Cylinder to case gasket odd sizes

[mike sampsel]

Does anyone know if someone makes odd sizes of the gasket between the case and the cylinder? I know 0.25 and 0.5 are common. In need of 0.43 (ha) maybe I値l get lucky and the 0.5痴 I致e ordered will be skinny.

Just wonder about some non-standard thickness ones.

I think 0.43 gets me level with my one which is too high (by about .2, with a 0.3 base gasket). If I could find a skinny 0.25 gasket at about 0.1 or so, this too would work as I could lower the odd ball which is too high.

[lite75]

Try Cometic gasket

[dannobee]

LN Engineering has them.
But first things first. Did you measure to see what's off? If the cylinders aren't exactly the same height, is there some wiggle room to swap them around? If it's the case (most likely), are the surfaces spotlessly clean? Did you check deck heights first? Are the sealing surfaces of the heads all the same depth, or do they need to be flycut to clean up?

[mike sampsel]

Originally Posted by dannobee

LN Engineering has them.
But first things first. Did you measure to see what's off? If the cylinders aren't exactly the same height, is there some wiggle room to swap them around? If it's the case (most likely), are the surfaces spotlessly clean? Did you check deck heights first? Are the sealing surfaces of the heads all the same depth, or do they need to be flycut to clean up?

Wiggle room, seems one of my used 3.2 SS Carrera cylinders is taller than the other two. And since I set all my ring gaps to each cylinder, I知 inclined to leave them.

Aluminum case is most likely? I thought it was pretty clean when I did the piston/cylinder install.

Check the deck heights now with cylinders installed? How?

Not sure about sealing surfaces, but flycut would be done at a machine shop?

Thanks for your thoughts dannobee.

I知 leaning towards sending my cylinders to a shop to make them right this morning.

[dannobee]

Re: Case. Porsche machining isn't as precise as we use on race motors. And I get it, for the vast majority of production engines, it makes no difference. And things happen when put in service, things shift around.

But if you've measured your cylinders and one is sticking up proud, then you've found your problem. You don't really need a base gasket, you could always seal it with threebond and be done with it.

We check deck height by assembling the cylinder and using the cylinder holding nuts to clamp everything down, without the head. Then rotate the piston up to TDC and measure how far the piston is down in the cylinder. Your 6 cylinders should be close.

[Neil Harvey]

Originally Posted by dannobee

Re: Case. Porsche machining isn't as precise as we use on race motors. And I get it, for the vast majority of production engines, it makes no difference. And things happen when put in service, things shift around.

But if you've measured your cylinders and one is sticking up proud, then you've found your problem. You don't really need a base gasket, you could always seal it with threebond and be done with it.

We check deck height by assembling the cylinder and using the cylinder holding nuts to clamp everything down, without the head. Then rotate the piston up to TDC and measure how far the piston is down in the cylinder. Your 6 cylinders should be close.

I respectfully disagree with everything said here.

It always makes a difference, hence the issue at hand. Building an engine always starts with establishing that every parts is correct and to spec. Checking the case halves are of equal width, the cylinder base faces are flat and parallel. The cylinders are all the same length and the heads are the same heights.

Engines should be assembled dry with the case, cylinders, heads and cam housings with no internal parts fitted, checking the cams turn in the cam housings. This takes little time to check and saves a huge hassle later when the engine is all assembled.

Do not use glue to take up any differences!!!!!! That is absolutely a "no no" and expect problems if you do.

Do not confuse "Piston" deck height with "block" deck height. They are completely different. When measuring the block deck height, ( which is the issue at hand) the crank stroke, rod length and piston compression height make zero difference. Piston deck height is all about the stroke, rod length and compression height, which in turn become a factor is piston to head clearance and compression ratio.

To measure the piston deck heights per cylinder and use this a factor in making sure the cam with turn is wrong.

[dannobee]

Since I’ve been following his build, I think he was well aware of the difference of the two, regarding deck height and cylinder height. If not, I’ll let him respond and I’ll correct it.
And my experience building them at dealership level would be to take measure, and if off, obtain a new case. Clearly that isn’t an option for him. Nor did it sound like a new set of cylinders were in the cards either. That leaves only a few options.

[r lane]

Simple math and geometry usually. Pull a straight edge across the case to determine the integrity there. Mag cases turn into bannanas. Measure the cylinders. I use a Starette height gage and leveling plate. .0015'' differences will pass. Cylinder bases can be machined if necessary.

[mike sampsel]

Well you gentlemen are more knowledgeable than I for certain.
What I did today was placed temporary shims on top of cylinder number two, which is clearly lower than # 3. With these shims in place I then torqued all my head nuts to 11# ad the cam spins like a top.

I知 not too worried about case integrity on an aluminum SC case with only 115 miles and worked well before this adventure.

I measured the base gaskets and got 0.23 under the middle cyl, and 0.3 under number 3. I値l be checking again. But seems to me a judicious choice of base gasket thickness might solve my problem.