Help! Roller Rocker Valve Lash

[Jake1798]

Hey guys,

I am having some troubles getting my roller rockers adjusted properly on my '76 350. We have done it going by the book and "removing the play and tightening it down another 3/4 turn." However this is clearly not working as my rockers are getting damaged by rubbing against the cylinder head and bending the push rods! Is there a special way to adjust the roller rockers or am I just doing something horribly wrong? Thanks in advance for any help!

-Jake

 

[Jack]

Jake:
I'm making an assumption here that you're working with hydraulic flat tappets.

As you're "removing the play" ... Are you sure you're not collapsing the lifter?

If you adjust the lifter so that it's collapsed ... and then it extends as it fills with running oil pressure & pumps up ... it will bend pushrod/break valve/break rocker.

 

[cinci5]

Hey guys,

I am having some troubles getting my roller rockers adjusted properly on my '76 350. We have done it going by the book and "removing the play and tightening it down another 3/4 turn." However this is clearly not working as my rockers are getting damaged by rubbing against the cylinder head and bending the push rods! Is there a special way to adjust the roller rockers or am I just doing something horribly wrong? Thanks in advance for any help!

-Jake

Hi I just did mine not to long ago. Did the same thing had to readjust 3 times so I ended up turning only 1/8 to 1/4 turn seemed fine no noise. Just spin till you feel a little drag on pushrods then tighten 1/8. I found with more than 1/4 turn you will not have them set right

 

[AdvancedAutoCC]

Hey guys,

I am having some troubles getting my roller rockers adjusted properly on my '76 350. We have done it going by the book and "removing the play and tightening it down another 3/4 turn." However this is clearly not working as my rockers are getting damaged by rubbing against the cylinder head and bending the push rods! Is there a special way to adjust the roller rockers or am I just doing something horribly wrong? Thanks in advance for any help!

-Jake

Two questions come to mind: 1) Is a high-lift cam in the engine? 2) Are these 1.5 or 1.6 ratio?

Either case - higher lift cam or 1.6 rockers (or worse, combo of the two) can/will result in the pushrod hitting the holes in the cylinder heads, unless the holes are elongated (slotted). This isn't an issue on the aluminum head L98's and LT1s as their heads have open areas, but 1970's style iron heads are another matter. You MUST elongate the holes, or the condition you're describing will result. There's no easy way of doing that job, especially with the engine together. Check your cam card and/or rocker instructions for more about interference.

Assuming for a minute that it's an adjustment issue, the proper way to adjust valves goes as follows: As the exhaust valve starts to open, adjust the intake on that cylinder. Rotate the engine around, and as the intake valve just closes, adjust the exhaust. This ensures the cam lobe is actually on the base for proper adjustment. To adjust the valve in question, back it off, and slowly tighten till you just take up slack and STOP! You should then turn the adjusting nut 3/4 of a turn from that point and adjust the polylock Allen screw down. Then tighten the adjusting nut to cinch the Allen screw in. Repeat as necessary. The key is not to overtighten the preload on the lifter.

Good luck to you!

 

[Jake1798]

Two questions come to mind: 1) Is a high-lift cam in the engine? 2) Are these 1.5 or 1.6 ratio?

Either case - higher lift cam or 1.6 rockers (or worse, combo of the two) can/will result in the pushrod hitting the holes in the cylinder heads, unless the holes are elongated (slotted). This isn't an issue on the aluminum head L98's and LT1s as their heads have open areas, but 1970's style iron heads are another matter. You MUST elongate the holes, or the condition you're describing will result. There's no easy way of doing that job, especially with the engine together. Check your cam card and/or rocker instructions for more about interference.

Assuming for a minute that it's an adjustment issue, the proper way to adjust valves goes as follows: As the exhaust valve starts to open, adjust the intake on that cylinder. Rotate the engine around, and as the intake valve just closes, adjust the exhaust. This ensures the cam lobe is actually on the base for proper adjustment. To adjust the valve in question, back it off, and slowly tighten till you just take up slack and STOP! You should then turn the adjusting nut 3/4 of a turn from that point and adjust the polylock Allen screw down. Then tighten the adjusting nut to cinch the Allen screw in. Repeat as necessary. The key is not to overtighten the preload on the lifter.

Good luck to you!

The cam is a Comp Camps High Energy with .454 lift which from what I have been told isn't an overly high lift. As for the rockers, I believe they are comp camp rollers but I don't know if they are 1.5 or 1.6, how do I tell? The heads are the 70s style cast iron that you spoke of. I believe it is just simply adjustment because it wasn't a problem with every cylinder.

-Jake

 

[goingballistic]

I just finished the build on mine and just got if off the dyno on Friday after two days of testing. I spent a few weeks researching the best way to do this and the critical component is the push rod length. The length sets the right geometry for the rocker on the valve stem. You need to make sure that the travel of the roller on the stem goes just beyond center of the stem ( outboard) to just beyond center slightly more toward inboard.

In other words make sure the travel of the roller is more toward inboard than outboard but should "roll" across the center of the valve stem. Once you figure this part and ensure that the geometry is correct then set the roller rockers. To do this place the active cyliner ( Start at one) loosen the roller, grab the rod with your fingers and spin the push rod between your fingers while finger tightening the roller rocker NUT screw. Once you feel enough friction to stop the rod from rotating thats where you want to tighten it.

To then tighten the roller, lock and hold the set screw and rotate the nut about 1/4 turn to lock everything, THEN rotate the entire thing, set screw and lock nut together another 1/4 turn.

Some may disagree but after my dyno, I swear by this last 1/4 turn, I did this proceedure with only a 1/4 turn and a roller loosened up at 6,000 RPM and tossed the rocker. The master engine mechanic that ran my engine showed me the tightening procedure. He is retired from Delco in Rochester after 25 years of running Dyno tests for Delco...............I trust his judgement and knowledge and had no reason to question,he reset all of my rockers to that spec and the engine ran fine out to 6500 RPM and ran MUCH smoother. Geometry is the key........make sure you are not floating the lifters.

Hope that helps.

 

[AKRAY4PLAY]

i'm a big fan of adjusting with the engine running. just get an old rocker cover from the junkyard and cut the top out of it. install as usual and start the engine. do not rev the motor or oil will splash all over the place (oil containment is the reason for the modded cover). it is also a good idea to have the garden hose handy incase oil hits the hot exhaust manifolds. one at a time, back your adjustment nuts out until the valve starts ticking, then adjust in until ticking stops. assuming you have hydraulic lifters, adjust nut 1/2 turn tighter after ticking stops. proceed with same proceedure for the remaining 15 rockers.