Author Topic: How do you check piston to valve clearance on hydraulic lifter engine  (Read 684 times)

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ace.cafe

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I suggest re-checking the free drop of the intake valve. I don't think that I have ever seen a head with as little free drop as .068".

And truthfully, I can't imagine the intake valve in that package is actually going to be more than .280" open at TDC, when the full lift is only .448" at 110 degrees later.

Something is not sounding right. A re-check is suggested.

The squish gap sounds like you have that nailed just right. :)


gashousegorilla

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Thanks for all the advice guys but I dont think  this project will work. I measured a few things as accurately as I could with only a dial indicator and micrometer. Final squish 1.1mm (.044")  measured with soft solder on piston.  Inlet valve free drop   1.7mm (.068") these 2 figures should be accurate .  Then  measured inlet cam lift at TDC as 2.56mm ( .102") this figure may not be accurate  but should be in the ball park. This was measured by placing dial indicator with extension rod down the pushrod hole of barrel onto the outside of the lifter  (head was off at this time) then rotating the engine several times  noting the distance lifter moves from base circle to TDC position. Factoring in a rocker ratio of 1.28 there will be interference. I hope I'm working this out wrongly.


    Free drop on a Bullet valve is 5mm...  it should be slightly less  I imagine with a GT valve, because they are a little larger.  I'm assuming you are factoring in your head and base gasket here ?  Also..  If you measured from the outer rim of the lifter  ?  There is a mile of difference between the outer rim of the lifter and down to the cup where the  ball end of the rod sits.  I measure 1.6 mm there.   Also...  if you have a stock dished piston, when your intake valve opens, it should move in towards the dish, if it is like the Bullets.   If you want be 100 % sure ? .... I'd Clay that motor.
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


Jako

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Yes obviously I'm doing something wrong.  GHG when I'm indicating from the outside of lifter I'm just measuring the cam lift from bottom to TDC  to determine valve lift not pushrod length, so shouldn't make any difference should it ?
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


gashousegorilla

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Yes obviously I'm doing something wrong.  GHG when I'm indicating from the outside of lifter I'm just measuring the cam lift from bottom to TDC  to determine valve lift not pushrod length, so shouldn't make any difference should it ?

   Lemme think about it ?  Hahaha !   This is unconventional way of doing things  !   ;)   Yes... lift is lift in this case.  So it shouldn't make a difference.


  I do think you are close Jako...  And if I'm following your math correctly and in round numbers.   Your piston is down in the hole at TDC .044"... measured around the outer edge of the piston.  Your total valve lift at TDC is  .131 "....so you need  .087 " or there or about  more room.   If you look at the spec's on that Hitchcock  sheet, they are checking the cam timing with 1 mm or .039" clearance.  That's almost half the height of your  .102 " cam at  TDC  . With Hydraulics pumped up or on that outer edge of the lifter , your going to see more lift at TDC  then they show in that sheet.  There is no clearance or lash with Hydraulics...  I think they include that 1 mm as a fudge factor on the cam timing.Your cam timing is going to vary a little bit with Hydraulics, depending on when the lifter locks as it is going up the ramp.   It would be MUCH more helpful  if they gave their timing in both advertised and at .050 lift.     

  The dish depth on a Bullet piston at least, is...071 "   Not sure if it is that same on the GT now !  So that's .016 " .   I think it is going to depend on the valve angle and the dish in the piston.  Whether or not the bottom of that valve  clears that inner edge of the flat area around the piston and as it enters the dish.     Again, clay is the way I think..
« Last Edit: March 12, 2019, 08:24:26 pm by gashousegorilla »
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


ace.cafe

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Okay, I did the multiplication wrong for the lift in my last post, and GHG gave the correct lift figure at TDC of .131" including the rocker ratio.

So, since the GT and UCE heads being the same,  and GHG says 5mm(.198") free drop on a Bullet, that means .067"  clearance around TDC.

 Now, let's look at the valve being about .050" larger than a 500 valve, and figure a worst case of half that in your situation. Take .025" off your clearance margin, for a new figure of . .042" clearance around TDC.

And let's figure in another .020" lift in case piston dwell allows a little more lift on the valve before it starts going down. So, that takes clearance down to .022".

But, we have .040" crushed head gasket clearance with the head on, so we can add that back to the clearance margin, and get .062" which is the correct suggested clearance safety margin for an intake valve.

Remove .039"(1mm) for the 1mm clearance regimen that they use for timing specification, and get .023" for clearance. This is too small, but it won't hit the piston.

BTW , the reason Hitchcocks specified the cam timing at 1mm clearance is to simulate the timing figures at .040"(mm) which is the metric standard that is used in place of the US standard of valve timing specs at .050". Just a convention of measurement.

So, I concur with GHG to run a clay test to see actual clearance. What I would do first is put all the new parts in and do a very slow and careful rotation of the engine over TDC, and if you feel any resistance happen, like a valve touching, then back it off to relieve the touching. Then you know it touches. If it doesn't touch, the you have at least some amount of clearance.

You could  put a clay disc that is .060" thick on the piston in the location where the intake valve will be closest. Put the head back on and turn the engine over TDC on the intake stroke. If there is no mark in the clay, you are good to go. If there is a mark, you need to measure how deep in the clay that the mark is.

In reality, rocker ratio is rarely as advertised. It is probably less.

If you run into a problem, just carefully grind a clearance relief into the piston where the valve would touch. Make it just deep enough to give .060" clearance, which is the accepted clearance safety margin for intake valves.

Always make pushrods preload less than the safety clearance margin, so if the lifters pump up from valve float, they cannot be pushed up enough to make the valve hit the piston.
« Last Edit: March 13, 2019, 07:31:29 am by ace.cafe »


Jako

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Data base errors are killing me
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


Jako

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Gaskets are included in all those calculations
Just redid the measurements .Valve drop is .068"  I'm confident in that . Cam lift is difficult for me but again I placed dial indicator down onto lifter and rotated engine , lift started around 30 deg BTDC and reached .80" at TDC  then increased to .100" before downward piston movement could be detected,  this was repeated multiple times with consistent results.
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


Jako

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With rocker ratio this will give between .102" and .128" valve lift at TDC
With gaskets in place  squish is .044"  and free valve drop of .068 for a total of .112"  Ace is it safe to dremel a relief in the cast piston ? it shouldn't need much as it will run into the dished section  . Also thinking of the Wossner forged piston with valve reliefs.
GHG the valve will catch the flat section of piston before it reaches the dish
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


ace.cafe

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Yes, it is safe.
Just don't go deeper than you need to just get .060" clearance.  The relief also needs to be wider than the actual valve because the valve does vibrate and flex some during operation. I would put about .020" extra side clearance in the relief to account for that.

The valve angle is about 26.5 degrees, so try to approximate that in the little half-moon shaped relief cut that you make in the piston crown. Soften all cut edges to prevent hot spots from forming.

Otto did it on his GT piston when he installed our head, and it came out fine with no drama. I don't think that you will have any trouble.


Jako

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My calculation on valve lift wasn't to far off the money, I just got these figures from Allan at Hitchcock's
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


Jako

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Thanks Ace  , a relief seems to be the answer . So no need to check the exhaust clearance. ?
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


ace.cafe

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Thanks Ace  , a relief seems to be the answer . So no need to check the exhaust clearance. ?

Might as well check, as long as you are doing all this anyway.
I haven't seen the need to worry about the exhaust, but our billet heads are so different that I can't tell you to not check.  It probably won't need it, though.

If you find it closer than .100" for the exhaust, then make a relief for it that will give the .100" clearance. The recommended safety margin for exhaust valves is .100".

Tom


gashousegorilla

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    You can use lite weight checker springs installed temporarily  and some clay at the same time for those valve reliefs Jako.    You will see contact with the piston , and then measure the deflection on the valve stem... then add your .060 to that number .   And in the clay, it will leave a starting pattern , so you know where to grind in .     Mark the center of that pattern,  then take your valve and center it on that mark.... line up the stem, then trace it out.   You will find that the valve is not centered over the piston , the valves favor the right side of the motor.
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


Jako

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Thanks Dan and Ace  your knowledge is appreciated. Cut the valve relief in piston and engine is running , just waiting for a break in the heavy rain  so we can road test .  Hopefully the PCV map provided by Hitchcock's for these cams and mods will run OK . 
On another topic  do you have  theories on why the  exhaust valve guide would be totally worn out in only 4000 km ,I assumed it was from  lean fueling   but the engine shop guy thinks the piston would have been damaged if that was the case .He thinks it may have been  faulty  from the factory.
B5 2013 ,Honda CT110 2011, Honda C90 cub,  C5 (wife's bike)


ace.cafe

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Glad it worked out well for you.

Regarding the exhaust valve, the typical causes could be lack of oiling, bad geometry, or bad clearance set up during manufacture. Or any combination of those.

Overheating the valve would cause lack of oil(burnt off), so that may have been a contributor. Very often, the geometry of the rockers is pretty bad. We saw a lot of bad geometry in the Iron Barrel engine rockers with similar block system.

It was good to get that exhaust valve out of the engine before it failed. A lot of them fail.