Adjusting valves "hot"
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schnyde
- Posts: 54
- Joined: Sat Dec 11, 2004 9:36 am
Adjusting valves "hot"
From reading previous posts, am I to assume that adjusting my valves (solid lifter, everything stock) while engine is hot is a good thing? Adusting them to .002 at TDC? I have them at .006 cold. Would I be better off adjusting my EX valve to .003 and intake to .002 hot?
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raygreenwood
- Posts: 11907
- Joined: Wed Jan 22, 2003 12:01 am
No applause from here (sorry D-star 
)....
Adjusting valves hot is vastly superior. No one cares what your COLD valve clearance is....as you wll never drive on cold valves. Want a good test of this? Take four valves...same brand..same lot. Put them in the oven and heat to ....whatever. Take each one quickly, out with tongs (metal tongs...no heat robbing contact!)...and quickly measure them with a micrometer held in a stand at room temp. For each valve....wait five minutes to let the anvils return to room temp. Generally you will find a range of variance of between .002"...and sometimes up to .005". This is because everdy piece of metal is different no matter what. And...many valves with stellite or hardened stems are two piece and have even more variation.
You can check this on your own car. Adjust it cold to whatever is right (.006...if you say so). Make sure you are happy they are perfect. Run them till its as hot as it ever gets. Quikly pull a valve cover...rotae engine before you do...and quickly check one valve pair. Record...replace cover and drive for 10 minutes. Rpeat until you get them all. See the difference ? You will. Not sure it wasn't a fluke....not sure one valve cooled faster than the other? Repeat it as many times as you like. There will be differences. Only .001 difference? No big deal. Lucky man.
Difference of .002" or more should be adjusted for. On injection...it is significant. Variances in valve adjustment cause variances in vacuum signature on the short sharp ramped cams in type 4's. These cause fluctuations.
But...I applaud the warning to inexperienced people. Wat I think should be said....is that you can get the experience needed to do this very good technique.....without having to change a single adjustment. The hard part is measuring without burning fingers and wrist.
So spend an hour driving...stopping...popping covers...measuring. Don't change anything. Just get the hang of it.
Now.....lets say you are out measuring....and find that over 3 sets of measurements...that #4 intke and #2 exhaust valve are consistantly out .002" larger when the engie is hot. Now you know something. They are going to be that way tommorrow too. So why not just let it cool then adjust that .002 out of them when they are cold?
.
See...the real point is....to have at least SOME gap....when the valves are at their hottest. Preferably as little as possible when all the heat is in.
Through thousands of measurements on valves set at .006 cold...i have found that when they are just about right...they are at .002" hot.
But.....you have no idea what brand valves I am running or anything else. Wouldn't matter anyway. You need to do this for your self.
Its also worth it to mention....and you should see this for yourself...it takes 10 seconds to find out....that there is no risk to this...because when you are at TDC on the puley.....you are not at the bottom of the base circle on ANY of the cam lobes....so they will never get totally tight...unless they arelike .005" too tight. This is why I have little sympathy for people who burn valves by letting them get too tight...you actually have that .006...and another .005"-.008"...in there.
Try it. Set to TDC. Close the adjuster screw all the way...and then...rotate the engine. You will find that you are not actually at the bottom of the base circle.
Do not be afraid of the technique. It makes a huge difference on most of the factory injections...for tuning...the closer you can adjust the valves.
We are NOT taking away from the valve gap. We are simply making it what it was planned to be ....when hot. Ray
)....Adjusting valves hot is vastly superior. No one cares what your COLD valve clearance is....as you wll never drive on cold valves. Want a good test of this? Take four valves...same brand..same lot. Put them in the oven and heat to ....whatever. Take each one quickly, out with tongs (metal tongs...no heat robbing contact!)...and quickly measure them with a micrometer held in a stand at room temp. For each valve....wait five minutes to let the anvils return to room temp. Generally you will find a range of variance of between .002"...and sometimes up to .005". This is because everdy piece of metal is different no matter what. And...many valves with stellite or hardened stems are two piece and have even more variation.
You can check this on your own car. Adjust it cold to whatever is right (.006...if you say so). Make sure you are happy they are perfect. Run them till its as hot as it ever gets. Quikly pull a valve cover...rotae engine before you do...and quickly check one valve pair. Record...replace cover and drive for 10 minutes. Rpeat until you get them all. See the difference ? You will. Not sure it wasn't a fluke....not sure one valve cooled faster than the other? Repeat it as many times as you like. There will be differences. Only .001 difference? No big deal. Lucky man.
Difference of .002" or more should be adjusted for. On injection...it is significant. Variances in valve adjustment cause variances in vacuum signature on the short sharp ramped cams in type 4's. These cause fluctuations.
But...I applaud the warning to inexperienced people. Wat I think should be said....is that you can get the experience needed to do this very good technique.....without having to change a single adjustment. The hard part is measuring without burning fingers and wrist.
So spend an hour driving...stopping...popping covers...measuring. Don't change anything. Just get the hang of it.
Now.....lets say you are out measuring....and find that over 3 sets of measurements...that #4 intke and #2 exhaust valve are consistantly out .002" larger when the engie is hot. Now you know something. They are going to be that way tommorrow too. So why not just let it cool then adjust that .002 out of them when they are cold?
.See...the real point is....to have at least SOME gap....when the valves are at their hottest. Preferably as little as possible when all the heat is in.
Through thousands of measurements on valves set at .006 cold...i have found that when they are just about right...they are at .002" hot.
But.....you have no idea what brand valves I am running or anything else. Wouldn't matter anyway. You need to do this for your self.
Its also worth it to mention....and you should see this for yourself...it takes 10 seconds to find out....that there is no risk to this...because when you are at TDC on the puley.....you are not at the bottom of the base circle on ANY of the cam lobes....so they will never get totally tight...unless they arelike .005" too tight. This is why I have little sympathy for people who burn valves by letting them get too tight...you actually have that .006...and another .005"-.008"...in there.
Try it. Set to TDC. Close the adjuster screw all the way...and then...rotate the engine. You will find that you are not actually at the bottom of the base circle.
Do not be afraid of the technique. It makes a huge difference on most of the factory injections...for tuning...the closer you can adjust the valves.
We are NOT taking away from the valve gap. We are simply making it what it was planned to be ....when hot. Ray
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Plastermaster
- Posts: 2762
- Joined: Sun Sep 30, 2001 12:01 am
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dstar
- Posts: 3733
- Joined: Tue Feb 25, 2003 12:01 am
Ray,
I agree that it is *best* to adjust valves hot, under SOME circumstances!
The specs were put there by engineers FAR more knowledgeable about
VW engines than you and I.....
THEY knew how Americans were\ARE about adjusting valves.
Most do NOT know how to do it correctly!
Notice that I said, that "if you are not very good at it, do it cold"......
A *newbie* doesn't need to try to start learning to adjust valves,
with the valves HOT, PERIOD.
Adjusting valves may be easy for you and I, because of the thirty or so years we have been doing it.
That is not the case for everyone. It's a good way to fry his engine.
IF schnyde wants to take the chance of buying another $2500 longblock, then heck, it's HIS ENGINE!
Don
I agree that it is *best* to adjust valves hot, under SOME circumstances!
The specs were put there by engineers FAR more knowledgeable about
VW engines than you and I.....
THEY knew how Americans were\ARE about adjusting valves.
Most do NOT know how to do it correctly!
Notice that I said, that "if you are not very good at it, do it cold"......
A *newbie* doesn't need to try to start learning to adjust valves,
with the valves HOT, PERIOD.
Adjusting valves may be easy for you and I, because of the thirty or so years we have been doing it.
That is not the case for everyone. It's a good way to fry his engine.
IF schnyde wants to take the chance of buying another $2500 longblock, then heck, it's HIS ENGINE!
Don
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BajaPorsche
- Posts: 320
- Joined: Sun Feb 20, 2005 2:40 pm
I'm a newby of 30 years....
a few questions...... do the valves expand contract much under heat?
how could you tell what the expansion of that valve is, especially with aluminum cases and head contracting/expanding while heating up/cooling down...
seems that if you adjusted 1 valve while hot, then adjusted it again 2 minutes later, that you might get two different readings, based on the cooling effect of aluminum....
like I said I'm a newbie....but it seems safe to me......that when the valves are cold, they will not be in any contraction expansion phase. They will remain consitant.
here is another question. When hot, would the exhaust valves be expanded more, then the intake valves..... could that be the reason for the .006/.008 combination?
what does make sense is, that certain cylinders will run hotter then others due to cooling...... and if you could adjust those valves to compensate for the different temps...... then it seems, part of a perfected fine tuning process, for the pros.... Good thinking!
but i'm new here, and maybe I should do more reading and less posting.
Day 4, still have access!
a few questions...... do the valves expand contract much under heat?
how could you tell what the expansion of that valve is, especially with aluminum cases and head contracting/expanding while heating up/cooling down...
seems that if you adjusted 1 valve while hot, then adjusted it again 2 minutes later, that you might get two different readings, based on the cooling effect of aluminum....
like I said I'm a newbie....but it seems safe to me......that when the valves are cold, they will not be in any contraction expansion phase. They will remain consitant.
here is another question. When hot, would the exhaust valves be expanded more, then the intake valves..... could that be the reason for the .006/.008 combination?
what does make sense is, that certain cylinders will run hotter then others due to cooling...... and if you could adjust those valves to compensate for the different temps...... then it seems, part of a perfected fine tuning process, for the pros.... Good thinking!
but i'm new here, and maybe I should do more reading and less posting.
Day 4, still have access!
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raygreenwood
- Posts: 11907
- Joined: Wed Jan 22, 2003 12:01 am
D-star...points well taken. But....adjusting a hot valve is no different than adjusting a cold one. Precision of adjustemnt is precision of adjustment. Thats why I noted...that the difficult part of learning to measure HOT..should be practiced before anything is adjusted. I drove around checking my valves daily for over a month before I adjusted them this way. The difference in smoothness and balance of power, from cylinder to cylinder.... is LARGE. Most especially so on the stock FI. Its much more senstive to valve adjustment.
The engineers had to give a measurement for adjustment. yes...we are less precise...as a motoring populace. It was a safe measurement....but only that. Notice...that I am NOT saying to decrease the gap on your valves......only to equalize them so they run equivalently.
A couple things I would bet....(1) is that the parts in the earlier engines had much better matching and consistancy than many we get today. It may have been less of a worry on original valves. (2) I also say that...No good practicing engineer would knowingly suggest to use a less precise adjustment, if it would mean a noticable imprecise state of running. This does. I'm not saying everyone will find their valves more than .001 difference. But i have found it on 3 of 5 engines with even the best valves.
Its also fair to note this.......It may not actually be the valve that is causing this. It can be the seat, head, pushrod, or lifter. But if its consistantly seen.....it should be corrected.
Its also common ...especially with the better new materials....most especially lifters and pushrods...to find valve gaps that do NOT close up as much as the original stock.
As I noted.....the object is to always have some gap...even when you are nearly overheating (especially then). But that does not mean that you need to run around with hot gaps of .004". Thats common. It wears out stem tips, promotes poor rotation, slaps the cam lobe hard......is noisey as hell.....and loses power.
If you are getting a consistant .002 or more difference hot.....adjust it out, .001" at a time while cold. Its simple.
Its worthwhile to learn. Also, it will NOT result in burning valves. If you can do them cold..you can do them hot. If you can't do them right cold...then you are gonna have a problem owning a VW until you do. Also.....you have got to be a whole heck of a lot off to mess this up...because you are not on the bottom of the base circle at TDC. There is more than .006" of slack in there. Generally when valves get tight enough to bind...they have either been hideously neglected...or you are about to pop off a valve head.
Not trying to be argmentitive
.....we are agreed...its advanced....but it can be learned without adjusting anything. Ray
The engineers had to give a measurement for adjustment. yes...we are less precise...as a motoring populace. It was a safe measurement....but only that. Notice...that I am NOT saying to decrease the gap on your valves......only to equalize them so they run equivalently.
A couple things I would bet....(1) is that the parts in the earlier engines had much better matching and consistancy than many we get today. It may have been less of a worry on original valves. (2) I also say that...No good practicing engineer would knowingly suggest to use a less precise adjustment, if it would mean a noticable imprecise state of running. This does. I'm not saying everyone will find their valves more than .001 difference. But i have found it on 3 of 5 engines with even the best valves.
Its also fair to note this.......It may not actually be the valve that is causing this. It can be the seat, head, pushrod, or lifter. But if its consistantly seen.....it should be corrected.
Its also common ...especially with the better new materials....most especially lifters and pushrods...to find valve gaps that do NOT close up as much as the original stock.
As I noted.....the object is to always have some gap...even when you are nearly overheating (especially then). But that does not mean that you need to run around with hot gaps of .004". Thats common. It wears out stem tips, promotes poor rotation, slaps the cam lobe hard......is noisey as hell.....and loses power.
If you are getting a consistant .002 or more difference hot.....adjust it out, .001" at a time while cold. Its simple.
Its worthwhile to learn. Also, it will NOT result in burning valves. If you can do them cold..you can do them hot. If you can't do them right cold...then you are gonna have a problem owning a VW until you do. Also.....you have got to be a whole heck of a lot off to mess this up...because you are not on the bottom of the base circle at TDC. There is more than .006" of slack in there. Generally when valves get tight enough to bind...they have either been hideously neglected...or you are about to pop off a valve head.
Not trying to be argmentitive
.....we are agreed...its advanced....but it can be learned without adjusting anything. Ray-
raygreenwood
- Posts: 11907
- Joined: Wed Jan 22, 2003 12:01 am
Bajaporsche..good questions!. Almost all materials expand with heat. Though metals tend to keep expanding, after acertain point, the measurable amount of expansion is negligable. This is why the gaps don't just keep shrinking to nothing on the valves when you overheat. Now...aluminum...having a higher rate of expansion...can quickly outrun its allowed gaps when overheating....as in the pistons siezing. But part of that is also lubricant failing as it overheats.
Yes...as I noted...it may not just be the valve. The valve clearance were designed with all of the parts combined...in mind.
And...how to tell if you just didn't get one set cooler than another when checking? Use temperature gauges. Once hese engines are well warmed up....the gaps are generally wherre the yare going to be. That means oil temps 185 or better, and head temps of 200-275. It also can help to buy a non contact laser thermometer....but is generally unnecessary.
As I have been noting.....this is not just a check it hot once and see a difference thing. Its check it several times...hot..under numerous sets of warmed of conditions...to see how the valve is running. If its out...it will be consistantly out. Only then do you do something about it.
As I noted....set them cold...check them hot.
For me...its pull over...brake, neutral... turn off the engine, pop the hood....wrench and screwdriver in hand, pop the cap...turn the pully while looking at timing mark, slide under side, pop valve cover....push down on pushrod end with scredriver to take out any slack.....slip in feeler gauge 1, gauge 2, gauge 3. Wipe them on damp cool rag to get back to cool temp. Check valve next to it. Time with valve cover open?....less than 1 minute before I start putting back on.
With a lot of experience.....you can adjust them .001" to .002" when hot. Its generally not necessary though. If you know how far its off..and it consistantly stays that way....just adjust that amount cold.....and check it again hot to see if your adjustment was correct.
I think this is the point everyone was missing. If you mis-adjust it slightly....so what? You will be re-checking it immediatly upon warm up. Ray
Yes...as I noted...it may not just be the valve. The valve clearance were designed with all of the parts combined...in mind.
And...how to tell if you just didn't get one set cooler than another when checking? Use temperature gauges. Once hese engines are well warmed up....the gaps are generally wherre the yare going to be. That means oil temps 185 or better, and head temps of 200-275. It also can help to buy a non contact laser thermometer....but is generally unnecessary.
As I have been noting.....this is not just a check it hot once and see a difference thing. Its check it several times...hot..under numerous sets of warmed of conditions...to see how the valve is running. If its out...it will be consistantly out. Only then do you do something about it.
As I noted....set them cold...check them hot.
For me...its pull over...brake, neutral... turn off the engine, pop the hood....wrench and screwdriver in hand, pop the cap...turn the pully while looking at timing mark, slide under side, pop valve cover....push down on pushrod end with scredriver to take out any slack.....slip in feeler gauge 1, gauge 2, gauge 3. Wipe them on damp cool rag to get back to cool temp. Check valve next to it. Time with valve cover open?....less than 1 minute before I start putting back on.
With a lot of experience.....you can adjust them .001" to .002" when hot. Its generally not necessary though. If you know how far its off..and it consistantly stays that way....just adjust that amount cold.....and check it again hot to see if your adjustment was correct.
I think this is the point everyone was missing. If you mis-adjust it slightly....so what? You will be re-checking it immediatly upon warm up. Ray
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BajaPorsche
- Posts: 320
- Joined: Sun Feb 20, 2005 2:40 pm
Wow Ray, that was a complete response, and backed up by experience, it looks like....
How about these questions
Do the valve clearances, as the engine warms up, get taller (wider clearance), so that the hotter the independent cylinder ran, the valve system itself would compensate for it, by expanding the clearance taller..... thus the hotter the cylinder, the taller the valve clearance, by design....
Wow, I'm scaring myself here!
also, i gave up trying to adjust the valves with the hood open, and looking for TDC...
what do you think about the;
pop off both valve covers, jack up one wheel, put it in fifth gear.......turn the wheel til the valves/valve rock, then set the oppsosite valve on the same lobe......
even if you have a good reasoning not to do it this way.....I will probably still do it this way, cuz it makes it so easy, and fullproof....in my opinion.
How about these questions
Do the valve clearances, as the engine warms up, get taller (wider clearance), so that the hotter the independent cylinder ran, the valve system itself would compensate for it, by expanding the clearance taller..... thus the hotter the cylinder, the taller the valve clearance, by design....
Wow, I'm scaring myself here!
also, i gave up trying to adjust the valves with the hood open, and looking for TDC...
what do you think about the;
pop off both valve covers, jack up one wheel, put it in fifth gear.......turn the wheel til the valves/valve rock, then set the oppsosite valve on the same lobe......
even if you have a good reasoning not to do it this way.....I will probably still do it this way, cuz it makes it so easy, and fullproof....in my opinion.
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raygreenwood
- Posts: 11907
- Joined: Wed Jan 22, 2003 12:01 am
Careful now... When you use the turn the whell method...you will be finding the true bottom of the base circle. If you put a dial indicator on the rocker arm, and find the place on the cam lobe wherin the gap is largest by turning the wheel while in high gear...you will then find .....that you are nowhere near TDC on the cylinder in question. You will also find gaps on properly set valves of around .010" or greater when at this position on the cam. If you then set it to .006"...you will be too tight...at the point that is normally TDC. I think it is important to maintain the stock TDC point as your valve adjusting point. As D-star noted...the engineers had a reason for this. This is because the actual factory TDC point more accurately is related to the point wherin ignition begins. Having extra slop after the fact....as the lifter rounds farther down the base circle...is no hindrance to that. Though you will most probably never actually have a valve bind by doing this....you may in fact prop the valve open just enough to get manifold detonation and valve burning at the start of ignition at TDC....or with advance....before it.
Yes...the extra slack at the TDC point that is adjusted in at the factory is needed to account for advance and make sure the valve is closed when the flames start. But...the pont here...is to have a safe margin, but not excessive amounts...and tomake sure they are all even. For instance, the stock injection is extremely sensitive to valve adjustment. Every .001" is like 2* of cam timing difference.
As far as heat expansion, the gaps get smaller....on stock materials. You go from .006 to about .002-.003" valve gaps. Except...on chromolly pushrods. They effectively stay the same....so everything else expands away from them...widening the gap, which is why you set them cold at "0" gap. Ray
When you use the turn the whell method...you will be finding the true bottom of the base circle. If you put a dial indicator on the rocker arm, and find the place on the cam lobe wherin the gap is largest by turning the wheel while in high gear...you will then find .....that you are nowhere near TDC on the cylinder in question. You will also find gaps on properly set valves of around .010" or greater when at this position on the cam. If you then set it to .006"...you will be too tight...at the point that is normally TDC. I think it is important to maintain the stock TDC point as your valve adjusting point. As D-star noted...the engineers had a reason for this. This is because the actual factory TDC point more accurately is related to the point wherin ignition begins. Having extra slop after the fact....as the lifter rounds farther down the base circle...is no hindrance to that. Though you will most probably never actually have a valve bind by doing this....you may in fact prop the valve open just enough to get manifold detonation and valve burning at the start of ignition at TDC....or with advance....before it. Yes...the extra slack at the TDC point that is adjusted in at the factory is needed to account for advance and make sure the valve is closed when the flames start. But...the pont here...is to have a safe margin, but not excessive amounts...and tomake sure they are all even. For instance, the stock injection is extremely sensitive to valve adjustment. Every .001" is like 2* of cam timing difference.
As far as heat expansion, the gaps get smaller....on stock materials. You go from .006 to about .002-.003" valve gaps. Except...on chromolly pushrods. They effectively stay the same....so everything else expands away from them...widening the gap, which is why you set them cold at "0" gap. Ray
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Plastermaster
- Posts: 2762
- Joined: Sun Sep 30, 2001 12:01 am
It seems to me if you have a non stock application (non stock cam timing) that the "turn the wheel" method would be best. Right? I am gathering here that valve clearance at the base of the cam is what is important. If a cam is advanced or retarded, the clearance at TDC (piston) is not the same as it is at the base of the cam. For that matter, a split duration cam can't have the valves adjusted at the same position. Whether cold or hot, If you turn the wheel to find the tightest clearance, you have found the position where the valve needs to be adjusted. Is that right?
Thanks
Ron
Thanks
Ron
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BajaPorsche
- Posts: 320
- Joined: Sun Feb 20, 2005 2:40 pm
from Bajaporschefrom Ray
You will also find gaps on properly set valves of around .010" or greater when at this position on the cam. If you then set it to .006"...you will be too tight...at the point that is normally TDC. I think it is important to maintain the stock TDC point as your valve adjusting point.
That's why it ran so quiet... it sounded good adjusted at that point.... I don't know which cam grind I have (it came with the car).....but if I set them at .006 .008..... i could hear the difference between setting them at .006 and .006..... but Ray it's so much easier setting em this way!
from Bajaporschefrom Ray
I think it is important to maintain the stock TDC point as your valve adjusting point. As D-star noted...the engineers had a reason for this. This is because the actual factory TDC point more accurately is related to the point wherin ignition begins.
I hope you all know, your way makes setting the valves that much more difficult..... but your explaination makes alot of sense.
from Bajaporschefrom Ray
As far as heat expansion, the gaps get smaller....on stock materials. You go from .006 to about .002-.003" valve gaps. Except...on chromolly pushrods. They effectively stay the same....so everything else expands away from them...widening the gap, which is why you set them cold at "0" gap.
That's where I read it at......on one of the post where the argument.....whoops, I mean discussion on where to set the valves on the chromolly pushrods..... zero tolerance or .006/.006...
My mistake again.... but I'm still learning!
Ray, is there an easy procedure for finding TDC, while under the car... so as to not have to get out get up, squeeze into the engine compart to look where the fan is at.....
oh yeah, on my car, it's lifted high enough, that I don't need to even to jack it up to get all the way under the engine... so it shouldn't be dangerous for me to be under the vehicle with one wheel up off the ground, but probably still is.
