Somebody (unsigned) said, > "Bigger valves also have more area to absorb heat."
True. > "I don't think that works out on favor of larger valves." Any particular reason you think that? > "Also stem area remains the same. That works out in favor of smaller valves." It does? Why? > "You can also take care in grinding seats to increase heat transfer area." I completely agree with that and in fact is why I wrote "Whether with oversized valves or OE valves, taking great care to optimize the valve and valve seat interface is one of several factors that differentiates between a well-done valve job and a buggyshop valve job." ************* The heat generated within the combustion chamber doesn't vary depending on the valve head size. That combustion chamber heat has to go somewhere. As the poster states, a larger valve head will absorb more heat. It won't get any hotter than a smaller valve head, it will just absorb more heat. Because the valve and valve seat contact area of the larger valve is significantly greater than the valve/valve seat contact area of a smaller valve, more of the heat generated within the combustion chamber is transferred to the head, the fins and away from the engine. ************* I've admired but not studied the R-2300 so don't know what valves are used and whether their head diameter has anything to do with the crack we saw between the inlet and exhaust ports. I would guess that crack was more the result of excessive cylinder head temperature (which larger valves mitigate) than anything to do with the distance between the two valve seats. The seats on the GP2180 and 2100D are quite close and the heads do not experience cracks - at least I've heard of none. If guides were bored off center as in Jim Hill's engine or if an engine is suffering some other defect in manufacture or in operation then anything is possible. The only semi-chronic problem with these engines I've heard of is cracked cases, especially the magnesium ones . . . and that is from - as is always the case with VW's - operating the engine beyond temperature limits for an extended period. These engines are remarkably forgiving of temporary abuse, but not if it continues. Robert Gill's account of his 18 months of headaches with his R2300 doesn't sound encouraging regarding this relatively new engine of Revmaster's. This is the second negative report we've had on this engine that I'm aware of. One would need to do a lot more research before writing this engine off - Revmaster is hardly a newcomer when it comes to building engines - but if I were engine shopping for anything larger than a GP2180 there's no question in my mind I would be thinking Corvair with an Ellison and all the goodies (like the one Dan Heath has for sale). Mike KSEE ____________________________________________________________ Buffett???s Warning for YOU 4 in 5 Americans aren???t taking his shocking advice. Click here now. http://thirdpartyoffers.juno.com/TGL3141/559a299d7caf4299d6d61st04vuc
