4.108 liner protrusion/cylinder head

[Scubaseas]

If you want to do it right use a torque plate and hone the liners before you reassemble the engine. Do not use your head to push in the liners. It's a good way to warp, scratch or crack your head especially if all the liners are not to spec height. If you don't have a torque plate two lengths of some heavy angle iron with holes drilled in it for the head bolts will work or even four fender washers around each head bolt to seat the liners. A press would be OK too. All your liners need to be the same height. Either you have crud between the liner and block or you need to machine the liner which is not that unusual. I doubt they cut enough off the head to be worried about valve clearance but modeling clay on the top of the piston and hand crank over the engine should show .040" or more clearance. If not machine the seat lower or notch the pistons but it's highly unlikely you will need to do this.



If you don't hone your liners you will get swarf off the liner which will scratch the hell out of the liner, rings and the piston and cause oil burning at best.

[Scubaseas]

The way the manual shows for checking liner height is fine. Feeler gauges and a straight edge are fine. Liners should be hand pressed in. It should not take torquing the head down on them to get them seated.



If you have new liners you may need to size them by honing to your piston size. Have you measured your liner and pistons? It's quite possible you do not have enough clearance without honing which can prove to be problematic when the engine reaches operating temperature.



I wouldn't be concerned about the head being cut.

[PCBPort]

The liners were bored and hone finished after being pushed in. All the bores are 3.1248"-3.1251" which is as good as it can get. There is no need for a torque plate on these motors they are not pushing 400hp. Not to mention good luck finding a shop that has a torque plate for a perkins. I would never torque the cylinder head on without the gasket to try and level the liners. Thats not a smart move.

Is there some reason why i cant take it to a buddys place and press the liner in the rest of the way with a press? or is it one push and done with these? There is no ring that prevents the liner from being pushed further, and the parent bore in the block doesnt have a bottom retainer to prevent the liner from being pushed all the way through.

[PCBPort]

Originally Posted by 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

The manual you linked to and my manual states .028-.039" for the inlet valve and .021-.032" for the exhaust valve faces below the cylinder head face on b.8. Two of the exhaust valves are at .009" and .014" so im going to take the head back and have the seat ground down a little more.

[model 10]

A thick bar using 2 head bolts would be an even push.
Those valve depths are crazy. He has more than a little to remove. I would want to see the valve seats myself. This guy is not doing a very good job.

[jimbunyard]

Originally Posted by PCBPort

The manual you linked to and my manual states .028-.039" for the inlet valve and .021-.032" for the exhaust valve faces below the cylinder head face on b.8. Two of the exhaust valves are at .009" and .014" so im going to take the head back and have the seat ground down a little more.

If you have an engine that is supposed to meet the smoke density regulations as noted at the bottom of the chart in my first post then that is correct. .048" would be great (for clearance at any rate), if .028/.039, .021/.031 is what you need and what you have is .009 and .014, you definitely have to get that fixed.





Not sure what you mean by deck variation, but the block height is 9.936/9.939". If you don't have at least 9.936, you'll likely have to get a thicker head gasket or machine a bit off the pistons. I couldn't see any different height pistons, but that doesn't mean they don't exist.

Probably the easiest way to match the liner heights is to get a .025 shim, place some on both sides of the liner and press the liner in until the tool you're using bottoms out on the shim, leaving the same .025 protrusion that the shim is made from. Why the shop didn't do this is a mystery to me. There shouldn't be any issue re-pressing the liner. If you can't get the proper tool to press the liner in, a 4" x 4" flat steel plate at least 1/2" thick should probably work, or possibly a 2" wide or so piece of at least 1/2" flat bar. You don't want to concentrate any forces at individual points on the liner...

[PCBPort]

Originally Posted by Ecos

A thick bar using 2 head bolts would be an even push.
Those valve depths are crazy. He has more than a little to remove. I would want to see the valve seats myself. This guy is not doing a very good job.

The guy who does my heads is different than the shop who did the block. My head guy has done around 10 sets of heads at very reasonable prices and always did a great job so im not to upset about him needing to remove a little more from the seat. But the fact that one exhaust valve is .014" too high has me worried about how much he did infact take off the head.

[PCBPort]

Originally Posted by jimbunyard

If you have an engine that is supposed to meet the smoke density regulations as noted at the bottom of the chart in my first post then that is correct. .048" would be great (for clearance at any rate), if .028/.039, .021/.031 is what you need and what you have is .009 and .014, you definitely have to get that fixed.





Not sure what you mean by deck variation, but the block height is 9.936/9.939". If you don't have at least 9.936, you'll likely have to get a thicker head gasket or machine a bit off the pistons. I couldn't see any different height pistons, but that doesn't mean they don't exist.

Probably the easiest way to match the liner heights is to get a .025 shim, place some on both sides of the liner and press the liner in until the tool you're using bottoms out on the shim, leaving the same .025 protrusion that the shim is made from. Why the shop didn't do this is a mystery to me. There shouldn't be any issue re-pressing the liner. If you can't get the proper tool to press the liner in, a 4" x 4" flat steel plate at least 1/2" thick should probably work, or possibly a 2" wide or so piece of at least 1/2" flat bar. You don't want to concentrate any forces at individual points on the liner...

Im talking about the variation in block deck flatness. aka the flatness of the block face where the head gasket sits on. I have a couple low spots around the liners up to .004" compared to the rest of the block that measure around .0025". Good idea with the steel plate. i found a 3/8" thick, 3.25" round plate on ebay for about $11 shipped and i can find a steel plate around the shed and drill it for 4 holes and use that to tighten the round plate down onto the liner. Ill Take some older harbor freight feeler gauge and cut the .012/.013 to make the shims and place it in 4 spots 90 degrees around the liner.

[Lepke]

Unless something has changed, 4108 piston tops have to be machined when fitted. British manufacturing practices at the time often required fitting some parts. Deck height and rod length can vary by small amounts. Fitting new 4108 pistons requires installing the pistons and then measuring each pistons height above the deck and then removing and machining each so all have the same height (and compression).
On some 4108 engines, failing to measure and machine piston tops can cause valve to piston clearance problems.

[PCBPort]

Originally Posted by Lepke

Unless something has changed, 4108 piston tops have to be machined when fitted. British manufacturing practices at the time often required fitting some parts. Deck height and rod length can vary by small amounts. Fitting new 4108 pistons requires installing the pistons and then measuring each pistons height above the deck and then removing and machining each so all have the same height (and compression).
On some 4108 engines, failing to measure and machine piston tops can cause valve to piston clearance problems.

Good lord i cant wait to have to pay more to this machine shop when it was already $200 more than what he said it was going to be.

Ive been referencing PorFin's old build on sailnet. On post 88 he installed the pistons and didnt measure the piston to deck clearance and his engine has been running strong. Hopefully when i check they will be in spec.

https://www.sailnet.com/forums/diese...rrative-9.html

[model 10]

This one reason to buy parts from a dealer who knows whats up. There are 4 different pistons available. If you have an engine that has proper clearances, a class "S" piston gives you the proper deck height. One of the pistons is a blank and it needs to be machined to the proper height.

[PCBPort]

Took the block to the machine shop today and he pressed it the rest of the way. Its still slightly off but i watched him press it to a .025" shim and bottom out. Im attributing it to deck variance. Now onto another problem the top compression rings end gap are off on all 4 cylinders and maxiforce was no help at all. book calls for .009-.014" and all 4 end gaps are .017-.018".

Piston protrusion gauge comes in tomorrow and i will check the piston height when the ups truck comes through.

Took the cylinder head back to the shop with the valve recess data. My guy said there would be no problem taking if off the seat as the exhaust valves are thin brand new from parts4engines. Hes also going to throw the orings on the inlet valves.

So all in all alot of work to fix a couple things that should have been done right the first time.