1200GXman
Firstly, i think you are writing "valve guide" but really mean "valve SEAT" This is the round ring that is inserted into the head & is machined so that the valve can seal the combustion chamber.
The valve guide can be seen up in the port & the top of it protrudes into the rocker area. These are to guide the valve as it moves up & down.

If you do suffer valve seat recession, the tappet clearance will close up, eventually to nothing. Then the engine will run rough, & if you keep driving it, you will likely burn out one or more exhaust valves. By this stage you will need to pull the head off for repairs, to find that they have NOT eaten their way into the aluminium.

Woody
You can not legaly buy leaded super grade fuel in NSW. I suspect that you are using "Lead Replacement" super, the same as I do. If you read the label at the bowser [fuel pump] in the service station, it will say "lead replacement". It is now being phased out by some companies.

If your Jeep is running a pre-crossflow Ford 6 the head will be cast iron.

250 precrossflow. Yes cast iron for sure.The ole infamous log head.

hey all sorry for runnin off topic heeps...
why are they called the log head.... this motor dosent miss a beat!
so being cast iron that means i MUST use the flash lube right?
thanx

Sure does I think they called them log heads because they are heavy ,I bet the manifold is cast onto the head .

yeh im pretty sure the manifold is cast...

After all this discussion i'm still a little lost. Can someone tell me if I can run unleaded in my A12? Sorry i'm not very mechanically minded.

Yes - it won't cause any problems.

not to hijack the thread too much, but the loghead was named due to the excessive weight, and that it as an ugly head both to look at and performance wise. with a cast on manifold, and unimaginative design, the head asnt a powerhouse. What saved this motor was its capacity and torque.
Basically its an ugly lump of underperformaing cast pig iron hence the nick name loghead. At least thats from my experience.
Still, not a bad donk overall. like you said, it never skips a beat. Throw a crossflow head on, and its a huge hp boost, plus all the dogifing options.

To make me feel a little better, running unleaded in an a series will do em no harm, and you ill need seom sort of lube additive like flashlube ith a cast iron head.

ahhhh, got that all out, ,much better.

Dodgeman

You 100% understood what I ment.
Basically why I am asking these questions is that I want to go over to unleaded.
If it damages my valves and the stuff Dodgeman mentioned I will then take off my head and prepair it for unleaded.
I am actually bargaining that this will never have to happen. But in this process I do not want to damage my head in ANY way as it is a genuine GX head.
I will cry myself to death if it gets damaged.

If only the valve guides gets damaged then I will replace them when they are damaged.
Thanks for all the replies.....