Valve adjusting problem on U20

[JT68]

To remove the rocker without removing had cam, turn the engine by hand or starter so that the cam lobe points straight up.

Use a large flat blade screw driver to press down on the top of the spring retainer while prying against the underside of the cam. While compressed (may need a second person) slip the rocker off the adjuster pedestal.

Before you do this try breaking the nut loose by holding the TOP of the adjuster (14mm) stationary while loosening larger locking nut ( not the 27mm). If you can do this, you should be able to screw the adjuster in.

You can call me if you have trouble visualizing. J

[Gregs672000]

Big bolt, aluminum head... firm tightening with a 1/2 drive 10in ratchet, used Loctite (and I said "tick tick" when I tightened it firmly). Sorry, no torque number! I know you're eventually gonna hate me...

[svwilbur]

yup. I said tick tick when I locked down the 19 onto the 27 and the 27 stops moving. it is probably over tightened already. but it would be nice to not have it back out when you loose. the lock nut.

I suppose if I did not wrench the lock nut down so hard it would not be an issue. but they were on really hard so I just put them back really hard.

visions of rockers going lose and valve adjustment gaps. going to 0 as the assembly works its way loose and falls apart. but I guess it is not going to go anywhere.

how tight should the lock nuts be?
just snug, good and snug, tight, or as far as you can go manhandling it with a normal 19mm hand cresent wrench?

mine were the later of those torque amounts.

tick tick and a 1/4 turn more (for Greg)

[svwilbur]

we all posted about the same time. I did it already a couple posts back on the bottom of the first page.

[msampsel]

I think I saw some torque numbers somewhere based on bolt size ...

here are a couple

http://www.engineersedge.com/torque_table_sae.htm

and

http://machinedesign.com/archive/nuts-a ... ner-torque

I did not see the tick tick though

[Linda]

Here's some info and caution with regards to torquing into aluminum on the R16, not sure how specific for the U20, but the aluminum is probably the same anyway. Helicoiling the head is exciting :
http://www.311s.org/phpBB3/viewtopic.ph ... ocker+stud

Linda

[svwilbur]

Here's some info and caution with regards to torquing into aluminum on the R16, not sure how specific for the U20, but the aluminum is probably the same anyway. Helicoiling the head is exciting :
http://www.311s.org/phpBB3/viewtopic.ph ... ocker+stud

Linda

Linda, is the rocker tower something different from the 27mm base nut that is below the adjusting nut or the same thing?

Sounds like torque for a rocker tower is 30-35lbs on page 31 of clymers for 1600 for the rocker bracket bolts. Not sure if that is what we are talking about. In the 2000 section towards the back they don't say anything about torque on the adjusters that I can find. Lots of other specs but not on that.

[Linda]

No the 1600 is different than the U20. But the point is be careful, as aluminum is softer than what is being screwed into it.
Tick, tick might be a bit too casual, but I am NO expert. But I did have to helicoil the head once.
So just follow the expert advice.

Linda

[svwilbur]

I did start it this afternoon and it still all sounds about the same after the valve adjustment and it has the new adjustable cam gear in it. Next thing is to tear it all apart and install new chains and lower sprockets. But I wanted to turn it around in the garage as I think I may possibly mess something up and need to pull the head or something and would need more space for a hoist. So I started it and turned it around and did a compression test hoping to verify that things were ok. So I would know if I needed to pull the head now or could wait.

I logged my results over on the compression threat. I did test with wide open throttle, no throttle, with Dashpots removed with and without throttle. They are posted in the link below if anyone is interested and wants to give me their thoughts.

http://www.311s.org/phpBB3/viewtopic.ph ... 05#p240605

[Gregs672000]

I don't reef down on anything. So the 19mm adjuster nut is tight but I'm not bracing my body and pulling super hard. I have not had any loosen up on me, but understand your concern. I note the size of the fastener, the material it's in, how it felt tightening, and if it stops clean and firm. Anytime I've ever overdone a nut or bolt you could feel it starting to go... It's a mushy feeling.

[svwilbur]

what is the "correct" way to position the cylinder valves before adjustment?

the wiki just says:
"Both valves for each cylinder may be adjusted while they are fully closed on the compression stroke. After the valves have closed, turn the engine another quarter turn to insure the the cam is not exerting pressure on the valves. This is easy to see on the 2 liter overhead cam but impossible with the R motor."

on a U20 you can see the lobes but they appear closed for a pretty good arc of the cam.

do you adjust the exhaust and intake at that position or move the cam and adjust the intake?

I can wiggle the rockers and it appears to have no pressure on them but that does not mean they are at their highest/ largest gap.

so how should I be doing it?

My issue is at what point in the turning of the cam lobes do you adjust the valves?

Do you do #1 at TDC according to the crank marks or based off the distributor which in my case is a bit advanced versus TDC?

Or like the tech wiki says TDC plus an additional 1/4 crank turn?

Or do you do each valve separate which the exhaust closes first so do you get it's lobe straight up an then set it and then turn the crank and get the intake cam lobe straight up and set it?

I ask as there seems to be several possible ways.

what way works best to get a consistent proper gap setting?

[msampsel]

Of course setting the valves hot is preferred where practical

Decided to remove the R16 stuff from the post. Can be reinstated only on request ...

[JT68]

The order of adjustment doesn't matter Stacey. Timing pointer and rotor position is not relevant for adjusting the valves. All that matters is the cam lobe position relative to the rocker arm.

With the lobe up between 11 and 12 oclock, the rocker is at maximum clearance.

Pick one lobe that is up at 12 o'clock or so and do that one. (Write down the number as you go 1-8) Notice that one other lobe on the cam will be up as well. Do that one. (Write it down)

Now rotate the engine so a different pair is at 11-1 oclock. Repeat.

Do this 4 times and you are done....

What Mike described for the R16 is basically the same, you just can't see the cam. (Another reason I always prefer OHC to pushrod tech.)

Don't over think this. It's easy as can be on the U20.

j

[svwilbur]

Mike,

ok so you do it at TDC. wiki says TDC plus 1/4 turn of crank pully which I think is 1/8 turn of cam. wiki does that to make sure they are fully closed.

only #1 has a TDC marker on crank pully, oh maybe #4 lines up there too?
but #2 and #3 dont so you just use relative position of rotor and cam lobe position?

you cant really see the valves. just the springs and rockers. rockers are loose at TDC.

you say my pully is off some based on what/why? my rotor position or that at the TDC mark my pistons likes to move backwards sometimes when blowing air in for a leakdown test?

looking at the cam lobes it appears that for about half the cam revolution the valve should be closed so setting the gap should work anywhere in there but the other valve is some number of degrees off from it, like 90-120 degrees? exhaust closes before intake does. so at TDC the exhaust valve is getting ready to open and intake just got closed in its cycle. but both should be fully closed I guess.



something wierd that I notice and dont understand (I dont have any experience or knowledge of valve movement/engineering ) when I do the leakdown tests and have the cylinders at TDC or a little after and I put pressure in the cylinder and increase pressure slowly often the air will leak out the intake valve until I get to 35-45 psi and then you hear a valve or something slap closed and psi comes up (leak is less) up to that point the psi is down 15 or 20 psi and then it shuts and is only down 1 or 2 psi. there is no cylinder or cam lobe movement at that point. just a thud and the leak goes away. what causes that?

so it seems like the valve is not fully closed by the springs lifting them up?
maybe it is just something to do with blowing air in the cylinder. but all the cylinders do that usually if you start pressure low at 10 psi and increase it up. then at 30-45 psi it closes (you hear a thud in the engine) and psi jumps up in the cylinder, the leak goes away.

so do the valve springs not fully close the valves when the rockers and cams get to the loose position? is there some slop?

or what would cause this thud and leak/no leak symptom when I increase air pressure in a cylinder during a leakdown test?

or is that thud a result of maybe my valve lash adjustment is too small and the valve is not fully closing without the cylinder pressure? I tried adjusting cold and I think I am getting them a bit too tight. im trying for .006 and .008 like gregburrows uses but not sure if im getting them right all the time. I checked them hot and they increase to about 8 and 10. maybe less.

so maybe I am not loose enough? and that causes the thud when I get enough pressure in the cylinder to fully close the valve?

my rockers are loose when the lobes are up in the 10 and 2 or 11 and 3 oclock positions. you can wiggle them side to side. but maybe they still have downsard pressure on ths valve and spring?

I don't know. that thud is just another wierd thing I noticed and dont understand.

quite the learning experience.

[svwilbur]

The order of adjustment doesn't matter Stacey. Timing pointer and rotor position is not relevant for adjusting the valves. All that matters is the cam lobe position relative to the rocker arm.

With the lobe up between 11 and 12 oclock, the rocker is at maximum clearance.

Pick one lobe that is up at 12 o'clock or so and do that one. (Write down the number as you go 1-8) Notice that one other lobe on the cam will be up as well. Do that one. (Write it down)

Now rotate the engine so a different pair is at 11-1 oclock. Repeat.

Do this 4 times and you are done....

What Mike described for the R16 is basically the same, you just can't see the cam. (Another reason I always prefer OHC to pushrod tech.)

Don't over think this. It's easy as can be on the U20.

j

jt68,

so you just do lobe position in its extreeme CLOSED position at 11-12 ish as the place it pushes on the rocker is 180 degress from that as the bottom of the lobe angles toward the driver side a bit at the 5 o'clock position (where it makes contact with rocker). and you use that position for both intake and exhaust?

do you do them hot or cold?

it seems to take a while for me to do them so the hot ends up not so hot by the time I am done.

I assume you take note of which type of valve it is and set intake and exhaust at different settings?

do you use .008 .0012 hot ?
or .006 and .010 cold ?
or .006 and .008 cold ?

after doing it cold do you recheck them hot to make sure the are set to 8 and 12 or 8 and 10?