What percentage of 80's need Head Gasket?

[timer00]

my truck has 198k and still rolling on the original HG. I'm on this site so much, I think about it failing everytime I drive it

Ditto here and I am only at 108k now haha

 

[Tools R Us]

I have a theory on why some of these head gaskets fail. I'm sure you have noticed that the tranny won't shift into overdrive until it has reach operating temp. This can be problematic if you jump into a cold truck and go straight to >50mph.

What I believe is happening on some rigs is that people hop in a cold rig and expect to accelerate to highway speeds. This is horribly bad for an fzj80 due to the tranny not upshifting to od. Therefore the motor is screaming and heating up a rapid pace different from the head. This combine with the water temp gauge being as worthless as tits on a bull.
Btw I'm at 155k original headgasket, fwiw.

imho Justin

What? Overdrive is to increase fuel efficiency at cruise, but lugs the motor, it runs under it's "best life" speed. Locking out O/D when cold allows for better fluid/temp flow through the motor, making for a more even/controlled warm up. IIRC 60mph = 3000rpm, a perfectly acceptable speed for the motor, I have run mine at 60mph in 2nd.

On the head gasket thing, drive any brand of vehicle long enough and you will have a failure. I have put head gaskets on just about all types that I have worked on. Anything designed/made the "asbestos outlawed" era (early-mid '90s) is going to have a slightly higher chance. The 1FZ fits this, but doesn't suffer nearly as bad as some, 3.slo anyone? There are 3 1FZ's in our family ('96 & '97) one has failed.

 

[Eric Hohlfelder]

183K on the original HG no issues.

 

[timer00]

One of the easiest ways to blow a HG is to rev fast while the engine is cold and to go high speeds before normal operating temp.. I think we all know that, as my sister did this to my mom's 86 Honda Prelude Si long time ago.

Take any motor and beat the crap out of over long periods while the engine is cold and its almost a sure thing.

In terms of LC's unless someone wants to do a study of

Location
Year/Mileage
Driving Habits
Maintenance Records
etc

and correlate them all together to find a pattern be my guest otherwise just drive her til she blows

 

[Tools R Us]

One of the easiest ways to blow a HG is to rev fast while the engine is cold and to go high speeds before normal operating temp.. I think we all know that, as my sister did this to my mom's 86 Honda Prelude Si long time ago.

Take any motor and beat the crap out of over long periods while the engine is cold and its almost a sure thing. ...

My years of building motors disagrees. By far the best method I have seen is to take out a head gasket is overheating. Even way over cooking a motor isn't 100% sure of blowing them, but is the most effective method that I have seen.

Cold over revving causes wear on lubricated sliding surfaces, (bearings, piston skirts, etc) has little/no effect on gaskets. This is only true until good oil circulation is established, a few seconds - minute? After that it's pretty much good to go within normal driving range.

In the "good old days" most thermostats blocked coolant flow. This causes the head to warm much faster than the rest of the motor. The 1FZ has a double acting, bypass thermostat system, making for full coolant flow through the motor when cold. This allows for much more even heating. The coolant carries the heat from the first parts to heat, (around the exhaust ports, combustion chambers, etc) and used it to warm other parts that are slower to heat. Running the motor slightly faster allows for quicker, more even/controlled warm up.

I agree that it's best to be somewhat easy on the rig until at operation temp. But 3000rpm is well within "normal operating" range. IIRC red line is 5200rpm, max hp is 4600rpm and max torque is 3200rpm. The designers didn't accidentally forget to make it into O/D or lock the clutch when cold, it's designed that way for the benefit of the rig.