I wouldn't use a VW head without the baffles that Bob Hoover is talking about in the link. About Revmaster heads-- Think I read somewhere that there is more fin area. Revmaster is the oldest VW aircraft conversion company in the business, I believe they started in 1968. To many people put VW engines in airframes that require the engine to be run to hard for the design.Pops,
I was going to make a similar comment about your cool running engine. If I throttle back to similar power levels I also get similarly low temperatures. 2400 rpm results in 70-80mph burning a couple GPH with temperatures in the mid 200Fs. You've definitely got me beat in a climb, though, but I don't think I've made any measurements at a similar power level. Most of my cruise hours are flown at WOT at around 140mph with measured temperatures between 300-350F. I'm sure I could learn a thing or two from your baffles, but I don't think mine are bad. What do you know about those head baffles I linked to earlier and have an opinion on them? http://bobhooversblog.blogspot.com/2006/12/vw-head-baffles.html
Thanks for reminding me about the Revmaster heads. I've read the same thing about their valve seats, but would like to find reports from people flying it in a similar application to know if I believe whether the valve seats are actually better. For all I know they're using the same material as my CB Performance heads and just marketing it better.
I don't necessarily disagree with those who would say I'm running my heads too hot/hard especially compared to Corvair heads and Pop's heads. I also understand that exhaust valve issues are a common maintenance item on many aircooled engines, except on a longer timeframe (300-500+ hours?). In searching for a difference between my engine and other aircooled engines that seem to go longer, I can't help but notice my valves don't rotate despite Lycoming engines using valve rotators, WW Corvair engines using valve rotators, documentation claims original VW valves rotate, etc. I'm not sure about Jabiru engines, but I imagine they tend to go a little longer than VWs. It makes me curious if something simple like figuring out how to allow the valves to rotate might get another hundred or more hours from them.
I also admit that I haven't performed leakdown tests on these valves, so it's possible I've removed my heads earlier than others would on other engines--I just turn the propeller over by hand and notice when one cylinder is lower than the rest. I also inspect the valves if the heads are off for another reason. The valves never have the classic burned look that you see from Lycoming valves on the Van's RV forum. The valves that I've worked twice were ones that I lapped the first time and didn't replace the valve or re-cut the seat. I suspect if I made a high quality cut in the valve seat and replaced the valves the first time, they would have lasted longer.