Replace motor or consider replacing head old with 650 k + km's 1hz 80 series ? (1 Viewer)

Joined
Oct 8, 2011
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761
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Toronto, NSW, Australia
I'm trying to get my bearings with this issue. My 80's original from 1992 1hz motor is near 670 k km's. It runs ok, but not awesome. I have no knowledge of or documentation to suggest that the motor has ever had the head removed/replaced. I've done some work to the motor as deep as doing valve shims but never pulled the head or inspected anything more internal.

I know that new 1hz heads are pricey and good remanufactured/refurbed exchange heads are not much cheaper.

I also know one of the big things with 1hz's is they are prone to micro-fine head cracking and cracked pre-combustion chambers. My motor has never been turbo'd as far as I know. It had reconditioned injectors and injector pump fitted about 8 years ago (around 520 k km's).

In my stock of bits I do actually have a full set of new genuine 1hz injectors that I could fit (and wouldn't hurt if I did).

So most opinions I get are saying it's not worth investing the time/money for a new head on a quite old motor but it is a job I could so myself so labour cost wise there's be zero impost (just the cost of my beer and parts).

An import 1hdt motor from Japan with unknown km's is going to cost me around A$8k at retail pricing, or a 1hdft A$10k up.

There was a rumour a while back that a Sydney-based Toyota dealership had new crate 1hdt motors available for about A$15k each, but that money is not falling off any trees near me. ;)

So what are your views on the idea of replacing the head (motor will be due for timing belt, tensioner and new water pump soon anyway), leaving the head and just going with the new injectors, or biting the bullet and getting a whole replacement motor (even if just a reco/refurb/reman 1hz not a turbo)?

Craig.
 
Joined
Mar 3, 2012
Messages
988
Location
Adelaide, South Australia
If you have minimal blowby and reasonable oil consumption I would not pull the head before I had baselined the other things that may have caused a drop off in your performance:

  • A fresh set of rebuilt injectors (can always go into your new head if thats what happens)
  • A check of injection timing
  • Valve clearances redone
  • Air filter checked
  • Tyre pressure good
  • Wheel alignment bang on
  • Load weight reduced where possible (it creeps up slowly as kit gets added!)
 
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Joined
Oct 8, 2011
Messages
761
Location
Toronto, NSW, Australia
One thing I have not done is a compression test. Is that a good idea to do with an old motor to get a bit more data on potential internal issues? I think I have a compression tester kit somewhere but not sure if it's for diesel motors (does it matter)? It might have the right fittings for the glowplug holes.

But I agree there's a lot of factors. Re injection timing - is that done with a special tool + a dial indicator fitted to the back of the injector pump? What is the right dial indicator to use (I don't have any)?
 
Joined
Mar 3, 2012
Messages
988
Location
Adelaide, South Australia
One thing I have not done is a compression test. Is that a good idea to do with an old motor to get a bit more data on potential internal issues? I think I have a compression tester kit somewhere but not sure if it's for diesel motors (does it matter)? It might have the right fittings for the glowplug holes.

But I agree there's a lot of factors. Re injection timing - is that done with a special tool + a dial indicator fitted to the back of the injector pump? What is the right dial indicator to use (I don't have any)?

Pull the oil cap off and see how much combustion byproducts are coming out (smoke).. I would not bother with a compression test if there's only minor blowby and you do not have difficult starts.

What is your oil consumption like?

Yes, injection timing is done with a dial gauge in the back of the pump.. the FSM describes the process, its a specialised task.
 

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