Originally Posted by nawlins-tim
I have a 355 SBC that has under 10000 miles. Cam, intake, and slightly worked 128 alluminum heads.
Problem started when I started to hear a rocker tap. I checked into it, probably should havr checked sooner cuz I knew there was a loose rocker but ir wasn't real bad. Well I went through them useing the EO/IC method and tightened a couple that seemed to have excessive clearence. That helped a little but looked further , this time to find half of the Valve keepers loose on 3 or 4 valves. All were the half closest to the carb. And one valve tip has uneaven wear.
What do you guys think caused this. I have screw in studs and valve guides WITHOUT self-aligning rockers. The rockers were running in the correct location on the valve tip before hand.
Except for the oddly worn valve tip , Can I try to fix this with out removing the heads. Or do I have a set of Dart heads in my future . Because if I pull these that is what is gonna replace them. PLEASE HELP!!!!
The 2-piece keepers are really not able to be loose unless the retainer or keepers are worn, or the retainer is made to use 10 degree keepers and the keepers (aka 'locks') are 7 degree instead.
The reason for this is the valve spring pressure causes the locks to engage the retainer in such a way that the two become tightly wedged together. So I'd be looking at the retainers to see if the locks are starting to pull through the retainers, or if the keeper grooves on the valve stem are sloppy. Check the springs to be sure they're OK, if the inner is broken the valve could float much easier and that can dislodge the keepers- but you'd be more likely to see the keeper halves popped out instead of loose.
The valve tip can be worn unevenly for a number of reasons. Check the pushrod alignment- you may need adjustable guideplates for instance. Could be a worn rocker arm trunnion, a very loose guide, bent p-rod, bad geometry, etc. If the rockers won't hold adjustment, the cam and lifters could be going flat.
Not to be too anal about nomenclature, but I believe you mean you have screw in studs and guide plates
. And you are correct to use non self aligning rockers if you have guide plates.
You can reseat the keepers by a quick whack w/a dead blow hammer on a socket that straddles the valve tip if the keepers are out of position, just be sure the keeper(s) don't come all the way out in the process. A much safer way is to use a valve spring compressor and air up the cylinder on TDC compression stroke, or fill the cylinder w/cord and bring the piston up towards TDC on compression to hold the valve closed.