12HT Garage Rebuild, yay or nay?! (1 Viewer)

[Fred12HT]

Hi all,

I'm looking to do a partial rebuild (pistons only) of my 12ht 390k with suspected blow by. After researching the wear and tear of worn pistons and rings and potential damage caused, it seems Alfin insert pistons are the way to make the most impact to durability and may be possible for a "home job". It's at the mechanics today for a compression test and will see what the results are. I would love to rebuild myself, (very handy with the tools and have done all other work to date and some engine work too) but I don't want to take on something I can't complete or risk messing something up. Does anyone have any idea or experience on the level of work, skillset, tools, processes involved and if a home garage job (clean and tidy one at that) would be out of the question??? I'm trying to save dollars but also really enjoy getting stuck in myself.

I know a full rebuild is the way to go but obviously, cost, time, and out of my scope for sure. My idea is to just replace pistons and rings, not a full rebuild and give a general once over as the engine runs well otherwise. Also for just pistons, would the engine be able to be worked on in situ, despite the awkwardness of restling the fenders???

Either way i'll be getting the injectors serviced, installing an intercooler and potentially having the turbo overhauled.

Please comment anything else i've missed, or should or should not do.

Cheers for any help.

 

[cruiserpilot]

Cost and time. Doing it yourself always takes more time. Pulling the engine will make it
longer but you will do a better job. Piston protrusion isn’t something you want to mess up
even with just a ‘piston and ring’ job. How is your head? Recent work?
I am in the same position as you but I already have the intercooler and GTurbo. I’ve done
the head and gasket a while ago. Injectors and timed the pump.
But I’d recommend going to Engines Australia and looking at everything. Make a list.
But some stuff I’d suggest you really will need to do, will really need professional service,
and in the end you will end up with a better engine.
Could you imagine pulling head, replacing just pistons and rings. Then finding out something
that was right there needed doing? How much would that cost, and how much more time?
Just my idle thoughts

 

[Earwigg]

It's really not that hard to pull the engine.
And will be much much easyer to work on out off the car.

 

[Fred12HT]

Cost and time. Doing it yourself always takes more time. Pulling the engine will make it
longer but you will do a better job. Piston protrusion isn’t something you want to mess up
even with just a ‘piston and ring’ job. How is your head? Recent work?
I am in the same position as you but I already have the intercooler and GTurbo. I’ve done
the head and gasket a while ago. Injectors and timed the pump.
But I’d recommend going to Engines Australia and looking at everything. Make a list.
But some stuff I’d suggest you really will need to do, will really need professional service,
and in the end you will end up with a better engine.
Could you imagine pulling head, replacing just pistons and rings. Then finding out something
that was right there needed doing? How much would that cost, and how much more time?
Just my idle thoughts

Thanks guys, really appreciate the help. I'd love to do this process but making the call to do it right and do it once seems key.
I've got it in to MTQ engines here in Brisbane for the injector servicing and had a compression test with all cylinders running well so at this stage i'll be leaving it be and reassess in the future. FYI results are:
1=380, 2=360, 3=360, 4=390, 5=380, 6=400

The workshop called to let me know which is always appreciated and after letting them know i'm only keen for genuine parts and ideally overhauling the exact injectors and ensuring they don't just swap out or replace with inferior parts, they've assured me they'll be swapped with already reconditioned genuine parts.
I haven't had it dyno'd pre injectors but i'll update once it's running but moreso once i've installed the new PDI HJ61 intercooler and GTurbo Grunter.

Are you running the intercooler and GTurbo already, or waiting to be fitted?

I know the fuel pump may need tweaking/timing, is this a specialist job?

Thanks again for the advice, it's all helped me to understand the full process and i'm sure i'll be referring to this when the full rebuild occurs.
Cheers

 

[cruiserpilot]

Are you running the intercooler and GTurbo already, or waiting to be fitted?

I know the fuel pump may need tweaking/timing, is this a specialist job?

Yes, home brew front mounted IC and GTurbo. Can’t go wrong with PDI IC. At the very least,
after the build get the injector pump timed properly. ( kinda obvious ). I know there are fuel
adjustments for throttle and low boost on one end of the pump, and fuel adjustments for
high throttle settings on the other end. I’ve been mucking with mine very nonscientific.
Probably making it worse. If you can find a a proper shop to adjust I’d recommend that.

 

[Fred12HT]

Yes, home brew front mounted IC and GTurbo. Can’t go wrong with PDI IC. At the very least,
after the build get the injector pump timed properly. ( kinda obvious ). I know there are fuel
adjustments for throttle and low boost on one end of the pump, and fuel adjustments for
high throttle settings on the other end. I’ve been mucking with mine very nonscientific.
Probably making it worse. If you can find a a proper shop to adjust I’d recommend that.

Cool, i've luckily saved enough to commit to the pair. Have you noticed much of a difference in performance or more peace of mind knowing the stock turbo can't explode on you??

Yeah very true. I've done similar tweaks when I put the boost T and EGT sensor in, upped the post boost fuel, (and even back down ) but once all modded, i'll take for a dyno and tweak. Do you know if the only mods to the fuel pump are the pre and post boost fuel screws, or is there a more advanced level adjusting internals and delivery time vs just the amount of fuel?

Cheers