Selecting head gasket thickness for turbo application (1 Viewer)

[lelandEOD]

1HZ:

How does one go about selecting the most appropriate head gasket thickness for a turbo application with modified internals? The factory service manual gives a protrusion test to select a head gasket of the appropriate thickness for an unmodified motor, but since I’m going to run lower compression internals, I’m not sure which head gasket to select. I have to confirm with my machinist, but I’m pretty sure he did not remove any material from the head face or deck the block.

Just going with the thickest available seems a little sketchy.

 

[Dougal]

Run the gasket which fits piston protrusion. Otherwise squish and mixing is impacted.

If you want to lower compression, then bowl your pistons. What is the engine?

 

[lelandEOD]

Thanks for the reply. I’m really lost on how to approach this since I’m changing my engine’s internals from the factory set up. The engine in question is a 1HZ to which I will be adding a factory CT26 turbo. I decided that since I needed to replace the oriinal pistons anyway (some were damaged by disintegrating pre-cups) that I would hop for a set of performance pistons from Engine Australia, along with A set of connecting rods intended for a turbo application.

If I go with Engine Australia pistons and rods, I’m not sure if I should still use the same piston protrusion procedure given in the FSM or if I would/should go with another approach?

I’ve had a couple people tell me to just go with the thickest gasket available since the goal is to drop compression... but that sounds a little haphazard to me.

 

[Nostradamus]

Thanks for the reply. I’m really lost on how to approach this since I’m changing my engine’s internals from the factory set up. The engine in question is a 1HZ to which I will be adding a factory CT26 turbo. I decided that since I needed to replace the oriinal pistons anyway (some were damaged by disintegrating pre-cups) that I would hop for a set of performance pistons from Engine Australia, along with A set of connecting rods intended for a turbo application.

If I go with Engine Australia pistons and rods, I’m not sure if I should still use the same piston protrusion procedure given in the FSM or if I would/should go with another approach?

I’ve had a couple people tell me to just go with the thickest gasket available since the goal is to drop compression... but that sounds a little haphazard to me.

which gasket did you end up going with?

 

[lelandEOD]

I ended up using a #5 head gasket as my piston protrusion was around .023". My block was faced by .007" and I ordered the pre-topped pistons from EA.

As Dougal noted, the head gasket thickness is dictated by the piston protrusion. I was operating on a set of false pretenses when I originally started this thread. At the time, I thought the Engine Australia 1HZ turbo pistons reduced the compression ratio; they don't.