Valve guide material for cast iron exposed valve engine

[bevanclark]

Hi folks,
I'd value some feedback as to whether the attached specifications could make this material a good valve guide choice for an engine with exposed valves and next to nil lubrication. G2 grey iron has been recommended, but is not available anywhere in Australasia as far as I can determine.
Thanks,
Bevan

[nevhunter]

It's not just the chemical composition . it's How it's cast .The carbon is NOT alloyed with the Iron which must not be steel. Cast iron is Like a fruitcake with bits of free carbon here and there and the fe is not hard. The tensile strength is quite Low. Don't use anything like window sash weights as they May easily have some scrap steel in there and Hard spots called "diamonds" that will blunt your drills and cutting tools. The free carbon Helps to stop Galling of the valve stems which is chronic if they are of stainless steel which has not been nitrided. If the stem galls it will wear out in no time flat. Nev

[paul.jameson]

I think you will find that Geoff Lord (AOMCC Singles Spares) has the guides you need in stock.

[paul.jameson]

Be careful about the lubrication of the guides. The inlet guide should have a drilling from the side about half way down. check that this drilling is the same distance down as the feed hole on the side of the head where the oil pipe from the crankcase just behind the cylinder screws in. On my LG 250 the two holes were not the same distance down but I was able to enlarge the hole in the head using a small circular file so that the holes aligned. Obviously, when putting the inlet guide into the head, try to get the holes opposite each other. There is a groove round the outside of the guide to take the oil if you don't line the holes up but it is better if they are opposite each other to minimise the danger of the groove clogging with burnt oil.

For the exhaust guide, there is only one rule, which is to use a piston without a scraper ring. Depending on engine size, you should just have 2 or 3 plain rings.

[bevanclark]

Thanks for the replies folks- plenty for me to ponder over.