oil and add a qt to your oil. See what happens, that stuff improves lifter noises (it doesn't fix anything but it does change the noise so it helps you to identify the source)

I don't believe the rocker nuts are the problem, why would it take them 500 miles to loosen ? If the spring pressure was the problem, either the rocker arm would break or the roller tip bearing... you would also see increased friction at the rocker arm's ball seat.

your valve lift is relatively high but as far as I'm informed (and I have the same heads) the heads and valve springs are good for .570" max lift. Edelbrock's RPM cam has about the same lift numbers as your cam (.510" or so) and is recommended with these heads. It appears that lift is fine and also the spring pressure. I have the same heads and roller tip rockers and no problems.

I'd try the MysteryOil first and see if the noise changes or disappears....

Well... keep us posted.....

 

Banker's hours eh?? Now THAT sounds like my kinda job!!
Sorry...didn't mean to hijack the thread.....carry on...

 

Though i can't single out ur problem to a specific part i does seem that its in the rocker assembly. If adjustment corrects the noise temporaraly then degrades - something's working loose. Now i had a surprise myself with my brand new CC Mag rocker nuts backing off on cam break-in. But with the vlv cover off this was easily found. Something to do with type of threads on studs and type of locknut (from CC). Solution was to install thin hardware store backup nuts to double nut the rockers.
BTW now i'm using only 1/4 turn preload and my rocker problem seems to be under control.

But only u can tell it if u adj the rocker correctly. Having read so many busted rocker arm threads lately only to discover owner had adj rockers incorrectly using zero p-rod movement then 1/2 turn tight instead of zero lash + 1/2 turn.
And u have to watch the vlv's to be sure ur on the compression stroke - dist rotor will be pointing to correct TDC cyl while pointing away from cyl with vlv's in overlap/rocking open.

Worse case and someone needs to say it is that ur cam lobes are becoming wiped rapidly - u would have to pull the intake and look at the cam/lifters to verify this. Sorry to bear the news but this is possible.

Hope this helps. cardo0

 

Cardo0. Thanks for the reply, I agree there are people doing this for the first time that misunderstand what they are supposed to do. I had a friend back in the '60s that was told to make sure the oil in his car was full. He did, right up to the top of the fill spout. I have done a few engines in my time and adjusted the valves several times. I know what zero lash is. I'm absolutely positive the valves are set at zero lash + 1/2 turn at 65 degrees F. The wear problem does not seem to be probable, since there are no metal particles attached to the magnet in the oil drain plug.

RedBad. I agree with you. Once the polylocks were installed the adjustment issue should be resolved. I was hoping someone might say something like: (1) the rocker arms are starting to bend slowly and will eventually break. or (2) That's what Crane hydralic roller lifters are supposed to do. or (3) Crane cams put out a bunch of crappy lifters and you must have gotten some. However it seems like there is no simple answer. I will try the Marvel Mystery Oil and a new filter and see what happens. I can mess around with some combinations of oil and filter changes. Do you have an RPM cam? I agree the springs and cam should be compatible, but the the magnum rockers may not be.

Is anyone using the Magnum roller tip rockers with a similar lift cam?

I guess what I am concerned about now is if I am going to have to put up with this noise on start up everyday. It can't be good for the cam or lifters. The setup may last a while but its life would be shortened significantly.

 

When I bought the car it had the RPM heads and cam installed, with the low CR L-48 bottom I did not have enough CR for the cam (Edelbrock recommends 9.5, better 10:1). I removed the RPM cam and installed the milder Performer version.
The engine did not run very good with the RPM cam but there was no problem whatsoever with the valvetrain. I did not run roller tip rockers with the RPM cam, I installed these when I swapped the cam.
Maybe you should just try some stock stamped rocker arms, there are several sellers on Ebay that offer these for $40/set (make sure you get the long slot rockers).

Try the Marvel Oil first, since you say the noise disappears when the engine gets warm I'm leaning more towards your lifters.... if something came loose the noise would be there all the time....

 

Not wanting to patronize ya NeverDude 'bout vlv adjust'n but some enthusiests here need the reinforcement.

Well now i hate to bash polylocks but u may want to go back to the locking nuts that came with the CC Mag rockers and use those thin hardware store back-up nuts to double nut tighten. Seems to be the fix for mine.
BTW i needed to use my 3/8" drive 5/8" socket on those CC locking nuts as the 1/2" drive is just to tight. But u really need an 5/8" offset wrench with enough bend and grind it down thin enough to fit - no Craftsman offsets are not steep enough bend (unless u heat and bend the wrench) so u can tighten the 9/16" backup nut on top. Or after u set the 1/2 turn preload u can jam something like a screwdriver in between the locknut & rocker sidewall and tighten down the 9/16" back-up nut (ooops did i say jam in a screwdriver - how Bubba and please don't tell anyone :o ).

Try the double nuts, u might like'm. cardo0