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Author Topic: Cylinder Shims  (Read 11248 times)

cranelift1

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Cylinder Shims
« on: February 22, 2014, 11:28:56 PM »
The shims or gaskets that lay on the deck under the cylinders would not add up to the required distance needed for the squish (.045 to .050) to be equal on both cylinders. The ones Willem sent were .019, .021, or .023.  I was under the specification with one shim and over with two shims. I made one out of brown kraft paper added to one supplied shim  and the squish is now exactly perfect. Does anyone see a problem with using paper to get the correct height on the cylinders? Thanks, Steve

BruceM

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Re: Cylinder Shims
« Reply #1 on: February 22, 2014, 11:45:06 PM »
No problem.  I use a few typing paper shims, so that I can just lift the cylinder just slightly and tear one or two of them out to get to down to the right clearance.

Best Wishes,
Bruce

cranelift1

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Re: Cylinder Shims
« Reply #2 on: February 23, 2014, 12:02:23 AM »
BruceM,
 I should have asked before I installed and removed and installed again 4 times to get it right.  Next time will be a breeze. Great idea and thanks. Steve 

ronmar

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Re: Cylinder Shims
« Reply #3 on: February 23, 2014, 12:32:10 AM »
Yep, typing paper, craft paper, thin gasket material, all will work.  It is also a good idea to measure squish above each end of the wrist pin.  I use #7 lead shot out of a shotgun shell for this. I position the 2 pieces of shot on the piston above each end of the wrist pin, as close to the edge as I can.  I make sure I am not under a valve and I keep the shot in place with a little dab of grease to insure it dosn't roll around.  SInce the shot starts at a uniform shape/thickness, it presses out into a neat little easy to measure pancake.  The reason to measure at each end of the wrist pin is to insure the cylinder bore is perpendicular to the crank.  This alignment is the sum of a lot of things such as the machining of the crankshaft main bearing carriers in relation to the block deck that the cylinder sets on, the cylinder case itself and the bore in the cylinder that the cylinder liner sets in. IF all the machinework dosn't line up correctly, it will show as differential squish across the piston top.  if you get differential squish, that measn the piston is most likley traveling back and forth on the wrist pin.  If it is bad enough, it will run out of travel at the extreme top and bottom and can cause the piston to touch/scuff the cylinders.  It can also cause abnormal ring wear. 

The real fix is to properly machine all these parts to get the final piston alignment in the bore correct.  Or do what the indians do and use shims under one half of the cylinder or the other untill the difference in squish across the top of the piston is 0.  Many listeroids have half gasket shims and I believe the indians use differential squish to determine what size half gasket to use to get the cylinder bore perpendicular to the crankshaft.  The mis-alignment was quite large on my 6/1.  I opted to fix the mis-aligned crankshaft bearing carriers to bring it in line rather than use half gaskets...     
PS 6/1 - ST-5.

BruceM

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Re: Cylinder Shims
« Reply #4 on: February 23, 2014, 03:34:28 AM »
I wish Ronmar had written most of the technical manuals I've read.

Great explanation, Ronmar.  The grease tip is a good one, thanks.  I've used snippets of solder successfully, as well as lead shot.
« Last Edit: February 23, 2014, 03:36:44 AM by BruceM »

cranelift1

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Re: Cylinder Shims
« Reply #5 on: February 23, 2014, 03:55:45 AM »
Excellent description ronmar, I did use two pcs of solder on the piston out to the edges over the wrist pin. There was a small difference  (3 or 4 thou.) that I was going to ignore, but it sounds quite easy to slip a half shim in there. I'll be on that tomorrow.
 Thanks,  Steve 

32 coupe

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Re: Cylinder Shims
« Reply #6 on: February 23, 2014, 04:50:58 AM »
Don't feel bad, I had mine off a few times before I was happy with the squash as well.
I like to use the brown or tan legal shipping envelopes. The come in several different thicknesses as well. I oil them well and
then put in position. Worked well so far !
Doc
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

ronmar

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Re: Cylinder Shims
« Reply #7 on: February 23, 2014, 05:27:19 AM »
Bruce, Thanks...   I think I write the way I do because I too have had to wade thru a lot of really bad tech manuals:)
PS 6/1 - ST-5.

mike90045

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Re: Cylinder Shims
« Reply #8 on: February 23, 2014, 05:40:20 AM »
.... I opted to fix the mis-aligned crankshaft bearing carriers to bring it in line rather than use half gaskets...     

I just got Brain Freeze.  I don't suppose it's as easy as a bearing carrier alignment cam ?

millman56

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Re: Cylinder Shims
« Reply #9 on: February 23, 2014, 06:32:25 AM »
Well, it`s cold where you are.  ;D   

Clear, concise and waffle free description of an engineering procedure, nice one Ronmar.

Mark.

Horsepoor

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Re: Cylinder Shims
« Reply #10 on: February 23, 2014, 07:42:51 AM »
I used thick paper filing cabinet file folders. For me, these worked great, oh in they come in mean green too.
GTC 20/2 down rated to 850 rpm - ST 15
Metro 6/1 800 rpm on cart - ST 7.5

cranelift1

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Re: Cylinder Shims
« Reply #11 on: February 25, 2014, 04:52:00 PM »
The paper shims worked well. Difference is now less than .002. I could live with that, but what do you fellas think?.
As a side note, how much fun is putting those crankshaft counterweights in? I have large hands and those two outer weights just don't allow the use of two hands. Oh well, it's done. I suppose everything gets easier the more times you do it. Cheers lads, Steve

32 coupe

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Re: Cylinder Shims
« Reply #12 on: February 25, 2014, 05:10:51 PM »
What engine do you have ?? Did I miss that info ??
On the twins the thing to watch is the camshaft center carrier......the bore in the block on mine was too large. I used a piece of
brass shim stock and a litttle JB weld to take up the slack......as well as a brass gear and offset bolt...I only have 25 or so hours so time will tell.
Keep us posted
Doc
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

cranelift1

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Re: Cylinder Shims
« Reply #13 on: February 26, 2014, 06:21:01 PM »
Hello There 32 coupe,
 I have a 12/2. I noticed you mentioned "camshaft center carrier", did you mean crankshaft center carrier? Camshaft won't affect shims or cylinder aligning. I was wondering if the less than .002" difference was acceptable for piston to head claerance measurement.The center bearing carrier for crankshaft was nice, no play at all. The camshaft center carrier is also fine. Thanks, Steve

32 coupe

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Re: Cylinder Shims
« Reply #14 on: February 26, 2014, 09:25:13 PM »
Steve,
Sorry I got off topic. I was just pointing out to pay close attention to the cam and everyhing associated wih it.
Most of the problems with the twins have been in the cam area.
Also take a look at the valve guides, mine had 2 left heads so I had to swap guides in one head to correct that problem.

With that said I personally would like to see a closer tolerance than .002 differance on the head squash but other people
here would have a better answer. I remember mine came out to less than .001.

That probibly didn't help much but I'm sure others will chime in with more/better info.
Doc
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"