Lead compression test

[taeuber]

Hello again.

Here is another question I have.
To make the »lead compression test«, does the cylinder head gasket have to be in place or should I remove it before testing?
I don't know if the distance between piston and head is with or without gasket thickness.

Thanks again
Lars

[Geno]

All gaskets should be in place and the head torqued down. Use 2 pieces of lead above the wrist pin ends. If you put several thin gaskets under the cylinder you can remove them one at a time to get proper clearance without removing the cylinder.

For Lister 6/1, 8/1 & 16/2 .....  0.060" - 0.065"
10/1 & 20/2............................ 0.080" - 0.085"
25/2 ....................... ................0.095" - 0.105"

Thanks, Geno

[cujet]

I put a twisted (4 wires) batch of solder down the injector hole. I then turn over the engine by the flywheel rim. The 6-1 clearance seems good about 0.045 inches. My 20/2 is set at 50 thousanths, however it got a bit tighter after the first run up and re-torque.

My head gasket was about 0.045 inches compressed. In my case, having some (0.005 inches) positve clearance without a head gasket ensures enough clearance with the gasket in place.

I also used the methanol/aviation gasket sealer on my head gasket to prevent leaks. So far so good.

Chris

[taeuber]

How comes there are different cylinder head clearances for the same type of machine?

My JKSON 12/2 had more than 0.080" on one and 0.075" clearance on the other cylinder.
I have changed that to 0.053" on both. Is that to few or to much?

In the manual the following is told:
- 0.040" - 0.050" for 6/1 and 12/2
- 0.075" - 0.080" for 8/1 and 16/2

Thanks
Lars

[biobill]

taeuber,
  Just a guess but I suspect on the higher RPM engines you need to allow for more crank flex and/or rod stretch as that big ol piston reverses direction

  Cujet,
 nice trick! I assume that you have DI engines?
   
                                Bill

[taeuber]

Hi Bill,

my question was more a question about the different cylinder head clearance for the same engine type.
Geno told me the clearance for the 6/1 should be 0.060" - 0.065" my manual says something about 0.040"-0.050" for the 6/1.

I think this has something to do with the presence or absence of the compression change over valve.

The trick with the solder through the injection hole works for the IDI engines to. I made it this way on my 12/2. The solder I used was thicker solder wire (3mm = 0,12") for water pipe installations.

Regards
Lars

[hotater]

Lars--

The original engines didn't have a liner and the top of the piston comes up level with the deck.  That means the clearance between the piston and the head is the thickness of the compressed head gasket.  The gasket will settle some after several hours of running and when re-torqued the gasket will be slightly thinner, hense the range of measurement. 

I set mine to .055 to start and it's usually .053 after re-torqueing.

Slick trick Chris.   

[taeuber]

Hi hotater,

my machine also has not this liner. But which clearance now is the right for a machine without this liner, the larger clearance or the smaller clearance?
I meassured a clearance of 0.053" and the piston comes nearly up with the deck.


Thanks
Lars

[cujet]

Taeuber,

The volume of the IDI combustion chamber is excessive on some Listeroids. Achieving decent compression ratio's is difficult when you are thinking about an 0.080 bump clearance. My engine has a bigger bore than standard and still cannot achieve 18 to 1 CR under any conditions deemed safe (enough bump clearance of 0.045 inches). This is with the COV in the start position.

Think about what I said for a minute, I have a COV, which should raise compression above optimal for start. I also have a bigger bore with a flat to piston. This should increase the CR also. Yet it is still TOO LOW.

I must give Hotater major credit for the head gasket trick, along with credit for some excellent advice on other subjects.

Chris

[hotater]

Lars--

If the top of the piston is level with the top of the deck at TDC then the clearance between the piston and the head is the thickness of the head gasket.....which is all that measurement given in the books is.

To get it right (since you don't have a liner in the cylinder) just add or remove spacer gaskets under the cylinder block until the top of the piston is exactly level with the deck.

The trick with the lead shot or solder wire is to calculate the same measurement without a depth micrometer and the math it takes to subtract the height of the liner from the amount the piston is below it.

SETTING PISTON/HEAD CLEARANCE--

In an engine WITHOUT cylinder liner---

Tools needed  to set up is a straight-edge and a set of feeler gauges.

  Run the piston to TDC, lay the straightedge over the top. 
Now, is the straightedge touching the deck or the piston?
 If there is a gap between the piston and the straight-edge, measure it with the feeler gauges and REMOVE a spacer from the bottom equal to that measurement.      If the straightedge rest on the top of the piston, measure the gap between the straight-edge and the deck and ADD that thickness to the gaskets down below.

Thats' all there is to it.

WITH cylinder liner, it's a little more complicated but not much. 

First measure the height above the deck of the liner using the straight-edge and feelers.  It should not be OVER .010".  .005 to .010 is good.
The piston top has to be level with the top of the *liner*, not the deck.   Use the same process as above, but use the liner top instead of the deck top as a reference point.

[Dail R H]

   Please permit me to demonstrate my total ignorance of all things diesel. Been following this thread,and ones pertaining to leaking head gaskets. It seems to me that the leaking gasket problem is caused by the protruding liners----right? If so ,why not machine off enough of the top of the liner to make it flush with the deck? Now the clearence is eaiser to check,and the head gasket leaks should not be so much of a problem. 'Course you might have to take the extra off the bottom of the liner instead.
   See how dumb I am. I'm sure it's not that simple ,but it sounded good in my head.

[hotater]

Dail--

Good thought, but the liner and the block have different rates of expansion and contraction so the liner needs to have about .005 to adjust.

Some Listeroids have more than .030 protrusion of the liner and head gaskets don't last long at all.

The FIRST fix is to take them apart and CLEAN the shelf the liner bears on, and the cooresponding shelf on the liner and put it back together.  Do this at LEAST THREE TIMES before believing it.  It's SO easy for a little piece of scrap to mess up the measurements.

[wirenutrob]

Hotater -

When I was putting things back together I noticed that My 20/2 was set up .010 below the liner top... I guess that is right; it comes close to what your measurements are.
Rob

[hotater]

Rob--

If you have .010 between the piston and the liner it means you have about .065 in the lead test...that means your compression ration is lower than it should be for clean running.    The proper set-up would be to remove .010 of spacer from below the blocks to let the block, with liner, to set down .010 further.

Try it the way it is and see how it works...if it's at ALL dirty burning I'd set it up to minimum clearance/highest compression.

Make spacers out of thin and thick paper and put too many in...then all you have to do is lift the block a little and tear out what you don't need.