My daughter's 85 C4 started burning coolant when taking the heads off I noticed quite a bit of play with the rocker arms. I wish I would have got a feeler gauge and determine how much Play There was but that's hindsight. I should be getting my heads back this week for an install over the weekend. Once all the play is out of the rocker arm how much is everybody then tightening down the rocker arm nut. Some are saying one half turn others are saying three quarters of a turn. So what should it be?

 

you’ll find opinions from 1/4 turns to 1 turn.
Im pretty sure I got a Haynes manual that says 3/4.
Honestly, if you’re setting it right, 1/2 turn or 3/4 turn doesn’t matter. I’ve done 1/2, 5/8, 3/4 over the years myself.
I prefer 1/2
too loose, it’ll clack, too tight, you lose compression.
I’ve also tried setting lash with the engine running, I’ll never do that again. Gains nothing but makes a huge mess.

 

Let me provide a more controversial method, and we can ferret it out. I got tired of playing the hydraulic lifter and rocker arm lash game, as when some of the valves are open, the lifters collapse the hydraulics, so there's lighter spring tension on them.

How my methodology was changed: So a few years ago, I installed Howards Max Effort lifters and Comp Beehive springs, TPI ZZ9 roller hydraulic cam, on a new engine that I put together. Adjusting the lash from pumped up lifters, it's always a PITA and is supposed to be readjusted hot, etc. Not for me, but I endure it. Removing the valve covers for adjustment was a PITA with the L98. The number of turns is determined by the lifter manufacturer and the thread pitch of the studs (different studs have different pitch, 3/8-24 or 7/16-20 so lash/preload means different turning)

Worked fine, didn't really have any issues, untill I trailered the the car to San Diego, and first start up it was making a racket, so I readjusted the rockers, but used a different method. So what I do is I start with a collapsed lifter (can be collapsed by pushing on it by hand) and setting the gap at 0.030 from fully collapsed. No troubles with it doing it this way, but I suppose some lifter and spring arrangements may be difficult to do this, I don't know.

Decades ago, I was assembling a for 4.6 engine which have small hydraulic lifters that are more accurately just lash adjusters adjusters than lifters... and people had issues at higher RPM's and higher spring pressures. So the trick was to adjust them fully collapsed plus backed off 0.025 to 0.030. I liked this better and decided it was the best way for SBC lifters also.

Currently I have Isky Red Zone Hydraulic lifters, same springs but more aggressive and higher RPM Jones cam... so these are some of the most aggressive and highest RPM hydrauic lifters short of going solid roller, so the lifters are the short travel kind. I used the gap from collapsed method, it works great, very consistent... I can turn the angine through a few revolutions and double check very quickly and efficiently, and not have to worry about inconsistencies with the lifter hydraulic state.

 

OMFG! Another one! This has to be the most discussed subject on this forum. Right up there with "Are the values of C4's rising?", it appears at LEAST three or four times a year. Dude, do a search and you will find enough threads on this subject to publish a book.

 

So when taking off the heads I noticed play in the rocker arms when the there was no lift in the cam. Is this common? Shouldn't they have had preload? Car has 95k miles and I've only put about 1.5k on it. Is this because they were collapsed? I do intend to pull them to make sure they are still flat. Thoughts.

 

The real thing to inspect is if you can move the pushrod up and down while the cam is on it’s heel.
if you can move it up and down then the lash was not set right. HOWEVER, you would know this because you would hear it while the engine was running.

with the engine off you can jiggle the rocker some and you might have a small amount of movement, but the pushrod should not be able to move up or down.