Lift on Cam #86

[Atazman]

Can someone please confirm the amount of lift  on camshaft # 86. 

Appreciate your help.

[JimVillers]

The #86 cam was used on the 230, 230S, 250S and 250SE.  The details on in the image.

[Atazman]

Thanks very much, Jim, for that information.  I'm trying to determine whether my intake valves are going to hit the pistons, so I need to know how far the intake valve has moved off its seat when the piston is at 5 Deg. ATDC.  Any thoughts on that, Jim?  Anyone have some advice to share?

My intake valve is only 0.010" above the milled surface of the head, so I'm more than a little concerned about hitting the piston.

Thanks again for the info....

[JimVillers]

Don ... My previous reply must have been lost during "our difficulties".

I could not find a specification for the Pagoda engine.  The 190SL engine requires 0.035 inch (0.6mm which is not much) between the closed intake valve and the flat of the head.  If it is less than that, it will begin touching the piston. 

If your pistons and intake valves touch, you can retard the cam one chain link, about 11 degrees, and the engine will run fine.  I ran my 190SL on a daily that way for about ten years.  You loose some power but it will run fine. 

[Atazman]

And I thank you again, Jim.  I was watching the forum very closely, so I saw your post before it was lost.  And my response to you was lost as well.  I'll try putting together that post again.

First..... I'm sure hoping that the 250 SL has a different specification for the distance between the intake valve (closed) and the flat of the head.  My measurements ranged between 0.010 and 0.022" for the 6 intake valves.

I went through an exercise of measuring everything before I installed the head, and here are the measurements I came up with.  I invite your comments (and other forum members as well) as to whether I am missing something with this exercise:  Here's what I measured:

"a" = distance from intake valve in closed position to flat of head:  0.010" min.
"b" = distance the piston is below the block surface measured at 5 Deg. ATDC:  0.015"
"c" = compressed head gasket thickness:  0.071"
        Note:  my new gasket thickness (uncompressed): 0.078"
"d" = distance the valve moved toward the open position by rotating the cam 8 Deg. from the position it was in when the valve just started to open.  This is the cam position when the crank is at 5 Deg. ATDC.  Intake valve opened:  0.023"
        Note:  I measured that my valve opened a total of 0.359" when rotated about 67 Deg.

Calculating the clearance between the intake valve and the piston at the crankshaft position of 5 Deg ATDC:

Clearance = "a" + "b"+ "c" - "d"

Clearance = 0.010 + 0.015 + 0.071 - 0.023

Clearance = 0.073"     I read somewhere on this forum that I need to have a min. of 0.035" clearance.

Basis this exercise, I put the head on and I have rotated the crankshaft a complete revolution.  I don't feel anything hitting, so tomorrow I am going to "light it up" and see what happens.

Thanks for your input..... and please let me know if you see where my calculations have an error in logic.

Many thanks........

[mbzse]

And I thank you again, Jim.  I was watching the forum very closely, so I saw your post before it was lost

Perhaps you saw my reply as well?  Anyway, the No for a M129 engine is 0,5mm minimum. For a ground seat and valve, 2mm is max.
(distance that the valve is lower (deeper) than head flat surface)
/Hans in Sweden

.

[JimVillers]

Hans/Don ...  Good discussion.

Don .... When you fire it up, if the piston touches the valve, it will sound like a loose tappet.  My guess that your thickness calculation of the head gasket is too large.  Hans specification equates to about 0.020 inch gap from the flat to the valve.  In any case, this is very close. 

[Atazman]

Hi Hans.......  No; I did not see your post before the deletion.  Thanks much for re-posting the specification.

Well, Jim & Hans, as you can see, I may have a complete head removal job ahead of me.  Within 2 hours I will know the answer....  I'll keep you posted.

Best wishes to you....

[Atazman]

Looks like good news, guys!!  I test drove my 250 SL........no sound of contact between the valves and piston.  In fact, it runs like a top and sounds very good.  I'm very much relieved, obviously.

Best wishes.......

[JimVillers]

Don ... Good news.  Now we know that 0.010 inches will work.

[JimVillers]

I found the specification for the 230SL while I was looking for something else.  The minimum distance between the face of the head and the crown of the valve is 0.4mm (0.015 inches) and the max is 1.9mm (0.075 inches).

[Atazman]

Thank you, Jim, for providing this feedback.  As I have stated......I have one valve only 0.010" away from the milled surface of the head.  Maybe my gasket thickness is all that is keeping me from doing damage.  I regret not taking the head back to the shop and asking them to make sure I have at least 0.020" between the valve and the head surface.  But.....I didn't.  Thankfully, I'm OK for now......but any carbon deposits on the valve may hit the piston. 

Best wishes....