4.108 liner protrusion/cylinder head

[PCBPort]

Hello all I'm currently rebuilding a 108 and recently got the block back from the machine shop. I checked it over today and two of the liners are at .031" and not the recommended .023-.027" the manual calls for. How big of a problem is this and is it worth taking it back to the machine shop over? The other two liners are right at .027/.028"

Also when i picked my cylinder head up they milled it flat after i told them it cant be decked. Has anyone had their cylinder head milled and did it prove to be a problem?

[model 10]

Man o man. I don't think you can do much about the liner height. The gasket should handle it anyway. How did they surface the head? If they just put it on a belt sander to clean it up, it would probably be OK. If they removed the combustion chamber plugs and ground or milled the head you may have to get different pistons. You need to find out the valve height to start with. If they got that right, a class S piston has the right height. If not, you have several choices in pistons and one of them you can machine to any height.
So, figure out valve height (depth) and piston height and then decide

[PCBPort]

Originally Posted by Ecos

Man o man. I don't think you can do much about the liner height. The gasket should handle it anyway. How did they surface the head? If they just put it on a belt sander to clean it up, it would probably be OK. If they removed the combustion chamber plugs and ground or milled the head you may have to get different pistons. You need to find out the valve height to start with. If they got that right, a class S piston has the right height. If not, you have several choices in pistons and one of them you can machine to any height.
So, figure out valve height (depth) and piston height and then decide

I can take the block back and have it pressed home i just need to know if .004" is too high over what the book says.

combustion plugs were left in and milled along with the deck. He doesnt know how much he took off. i know i know.

What do you mean by find valve height? how much the valve opens at max cam lift? it has brand new guides, valves, springs, retainers, and seals.

[model 10]

Not sure they can be pressed in further. They may need to be removed and re fit. You may not be able to re-use them so that might mean new liners. There is some wiggle room in the gasket crush.

There is no combustion chamber in the cylinder head, just the valves in a flat surface. The lower the valves, the lower the compression. When you grind valve seats you only have so much you can do to keep the valve height up. New valves are the best way to maintain compression. But if they have ground much from the head surface, you would need to install shorter pistons. There is not much leeway in piston height.
All you can do is measure things and see what you have. I doubt you are going to get the shop to re-do everything without knowing what is what.

[PCBPort]

Originally Posted by Ecos

Not sure they can be pressed in further. They may need to be removed and re fit. You may not be able to re-use them so that might mean new liners. There is some wiggle room in the gasket crush.

There is no combustion chamber in the cylinder head, just the valves in a flat surface. The lower the valves, the lower the compression. When you grind valve seats you only have so much you can do to keep the valve height up. New valves are the best way to maintain compression. But if they have ground much from the head surface, you would need to install shorter pistons. There is not much leeway in piston height.
All you can do is measure things and see what you have. I doubt you are going to get the shop to re-do everything without knowing what is what.

I was told it was around .003" to get the head flat again. When he put the new valves in im sure he took off a couple thousandths to get a fresh seat for the new valves. the pre-combustion chamber inserts were also left in and milled flat.

So there is no just having him press the liner a little further down? why cant that be done on a insert that was pushed in place to begin with.

[jimbunyard]

Not exactly sure how milling the head could require you to use shorter pistons, but if you've paid the shop to machine the block, the liner protrusion should all be the same.


That being said, not so sure if .003-.004" is really enough to worry about though.


Likewise with the head, .003 is not very much, and as long as the valve protrusion from the head surface is in spec, you shouldn't have any problem. I don't think .003 is going to upset the valve train geometry.

[model 10]

I'm a little iffy on the wet or dry liners. Some have a seat at the top and won't go down any further.
There is no regular combustion chamber. The piston is flat and so is the cylinder head. The only space is the clearance between the piston crown and the cylinder head at TDC. The depth of the valve heads is important. If you mill the head the valve depth will be less. Pistons come in about 4 different heights so you can get the corect clearance and compression ratio.

[PCBPort]

Its dry liner with no lip.

4.99 and 107s are wet liners.

My guy said he gound the valve seat down to make up for the milling but i didnt know if that was the only thing that mattered.

[model 10]

He is only making a guess but it should be ok. It would be pretty hard to figure out exactly. That may be the reason it's not approved by Perkins.

[jimbunyard]

On the 4108 the combustion chamber is in the head. The valve recess from the surface of the head should be .048".

From the Perkins service manual http://www.google.com/url?sa=t&rct=j...vAxdQCPNG0nakC

If the liners have a depth limit and are pressed there, it should be a simple matter to machine them all to the same level, if you wish to pursue it that far. Three thousandths is about the thickness of a sheet and a half of notebook paper, so it could conceivably interfere with getting an accurate and uniform head torque.

Not saying it will, just that it could...

[Wotname]

Originally Posted by PCBPort

Hello all I'm currently rebuilding a 108 and recently got the block back from the machine shop. I checked it over today and two of the liners are at .031" and not the recommended .023-.027" the manual calls for. How big of a problem is this and is it worth taking it back to the machine shop over? The other two liners are right at .027/.028"

...........

Welcome aboard CF, PCBPort.

I can't tell you if this is a big problem or not but I would not be happy to accept these errors. If the manual calls for .023 - .027, they are really saying it should be .025 +/- .002. You have two liners at +.006. That's 3 times greater than what is called for.

The manual sort of suggests the gasket can accommodate a 4 thou variation but....

This is time to get it right; if you leave it and it doesn't work out, then you will have a big problem.

[Scubaseas]

Originally Posted by PCBPort

Hello all I'm currently rebuilding a 108 and recently got the block back from the machine shop. I checked it over today and two of the liners are at .031" and not the recommended .023-.027" the manual calls for. How big of a problem is this and is it worth taking it back to the machine shop over? The other two liners are right at .027/.028"


Also when i picked my cylinder head up they milled it flat after i told them it cant be decked. Has anyone had their cylinder head milled and did it prove to be a problem?

Take it back to the machine shop. The lower shoulder of the liners can be cut or the top of the sleeve can be cut. .006" is NOT GOOD you will blow out the head gasket or crack the head. Decent machine shop should be able to get it withing less the .001" between liners.

Depending on how much they took off the head you may be able to buy thicker head gaskets. If they only took off 5 to 10 thou you should be fine BUT all four of your liners have to be the same height.

43 years ASE master mechanic. Advice worth what you paid for it.

[a64pilot]

Originally Posted by Wotname

Welcome aboard CF, PCBPort.



I can't tell you if this is a big problem or not but I would not be happy to accept these errors. If the manual calls for .023 - .027, they are really saying it should be .025 +/- .002. You have two liners at +.006. That's 3 times greater than what is called for.



The manual sort of suggests the gasket can accommodate a 4 thou variation but....



This is time to get it right; if you leave it and it doesn't work out, then you will have a big problem.

This, and I’d dry fit the head, tighten the head bolts loosely, no gasket and turn the engine over by hand and see if the valves hit the pistons. Leave injectors out of corse so there is no compression, if it binds, stop.
You could also install the head gasket and use a thin layer of putty on a piston to see how much clearance there is between the piston and valves.

An issue is I don’t know how much is required. There is some stretch of a rod at operating RPM of course, how much?

[model 10]

The liner height has nothing to do with piston to valve clearance or compression. The copper sandwich head gasket is plenty thick and the liner sticking up a extra few thou will have no effect on either of those issues.
I would think about putting the head on without a gasket and pressing the liners down a bit

[PCBPort]

Originally Posted by Scubaseas

Take it back to the machine shop. The lower shoulder of the liners can be cut or the top of the sleeve can be cut. .006" is NOT GOOD you will blow out the head gasket or crack the head. Decent machine shop should be able to get it withing less the .001" between liners.

Depending on how much they took off the head you may be able to buy thicker head gaskets. If they only took off 5 to 10 thou you should be fine BUT all four of your liners have to be the same height.

43 years ASE master mechanic. Advice worth what you paid for it.

My head guy will only take off enough to make the head flat again and he said he probably took off .003" i know thats negligible, but it still has had me worried since he told me.

The liner aspect im not very happy about though... I've read too many storied on forums with cummins diesel having the liners being slightly too tall and cracking the sealing ring on the gasket or cracking the head. My method of measuring might not be very precise, striaght edge on the liner and feeler gauges, but i shouldn't be getting .006" more than what i told him i wanted, .025". Does anyone know what the deck height variation allowed is? ive searched but i dont think its listed in the book along with piston to cylinder wall clearance.

It took almost 3 months to get my block back. He lost my fuel pump brass bushing thats almost $60 for a used one and now i have to disassemble some stuff off the motor to bring it back to him. I wish there was more than two terrible machine shops in panama city.