How to tell if a 12ht has alfin pistons (1 Viewer)

[gerg]

Thanks for posting that up. It sort of confirms that it's not an "if" situation, but rather a "how much".

 

[GTSSportCoupe]

Reviving an old thread. I was just searching around to see if anyone has posted pics of the damage that is common in the stock 12HT. I have rebuilt 5 and all have had this damage. Its been most severe in piston 1 and 2 in the ones I have done, and its always most prominent on the intake side (also where the injector is). I think the condition is accelerated by neglected injectors. Sticky and leaky injectors wash the cylinder wall.

Rebuilding one now. Piston 1 and 2 below. This engine ran OK. Sounded a little off to me but I dont think most people would have noticed.

Thanks for sharing your experience. How many kms were on the pistons shown above? This motor was at a stock tune?

Toyota's piston technology seemed to really improve around 1990, as the 1990+ turbo diesel engines don't seem to have this ring land problem.

 

[lynchmob]

Thanks for sharing your experience. How many kms were on the pistons shown above? This motor was at a stock tune?

Toyota's piston technology seemed to really improve around 1990, as the 1990+ turbo diesel engines don't seem to have this ring land problem.

This engine was unknown to me. Rebuilding for someone who had a conversion done 6-7 years ago. The engine was imported by someone else from NZ I believe. Sold as "low mileage" most likely.

The engine was stock as were the others I have done.

All the 12HT I have had were from AU and all over 300K (km) which seems low for this type of damage.

This damage does not appear in HZ/HD engines as those do have a hardened insert for the top ring.

 

[dare]

Thanks for posting. It's interesting it's just effected the top of the ring land. That shows it's not an outright cylinder pressure issue, more ring flutter.

It still strikes me as bizzare that Toyota didn't fit alfin pistons to the H series. Their other diesels of the era (even non turbo) had alfin pistons, as did virtually everyone elses.

Here's a pic of when it's left to develop.

 

[lynchmob]

Found another set of pistons while cleaning out storage. 1-3 on top 4-6 on the bottom. As with the last pics #1 is the worst, they all are bad.