Author Topic: Cylinder Shims  (Read 11256 times)

32 coupe

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Re: Cylinder Shims
« Reply #15 on: February 26, 2014, 09:36:44 PM »
After looking back at the posts I wanted to clairify.
When I said less than .001 I meant on the top of 1 piston from side to side.
I think a few thousands differance in squash from one cylinder to another is fine.

Doc
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38ac

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Re: Cylinder Shims
« Reply #16 on: February 27, 2014, 03:54:31 PM »
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  
I have been reading along here trying to decide if to keep my trap shut or speak on the matter.
 Truth is,  Nobody on this side of a computer screen can honestly say if .004 is good enough or not on any particular engine. It is entirely possible,, no actually it is probable  that shimming the squish to exactly even would NOT be the thing to do. How is that??? Because the machine work on your Indian engine only looks flat, and it only looks square. The facts are block isn't machined square, the crankcase isn't either. The head gasket only looks like it is flat meaning the same thickness all the way across. I have never seen a head that had a flat deck as shipped from India and after it has been torqued down they move around even more. I have never measured a used head gasket that was closer than .004 from being flat. Have you had the rod checked?? bet ya it isn't straight. What about the wrist pin bushing? was it installed and sized correctly? likely not.  How many have ever bolted a  cylinder head down on a known flat plate using the gasket  intended for use and squashed some lead to see how even things are?  This test can give a difference of .010 from side A to side B and the plan is to fix it by cocking the base around with half gaskets around so the assembled clearance distance is the same??  Jig or no before you shim the block around try changing over to a spare gasket and check again, the toatl distance will change as will the difference side to side. The GTG gaskets are much better in this respect. The pistons are usually right on and a person can take them out of the equation.  The prim and proper route would be to re-machine the entire engine to tolerances that allow you to use .00?? whatever for your squish tolerance side to side.  BUT as received from India trying for a .001 side to side squish is like applying rocket science to a rock boat, it dont work.

So what does a person do?
Think about it. If your parts are new or not worn the piston has .006-.010 clearance to the cylinder wall. I have already stated that the pistons are usually dependable, measure your pin heights if you have doubts. And you are going to use the wrist pin as a lever to cock it around in the bore and correct all the other problems??
Only the worst of the worst engines need things like half gaskets under the cylinder and you do not determine that need  by measuring squish. What you do is assemble the short block without the head or piston  rings or gaskets under the block. Spacers for the head bolts can be anything from hardwood to washers. it doesn't need torqued just snug so  it doesn't move. While rotating the crankshaft I watch the rod for side to side movement. this requires a mirror and some patience. I usually do this prior to installing the cam or ider. If the rod doesn't go back and forth on the wrist pin then you should NOT be using half gaskets period. In lieu of remachining the block and crankcase half gaskets can be used to correct errors that cause the rod to move side to side as the piston travels up and down ONLY. Because of the other things mentioned above squish distance will very likely vary from side to side. Average it from side to side to come up with a figure.  .040 one side and .050 the other would be .045. etc.
Hope this helps some of ya'll out,
Butch
« Last Edit: February 27, 2014, 06:38:13 PM by 38ac »
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Tom

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Re: Cylinder Shims
« Reply #17 on: February 27, 2014, 06:01:36 PM »
Some very good points there Butch!
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

38ac

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Re: Cylinder Shims
« Reply #18 on: February 27, 2014, 06:22:06 PM »
Thanks Tom, When I get the jigs finished for the boring mill I will be able to mount a CS or clone  crankcase by the main bearing housing bores and have crank shaft centerline square to the spindle. From there a light cut on the cylinder mounting area will square things and eliminate the concern. This is an area of huge error in most of the Indian crankcases but doesnt help the guy out in the bush who is trying to get his engine up and running. Watching the rod move has worked for me, it just kinda goes against my grain if you know what  mean? ;)
« Last Edit: February 27, 2014, 06:29:56 PM by 38ac »
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32 coupe

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Re: Cylinder Shims
« Reply #19 on: February 27, 2014, 06:55:20 PM »
38ac,
I could not have said it better !!!
Doc
« Last Edit: February 27, 2014, 08:57:02 PM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
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"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: Cylinder Shims
« Reply #20 on: February 27, 2014, 08:39:52 PM »
Thanks for your insights, Butch.  Good to know the pistons are usually true, as without that we are lost. 
I measured my connecting rod small end to cylinder side at the top and bottom of travel with the head off to get an idea of how much lean was needed, it was a pain and I don't suggest that method.

After running it for a few hundred hours with the shim, I took it out and I got less side cylinder hone mark wear,  so there was more going on that just cylinder deck misalignment. 

I can attest to the connecting rods NOT being machined with much effort for accuracy and alignment. I have two and neither are right, so I run the one that fit the crank more uniformly by plastiguage. 

Watching the piston side to side movement on the wrist pin at top and bottom of travel seems like a good check. 

cranelift1

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Re: Cylinder Shims
« Reply #21 on: March 01, 2014, 04:48:03 AM »
Outstanding description Butch. I did measure the pistons and they were right on. I will check for big end back and forth on the crank and if it looks like there's no side to side play from top of travel to bottom, I will leave shimming of the jugs right were it is.
 Wow, it ain't easy. If it were, anybody could do it. ;)  Steve

38ac

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Re: Cylinder Shims
« Reply #22 on: March 03, 2014, 03:38:16 PM »
We set the squish on this 1949 6/1 yesterday. Top of block and head were machined here. Head gasket is NOS India. Had .002 side to side difference. I add extra gaskets at first and waste them to set the squish. Gonna miss this one  :-\  As nice a CS as I have been into.
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ronmar

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Re: Cylinder Shims
« Reply #23 on: March 04, 2014, 12:30:27 AM »
Because the wrist pin and pistons are usually correct, I think you will find that when you have no side to side piston movement on the wristpin, you will probably have nearly uniform squish across the top of the piston.  I would agree that the usual place for error in machining is the engine case bearing carrier holes.  That is where mine was.  All the other machine work was not too bad.  The liner was true, the cylinder bore was also true. These are also not very difficult to confirm without anything more sophisticated than a drill press tall enough to accomidate the cylinder and a dial indicator.   The bored holes for the TRB carriers were off by a large margine with the side away from the starting/IP side being lower. This was also easy to confirm with a straight edge across the deck and a dial indicator attached to a rod to measure down to the TRB hole.  Mine had a half gasket on the IP side under the cylinder to compensate for this.  I didn't like that, so I removed a little material from the top of the bearing carrier and welded a .030 shim for the TRB to set on. This put the crank parallel with the deck and then everything else was in line so it went together without the need for the half gasket...  A machinests precision level is a handy item to point out the errors quickly, but not necessary if you put a little thought into comparitive measurements... 
PS 6/1 - ST-5.

38ac

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Re: Cylinder Shims
« Reply #24 on: March 04, 2014, 01:23:57 AM »
 Yes, Some measuring first is needed to decide what you are going to call right, the boring for the block, or the main bearing bores.  If you try to adjust the wrong one a person could end up with a new yard ornament.  I own a Metro 6/1 DI engine that the surface for the cylinder block was turned on a lathe. Id like to see the set up the the Indians dreamed up to do that, or for that matter the lathe they did it on, LOL. With the boring mill I can correct either. The plan for the main bearing bores, if I ever have to do them,  is to bore them oversize and fit a ring to each housing.

Until you lay some straight edges and measuring tools on a Listeroid a person just cant believe how crooked and miss aligned they can be and still operate reasonably well.
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