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Discussion Starter · #1 ·
327, double hump heads. I don't know anything about the cam. A while back, I winded it up pretty good and a rocker started knocking. After a few posts here I was able to rule out any major damage. Build these to adjust the rockers.

I backed off the rocker nut until it made a racket, then tightened the rocker nut up. I made this adjustment with the engine warmed up. I did not do the 1/4 turn, 1/2, turn or 3/4 turn after the noised stopped, because I did not know which to do.

After I did one side, the other side started rattling again. SO on a used in good condition engine, how far should I tighten the rocker AFTER the knocking stops?
 

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On stock(ish) type setups, I usually go 1/2 turn after the clatter stops if I set them while running. There are different methods to set the lash while the engine is not running, too. The method that has worked well for me is to set the engine at #1 TDC on the compression stroke, and back both rockers off until they are loose. Slowly tighten each one until you just take the play out of the pushrod. (Not spinning the pushrod, I'm talking about 'vertical' movement.) Once you get the play out, then I go 1/2 turn past that. Rotate the engine 45° and do #8, and so on through the firing order. That way takes longer, but makes no mess from flying oil. You do have to be careful to not push down on the fulcrum ball while tightening the nut, though.
 

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I haven't adjusted a rocker running in decades, and wouldn't unless I had too for some strange reason.
I was taught there are 3 methods to consider for preload. Method #1 is for granny's daily driver that you don't car about maximum HP, or rpm's. That's 1 turn tighter than zero lash.#2 is for more performance, but mostly street use and is 1/2 turn after zero.
#3 is for high performance and those wanting the most lift out of their valves, and best performance, and it's 1/4 turn after zero.
I've found it fairly easy to end up too loose if adjusting valve lash on a running engine. You can get them all quiet, and then shut it off and wiggle the rockers, and often find some that feel pretty loose. So I prefer adjusting them with the engine off to get more precise settings.
 

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On basic Chevy engines and with it running, back off the adjustment until it rattles, then adjust it down until it just stops and then give it 1/2 turn - move to the next one and do the same. There are a couple of methods to keep oil from going everywhere - cut down old valve covers or a set of springs that plug the oil holes on the rockers.
 

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If you look at the GM service manual it tells you to bring #1 to tdc on compression stroke you then can adjust 4 intake on specified cylinders & 4 exhaust valves on the cylinders specified turn the engine 360* #6 tdc compression stroke & adjust the other 4 Cylinders as mentioned check pushrod for end play not by spinning they recommend 1 turn I set them at 3/4 on a stocker 1/2 anything with mild cam put the valve covers on & forget it. With much cam at all I use a different procedure turning the engine over till one valve fully opens then adj the other on the same cylinder repeat for the same cylinder on the other valve then go to the next cylinder takes longer but likely a little more accurate with larger cams. Not hard if you use a starter button provided the engine is installed. If choosing to adjust running a little trick I learned is to pull one cover start at the front on that bank back off till it clicks tighten till it just quits go to the next do the same till the entire bank is done shut it off then turn all down 1/2 turn or 3/4 put that cover on & go to the other bank just makes it a little quicker with less mess. Sometimes setting at 1/4 you may have a little tick especially on cold start.
 

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Looks like a lot of work but if wanting to adjust with engine running it should make for less mess.
 

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The best way to adjust the lifters is the EO/IC method. To adjust an intake, rotate the engine until the adjacent exhaust valve is just opening. Adjust the rocker arm nut until you have zero lash. Don't spin the pushrod, move it up and down to detect the zero lash. Most lifters don't have enough friction for you to notice zero lash when rotating the pushrod - you're past it before you know. Vertical movement is more precise. After detecting zero lash, tighten the adjuster the recommended amount. To adjust an exhaust, rotate the engine until the adjacent intake valve is about to close, then adjust.

The amount you turn the adjuster after zero lash has been covered pretty well except for one situation. 3/4 to 1 turn for the older stock stuff. 1/2 turn for newer stock stuff. 1/4 turn for most performance cams. The one exception is for the newest high performance high rpm roller lifters. Many of them require more preload than previous high performance lifters. The preload on those is often as much as .050" or .060", which is quite a bit more than 1/4 turn. Check with the manufacturer on those lifters for the recommended preload.

The EO/IC method will work on any 4 stroke engine. You don't need to use timing marks, you don't need to know the firing order, and you can adjust the valves in any order, you just need to keep track to know you've done them all. All you need to know is which ones are intake and which are exhaust.
 

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You can adjust half of them with the engine at #1 TDC and the other half at #6 TDC. It"ll get the job done and not be as messy. I will see if I can find the sequence for you if youre interested.
 

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You can certainly find it online I can't ever remember the sequence & will look it up print it off then still can't find it the next time I need it.
 

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The reason that ‘PolyLocs’ were invented long ago is because the old adjuster nuts would lose friction, back off some, and thus not hold the rocker in proper position. This was especially true with big lift solid cams in engines that were run hard. Race and hotrod guys were in valve adjustment heaven when those PolyLocs came out, and still are.

In your case it’s possible that your adjustment nuts might be losing tension and backing off. When that happens the clicking starts becoming apparent. As those things get older and older they lose a ton of tension. One thing you could try is buying a new set of those locknuts. Not very expensive these days to score a set.

Use the info provided above to run through the valve adjustment.
 

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Some of the new poly locks are designed to work with stamped steel rockers, and stock height valve covers also. I bought Comp roller tip rockers for my SBC and they came with poly locks, so I figured I'd need taller valve covers. But after trying my old valve covers back on they fit fine.

 

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They also make shorter poly locks I had to swap a set to be able to use stock corvette covers on one of mine but you have to also have the right length rocker arm studs to make things work together + thick gaskets.
 

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Discussion Starter · #14 ·
Yes, I have polylocs. I just kept bumping the engine around and feeling the push rods, Rotated the engine at least 8X checking all the slack out of the rods until I could just spin them. Warmed it up, let it cool down and checked again. All is pretty good. Car runs a lot smoother now. I think it has a mild cam so it only needed 1/4 turn or less after 0 lash. A 3/4 turn was not working on this engine, and at a full turn it would not run. I need to pull a few plugs and check their condition. I'll retune the carb, check for max vacuum and RPMs.
 

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That's because you checked pushrods by spinning instead checking up & down endplay likely you have more than a 1/4 preload but if it's now quite then you have them adjusted good enough.
 

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Discussion Starter · #16 ·
I had a rag and wiggled the push rod up and down and tightened the polyloc 1/8 to 1/4 turn once I felt the lifter catch, meaning... not being able to move the push rod up or down but able to spin with just a little effort. ...but not until I could not spin it.
 
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