Just took the 71 BB with new alum heads out for its first high rpm cruise. After first redline blast, lost power and loud knocking. Pulled over, removed left valve cover, rocker arm slid off pushrod, just hanging there. Am I supposed to torque the nuts down as hard as I can, then torque down the allen screw in the middle...never installed rocker arms before

 

Ummm, NO!
Do a search, there are several good threads in here on the subject

 

Member Since: Jan 2000
Location: Houston, Tx

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This is from 427HOTROD
No..that will be too tight. When they say *0* lash..that's a little tricky to describe.

First you have to roll the motor around to set each valve right? The cam has to be on the base circle. Easiest way for me is to set them as follows:

1) When the exhaust on a cylinder is just starting to OPEN...set the intake valve on that cylinder.
2) When the intake is almost CLOSED..set the exhaust on that cylinder.


So back off all the valves until they are loose and then start bumping motor over watching the valves as above.

Once you get it on correct position to set each valve...you want to reach down and pinch the pushrod between your fingertips right below the rocker arm. Lift it up and down with the nut backed off. You want to slowly tighten the adjuster nut just until that up and down slop just barely disappears. You want to just BARELY take all the slack out of the assy. Don't overtighten...you just barely want that up and down wiggle to be gone. It only takes finger tip action...you will likely still be able to spin the pushrod when you have just barely got it to *O* lash.THAT is *O* lash.....the lifter plunger is up and you have no play in the pushrod/rockerarm/valve. THEN you tighten the 1/4-1/2 turn to put the lifter plunger down in the lifter slightly.

Repeat by bumping the motor around for each valve....it will run then just fine.


Good luck!


JIM

427 HOTROD wrote these instructions

 

I'm thinking after your first redline blast is not the best time to be asking how to adjust your rockers. Sorry for you misfortune, is it a hydraulic cam or solid ?

 

I had one of my roller rockers come loose, too. Make sure they are adjusted correctly and that the set screw is tight. Also, check the pushrods. If you had one come loose, it probably beat up the pushrod when it bounced around.

 

If your having trouble with adjusting those rocker arms your best bet is to go back to the OEM style of rockers with a set of new rocker arm nuts and forget about rollers. They dont manufacture HP anyway and are really racing parts and only good for bench racing at the local cruises and bragging rights on most street machines. None of GM`s high HP engines were equiped with them. And that includes the L88`s, ZL1`s and LS7`s all at well over a honest 550HP when set up correctly.

 

Do you have guide plates?

 

1. Set the lash to the proper spec first, then back off the nut (about 1/4 turn or so) but remember where you had the nut set.

2. Then tighten the set screw snug but no need to crank down hard on it.

3. Screw down BOTH the set screw allen wrench AND the rocker arm nut at the SAME TIME to go back to the original nut position.

4. Verify the lash is now adjusted back to spec.

The trick is to tighten both nut and set screw together at the same time.

You probably don't need those poly locks in the first place. I would not use them myself. Stock style prevailing torque nuts are very reliable and much more goof proof.

-Mark.