Cylinder wall thickness vs head sealing

[Massive Type IV]

Themain problem with head sealing is having different expansion rates for the case, head studs, cylinders and heads. It is made worse by the unequal lengths of the upper and lower head studs, which gives them unequal expansion rates. This problem is multiplied by the "Non square"pattern of the entire stud arrangement.

When the cylinders grow in size, all these problems and their effects become much more apparent.

The reason Nickies work so well is that the studs they are designed with have the correct expansion rates for the engine, since all the materials now grow at more equal rates. When a cast iron cylinder is used it has a very different expansion rate and really can screw things up. alot of machining and hand sealing methods make them acceptable, but they are no where near what an aluminum cylinder is in the sealing department- no matter what you do.

As for sealing surfaces, as I have seen its a very small portion of the answer, many many stock engines have head leaks.......with thick cylinder sealing areas.....The 1.7 just isn't as prone because like I explained above, bigger bores make the problem more apparent.

I'm working on a small bore long rodded, long stroke Turbo configuration that will use a modified 1.7 cylinder and a different piston.....hopefully it will be a good combo and will be a Turbo that will not require Nickies for us to assemble.

as it stands now ANY Turbo or ANY engine with a bigger than 96mm Bore requires Nickies at my shoop.