77 El Camino SS, original 350 engine removed, boiled and steamed, bored to 355 and completely rebuilt.

Installed Comp cam 12-210-2 with .454 lift, 2.02 heads, Edelbrock Performer RPM intake, Carter 750cfm carb, HEI distributor, Hedman headers.

When I first got the car after the rebuild I was unhappy with the performance.  Sluggish with no response.  Took it back to the engine builder after throwing a push rod.  Was told the springs were too strong on the heads and they rebuilt them again.

Performance improved but shortly after, the rockers started clacking.  I adjusted the valve lash out but after an hour started clacking again.  Enough... took it to another performance engine builder, had all the lifters, push rods and rockers replaced again. Engine sounded good, performance was good.

After 1000 miles the rockers started clacking again.  Removed the valve cover and noticed the rocker sitting off to the side of the valve stem.  Removed the (bent) push rod and replaced it.  Adjusted the lash out, again rocker off to the side, bent another push rod.  I've inspected the rocker and see no damage at all.

Am I using the wrong lifters, push rods and rockers because their stock?  Have I collapsed a lifter?  Can I replace just one lifter?  Or have I damaged the lobe of the cam?  Very frustrating....  

Wow!  Did the first shop check for spring retainer to valveguide clearance?With only .450 lift this seems odd,how much was taken off the block deck and head?Was a adjustable pushrod used to check for proper length? If you can maybe start over with a new complete camkit and check pushrod length.Do you have screw-in studs? Keep us tuned in      WIEDER  

I second the Wow! There must of been some incompetent people working on this vehicle for you.

Stock pushrods are a no, no. You need some stiffer pushrods even for a slightly 'warmed-over' cam. Also, how are your locking nuts that are being used on the rockers, if they're GM pieces they should be replaced with polylocks.

By the way, replacing lifters is NOT a good idea. Lifters should stay matched the camshaft they were broken in on. If you put new lifters on an old cam it's possible for the setup to work, but only if the cam is broken-in again EXTENSIVELY. There is already a wear pattern on the camshaft so you need to mate those new lifters to it. A camshaft going out may be a possibility, but for your sake I hope not.  

Don't know the specifics (block milling) of the original rebuild.  The studs are pressed in and don't appear to be pulling out.  If the push rod lengths were wrong, I would expect problems with the other ones as well.  All other cylinders firing and running smoothly.  

Am I hearing this right? You only had problem with one cylinder, or is it one valve?

That can change things a little...  

I agree, they were incompetent and are no longer in business.  The rocker nuts are polylocks.  Yes, only having problem with the #6 intake valve which constantly rolls the rocker off to one side of the valve stem, clacks and bends the push rod.  I'm thinking of replacing that lifter and push rod this weekend.  As long as the rocker stays in place, can I do a break-in of the new lifter?  

Take out that lifter and inspect it first. Put a straightedge (a new valve stem is useful) over the bottom and check if there is any crown left. Also check to see if the bottom of the tappet has a even wear pattern and that there are no grooves or nicks.

Are you replacing the pushrod with a NEW straight pushrod every time it fails?

I imagine you could try to break-in a new lifter but I'm afraid that every time you put a new lifter on that used cam your chances of it staying together decrease.  

I'm not sure if you solved your problem as of this date, however, I would like to help you..in a couple of areas.

First, I have seen this problem three times. The first was a problem with a broken valve spring. It is tough to notice unless you know what you are looking for because a double wound spring will-not fall apart when removed.

Second time, The stud was slowly pulling out of the head and each time the critical angle of slack/clack occurred, the push rod broke.

Third, the lifters were mismatched. Your cam is a widely used cam for moderately warmed up stock street machines but still retains enough of a lobe center that it is a favorite of boat fanciers as well. Not withstanding this, some mismatched lifters are being chosen and are creating havoc with valve train. I always double chech the part numbers and also check the lifters for the tell tale bleed holes on the side of the lifetr for hydraulic. In the last five years, I have received two sets from the Florida cam company that were solids when I needed hydraulics.

Lastly, as a friendly piece of advice, the carburetor that you have is too much for your motor unless you are turbo/supercharged or running high compression. You can rejet and change metering rods, however, your power will still not be what it should be. Find a buddy with a 402+ cu. inch motor and see if you can sell or trade your carb.  Carter has a 625 that would be good if Holley isn't your game.

I use a carter on my road car that I use when I drive over the mountains so I don't have to rejet along the way. I have played the rejet game too many times to be fun. Around town I use Holley.

I hope that this helps-

Roc      

Thanks for all the suggestions, here's an update...

The studs are screwed in instead of pressed in as previously thought (had one back out while undoing the nut, different cylinder).

Replaced the lifter and all the push rods with new high energy push rods from Summit.  Replaced all the spark plugs and wiring as well.  The old lifter showed no wear or marks of any kind, was hydraulic and looked new.  Put it all back together with new gaskets.

Fired it up and clack, clack, clack.  Removed the valve cover and the rocker was now jammed beside the valve spring instead of just off the valve stem.  The new push rod was now bent instead of just bowed.

I can only conclude that there must be a problem with the valve or valve stem and need to remove the head and inspect the valve.  Am I missing anything?  

wow, this might be a stupid question but whats alligning your rockers? guide plates? self alligning rockers, or did they install non self alligning rockers on a non alligning head with no guide plates?

only time i have seen a motor kill so many push rods is when a freind of mine used non alligning rockers with no guide plates on a non alligning head  

yes i have to agree i was thinking the same thing. i just did the new gm fast burns and they are non aligning heads so i had to forfit my roller tips. the other thing is that i had a similar problem , i lost a rocker and threw the push rod under the intake. i went back and reset all my rockers after that and been beating on it ever since.  

The rockers were not self aligning and there were no guide plates on these stock GM #333882 heads... trash!

Bought new Edelbrock aluminum Performer RPM 2.02 heads (60739) and Summit aluminum roller rockers (G6905) that match my Edelbrock Performer RPM intake (7104).  Also all new Pushrods, Hardened Steel, Heat-Treated, 5/16 in. Diameter, 7.800 in. Length.

The rocker,valve stem and push rod alignment with the guide plates look great.  Fired it up and no clacking, thank goodness, everything stayed in line.  Now I'm getting a backfire (on throttle up) through the carb or the exhaust depending on how I rotate the distributor.  Wondering if 3/4 turn on the rockers after 0 lash was too much?  Maybe only 1/2 turn?  Checked all the vac lines and plug wires were good.  

ever get it figured out?  

I dig your name import."Aint it the truth though"