# Valve Problem

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#### Vigilant1

##### Well-Known Member
I don't know what's going on. Next time I land in Hesperia I'll stop over and see what's going on with their shop.
I don't want to come across as overly critical. Joe and his guys know more about VW engines than I could ever learn. I just want Revmaster to be around for a long time.
And while you are shooting the breeze in beautiful Hesperia, ask 'em if they would ever considered selling a Type 1 head made just for airplanes. The head they use now has very good cooling, but at our RPMs we don't need valves as big as the street racers use. At our RPMs, smaller valves would give better VE and (more important) more metal/less cracking between the valves. Oh, and just put the second plug where everyone else does, eliminate the access port Revmaster puts in the valve cover.
There, >that< should start a conversation with the good guys at Revmaster!

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#### Mike Stewart

##### Well-Known Member
I don't want to come across as overly critical. Joe and his guys know more about VW engines than I could ever learn. I just want Revmaster to be around for a long time.
And while you are shooting the breeze in beautiful Hesperia, ask 'em if they would ever considered selling a Type 1 head made just for airplanes. The head they use now has very good cooling, but at our RPMs we don't need valves as big as the street racers use. At our RPMs, smaller valves would give better VE and (more important) more metal/less cracking between the valves. Oh, and just put the second plug where everyone else does, eliminate the access port Revmaster puts in the valve cover.
There, >that< should start a conversation with the good guys at Revmaster!
Yeah . . . that plug access through the valve cover has never been a good solution. Great Plains does a much nicer job of that.

Re valves, I'll certainly bring it up when I have an opportunity but my thoughts on that issue are a bit different from yours. Since heat is the major bugaboo with the VW, large diameter valves allow better cooling - I forget the percentage but a very large percentage of cylinder heat is transferred out of the cylinder through the contact between the valve and the seats.

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#### Mike Stewart

##### Well-Known Member
I think I can get my head around a smaller valve having a higher percentage of its radius giving more percentage surface available for heat transfer, but still . . . doesn't the larger valve have more actual seat surface? The more seat surface, the more heat is transferred from the head to the valve. Heat, along with other (less important) paths, then is carried up the stem and dissipated. Excess fuel is used for heat dissipation too when we (wastefully) use it in that way. It's been ten years since I studied this stuff so obviously I could easily be mis-remembering things. I hesitate to question my understanding of valve size/function though since it seems to violate common sense. Or maybe there's just some confusion of ways of thinking about this. Quite apart from any geometry considerations, it seems if there is more seat surface (there's gotta be . . . it's a larger valve!), there will be more heat absorbed, thus a hotter valve. Heat transfer is one of the primary functions of the valves so it only makes sense that if the larger valve absorbs more heat, it's going to run hotter than a smaller valve. It's also going to do a better job of heat extraction due to its larger mass with which to absorb this heat. A smaller valve is of course going to run cooler in this comparison but since a primary function of the valve and seat is to transfer heat, what is the advantage of the smaller, cooler valve?

I've had no trouble at all from combustion chamber cracks between the valve seats. No trouble with over heating (because I prevent it through attention to oil temp and through extracting power using what I think of as torque as opposed to running it at a high RPM.) Other than the broken springs problem I've had no troubles at all with this GP 2180. My only problem was due to RIMCO re-using old valve springs when they did the TOH for Steve. Since I've no doubt they re-used the valves as well, given enough time I could have eventually had a valve failure. Putting things back together using the best components I could buy and operating the engine within its heat limitations has prevented any of the issues mentioned on this thread. I think if everyone carefully built their own engines from kits and, if not, re-built their engines to make sure everything is correctly lined up (replacing parts with better ones if necessary), there wouldn't be much discussion about problems with aviation use of the VW.

The idea of sodium-filled exhaust valves is a good one but when I went looking I didn't find any that would fit my engine. Maybe I just didn't look hard enough but don't think so . . . they just weren't made for the VW at that time. Since the D-3000 uses Chevy pistons and cylinders (I think), it's not unlikely there might be sodium-filled valves available for this engine.

#### Vigilant1

##### Well-Known Member
The exhaust valve is hotter than valve seat. Heat doesn't flow from the seat to the valve, it goes the other way.

The valve gains heat through the valve face, and some through the back side. It loses heat through the valve stem and the valve seat. Lets look at 2 valves, a 40mm and a 48mm. Assume both valve seats have a contact area width of 3mm.
40mm valve face area: 1257 sq mm
40mm valve seat area: 377 sq mm.
Ratio of heat gaining area to heat losing area: 3.33

48mm valve face: 1810 sq mm
48mm valve seat area: 454 sq mm.
Ratio: 3.99

The bigger valve has proportionally more heat gaining area than heat losing area compared to the small valve. We can disregard the valve stems, they will be the same. If we added the heat gain on the back side of the valve, the bigger valve does even worse.
Mark

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#### Mike Stewart

##### Well-Known Member
> "The exhaust valve is hotter than valve seat. Heat doesn't flow from the seat to the valve, it goes the other way."

Of course. Not awake yet.

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#### Pops

##### Well-Known Member
HBA Supporter
Log Member
JP sent me an email on where to find the drawing of Bob Hoover's heads that he designed. January 23, 2009. Thank you JP.
Here is also a picture of Steve Bennett of Great Plains visiting Bob Hoover.