Air in the fuel line

[RobHomewood]

Thanks for that Luli. Are you saying that you need to change the valves and valve guides as well as the valve seats in order to run unleaded without additives?

[luli]

The original exhaust valves are made of steel (they are magnetic) and would not withstand the high temperature that unleaded fuel heats them to. Therefore they are replaced with stainless steel valves (not magnetic). Those require bronze valve guides.

[chris dancey]

I have replaced the valves and the guides on my 10s, exactly as Luli described with bronze guides and hardened valves, makes a big difference to the running. Also check the rocker pads for wear and the rocker shaft, makes tappet adjustment very precise when in good condition. Good luck. Chris

[Phil - Nottingham]

Done same with our 16 too - much better

[jp928]

I would be looking at the cast reserve unit body, where the pickup pipe enters the casting. You could test by removing the unit from the tank, blocking all but one inlet/outlet and see if it will hold vacuum. Also do the test with and without the reserve unit attached, if possible. Dont forget that with a pump higher than the tank sucking fuel you are lowering the boiling point and promoting vapour lock.
jp 26 Rover 9