Zero Clearance valve lash ?

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65CudaFish

65CudaFish

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I'm currently installing adjustable rockers on a engine with a hydraulic lifter cam. I have read that the setting is suppose to be 1/2 turn after the pushrod end play is removed from lifter plunger to rockerarm. Cant I just eliminate the guess work and set them at zero clearance?:smilebox:
 
65CudaFish said:
I'm currently installing adjustable rockers on a engine with a hydraulic lifter cam. I have read that the setting is suppose to be 1/2 turn after the pushrod end play is removed from lifter plunger to rockerarm. Cant I just eliminate the guess work and set them at zero clearance?:smilebox:
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Oh it's a Mopar Smallblock!
 
Yes, IF you have the correct type lifters. Anti pump up lifters are supposed to be run at either zero lash, OR .002 lash. I would not recommend running like that with regular hydraulic lifters.
 
StrokerScamp said:
Yes, IF you have the correct type lifters. Anti pump up lifters are supposed to be run at either zero lash, OR .002 lash. I would not recommend running like that with regular hydraulic lifters.
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So they have to be fast bleed? I have set many of engine with hydraulics to zero clearance and not ever had a problem, but have never set a Mopar to zero clearance with regular 2011 hydraulic lifters, hmmm, sure don't want them pumping up and bashing a piston. I wonder if I set them to zero and then backed them off 1/2 turn. I'm just looking for eliminating the guess work of the other half measured setting?:help:
 
65CudaFish said:
So they have to be fast bleed? I have set many of engine with hydraulics to zero clearance and not ever had a problem, but have never set a Mopar to zero clearance with regular 2011 hydraulic lifters, hmmm, sure don't want them pumping up and bashing a piston. I wonder if I set them to zero and then backed them off 1/2 turn. I'm just looking for eliminating the guess work of the other half measured setting?:help:
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Hello anybody out there?:protest:
 
If you run any regular hydraulic lifter at zero, it slams the valve shut with no cushion. Just because you've done so in the past doesn't make it right. It makes you lucky. You asked for an explanation and I gave you the correct one. I don't know what else to say other than run it like you want to.
 
StrokerScamp said:
If you run any regular hydraulic lifter at zero, it slams the valve shut with no cushion. Just because you've done so in the past doesn't make it right. It makes you lucky. You asked for an explanation and I gave you the correct one. I don't know what else to say other than run it like you want to.
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I see what your saying. I'm just looking for the simplest way to set them with adjustable rockerarms. I got it now though. Since I'm currently doing it I set one to just no end play and gave it a half turn. Then I turned it just until the valve started to open and guess what it was 1/2 turn as well. So now I know for sure that at TDC Compression set it to zero lash and back it off 1/2 turn and it will be a true adjustment throughout the valvetrain for normal lifters!:cheers:
 
Thanks for the input, it was certainly helpful, got me to a certain set adjustment!
 
Use the search feature here @ FABO to find how to get each cylinder on the proper stroke so you can adjust them properly. The reason that you adjust hydraulics by turning the adjuster past zero lash is to preload the lifter. It puts it in the middle of it's stroke. Gives it a cushion so to speak. The Chevy guys tighten them until the tick noise goes away (zero lash) and then a 1/2 to a full turn. Mopar adjustables are harder to do with the engine running because the adjuster is on the pushrod end of the rocker instead of on the pivot point like the Chevy's are. toolmanmike
 
70aarcuda said:
follow the same sequence as if you were adjusting for a solid lifter...turn the adjuster until you have zero lash then add the preload on the lifter....020 preload...

http://www.hughesengines.com/Upload/productInstructions/ValveAdjust.pdf
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^^^THIS^^^ is what I'd do

Set them at zero, either with engine off or running if you can

If you set them engine off, learn the thingie EOIC

which means

Wrench the engine until the EXHAUST just starts to OPEN on a given cylinder and adjust the intake valve on that cylinder

Wrench the engine until the INTAKE first opens, then is almost CLOSED and adjust the exhaust for that cylinder

Figure out how much preload / turn of adjuster you get (turns per inch of thread x rocker arm ratio, best to actually MEASURE that

Then just turn them all down by the amount you "figgure" to get the preload.

Last, if you don't know what lifters are in the engine, all the above is just guesswork.
 
65CudaFish said:
I like this chart because it follows the firing order, nice. More thorough than the 4 point adjustment!
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I uderstand this method of adjustment except for the preload direction. On the solids it's a gap and on the hydraulics your saying it's negative which would just start opening the valve while setting the lifter prelaod. Strange because in my minds eye the valve must close completely. It is confusing to me but I do believe in the mechanical sense that I have it right. Right now I have them set to zero clearance just before the valve opens and then backed off 1/2 turn which puts the negative on the lifter plunger rather than opening the valve. Even on the solids the valve closes completely. So confusing yes. So .020, 20 thousand's of a inch is a negative factor that is set at the lifter plunger right? Not at opening the valve past zero clearance. Also my saying zero clearance may be confusing everyone else into mistaking it for lash. My zero clearance means right before the valve opens, so to add to that would open the valve!
 
65CudaFish said:
I uderstand this method of adjustment except for the preload direction. On the solids it's a gap and on the hydraulics your saying it's negative which would just start opening the valve while setting the lifter prelaod. Strange because in my minds eye the valve must close completely. It is confusing to me but I do believe in the mechanical sense that I have it right. Right now I have them set to zero clearance just before the valve opens and then backed off 1/2 turn which puts the negative on the lifter plunger rather than opening the valve. Even on the solids the valve closes completely. So confusing yes. So .020, 20 thousand's of a inch is a negative factor that is set at the lifter plunger right? Not at opening the valve past zero clearance. Also my saying zero clearance may be confusing everyone else into mistaking it for lash. My zero clearance means right before the valve opens, so to add to that would open the valve!
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I've also read to set the rockerarm system to (zero lash) then turn the adjuster an additional 1 & 1/2 turns, hah, I haven't tried that one yet. I personally like zero clearance myself, but want to do it right. I built a 400 Pontiac once and it set at zero clearance. I built a HO 305 once with roller lifters and set them at zero clearance. Both ran excellent! Built the little 273 Mopar with adjustable rockers but that was a solid lifter build and it ran excellent! Everything else Mopar I built has been the stock 1.5 ratio hydraulic system which is a sinch!
 
Hydraulic lifters are like a hydraulic cylinder. By tightening the adjuster past 0 lash, you're pushing the plunger towards the center of it's stroke. Because it has a piston and has oil inside it provides a self adjusting cushion when the cam lobe comes up to open the valve. If it's too loose it will clatter like a loose solid lifter. Too tight and there's no cushion and it would flatten your cam lobe.
 
Even if you adjust it to zero lash and go a little farther it won't hold the valve open because hydraulic lifters bleed down due to their design. If you do it right they will essentially keep the lash at zero. Setting them at zero lash and backed off 1/2 turn, like you say you have them now, puts lash in the valve train. Std. hydraulic lifters are not designed to operate with lash.
 
Just because Pontiac's don't have an adjuster and you torque the rocker arms down doesn't mean their at zero lash. They don't use an adjustable nut like a small block Chevy does but a lot of Pontiac guys swap them over to an adjustable nut to properly adjust the lifter preload. That's an old racers trick to get a couple hundred more RPM from them.
 
adjust each valve...turn adjuster until there is NO lash....the pushrod should be hard to turn at this moment...they add preload by turning adjuster 1/2 or 3/4 of a turn to pre load the lifter...\\\


the ideal is to have the valve that you are adjusting on the base circle of the cam...not on the ramps....so choose whatever method you like...
 
65CudaFish said:
I uderstand this method of adjustment except for the preload direction. On the solids it's a gap and on the hydraulics your saying it's negative which would just start opening the valve while setting the lifter prelaod. Strange because in my minds eye the valve must close completely. It is confusing to me but I do believe in the mechanical sense that I have it right. Right now I have them set to zero clearance just before the valve opens and then backed off 1/2 turn which puts the negative on the lifter plunger rather than opening the valve. Even on the solids the valve closes completely. So confusing yes. So .020, 20 thousand's of a inch is a negative factor that is set at the lifter plunger right? Not at opening the valve past zero clearance. Also my saying zero clearance may be confusing everyone else into mistaking it for lash. My zero clearance means right before the valve opens, so to add to that would open the valve!
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............If i'm reading this rite......u want to bottom out the plunger then back off the adj to set ur preload....thats totally *** backwards.......set ur preload to 0 lash then 1/4 turn more.....u will b at approx.010 then......compernday........ur going to eat the cam ur way..............kim.......
 
fishy68 said:
Just because Pontiac's don't have an adjuster and you torque the rocker arms down doesn't mean their at zero lash. They don't use an adjustable nut like a small block Chevy does but a lot of Pontiac guys swap them over to an adjustable nut to properly adjust the lifter preload. That's an old racers trick to get a couple hundred more RPM from them.
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Yeah that is what I did, put the lock tights on and turned them just until each valve started to open. Your right the RMP's were quite impressive!
 
fishy68 said:
Even if you adjust it to zero lash and go a little farther it won't hold the valve open because hydraulic lifters bleed down due to their design. If you do it right they will essentially keep the lash at zero. Setting them at zero lash and backed off 1/2 turn, like you say you have them now, puts lash in the valve train. Std. hydraulic lifters are not designed to operate with lash.
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Ok so I have to run through them again and set them 1/4 or more turns past zero clearance. Right is right and wrong is wrong and I sure don't want to be flattening a lobe or eating a lifter, Thanks!:blob:
 
70aarcuda said:
adjust each valve...turn adjuster until there is NO lash....the pushrod should be hard to turn at this moment...they add preload by turning adjuster 1/2 or 3/4 of a turn to pre load the lifter...\\\


the ideal is to have the valve that you are adjusting on the base circle of the cam...not on the ramps....so choose whatever method you like...
Click to expand...
Thanks I will try 5/8 of a turn at least they will be set with preload and I can add or subtract since they are adjustable now. I don't like working in oil, it causes things to strip out, so if I don't like it I will have to remove the rockerarms and wash them with gas and do it again. Sometimes more work than I want to do to preserve parts but worth it!
 
oldkimmer said:
............If i'm reading this rite......u want to bottom out the plunger then back off the adj to set ur preload....thats totally *** backwards.......set ur preload to 0 lash then 1/4 turn more.....u will b at approx.010 then......compernday........ur going to eat the cam ur way..............kim.......
Click to expand...
Okay will do!:eek:ops:
 
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