I can't quite figure it out. I have 4500 miles on my new motor. I installed a cam with the stock roller lifters and used the same GM pushrods with 4340 1.6 roller tip rocker arms. After about 3000 miles, I noticed I had to continue to reset the rocker arms, so I figured I'd get a set or polylocks. The other side started tapping a couple days later, BADLY, so I pulled the valvecover and noticed a very loose rocker arm, but the locknut didn't move but when I pulled it to check, both the pushrod tip and the area where the fulcrum meets the rocker arms were chewed up. I removed the rocker arm and 2 days later it happened to another on the same bank. Now I know I set these right, I did it on the stand. What I don't understand is how that happened...hasn't happened to any others since...I did find oil in the pushrod...and there is oil in the top of the motor, but when I start the engine with the valve covers off, they don't sling any oil like I thought they would. Any ideas? I did find some jagged edges, from what looked like machining, in and around the pushrod slots. Wierd...thank *** for oil filters

I'm tired of taking the valve covers off...

BTW: I bought these from ebay new, from some company, for like $66 dollars. Supposed to be 4340 forged 1.6 roller tips, self aligning, for centerbolt valvecovers...

Glad I got Comp's for my 383

 

Are you using the press-in rocker arm studs, or screw-in?

 

Sounds like what happens when you use 1.6 rockers and don't lengthen the push rod guide slots, or enlarge the holes, as the case may be.

Eh?

 

i was going to say bad geometry but i think rb has it covered pretty good.

 

Could be the studs pulling out because of the increased pressure, or maybe binding.

 

These are long-slot rocker arms, and lift is only .525" with the 1.6 rocker. It's an LT4 hotcam with matching springs.

These rocker arms are self aligning, and I did open up the pushrod passages in my Vortec heads with a 1/2" drill bit, like you're supposed to. Pushrods doesn't come close to the heads.

I also double checked for interference. None I can see. Pushrods weren't bent, as I clearanced the valve guides down for the additional valve lift.

and it hasn't happened on any other cylinders...I've taken them apart and checked...

...which is why I don't understand it at all! Is there something I'm missing here? I didn't check the 'witness mark' on the valve tip when I installed the rocker arms, but I didn't think it would make a difference. Maybe the wrong length pushrods? They're stock GM for a roller motor...

BTW:they're stock studs. I checked to see if any studs were higher than others, and after like the 6th time readjusting, I marked them. The same ones keep backing off on the passenger's side so I'm going to order a set of polylocks. The driver's side ones are the ones that balled off...I never planned on installing screw-in studs because I didn't think the LT4 springs would pull them out and I never intended for this to be anything more than a street motor.

 

yep it sounds like interferance or wrong length push rods. at the very least check the push rod length so you know for sure it's wrong, or right.

 

Coupla guesses.....

You machined the guides down some but did you take into account that the valve guide SEAL would have to fit between the retainer and guide at max lift, too?

Did you actually measure the pushrods to make sure they are for a roller motor. I'd hate to find out they're flat tappet length pushrods after all the work you've done so far.

FYI- Big lift cams require SHORTER pushrods, not longer. Your big cam is going to tilt the rocker a lot further FORWARD at max lift so the rocker needs to start from a position that is tilted slightly further BACK than it is stock, if that makes sense. I would think long slot rockers should work OK with stock pushrods and this cam but you're at the point you can't take "should work" for granted. Checking and measuring costs little or nothing if you have the tools.

Having the adjusting nut keep backing off us almost always a sign that something is binding on the VALVE side of the rocker arm. Just FYI from my expereince.

 

True,true...

I never heard any tapping noises of any sort, so didn't think the guide clearance was a problem. Also don't have any problems whatsoever with smoke at startup, which also backed up my belief that the seals were OK. I agree, I'll go check the pushrod length tomorrow.

As for the pushrods, I know they're from a roller motor, as they're the ones that came off the exact same motor, that came from a '98 Vortec 350 when I worked at the dealership. I pulled the motor myself. It's the same heads and pushrods that are on my 350 now...the block is now occupied by my HT383 guts that I got for free that I 'upgraded' when the original block gave way. I love customer pay :hail: