# '70 Ram Air 3 lifter preload



## Ramjet (Feb 24, 2020)

Hello everyone,

To make a long story short, I've got an original, unrestored, '70 Judge (I've been blessed). I was inspecting some valve train components and I confirmed that all the rocker arm nuts were torqued to 20 ft. lbs. After marking the nuts before loosening and ensuring that I was on the heel of the cam for the associated valve, I noticed that each nut had to be turned 1 1/4 to 1 1/2 revolutions to get back to "0" lash. With the 3/8" studs, that's .052"-.063" preload. Is this considered normal for this engine? I can't find any associated information in the service manual. Any preload instructions that I've ever read on after market components only want 1/2-3/4 of a turn which would be .021"-.031". Has anyone ever encountered this discrepancy. Thanks for your time!

Roger


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## armyadarkness (Dec 7, 2020)

This has been my life for the last 4 months, but there are many more knowledgable than I, in the procedure that you're using. I'll let them advise. In my case, I had to adjust them while the engine was running. That was the advice of the forum.


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## LATECH (Jul 18, 2018)

IIRC .060 is the maximum amount of travel for the plunger on a poncho lifter

Some aftermarket brands may have more.

Probably best to set up a dial indicator on one and check that spec.

.060 sounds tight.

I would adjust somewhere in the middle like you are thinking.

I am running a Crane Cam and I have 7/16 studs.I have them at around 3/4 turn past zero lash. I revv the Stink out of it and it has been fine .

7/16 x 20 TPI . at 3/4 turn I should be at around .037 in past zero lash
Multiply that times the rocker arm ratio ( 1.5) and It should end up at about .055 
Hmmm... maybe I should back mine off a tad...


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## PontiacJim (Dec 29, 2012)

Ramjet said:


> Hello everyone,
> 
> To make a long story short, I've got an original, unrestored, '70 Judge (I've been blessed). I was inspecting some valve train components and I confirmed that all the rocker arm nuts were torqued to 20 ft. lbs. After marking the nuts before loosening and ensuring that I was on the heel of the cam for the associated valve, I noticed that each nut had to be turned 1 1/4 to 1 1/2 revolutions to get back to "0" lash. With the 3/8" studs, that's .052"-.063" preload. Is this considered normal for this engine? I can't find any associated information in the service manual. Any preload instructions that I've ever read on after market components only want 1/2-3/4 of a turn which would be .021"-.031". Has anyone ever encountered this discrepancy. Thanks for your time!
> 
> Roger


Pre-load should not be an issue. *If you are using stock nuts and have bottle neck rocker arm studs, torque to 20 ft lbs, period.* No need to mark anything or put each lifter and the cam base - you are making more work for yourself that won't yield any results.

Stock nuts are not to be used as an adjusting tool to set pre-load - just torque down and forget them. If you are trying to use the stock nuts to create an adjustable valve train, they will loosen, back off, and could eventually cause a rocker arm to go side ways and fall off the valve.

Get poly locks if you are trying to make the valvetrain adjustable and "zero lash" the lifters.


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## LATECH (Jul 18, 2018)

Torque to lash can be affected negatively if a valve job has been done and the valve stems were not cut to compensate for the added height. Seen it before on an SBF . I had to shim the rocker pedestals on a SBF for a guy to get it right as the guy who did the valve job did not remember (or know) to cut the stems to compensate for the increase in depth due to cutting the seats and valve faces.


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## LATECH (Jul 18, 2018)

X2 with Big Jim

I agree with the need for poly locks
I changed my stud to BBC and I am running poly locks with a crane cam 
Fully adjustable. Sweet.....


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## BearGFR (Aug 25, 2008)

Ramjet said:


> Hello everyone,
> 
> To make a long story short, I've got an original, unrestored, '70 Judge (I've been blessed). I was inspecting some valve train components and I confirmed that all the rocker arm nuts were torqued to 20 ft. lbs. After marking the nuts before loosening and ensuring that I was on the heel of the cam for the associated valve, I noticed that each nut had to be turned 1 1/4 to 1 1/2 revolutions to get back to "0" lash. With the 3/8" studs, that's .052"-.063" preload. Is this considered normal for this engine? I can't find any associated information in the service manual. Any preload instructions that I've ever read on after market components only want 1/2-3/4 of a turn which would be .021"-.031". Has anyone ever encountered this discrepancy. Thanks for your time!
> 
> Roger


With the stock valve train, there is no adjustment. Just torque the nuts to spec. All the "aftermarket component instructions" are either for chevy, or require additional component changes in the valve train such as poly-lock rocker nuts. You're working with a Pontiac, not a chevy --- Pontiacs are different.

Bear


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## GtoFM (Mar 23, 2018)

Let me jump in here to be clear. 20 ft/lb torque with no reference to lifter location on the lobe? Correct?


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## BearGFR (Aug 25, 2008)

GtoFM said:


> Let me jump in here to be clear. 20 ft/lb torque with no reference to lifter location on the lobe? Correct?


Correct.


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## PontiacJim (Dec 29, 2012)

GtoFM said:


> Let me jump in here to be clear. 20 ft/lb torque with no reference to lifter location on the lobe? Correct?


First, are you having some issues, or just wanted to check the rocker arm nut torque?

The lifters may have oil in them and some may be "pumped" up, but letting them sit, they typically bleed down. Once the engine is started, hydraulic lifters do what they do - self adjust.

If you were to install a set of Big Block 7/16" rocker arm studs, this makes the rocker arm stud stronger due in part that the stud is a straight threaded 7/16" diameter stud. The Pontiac uses a 7/16" base that screws into the head. About midway on the stud, it is cut down to 3/8", thus the term "bottle neck" stud. This is what the rocker arm nut gets torqued onto as it has a slight taper (as I recall) to match the taper of the stud neck. That bottle neck transition is a weak point when using higher lift camshafts that require additional spring pressures AND the factory rocker arms do not have the elongated rocker arm slot to pivot on the rocker arm ball and with a high lift cam, you could be forcing the rocker arm into the 3/8" top section and then it breaks off.

So the solution in strengthening your heads for higher lift cams/heavier spring pressures is to go with the the BB 7/16" rocker arm studs. Then in order to adjust the lifters, you need the poly locks. You can then "zero lash" the lifters so the lifters don't pump up at higher RPM's - which is what was done by many hot rodders and racers to include Royal with the Bobcat application.

You will also want to get the aftermarket stamped steel rocker arms having the longer pivot slots and the grooved rocker arm balls for additional clearances and better oiling in the rocker arm cup.

The only draw back that I am aware of is that on some heads having the factory type bolt-on oil drippers/deflectors is that they may not fit with the poly locks - which is not an item you must have, so they can be left off. I am thinking that the taller height of the poly lock actually blocks the oil that spits out of the rocker arm hole and deposits down into the rocker arm ball cup anyway. But, I have never actually looked at this, and have used poly locks.

So other than that, you do not need to find the base circle on each lobe - although you will read that some do, it will not hurt anything if you feel you want to do this to know that there was no tension fighting the rocker arm (valve open) when you did your torquing. I have never done it this way, just torqued to spec. so whatever you choose to do, Simply torque to spec and you are done. If the nuts have been tigthened and untightened several times, it is possible that the rocker arm nut can still back off. In this case, new rocker arm nuts will be needed.


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## LATECH (Jul 18, 2018)

OP is clearly questioning the depth of the plunger at 1 + 1/2 turns of the nut.
At 24 threads per inch, one turn would be around .040 in.
1 + 1/2 would be .060 in.

BUT with a 1.5 to 1 rocker that would make the travel .090 in.

IIRC a stock pontiac lifter has around .060 in travel in the plunger from zero lash. So 1+1/2 turns past zero lash at the lowest point of the cam, would actually start to hold the valve open.

I think that is what OP is trying to sort out here.

YES ...NO ...???


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## LATECH (Jul 18, 2018)

And BTW, I am running stock stamped rockers arms and pivots , with 7/16 BBC studs and a crane cam with .480 lift.

I have checked before installing and there is no binding of the rocker arm slots.The slots are plenty long enough.


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## LATECH (Jul 18, 2018)

My 400 (389) is a beast

( this is an early photo, it is mice prettier under the hood now )


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## BearGFR (Aug 25, 2008)

As PJ asked, if you're having some problem that you're trying to solve, then let's talk about the problem you're having and what's going on with that. Otherwise, if you're just wanting to verify that everything is correct on your engine then that's a separate topic. Pontiac factory valve trains using the stock 'bottleneck' studs, stamped rockers, rocker nuts, and hydraulic lifters aren't adjustable like chevys. They are deceptively simple. Just torque the nuts down to 20 lb ft and be on your way. That's the reason the studs have that bottleneck: the nuts are supposed to be snugged down onto them so they will stay put. If you try the chevy method of attempting to 'adjust' everything to zero lash, they won't stay there They WILL loosen up and you'll have all the problems that causes. 

In order to get an adjustable system, either because you just prefer it or because of other parts changes that require it, you >must< use positive locking poly-lock rocker nuts, regardless of whether the stock bottleneck studs are still being used or not.

Bear


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## LATECH (Jul 18, 2018)

I think the problem OP IS eluding to is that to get to 20 Ft lbs he turns the nut 1 1/2 turns to get there after zero lash is achieved. 
I think he is concerned with how far that is driving the plunger into the lifter. I dont think he is doubting 20 Ft lbs as the spec. I think he is more concerned about having the valves too tight because of how far the nut has to turn after zero lash too the torque spec. It is a viable concern.


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## Ramjet (Feb 24, 2020)

Hello Jim,
I just simply wanted to know the exact lifter preload on a stock, 20 ft. lb. torqued rocker nut on a 3/8" stud. The 1 1/4 to 1 1/2 turns that I encountered to return to "0" lash is .052" to .063". That's why I marked the nuts - to reference the amount of rotation. If I ever decided to substitute a 7/16" x 20 stud, I would have to turn the polylock adjusting nut 1 to 1.2 turns past zero lash to obtain the same preload and all I've ever heard on adjusting lifter preload on any engine is 1/2 to 3/4 of a turn past zero lash which is .025" to .037" using the 7/16" x 20 stud and is 1/2 of what I initially measured - That's a big difference and I was just wondering if someone could give me some insight on that discrepancy. So, I guess my question would be: How much lifter preload or how many turns on a 7/16" x 20 adjusting polylock nut using the stock lifters? Thanks for everyone's help!

Roger


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## PontiacJim (Dec 29, 2012)

Ramjet said:


> Hello Jim,
> I just simply wanted to know the exact lifter preload on a stock, 20 ft. lb. torqued rocker nut on a 3/8" stud. The 1 1/4 to 1 1/2 turns that I encountered to return to "0" lash is .052" to .063". That's why I marked the nuts - to reference the amount of rotation. If I ever decided to substitute a 7/16" x 20 stud, I would have to turn the polylock adjusting nut 1 to 1.2 turns past zero lash to obtain the same preload and all I've ever heard on adjusting lifter preload on any engine is 1/2 to 3/4 of a turn past zero lash which is .025" to .037" using the 7/16" x 20 stud and is 1/2 of what I initially measured - That's a big difference and I was just wondering if someone could give me some insight on that discrepancy. So, I guess my question would be: How much lifter preload or how many turns on a 7/16" x 20 adjusting polylock nut using the stock lifters? Thanks for everyone's help!
> 
> Roger


OK, here is what I found in one of my engine build books. Pontiac used 4 different type hydraulic lifters. The "High Ball" lifters, part #5232265, is used in most engines between 1956-1979. The plunger travle is .125", leak down rate of 20-90 seconds, and has a height of 1,759".

The only way I have ever adjusted a Pontiac for "zero lash" is with the use of poly locks and the engine running and adjusting according to the "clacking" sound of the lifter/rocker, getting it to stop, then 1/4" turn more after the lifter quiets down. This method won't work with stock rocker arm nuts.


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## Ramjet (Feb 24, 2020)

PontiacJim said:


> OK, here is what I found in one of my engine build books. Pontiac used 4 different type hydraulic lifters. The "High Ball" lifters, part #5232265, is used in most engines between 1956-1979. The plunger travle is .125", leak down rate of 20-90 seconds, and has a height of 1,759".
> 
> The only way I have ever adjusted a Pontiac for "zero lash" is with the use of poly locks and the engine running and adjusting according to the "clacking" sound of the lifter/rocker, getting it to stop, then 1/4" turn more after the lifter quiets down. This method won't work with stock rocker arm nuts.


Awesome, thanks again for your help!
Roger


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## LATECH (Jul 18, 2018)

PontiacJim said:


> Pontiac used 4 different type hydraulic lifters. The "High Ball" lifters, part #5232265, is used in most engines between 1956-1979. The plunger travle is .125", leak down rate of 20-90 seconds, and has a height of 1,759".


Thats excellent info Big Jim.
So then .060 should center the plunger in the lifter. Perfect.

Mine should be close as they are at around 3/4 turn past zero lash before I tightened them down.

I know OP is using stock nuts, but if he is turning them 1 1/2 turns pash zero lash to get to 20 ft lbs then the plunger is pretty deep in the lifter. Still seems like a safe enough distance though


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## Old Man Taylor (May 9, 2011)

There's nothing unique about the RA III lifter. The RA IV lifter is the one that is different.


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