ktthecarguy

Hi there,
I am putting together a 355 for the first time, and I have no experience setting the proper lash. Right now, I have the heads on, set to #1 TDC, timing chain cover off so I can see the cam and crank gear marks. On #1, I have the rockers assembled, and the locknut tightened so there is no up-and-down movement of the pushrod, but I can turn the pushrod with my fingers, with a small amount of resistance. The rocker arm has some slight side-to-side movement.

My question is, should there be any movement of the rocker arm? When the lash is set correctly, should I be able to turn the pushrod, or not at all?

Thanks in advance.

cuisinartvette

long as you cant move it up and down youre ok.

AlkyIROC

Hydraulic lifters need some preload. With the lifters on the base circle of the cam, tighten the rocker nut until the rocker just makes contact with the pushrod. This is zero lash. Now tighten the rocker nut 1/2 - 3/4 turn more. That's the preload inside the lifter. The pushrod will feel loose enough to spin after the rocker has been tightened but this is normal. Don't tighten the rocker any more. Go on to the next cylinder.

ktthecarguy

Thanks for the replies. I think I have an understanding of the pushrod, but what about the rocker arm? Should it have any movement, or should it be pretty solid?

AlkyIROC

With the lifters on the base circle of the cam, there's only a very slight preload on the rocker from the lifter so it will feel slightly loose. Once the engine is running and the lifters pump up with oil, any looseness will be gone.

An OEM style rocker with pivot ball will always feel loose. It's not a very precision component. Swapping over to any roller rocker system with a polylock nut will greatly reduce the sloppiness felt in the rocker and give a more precise rocker ratio as well as reduce valve train friction.

ktthecarguy

Okay, thanks everyone. So I think I have it now... From where the assembly sits right now, where I have no up-and-down movement in the pushrod, and the pushrod spins with my fingers with slight resistance, and the rocker feels slightly loose with a little side-to-side play, I should now tighten the locknut down 1/2 turn, to give it the correct preload.

Does this sound correct? If so, I am comfortable setting the rest of them.

If not, please correct me.
Thanks.

TreeFiddy

Just checking since you haven't mentioned it - you are setting the preload after ensuring each lifter is on the base circle of the lobe before you adjust it? Like putting crank at no1 tdc firing and set half the rockers, then rotate 1 turn and set the other half; or EOIC etc.

ktthecarguy

Sorry I forgot to mention it. Cyl #1 is at TDC, both valves closed. The method I am going to try is to set both valves on #1, then rotate the engine 90*, then set both valves on #8. then rotate another 90* and set the next cylinder, etc. until I get all 8.

ktthecarguy

One other thing I forgot to ask... am I measuring 90* rotation of the crankshaft, or the camshaft? And the firing order on the 355 is 1-8-4-3-5-6-7-2, correct?

TreeFiddy

Crankshaft degrees, and you have the correct firing order.

This being your first time, just wanted to make sure you were aware of the base circle thing. Read at least a couple of threads where guys just snugged them all down at once without turning the crank.

Edit: Damn I'm tired, wrong firing order. Before I get shouted down, should be 18436572

ktthecarguy

Thanks, yes I read about the base circle part. In layman's terms, it's the part of the egg shape of the cam that is round, not pointy.

ktthecarguy

Well, I think I got them all set correctly! What I did was, I started at #1 cyl TDC. Both valves were closed, the tappets bottomed in their bores. So I tightened down the locknut until there was zero lash at the valve stem, but I could then turn the pushrods with my fingers, and there was some side-to-side play in the rocker arm. then I tightened the locknut in 1/4 turns until there was no more play in the rocker arm, and the pushrod would not turn. Then I backed off the locknut until there was the slightest bit of side-to-side play in the rocker arm. I then tightened the locknut 1/16 turn until there was no more side play in the rocker arm. So, the rocker arm and the pushrod were just tight enough, but not too tight. I then turned the flywheel until the crank was 90* and did the next cylinder. I kept going until I did them all, then I went around one more time, checking every rocker for side play.

Now they are all tight, but just barely.

Does this sound about right?

1986Z28OWNER

iTrader: (1)

An easier way is to watch the rockers, for each cylinder as the exhaust valve starts to open set the intake, and when the intake is 3/4 closed set the exhaust. Makes sure the cam is on it's base circle. GM calls for 1/2-3/4 of a turn, on a stock deal ive always went 1/4 to half at the most, on my current 383 I went a 1/8 turn past zero lash.

TreeFiddy

When the rocker stops wiggling side to side is not a reliable indicator of zero lash. You need the point where drag increases on the pushrod as you spin it while snugging down the nut, or when the up-down play in the pr disappears.

Given that you've probably gotten somewhere close to it on most valves, you've then only added 1/16 turn preload, which is not enough. The accepted rule of thumb is 1/2-1 turn. As mentioned above, you need to place the piston inside the lifter a little way down inside it's bore, so it has some operating range to remove valvetrain slack.

ktthecarguy

Thanks for this. At this point, I have zero lash and no
movement in the pushrod or the rocker arm. So, I need to add about 1/2 turn more for the proper preload?

John in RI

iTrader: (167)

That doesn't sound right ...... If you had the engine @ #1, set both #1 valves, then rotated it 90 degrees wouldn't you be @ cylinder #4 ?? ( To start with #1 and then move to # 8 you'd just rotate the crack 1'4 turn,... correct ?? )

I prefer to grab each pushrod with my thumb and finger, squeeze tight and push/pull it up/down while turning the rocker nut until I no longer hear the "rattle" caused by the rod hitting the lifter than the rocker. When the "ting-ting-ting" sound is gone; your @ zero lash. I find that it's easier for me to find zero this way because sometimes a rod will continue to spin after reaching zero.

I also prefer to set the lash to 1/2 the valves while @ #1,... once all the lash is removed from the first set of valves I give each rocker nut 3/4-to 7/8 of a turn to set the pre-load ( for USED lifters ). After that I set the locking nut in each one that's been set. Rotate the crank 180 degrees to the #6 position and finish the remaining valves in the same manner.

It's not like I'll ever forget, but I always print this thing and set it in the lifter galley while setting valve lash....... Just in case ! If your using new lifters be sure to follow their recommended preload instructions. The ThirdGen shop manuals call for 1 full turn for used lifters I used 3'4 to 7/8th of a turn for dozens of re-builds and have never had a problem. ( If your using new lifters be sure to follow their recommended preload instructions. )



I built this engine about 2/3 months ago and just started it for the first time last week...... I used approz 7/8 of a turn to set the preload to each (used )lifter, & the engine runs great.




Do not worry about side-to-side play in the rocker and do not worry if a couple seem a bit loose when you've finished. Take your time and follow what-ever method you prefer closely and you will be fine.

Hope this helps !

ktthecarguy

Well, now this is getting really confusing. So at this point, do I have TOO MUCH preload set? These are new lifters. I have zero lash on all valves, no movement in any pushrods, and no movement in any rocker arms. Is this too tight?

John in RI

iTrader: (167)

If your using NEW Lifters I'd recomend 1/2 -to- 3/4 of a turn to set the pre-load,.... but no more than that. If you got a spec sheet with your New lifters than follow the instructions they provided.

From the web:


The reason I like UP/Down with the rod rather then spinning the rod is because there's no mistaking when the rod will no longer move up & down. When spinning the rod,......... "slight resistance" could mean 1 thing to you and another thing to me. Since some rods still spin when they have reached zero lash some guys will try and tighen a bit more ( past zero ) before setting the additional 1/2 ( to 1 full ) turn of the nut. The reason I prefer to set 1/2 the lifters at a time is becasue your only turning the crank once. Much simpler than setting each valve individually.

Don't overthink it; the fact that people recomend anywhere from 1/2 turn to 1 full turn indicates that there's a lot of "wiggle room" when setting preload - so much so that you (almost ) can't screw it up!

ktthecarguy

Hi, thanks for clearing that up. I think I am set correctly now. I don't know how to measure the plunger depression, but I am pretty sure they are all slightly depressed.

So I have no movement in any of the components, but I don't think they are so tight that they will cause the valves to bind (they are going up and down when I rotate the crank) but not so loose that they will rattle like an old diesel engine when running.

Or do you think I should give them 1/4 more turn just to be on the safe side?

Kelton1994

I been looking for someone else that had the same problem as me. I would adjust my lash to 0. And when I go to pre load 1/4-1/2 the pushrod tight as hell. So I had to fine fine tune between not having any play on rockers up and down and also my pushrod still able to spin.

FRMULA88

Old rule of thumb to set valve lash (cold setting) for solid and hydraulic lifter.

Rotate crank by hand or bump starter and watch the valve train:

Start with #1 cylinder
a) When exhaust valve starts to open: set intake.
b) When intake valve opens and then half closed: set exhaust.

https://www.chevyhardcore.com/tech-s...sh-like-a-pro/

Then there is this nice shortcut. This is a great time-saver but I would not recommend it to the novice or anyone running a cam with alot of duration and lift.

http://www.thedirtforum.com/chevyvalves.htm

NoEmissions84TA

iTrader: (1)

This article covers it all - the correct way: https://www.centuryperformance.com/v...procedure.html

8Mike9

So here's my advice, take it or leave it.

Back all the rockers off first.

Rotate to the base on # 1...assuming a stock/mild cam. Then begin tightening the rocker nut until you feel drag...thing is, once you feel drag, you start to compress the lifter. Now tighten 3/4 of a turn. Do the next valve the same way.

I used to then jump to another set of valves, I'd have to search google to remember. Thing is, once you set a cylinder, you have started to collapse the lifter, most likely when you "come back to check it", it'll be loose again...no worries, the lifter has no oil it it at this point (you didn't soak the lifters I hope)...If you can't find the "do #1 and # 6. rotate, and do XXXX" do them one at a time, no need to go back over them...leave them from first adjustment.

Just understand when you are looking for "just contact-zero lash", you've probably went a scooch too far.

GM always went 1 full turn, I've no reason to argue with them... But those that do it daily probably have a better feel than I, hence why I go 3/4 of a turn.