[MGNZ]

Rebuilding a G16B to go into my Sierra and just found 2 hair cracks on cylinders 2 & 3 between the spark plug and valve seat. The cracks go down about 3 threads up the spark plug hole.

Anyone else seen this on their G16's? still run OK?

It looks like both cylinders cracked from where the thread exits the surface - assume it's a stress riser

[Gwagensteve]

Head cracks in g16B’s are super common.

My opinion is it’s time for a new head/motor. Sooner or later it will put coolant in the cylinder.

Out of interest, is it a vitara or baleno motor?

[MGNZ]

It came out of a vitara.

[Gwagensteve]

Thought so.

[MGNZ]

Are the baleno heads more reliable?

[Gwagensteve]

They are less prone to cracks. It was generally thought that this was due to balenos being used more lightly, having better castings, or being newer, but I have another theory.

Balenos have better coolant flow that prevents hot spots in the head - the full coolant flow passes enters the head at the water pump end and exits at the flywheel end. In a vitara, only the heater flow exits the back of the block, the primary flow is turned around and heads back to the water pump.

When people install G16B's in sierras, they hook the heater hoses up as they were in the sierra, but in a sierra the heater tap isolates the flow which prevents any flow out the back of the head. A vitara has heater flow at all times and in my opinion maintaining heater flow is critical to preventing head cracks in sierra G16B's.

I know this is off topic but assuming you complete your conversion it's worth considering to prevent further issues.

[MGNZ]

I saw your thread a while back about this and it makes good sense. I was planning on installing an external Y valve for the heater to get water moving out the back of the head when heater is off. I didn't realise that the G16 vitaras had flow issues in their factory configuration.

[Gwagensteve]

I think you could find a bypass heater tap which would solve the problem.

In my opinion the best solution from a cooling point of view is to use the rear mounted thermostat housing, but this is a pain to install and work on.