To clarify an earlier point, my InterEurope Datsun 1200 workshop manual says that the inlet seats are made of an aluminium/bronze alloy, which is why the South African cylinder head speacialist refered to them as "copper"

This is of course of no consequence since it's the exhaust seat that needs to be a very hard steel.

correct me if i'm wrong, but we have ali heads, ali is soft, so the seat has to be hardend, so you can run unleaded no problem.

since my rebuild(5000km) i have used unleaded no problen at all with high compression.

just use it i've had no problems even with my 1200!!

what is you octane rating over there we get a 95 and 97 unleaded

not meaning to add to the braindamage, I feel a need to clear up a few things.
the US has been using unleaded fuel since 1975, that means that we've had to put up with it for almost 30 years.
up until about 1978, all Nissan/Datsun vehicles sold in the US came with hardened bronze intake seats, and hardened steel exhaust seats, after that Nissan began to install hardened steel valve seats in both intake and exhaust seats.
use of unleaded fuel will cause the valves to "sink" into the seat, however the majority of wear will occure to the valve not the valve seat, because the seats are harder than the valves. when this happens, all that is necessary is to recut the valve seats and install a new valve. (this is assuming that you already have hardened steel seats in your head) bronze seats will, over time wear out and need to be replaced even with leaded fuel. the cure for this is to use the engine normally and when it's time for a rebuild, have hardened steel intake seats installed as part of the valve job. my own had over 100,000 miles (160,000 km.) on it when it came apart, being as unleaded fuel has been used in it WITHOUT any lead substitute for over 20 years, all that was necessary to return the head to factory spec was to replace the bronze intake seats with hardened steel seats, reface the intake valves, replace the exhaust valves because of stem wear, and recut the exhaust seats.
IF you believe all those horror stories about unleaded fuel, your an idiot, yes the octane sucks, and the lead aint there to help the valves last a few thousand miles longer, BUT IT WON'T DESTROY YOUR ENGINE.

In the US we don't have LFF vs LRP -- I think all fuel has lead-replacement additives. in any case we have run the A-engines for over 15 years on unleaded.

Teretonga
When 1200GXman writes "guides" [in an earlier post] he actually means "seats" & if you look at the inlet seats of an A12 head [at least the early ones] they have a brass-like appearance. The exhaust ones are of course, a suitable grade of steel.
I have no idea what these inlet seats are made of, but they sure do look a lot like a brass derivative.

The actual valve guides, as we all know, are steel [sometimes refered to as iron]

I don't know what the story is with L series engines, but none of the fuel companies recomend using LFF [lead free fuel] in these, so my 200B soldiers on by using lead-replacement fuel.

Sounds like the Cylinder Head guy is only remembering as far as his wallet! I don't think even pre-war English motors would use copper valve guides! Datsun certainly didn't and it sounds like you are starting to get yourself stressed out again by doing too much research on this. Many of us on here have been running unleaded in these motors for over 5 years with absolutely NO problems - and yes these are daily drivers.

Baloney! No heads come with copper valve seats.

The same 'warnings' and 'dire predictions' were made here in the US prior to phasing out unleaded. Nobody has needed to replace valve seats.

In any case all A-series cylinder heads have replaceable valve seats and replaceable valve guides, so why don't you just wait and see what happens?

DAMN IT!!!!!!

I just phoned a Cylinder Head repair shop.
The guy said that as far as he could remember all datsuns that came in the 70's to south africa has copper valve seats or a soft metal valve seat.
He said that over time these will wear out and I will have to replace them with hardened valve seats for unleaded.
As far as I remember Dodgeman is busy with this on his GX head.

I will maybe do it then next year.
While my cylinder head is of I can admire the nice and new looking cylinder bores asif they have'nt driven even 2 kilometers while in fact they will have about 70 000km on them by that time.
My datsun is a daily driver, mostly because I enjoy driving it.

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.....

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.