The V8 Owners Forum -

I've recently purchased a Land Rover fitted with with an early (circa 1970) range rover 3.5 V8.

On overrun going down hills it smokes quite a bit, blue oily smoke, due I'm sure to worn inlet valves. So I'm planning to swap the heads for a later version which has better valve seals, and also which is suitable for use with unleaded fuel.
I understand that the unleaded heads were introduced around 1980, how are these identified?

Looking at the information in this forum the numbers that are stamped into the casting span this date, so are there any other markings that identify the introduction of the harder valve seats?

All RV8s are fine with unleaded as regards valves and seats.

My understanding is that the very early heads had iron valve seats and these are not really suitable for unleaded unless you use an additive. Heads from 1982 onwards had harder valve seat material and these are suitable for unleaded. (Info taken form Des Hammills book, page 136-137)

sidecar wrote:My understanding is that the very early heads had iron valve seats and these are not really suitable for unleaded unless you use an additive. Heads from 1982 onwards had harder valve seat material and these are suitable for unleaded. (Info taken form Des Hammills book, page 136-137)

There are lots and lots of people running pre '82 RV8s on neat unleaded without problems.
If you are going to use that engine for competition it would be wise to fit harder seats - but then you'd likely be making other head mods. For normal use any will be fine.

I was lead to believe all RV8 heads were fine for unleaded due to the origin of the engine, USA, where they have had unleaded for decades and very tough emission laws so yank engines run on unleaded normally.

I'm running '64 Buick 300 alloy heads and use BP98 Ultimate unleaded fuel with 50ml of Flashlube added per tank on my SD1. Seems fine.

marcjagman wrote:I was lead to believe all RV8 heads were fine for unleaded due to the origin of the engine, USA, where they have had unleaded for decades and very tough emission laws so yank engines run on unleaded normally.

Basically any ally head with valve seat inserts from the start of time will be ok on unleaded, as you simply wouldn't bother attempting to make such inserts from low grade cast iron. Of course if you intend running at very high continuous engine speed and load you'd specify the very best. But it's impossible to do this on UK roads.

In the 70's and 80's whole heads were made out of cast iron which was not suitable for unleaded so it's not totally unbelievable that Rover made seats out of a grade of cast iron that was not suitable or unleaded.

EDIT.. Infact after doing a bit of research it appears that the problem has nothing to do with the ‘grade' of cast iron, the problem is that the material is cast iron, period. Tiny specs of cast iron form hard iron oxide particles which imbed them self’s into the valve, the valve then slowly grinds away the valve seat causing recession.

Alot of these old heads are now running on unleaded seemingly without a problem, the reason is that enough lead oxide has been deposited on the seat in the past to protect the seat for many miles of running on unleaded. In the case of Rover engines the cam lobes and valve springs are probably worn on these engines so the seats have an even easier time due to the whole setup going 'soft'

So in my humble you maybe able to run an old Rover head on unleaded assuming that you have not lapped the valves in and therfore removed the lead oxide layer and even if you have it still may run OK for a fair amount of miles but really only the later heads are truely designed to run on unleaded.

On your head(s) be it!

LandRoverNut wrote:I understand that the unleaded heads were introduced around 1980, how are these identified?

I believe that any of the heads with the larger valves and wasted stems will have the harder valve seats. SD1 heads or any of the 10 bolt heads. (If you do get hold of 10 bolt heads then you should use comp gaskets if you want the same CR)

I'd use comp gaskets on the later 14 bolt heads and get 20 thou skimmed off them. I would not use the outer bolts either.

I can't believe a coating of lead from petrol would last for more than a few hundred miles once you stopped using leaded fuel.

My brother found just that with his A Series car - can't remember if it was an Allegro or Marina. I suffered severe valve seat regression - and the same happened to another head he fitted in short order. he eventually got one from a later engine with seat inserts.

Rover would have bought in the valves and valve seats.
If *you* were making valve seats inserts, would you make them from cast iron rather than steel? If so, why? The cost of the materials would be tiny compared to the end value. And cast iron is more difficult to work - precisely due to the impurities.

Hi
Valve inserts for ally heads, even ones for mid sixties cars would bave been steel rather than cast iron, cast iron valve seats generally occour as a result of the head being cast iron and the seat bsing just cut into the head. Hardening a decent grade steel is relativly simple cheep thing to do once you have made the insert and if it results in 2% fewer returns under warrenty then it is a no brainer if you are rover. However boring out a cast iron head for an insert when you could get away with not using an insert because your head is cast iron and you are running leaded fuel, then that is also a no brainer. I am pretty sure it was only the early P5 and very early P6 heads that had non hardened seats and even those were a fine grade steel that would hold up much better than cast iron without lead. The other thing is that the lead was retained in the surface grain of the steel, and to an extent formed a solid solution in the very surface, it persisted in the head insert for quite a few thousand miles when lead was used from new (much like the Zinc compounds in the surface of your cam lobes and tappets).
Best regards
Mike

Like I said, it's just what I've read. Now just because it's in a book that does not make it true but if I was publishing a book I'd want to make sure the basic facts are correct.

kiwicar wrote: I am pretty sure it was only the early P5 and very early P6 heads that had non hardened seats and even those were a fine grade steel that would hold up much better than cast iron without lead.

That's how I understand it. Once Rover decided that they wanted to enter the American market with the NADA cars in about 1968 all heads were unleaded compatable from that point onwards.

Wow, my first post and a wealth of information, thanks Guys.

I'm watching a later thread in the same section regarding oil seals, as it was the smoke on overrun that made me think of changing the heads in the first place.

So, I think I'll keep these heads, try fitting the Manta oil seals as suggested elsewhere, see if that clears my smoke problem. If it does, excellent.

If not, then eBay for a set of 10 bolt later heads.