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MG MGA - Which Valves Stellite or SS?
|exhausta B head (12H-2389) I|
|Hi Bruce. I have been running stellite valves and siicone bronze guides in My 1500 roadster for several years, and have had zero problems. THe stellite valves are very tough! I cant comment on stainless valves since I havent tried them. Cheers, Glenn|
The term "gas-flowed" is generally synonymous with "porting and relieving".
In other words, using rotating grinders, material is ground from the rough surfaces of the inlet tracts allowing the gas to flow with reduced friction, making the delivery of gas/air mixture to the cylinders, more evenly mixed and consistent.
On my TF, I did this many years ago, and at the same time, I "CC-d" the individual combustion chambers. (CC in this case, refers to Cubic Centimeters).
This is done using a plate of glass acryllic, or clear polycarbonate with a hole in it. You will need a burette. Clamp the clear plate (taking care of course, not to break it) over one combustion chamber, sealing it, and using the burette, drip oil through the hole into the now-sealed combustion chamber, making note of the amount of oil needed to fill it completely while purged of all air.
Do this with each combustion chamber, making note each time, of the volume of oil in each chamber. To bring them all to identical volumes, means grinding away material from non-critical surfaces.
Improved and equal volumetric efficiency will produce nice power results and improved fuel efficiency.
|Gordon A. Clark|
|Glen , Gord, thanks for the input.|
After further investigating it seems that the stellite valve is SS with a coating added. And I would imagine that the Gas Flowed valve is a stellite that has been "polished"?
Anyway based on their good reputation I will go with the stellite.
|Give Barney's page on this a read:|
Note the warning about slightly more valve guide clearance.
|Bruce, I think "gas flowed" means the stem is a narrower profile at the head. Stellite is actually a form of stainless.|
|Stellite is a trade name for a hard coating process. The valves are usually stainless steel before coating. I've been using Stellite exhaust valves for about 15 years with very good results. When I was autocrossing nearly every weekend and trailer towing a lot I used to have exhaust valve problems every 40,000 miles or so. Stellite exhaust valves and bronze valve guides outlast the rest of the engine with ultimate failure being piston ring wear. K&N air filters have been extending life of piston rings.|
|Yes, but the hard coating is in fact Stellite alloy!|
|Thanks Guys, |
Lotsa information. Looks like bronze valve guides are also on my shopping list, longevity is always good.
|If anyone is interested, here is an MSDS for various forms of stellite:|
In the second table you can see the composition of the various types of stellite alloy. The primary component is Cobalt. While there is iron in most of the stellite alloys, it makes up only a few percent of most of them. It would be more accurate to call stellite a cobalt alloy than a stainless alloy. Of course, none of this matters at all when selecting valves. This thread just got me curious enough to fire up google and learn something.
This thread was discussed between 17/07/2009 and 19/07/2009
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