Cast iron VH Cylinder Head Temperature

[Keith.owen]

Hi!
Here comes another mad question.................

Does anyone know at what temperature a cast Iron VH cylinder head will typically run (1950 VH)?
The raeson I ask. I have fitted new valves to my head and they seem a little tight, i.e. the inlet does not drop out under the force of gravity although it does nove fairly freely. Not having the means by which to measure the clearances of the stems within the guides I though that if I put the whole cabudle in the oven and heated it to typical operating temperature then, provided they did not stick there should be no risk of wrecking the engine.

Keith

PS. I used assmbly oil to lubricate them in the guides and have just finished grinding them in but have not fitted springs.

[nevhunter]

The exhaust port area runs significantly hotter than any other part. The clearances for the valves can be reliably determined from experience. If you have cast iron guides with a good accurate finish .003" for the exhaust and .001" for the inlet are the recommended figures. You can still carbon up the exhaust stem if the oil forms carbon. Some valve metals are a little prone to "galling" which is a rough wear surface where the metals are not wearing in the normal sense but "picking up bits from the other. Hard chroming of the exhaust stem helps prevent this, but requires grinding to size after the plating is done. Some so called "stainless" valves seem to be the worst for this. Nev.

[Wali.Badger.Taylor]

I would be wanting a couple of thou between stem and guide do you have a reamer you could pass through or you could knock up a brass lap.

[Keith.owen]

Hi,
I'm not quite sure how you go about measuring the internal diameter of the valve guides along the entirity of their lengths?

I'm able to borrow some expanable reamers as a friend has ofefred me them to ream the bushings in my gerabox.

Keith

[nevhunter]

You use little "T" shaped things that transfer your measurement to an outside micrometer. It requires more skill than I have to do those smaller sizes, accurately but it is everyday to cylinder head speciallists. A pretty rough but effective way is to cut a strip (narrow) of shim brass of the right thickness and insert it with the valve. You will have to rub the curled edges flat after you have cut the strip so you don't get a false reading. . 003" and 001" are the fit for the EX and IN valves respectively. The inlet needs hardly any clearance, but the exhaust is a different matter. If you use the wrong materials or fits you can seize a valve in a guide easily, and this doesn't make your day. Nev