International Lancia Forums

Good question.

From the pics the size of the rings looks ok. If the angle of the bore is correct, the oversize of the rings should be equal everywhere. I fix the gasket to the block with a few drops of instant glue and put studs diagonally to guide the head when lowering it onto the block. Long stud at the last hole exhaust side. Short stud at the front inlet side. Then put the slightly thicker (8,5mm) head bolts on the ends of the other diagonal. Then remove the studs.

I am not always happy with the CAV pistons. The distance to the top of the block is not always consistent. As you notice the piston should never protrude from the block. I change thickness of foot gasket to make sure it does not. Better 0,1mm too low than 0,01 too high. If the highest point of any of the pistons is at the correct level, often the distance at other points may be lower.

Make sure that the foot bolts are the correct strength (10.9) and correct length and torqued equally preferably to the right value. This requires special tools.

Also make double sure that the distance between head and piston is never less than 1,2 mm. Put clay on one of the pistons. Put the head on without rockers (or without camshafts, the valves should remain closed.). Fasten the head with two bolts next to the cylinder where the clay was put on the piston. Turn the engine. I tape a stick of thick plastigauge to the piston. Some use solder tin. I think I may try that next time. The danger area is the edge of the chamber in the head. The diameter of the chamber is about 2 cm less than the diameter of the cylinder. Often the dome on the piston starts too early and the piston comes too close to the head. On the end of the compression stroke the air from the edges can no longer escape into the combustion chamber. Compression goes towards infinity locally resulting in detonation around the edge. It is usually not going to ruin the engine but it is the difference between between a rough noisy engine and a silk smooth Lancia engine.

In addition to Huib's advice, you can also buy thicker and more robust head gaskets, see for instance https://www.pieces-fulvia.com/gr4-head- ... 755484.htm. Of course, this is more expensive but also a lot stronger. Andrea

Thank you both. Huib, for the 1.2mm test with the head on the block - it would make sense that this is the thickness of the gasket if everything else so correct. If it is less I will need to get a thicker head gasket, as the rest of the engine is completely assembled now.

The distance between the head and pistons measured at between 1,0 and 1,2 mm today, so the engine builder will put a thicker gasket between the block and crankcase as per Huib's advice - thank you so much!

I do not have the parts themselves in front of me to inspect and feel, but I would probably decide to use some sanding paper on the sharp edge between combustion chamber and under side of head. If that is where the lowest value is. And if the fuel in your country is good quality.

I also vary the thickness of foot gasket but only to make sure piston does not protrude from the block. Not even one micron.

As Andrea says thicker head gaskets are available. 1.4 is good most of the time.

Dear Huib,

I know it is an old thread, but I have just found it. I will need to prepare a new low-end for my Fulvia, so I am really interested this information.

"Maybe the "hidden" bolt fastening the cylinder block to the crank case was forgotten or not properly torqued."

Clould you please let me know which is the "hidden" bolt?

Thank you in advance, Peter

It sits where the red arrow points. It is all the way down in the cylinder block. Not really hidden but if I ever forget to take out a bolt, this would be the most likely candidate.