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MGB - MGB on premium petrol

One of the most recent 'Ask HJ' questions was about running a 1971 MG on 'premium petrol' (link: classics.honestjohn.co.uk/askhj/answer/94659/shoul...l-).

My old '73 BGT was happy on super unleaded, but needed the ignition timing retarding slightly to stop it pinking (the engines were designed with the old 5-star 100-octane fuel in mind).

Valve seat recession usually isn't a problem on older engines, as the valve seats will retain traces of lead from older use which will offer some protection. If the owner has any concerns, an occasional dose of lead substitute is a LOT cheaper than having hardened valve seats fitted.

Comments

Glaikit Wee Scunner {P}    on 12 February 2018

The lead substitute additive is potentially toxic to handle iirc.Not seen it on sale recently. What you say about recession is correct, but most people seem to get the hardened valve seats and new valves fitted when an engine is overhauled.

Ah the delicate sound of pinking, that takes me back.

craig-pd130    on 12 February 2018

The lead substitute additive is potentially toxic to handle iirc.Not seen it on sale recently. What you say about recession is correct, but most people seem to get the hardened valve seats and new valves fitted when an engine is overhauled. Ah the delicate sound of pinking, that takes me back.

Interesting, it still seems to be freely available online from Wynns, Castrol, Redex and other brands ...

To be fair, I believe the pinking on my old BGT was a worn vacuum advance on the distie. I fitted a Ford 'spark delay' valve (basically a vacuum restrictor) in the vac line and it stopped the pinking completely without affecting pick-up or throttle response at all.

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