Unleaded fuel/valve seats

O

Overover

New Member
Just considering my options- just got a P6 with 58k on a original compression 10.5:1 73 engine. Have some newer/unleaded heads but these are in poor condition and would need a lot of work. RPi do recondition the P5 heads at about £350 or should I use the newer ones?
Seems to be running ok at the moment considering it has been stood for 7 years and the fuel is probably stale-Getting occasional erratic idle ?possibly the start of sticking exhaust valves
 
Overrover,
I suggest that you keep the original heads on your engine and use a good quality fuel (super unleaded, Shell Optimax, BP Ultimate etc) and an additive approved by the FBHVC. I use Shell Optimax with Castrol Valvemaster Plus has has anti-wear and anti-knock qualities and an octane improver.
BP are now selling a fuel called Ultimate 102 that has an octane rating of 102 ron which is higher than the original 5 star fuel (101) that your engine was originally designed for.
The alternative is to spend a lot of money to fully convert to un-leaded so that you can use a cheaper fuel. Depends on the mileage you cover and the length of time that you intend to keep the car!
Hope this helps.
Regards, John.
 
Quite tricky trying to work out which of the snake oil treatments to use though I'll stick with Super Unleaded +Redex as the previous owner used it. I have heard using a mixture of additives is likely to make things worse. Anyway like you say probably best to wait until it actually needs a rebuild and stick with the original heads. I did run a 10.5:1 engine in a Land rover for several thousand miles with no special fuel or additives and the valve seats were fine at the last rebuild with great compression though it did frequently stop running due to too much muddy water.
 
Hi Overover,

The other option is to do nothing!

I've run a 3500S (early 10.5:1 comp engine like yours) on neat unleaded for 32,000 miles without a hitch. I did a compression test a few months ago & all cylinders were still good & only a little down on spec. Given the engine's mileage, this is perfectly OK.

I've also got some spare heads just in case, but have never had to use them.

Phil. :)
 
I've stuck a set from an SD1 on mine. They have the hardened seats fitted already, so that could be another option.
 
right someone educate me. the heads are alloy so need some sort of instert so are the early heads P5 and maybe P6 not got right type of inserts for unleaded?
 
You're right the heads are alloy, so inserts are already fitted for the valve seats. Whether or not they are suitable for unleaded is the problem. Apparently after November 1970, the V8's were all fitted with harder seats for the Range Rovers that were for the American Market. Check the date stamped on top of the Intake manifold to see when it was built.
 
Looks like no need to panic about the lead as it has iron inserts, and I'll use an additive for now. It is running very nicely using high octane fuel. Probably not a good idea to run on plain unleaded, unless you have composite gaskets- likely to risk detonation which can blow your pistons to bits and retarding the ignition wastes a lot of power.
Think I'll recondition the later heads I have though if it comes to a rebuild as they flow slightly better.
 
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