My understanding is that, assuming you aren't using adjustable rockers, you adjust the pushrods until your wipe pattern on the valve stem is correct. If you are using solid lifters for this test, you then add the desired preload amount to this amount.

 

Can you add a bit of detail to this? With check springs the lifters will be 100% extended all the time so we can think of them as fixed. Changing the pushrod length to anything other than zero preload (aka zero lash) should just force the valve open (Yes, I'm assuming and using standard rockers).

How do you adjust wipe pattern when using non-adjustable rockers in a normal configuration (no check springs)? I didn't know this was possible. If I'm thinking about this correctly the only variable is pushrod length which changes lifter preload not the position (via a new rocker angle) of the rocker tip to valve stem.

 

With hydraulic lifters we should determine pushrod length based on desired lifter preload, not wipe pattern.

If you want/need to change the wipe pattern you should raise or lower the rocker. (In most cases you don't need to. Certainly if you change valve stem length you would.)

That's my understanding.

 

Ok, so when using solid "test" lifters (no test springs), you simply adjust the adjustable pushrods until zero lash. Is the lingth of the adjustable pushrod your desired pushrod length? or do you add a lifter perload amount to this length?

If we don't add to this length, than I am assuming that the lifters are pumped up immediatley upon start up and stay pumped up the whole time? I originally assumed that hydraulic lifters were somewhat compressed a bit and only got "pumped up/extended" at high RPMs.

I've been reading so many articles and I think I have confused myself

 

I read that the hydraulic lifter plungers travel about an eighth of an inch when the car is running. I think the idea behind the preloading is that we don't want the plungers to bottom out or top out too often if at all, they should stay in the middle of their range of travel.

 

It would depend if your solid lifters are the same height to the pushrod seat as an the hydraulic guys. For a set of stock lifters modified to prevent internal travel your second statement is correct. Correct pushrod length = adjustable pushrod dialed to zero lash + desired preload.

Agreed. The lifter takes slop out of the system but it shouldn't travel much. If oil pressure pumps it up too far, your valve wouldn't close all the way and your engine would become inefficient very quickly.

 

OK, so I checked everything again. The pushrods were adjusted until I had zero lash (using my home made solid lifters). I removed the rockers, and measured the overall length, which was 7.200. I called Crane cams since I was using a crane adjustable tool. THey said whatever my overall measured length was plus my desired lifter preload would be the length needed. I believe .050" of preload is fine with new OEM lifters, correct? If so, then that means that I need a set of 7.250" hardened lifters.

Does anyone disagree?


This was some good reading on lifters:
http://www.cranecams.com/?show=faq&id=3


Frijolee, sorry again for jacking your thread.

 

Rocndav,

I agree with your methodolgy. However, that seems really short to me conisdering the stockers are 7.400. Are you running decked heads, adjustable rockers or anything else that could explain the difference.

On my end I just installed my Futral F13 (230/232). I was annoyed to discover I had only 0.065 intake to with a healthy 0.130 on exhaust. My first thought was that I might be tooth off on the timing chain but I've checked it every way I know how and it looks good. What the heck's going on here? Do I need to retard timing (which would mean throwing down for an adjustable timing set...)?

Joel

 

my AFR 225's were milled for 66cc and my block was also decked (my pistons come out of the block .015 isntead of the usual .005-.008.

Did you get solid lifters, or make your own? try swapping the lifters and see if your readings change.

 

You are perhaps forgetting additional clearance for valve float and/or over revs. If the spring cannot control the valve for one of these reasons, the additional clearance saves you from PTV contact. I doubt that preload makes up much, if any, of the recommended minimum clearance.

Great discussion here though!

 

I realize this is kind of an old thread, but I came across it doing some research for a build I'm doing at the moment.

First of all, NO, that is absolutely NOT what lifter preload is.

Here's an example, I'm doing an LS3 build. The hydraulic lifters have a maximum expansion of 3.20mm, so with 0 oil pressure they have to potential to compress 3.2mm. I say potential because the spring is keeping them expanded until you set preload. Factory preload spec is 1.58mm or .062" What that means is that you are compressing the spring in the lifter 1.58mm, so there is still 1.62mm of travel left in the lifter, which if you turn the motor over and the cam pushes against it, will compress. The problem with this is that, just like you imagined, if the motor was running it would absolutely not compress that last 1.62mm as it would be filled with oil allowing the valve to move farther i.e. less valve clearance.

Converting to inches and multiplying across a 1.7 rocker arm that's actually .108" difference. While I realize 102 to 108 isn't a huge difference, it could be depending on your exact preload spec, and that is really why it's so bad to check this with hydraulic lifters, it's very hard to know exactly what your preload is set at with any real precision especially multiplied across a rocker arm.

Having said that, if you subtract .105" from your measured valve clearance and you still have plenty, yes, you are probably fine. However, it is worth knowing that you could always lose valve clearance with lifter pump up, but... that's not going to matter whether you checked it with solid or hydraulic lifters.

I honestly don't see a huge problem checking p/v clearance with hydraulic lifters if you have all of the information and understand how they work, especially when you consider that the solid lifter measurement may not be as accurate based on your individual preload setting, and some people do change preload settings based on RPM requirements... higher RPM motors often get a little less preload, etc.

 

High 8s? Am I right?

 

They work like shock absorbers.

 

It's actually a piston inside the lifter housing that, when the valve is closed, has oil pressure push the piston up and keep the valve lash tight. When the lifter pushes up to open the valve, the captured oil keeps the piston in position until the valve closes again.