Exhaust valve material

[michaelhoyle]

Hi - I wonder if an engineer amongst us can tell me what easily machinable and available material should be used to make exhaust valves, without needing heat treatment?

[Guest imported_PackardV8]

U need to find a valve from some OTHER engine application that is a close fit and remachine it to your engine.

HOWEVER, Your question is somewhat vacuous in that u make no statement as to wheather it is an air cooled engine (static or forced) nor any other relevent info about the engine. IT MATTERS!

[michaelhoyle]

Thanks for the reply - I have used other valves in the past but found it difficult to find valves with long enough stems and when I have found them, some are very hard to machine, so thought it might be easier to start from scratch. The motor is a 1912 Renault, watercooled, low speed, used with unleaded gasoline.

[Ivan Saxton]

You should be able to find valves that are long enough, but the head are stem diameter are far too large: These are what you should look for. Probably the best source may be someome who rebuilds big truck engines, because you know the quality is right. Nobody wants valves with worn stems so they may not cost you, and that is exactly what you need.

Ream your valve guides to the smallest oversize that will clean up the holes so they are round and parallell; and they should all be the same size. This will only be a few thousandths of an inch oversize. Then you take your truck or bulldozer-engine valves to someone who has a centreless grinder in their workshop, and get them to the stem diameter that suits your recoonditioned guides. For this you need to grind the stems to a stop. You machine the heads in your lathe at slow speed with a tungsten carbide tool. The centreless grinder is a production machine that is very quick and accurate to perfect finish. In manufacturing you would use a form dressed on the leading edge of the main grinding wheel to finish the underside of the head to shape. If you want to understand better, buy a copy of Shop Theory, from the Henry Ford Trade School. Mine is 1942 edition and cost me US$8 on the internet. My 1953 Lancia Aurelia has valves I made from GM Holden discards; and I just did these on the lathe before I aquired a centreless grinder.

I think Dufor in Sydney still make valve blanks, but the size range may be more restricted than in the past.

There is also someone in New Zealand who advertised that they make valve blanks. I have this written down somewhere, but it is possibly easier to re-source the information than find my note. (That is why it is often better to commit things to memory.) Ivan Saxton

[Mark Shaw]

For what it is worth, my 13 Buick has valves from a Mercedes diesel car. Just the stems needed to be cut shorter to fit.

[michaelhoyle]

Thanks - If the stem is tough, its not just the stem diameter that is hard to machine but also the slot for the cotter. (I have had no trouble with the heads so far). I guess I could take old valves to be centreless ground and the slots to be sparked but the idea is to do the work myself if possible.

[Ivan Saxton]

My sentiments entirely. My formal training is as an agricultural scientist. I do not have a crankshaft grinder or a camshaft grinder. I have never attempted electroplating, and I am happy not to cut gears though I machine the blanks; because this work can be done very economically with much better equipment than I have. Making pistons or carburettors is not a problem; and there is little on and old car that you cannot replicate if needed.

To cut the retainer slots in valve stems you may have to reort to some trickery. Presumably you have a vertical mill or honourable economical oriental mill/drill, whereby you can hold a valve stem so you can machine on the axis. The way I would approach this is to machine a flat entry for drill holes with and end mill. There are two ways you can go with drilling. You can sharpen a small masonry drill on a diamond wheel so it has the conventional cutting shape of a metal drill. You can buy "Superdrills" already like that at a cost. The other way is to "zero angle sharpen" a conventional drill. A man by the name of Tyson (sp?) at New Zealand Airways used to supply a book of instructions on how to do this, and even a jig to enable you to sharpen both sides evenly. I regret I did not get the jig at the time, but do it by eye which is good for most purposes. You sharpen the drill with a fine white aluminium oxide grinding wheel with a 60 degree angle dressed on the right side to produce the centre tip. you plunge-sharpen the drill above centre on the stone and roll it slightly clockwise to get relief and currect cutting ofr th centre. This probably seems as clear as mud; but I will dig out the instructions to scan for you. You might be able to source the original on the net. A high speed steel drill sharpened like this will drill a straight hole, true to size, and will also drill a hole overlapping the edge of the material; and it is written will drill work hardening stuff like titanium. You do have to use cutting fluid, because as always, heat will quickly ruin a cutting edge. The other trick you can do with this drill type is to gring the centre off-centre so the longer side does extra to give a slightly oversize hole. I'll look for the instructions to get Stirling to scan it for you.

You may be able to clean up the sides of the slots with a fine file, being carefull to move it slowly and clear the chips. Somewhere I have copy of a magazine article about 25 years old which tells how to make and operate an EDM device which you can make for a few dollars. This may be harder for me to find, but you might track the same information down on the internet.

Slot/plate valve retainers I have no problem with on a slow revving engine. Threads are a risk, except the way Stutz did it on the eights perhaps. When I get to restore my Tipo 8 Isotta Fraschini I shall definitely discard the original arrangement which doubel as valve clearance adjustment. I have one spare cylinder head which has dropped a valve which has then punched a hole through its port into the water jacket. I know of other engines which suffered the same disaster. This is one case where you need to ignore Phil Irving's dictum that after you change this you are likely to find that the designer was right in the first place. (Phil created the Formula 1 champion Repco Brabham engines). Ivan Saxton

[michaelhoyle]

Thanks for your encouragement Ivan. Yes I have an old lathe and a mill. I would be really pleased if you could scan that info for me. Regards Michael