My year long project is coming to the final stages - I got to turn the key on my new engine and transmission last Friday!!! Once I got the distributor in correctly (a gear off) it started right up and sounded great.... for a few minutes. While trying to get the cam cured in, I noticed it started sounding like a lawn mower and shut it down.. The noise appeared to be coming from under the valve covers and when I took them off the nuts on the rockers appeared loose. I went thru the whole adjustment process of the pushrods/rockers/lifters. I put the valve covers back on and it started right away and sounded really good again. 12 minutes later it started sounding strange again. The nuts came back off slightly again. These are the nuts that were on before, not sure if I was supposed to put new ones on (everything else on the engine is new) but I ordered the rocker nuts that have a locking nut on them. Has anyone else ran into this before? Is the fact that I used the old nuts what is wrong? Is there any reason to believe that the problem revolves around the fact that the heads have the smaller 5/16" studs, which I found out much later when I tried to put roller rockers on these heads but could not find rollers for studs smaller than 3/8". I'm concerned that the smaller studs might be my problem and hoping the locking rocker nuts fix this problem...
Any advice or has anyone else had something like this happen?

 

Sounds like you have it figured out. Get the right sized locking nuts on there, then get back to tell us if that fixed it.

 

Last night I went to install the locking rocker nuts, which went fairly uneventful until I went to put my "Mustang Powered By Ford" valve covers on. The nuts stick up too far and I took the splash guard off the underside of the valve covers and then I could put them on.... but when I started the engine there is vibration inside, the rocker nuts are sticking up too high.
Are there thicker valve cover gaskets available or do I have to get either different rocker nuts or different valve covers? I really like these valve covers, not sure what to do but obviously what I have doesn't work. It was just enough vibration to make me shut the engine down immediately. Thicker gaskets would raise them up enough, never heard of doing this though. I got the rocker nuts from Napa, never heard of the brand.... any ideas?

 

IDK,,, I can't imagine the nuts sticking this high above the studs,,, do you have a cam that has quite a bit of lift above stock installed in the engine? The stock rockers do have very real limitations in their response to increased cam lift....

If this is not an issue, and the added height of the lock nuts is an issue, you mightrisk using the non lockers with some "blue" locktight. I think I would probably try this in a pinch.....

 

Or just double the gasket to get that little bit more of clearance.

 

I am no pro here but I remember from past experiences that going with rockers requires taller valve covers. Hopefully someone can verify. Good luck!

 

Roller rockers will not clear most "stock" hight valve covers. Glue two rubber gaskets togeather. It works great.

 

and yes thicker gaskets are available from felpro. i cannot remember the part number though

 

My reading of the original post indicates that the poster is still running the stock rockers because he could not find rollers to mount on a 5/16 stud....

Which raises more questions... if so, then is the cam lift too much for the stock rockers? and,,, some of those stock rockers are supposed to be torqued down, not adjusted, right? I would assume that his stock rockers are of the torque down variety as theydon't uselock nuts.....

Of course, if things have changed in the valvetrain, torquing these down may no longer be an option....

 

My bad - you are correct.