TD42T Piston protrusion

[Andre Steyn]

Good morning everyone, what is protrusion of the pistons above the sleeve. I need to remeasure the pistons so as to know If my 1.25 head gasket is correct.

[ricster]

Piston protrusion or sleeve protrusion? I just want to make sure

[Andre Steyn]

Hey cedric, Sleeves I know are 0.02-0.09 what exactly? Also what is the piston protrusion the deck hight, maximum of the piston above the liner.

[ricster]

Depending on the head gasket used

1.15mm head gasket for piston protrusion of up to 0.118mm
1.20mm head gasker for piston protrusion between these sizes 0.118mm to 0.168mm
1.25mm head gasket for piston protrusion between these sizes 0.168mm and bigger. It shouldn't be bigger than 0.05mm bigger than 0.168mm ( total 0.218mm) otherwise I think you could run into problems. I don't know if you can get thicker head gaskets, or even if that is a good idea.

[ricster]

Those sizes would be from the block top to piston top. Considering that both the cylinder head surface and the piston/block height is almost flush.... I went with the slightly higher head gasket on mine to make sure. I am amazed that the two surfaces don't come into contact with each other with virtually no gap between the two surfaces.....hahaha.... The loss in compression ratio between the slightly higher head gasket and the correct size head gasket I doubt will make any difference to the 22.7:1 compression ratio

[Andre Steyn]

The information I found on patrol forum aus was that max protrusion was 0.177/7thou. So the 0.168 measurement on the 1.25 gasket would be in order, I really don't want the pistons to be topped. Got the set of Nural (ae) pistons with goetze rings on saturday, huge difference between the other brands and nural they're heavier as well.

[ricster]

That's brilliant mate !!!

If the piston is heavier then that hopefully means that the piston crown is thicker. That is a definite plus!! Heavier pistons mean more torque i guess....hahahaha. Are they Alfin rings and pistons?

[Andre Steyn]

Jip keystone with alfin also I noticed it has an improved oil gallery in the crown which not even the original factory pistons had, so therefore improved cooling via oil! And also the piston has been coated with a friction reducer.

[ricster]

sweet !!!!

Post a few pics of them.

[Peter Connan]

Andre, everything manufactured has a specified tolerance. It means that if it is within the two limits, it will be fine. These limits would already have a safety factor built in, so if you are in the specified tolerance you will be fine and you needn't spend lots of time and effort getting it closer than that.
Since a human hair is generally about 0.07mm thick, you can see that the specified tolerance is already very small.

As for heavier pistons, personally I don't like them (but I am a petrolhead). All they really do is to increase the loads on the crankshaft, conrods and bearings exponentially.

The pistons tend to fail due to changes in their molecular structure due to high temperatures, and adding a couple of mm to the crown thickness makes little difference to this, so just keep your EGT's within limits and you should be fine...