GordnadoCRD wrote:
BlueCRDinAZ wrote:
My local Chevy dealer was kind enough to order in an exhaust valve for the Duramax 2.8 and the valve was identical with the exception of the keeper slots, the GM slots sit a few millimeters lower than the VMs. I don't know what that difference would make beside the spring having more tension on the valve at full extension.
You beat me to the punch!
That was my plan for rebuilding my spare head (original). I suspect the difference you noticed could be offset by using the Duramax springs, keepers, and locks. I won't know for sure until I get a set installed and compare installed height, spring tension and spring clearance at lift. (no binding). I just haven't gotten around to that yet.
Although they look mostly alike and are the same head size, it's likely they are an improved alloy. How does the price compare? That's another thing I was hoping to compare, since some duramax parts will work interchangeably, and are much more reasonably priced.
Another thing to add to the 'overall' spring tension is total installed height. You mentioned keepers and locks, but need to also figure in any difference of the jeep head and duramax head's machined pocket where the spring sits. Could be different there. Also, what does the spring sit on; Just a shim, or some other sort of end cap to keep it from chewing into the aluminum...and how thick each variation is.
BlueCRDinAZ; Lower keeper grooves has more tension at all positions, not just when extended.
It wouldn't be the first time a mfg. changed the wire specs on valve springs in a 12 year span.. maybe it's all factored in! Chevy should've done their research/history on this engine, and noticed a 'problem' with the valves. And not to replicate OUR issues of broke exhausts had VM make design changes.. VM may have beaten them to the punch too.