Hydraulic lifters and piston to valve checking
#22
Teching In
Thread Starter
iTrader: (12)
Join Date: Mar 2006
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by ROCNDAV
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.
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.
#23
TECH Addict
iTrader: (4)
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.
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.
#24
TECH Junkie
iTrader: (100)
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
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
#25
TECH Addict
iTrader: (4)
Originally Posted by ROCNDAV
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
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
Last edited by ShevrolayZ28; 09-21-2006 at 12:19 PM.
#26
Teching In
Thread Starter
iTrader: (12)
Join Date: Mar 2006
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by ROCNDAV
Ok, so when using solid "test" lifters (no test springs), you simply adjust the adjustable pushrods until zero lash. Is the length of the adjustable pushrod your desired pushrod length? or do you add a lifter perload amount to this length?
Originally Posted by ShevrolayZ28
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.
#27
TECH Junkie
iTrader: (100)
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.
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.
#28
Teching In
Thread Starter
iTrader: (12)
Join Date: Mar 2006
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
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
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
#29
TECH Junkie
iTrader: (100)
Originally Posted by frijolee
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
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
Did you get solid lifters, or make your own? try swapping the lifters and see if your readings change.
#30
TECH Fanatic
iTrader: (1)
Originally Posted by frijolee
You're basicaly measuring the p to v clearance at nominal lifter preload. With more oil pressure the lifter extends even further. As I see it this is WHY we need 0.080 and 0.100 clearance. Those numbers always seemed way to large to account for thermal expansion and tolerances of stretching parts.
Great discussion here though!
#31
Teching In
Join Date: Nov 2009
Location: Bethesda, MD
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
This is a pretty good article. However, as I thought about it a bit more I wanted to clarify something about lifter preload.
According to the above: lifter preload is the amount the lifter can collapse due to the greater spring rate of the valvesprings (measured with the valve closed). It's worth noting that oil pressure must be absent to correctly measure deflection hence the bleed down period required.
According to the above: lifter preload is the amount the lifter can collapse due to the greater spring rate of the valvesprings (measured with the valve closed). It's worth noting that oil pressure must be absent to correctly measure deflection hence the bleed down period required.
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.
#33
hydraulic lifters
I'm still looking for a good theoretical explanation for how hydraulic lifters actually work.
From a few of the above responses I'm picturing a diaphram driven by both a preloaded spring (of lower rate than the valve spring) and by oil pressure (hence how slop is removed and the startup clatter goes away...) The combination of oil pressure plus spring is then sufficient to overcome the force required to open the valvespring and the lifter moves smoothly thereafter.
From a few of the above responses I'm picturing a diaphram driven by both a preloaded spring (of lower rate than the valve spring) and by oil pressure (hence how slop is removed and the startup clatter goes away...) The combination of oil pressure plus spring is then sufficient to overcome the force required to open the valvespring and the lifter moves smoothly thereafter.
#34
TECH Senior Member
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.