[Tarl]

Which is the best method for cold rocker arm adjustment? unless they are the same when you work out the numbers, but I can't see it.

http://www.bafb.org/1968firebird.org...harticles7.htm

http://www.boyleworks.com/ta400/psp/rockers.html

[rustyrelic]

I prefer option #2. Less effort in turning the engine and looking at timing mark alignment. Works well for me.

[Blued and Painted]

The running valve adjustment method was developed under a shade tree back in the 50's. IMO.

[jonmachota78]

Neither!

1 turn crank to tdc.
2 loosen all rockers
3 set all rockers to zero lash
4 turn crank exactly one revolution (back to tdc)
5 set all rockers that have loosened to zero lash
6 add your favorite preload to all rockers and lock them down (I like 1/2 turn)

[David Jones]

Originally Posted by jonmachota78

Neither!

1 turn crank to tdc.
2 loosen all rockers
3 set all rockers to zero lash
4 turn crank exactly one revolution (back to tdc)
5 set all rockers that have loosened to zero lash
6 add your favorite preload to all rockers and lock them down (I like 1/2 turn)

Is that not Bill Boyle's method explained differently?

[Schurkey]

Originally Posted by David Jones

Is that not Bill Boyle's method explained differently?

No. Boyle's method is slower and needlessly complex. He specifies certain valves to be adjusted in a sequence. That is completely un-needed, they can be done in three steps by tightening ALL of them to zero lash, turning the crank one revolution, then tightening only the loose ones to zero lash. Then tighten ALL of them "your choice" of preload, typically 1 full turn or less.

I also disapprove of him saying that the rockers need to be "adjusted" but failing to specify that the rocker studs and nuts may need to be replaced to achieve an adjustable valvetrain.

Since when do rockers need to be made adjustable just because the heads have been milled? If the lifter plunger has enough travel, the net-lash system will be just fine. I've seen lifters with nearly a quarter-inch of travel.

[old66tiger]

I do it the simple way. Locate #1 TDC, #1 timing mark. Adjust # 1 cylinder both intake and exhaust. Turn the crank 90 degrees, adjust #8, turn 90 degrees, adjust #4, etc for 3, 6, 5, 7, and finally #2. Point being is that every adjustment, you will be at top dead for each cylinder for compression/firing sequence and the cam had better be on the base circle or you have some serious problems with your cam timing. This method keeps a guy from having to remember when things are opening and closing and what cylinder you are on.

[steve25]

Also note that on alumminum heads with there expansion rate that your valve lash will open up by .007 to .010" when hot so you need to factor that in.

[David Jones]

Originally Posted by Schurkey

they can be done in three steps by tightening ALL of them to zero lash, turning the crank one revolution, then tightening only the loose ones to zero lash. Then tighten ALL of them "your choice" of preload, typically 1 full turn or less.

Never seen this method before and I swear I called myself looking.

Starting with #1 at TDC?.....with #1 at TDC (compression?) set all of them to zero lash then turn the crank one revolution and adjust only the loose ones to zero lash. Then in no particular order simply set the pre-load by (this is my #) adding 3/4 turn of the adjuster nut and locking them all 16 down?

"loose ones" being the rockers?

Just looking for clarification because it seems....to simple.

[quicksilver97ta]

Originally Posted by David Jones

Never seen this method before and I swear I called myself looking.

Starting with #1 at TDC?.....with #1 at TDC (compression?) set all of them to zero lash then turn the crank one revolution and adjust only the loose ones to zero lash. Then in no particular order simply set the pre-load by (this is my #) adding 3/4 turn of the adjuster nut and locking them all 16 down?

"loose ones" being the rockers?

Just looking for clarification because it seems....to simple.

It is the same as the Boyles method, basically. Difference is one way you are paying attention/keeping track of specific valves at each rotation, one way you are not. so which ever is faster, I dont know. The latter way does sound easier.

But I have read, and seen, that a cam lobe may need more rotation required than you would think before it gets to absolute zero baseline. In that case, the more assured you are to being on the base circle the better. I dont remember the specifics but I do remember being surprised how much I had to rotate my engine to get rid of the last .001 or .002 of lobe lift when I was degreeing my cam.

[jonmachota78]

David, I really didn't leave any steps out and yes it is too easy and works great. You really don't need to put the crank at tdc. It just makes it easier because it gives you a reference point when its time to turn the crank 360°. It doesn't matter if its on the compression stroke if you follow the steps exactly.

So yes after you turn the crank 360° any lifter that was not on the base circle will be now so they loosen. Once you set all those to zero you have set all to zero on their base circles and you are ready to add your preload to all rockers and lock them down.

I cannot claim credit for this method. I originally saw it in a thread by Motordaddy some years ago. I've been using it ever since and it is precise and very easy to do. Fwiw
Jon

[78w72]

although alll the mentioned steps should work fine, & yes the procedure from jonmacho sounds too easy it probably works fine too.

but what is wrong with the common way of doing each valve when its verified to be on the base of the lobe? might require additional turning of the engine but you are sure the base of the lobe is properly located, fool proof accurate way to do it.

as mentioned, these "quick" ways of doing it dont ensure the lifter is on the base of the circle. the procedure in most chilton type manuals for adjustable valvetranes are for stock or close to stock "mild" street cams. once you get into larger duration cams, those procedures dont work because the valves they say to do at any given point of engine rotation arent always on the base of the lobe.

i like jonmacho's steps & may give that a try next time i need to adjust all the rockers, but the foolproof way is to just do each lifter individually.

http://www.dragzine.com/tech-stories...sh-like-a-pro/

[screamingchief]

Originally Posted by 78w72

as mentioned, these "quick" ways of doing it dont ensure the lifter is on the base of the circle. the procedure in most chilton type manuals for adjustable valvetranes are for stock or close to stock "mild" street cams. once you get into larger duration cams, those procedures dont work because the valves they say to do at any given point of engine rotation arent always on the base of the lobe.

Agree,but dont be surprised if you get a lot of people that will argue this with you.

But in their defense,those are likely cams best discussed in the drag forum.

Having BTDT,when you try these "quick" adjustment methods with a big 'ol solid roller,there's a real good chance that the engine is'nt even gonna start because it'll be hanging the valves open.

And yep,the only way to be sure that does'nt happen is to do them a cylinder @ a time,either by adjusting the rockers for each cylinder @ TDC compression,or by using the Exhaust valve just opens/Adjust intake ~ Intake valve just closing/Adjust exhaust method that some cam co.s recommend (Crane et-al).

FWIW

Bret P.

[Old Man Taylor]

Originally Posted by jonmachota78

Neither!

1 turn crank to tdc.
2 loosen all rockers
3 set all rockers to zero lash
4 turn crank exactly one revolution (back to tdc)
5 set all rockers that have loosened to zero lash
6 add your favorite preload to all rockers and lock them down (I like 1/2 turn)

That's only good for hydraulic lifters.

[jonmachota78]

Originally Posted by Old Man Taylor

That's only good for hydraulic lifters.

True ^^^^^^^^ I should have specified that.

For this procedure to NOT work, the base circle would have to be less than 360° duration. (Expressed in crank degrees. There's 720 crank degrees on a cam, right?).
For that to happen the advertised duration of the lobes would have to approach or exceed 360°.
That's a big honkn bump stick! Hydraulic cams generally don't get near big enough to worry about that being an issue. I would think like screamingchief eluded to that's solid race cam territory. But I'll be the 1st to admit I have NOT seen it all!

The concept behind this procedure is that at Any given point on a cam lobe, 180 cam degrees from that point will be base circle. When you turn the crank 360° you're also turning the cam 180° so all lifters will hit base circle on one of the two cam positions.

[Schurkey]

Originally Posted by David Jones

Starting with #1 at TDC?.....with #1 at TDC (compression?)

That works. It DOES NOT MATTER where the crank is. Any random place is fine...as long as you turn it exactly one revolution for step 2. If you start with the timing marks on the damper and front cover aligned, it makes it easy to turn exactly one revolution. That's the only benefit to starting at #1 TDC--the alignment marks are ready for you.

Originally Posted by David Jones

set all of them to zero lash then turn the crank one revolution and adjust only the loose ones to zero lash. Then in no particular order simply set the pre-load by (this is my #) adding 3/4 turn of the adjuster nut and locking them all 16 down?

"loose ones" being the rockers?

Just looking for clarification because it seems....to simple.

Yes. You have the rest of the procedure correct. It really is that simple.


There is no point to finding that last one or two thousandths of "base circle", because 1) the lifter preload even at 1/4 turn completely obliterates a mere thousandth or five, and 2) that's probably not true base circle anyway, it's more likely to be camshaft runout or a machining abnormality on the lobe. It therefore works on any hydraulic-lifter camshaft with less than about 350 degrees of advertised duration, because the last few thousandths of clearance ramp don't really matter if you're using more preload than 10 thousandths at the lifter plunger.

[David Jones]

I just finished swapping valve stem seals. I'll be using this method in the next day or two.

[Blued and Painted]

If the distributor is in correctly, adjust the 2 valves on the cylinder the rotor is pointed at.

[David Jones]

Worked like a charm. Loosened all lock nuts. Pulled it around to tdc line / zero and took every rocker to zero lash. Rotated the crank one revolution. Zero lash on the loose ones again. Then added preload to each nut and locked them down. Really just took a few minutes. Engine runs great.

[68 Firebird]

wow learn something new every day

Gerry