Pietenpol-List: Corvair info
Posted: Thu Jan 10, 2002 7:57 am
Original Posted By: "Oscar Zuniga"
Larry wrote:>It sounds to me that at aviating rpm four carbs would not do much>other than add weight.Yep. One carb can do it all, at our RPMs. If you want to use 4 carbs, don't hook up the other three- just use them to help your Wo)>Adding carb heat to them all or plumbing to single carb it would>also be a mess.Yep. No need; use the single-port heads, and mount the carb underneath.>Is anyone running stock carbs?I believe I've seen pictures of a Piet with a Corvair engine pretty much as it came out of the car... blower fan, ignition, carbs on top, fuel pump, everything. But if you have the Pietenpol manual from Don Pietenpol, there is info there from BHP's experience with the Corvair when he first fitted it to the airplane. Carburetion was one of the things that he fiddled and diddled with, and he did not stay with the stock carbs. There are better options. Dave Stroud up in Canada is running a Zenith off a motorcycle on his Corvair in a Christavia, with good results. Many others are using the Stromberg (as used in Cessna 120/140's, or other C-85 engines), and it's well supported and can offer mixture control. The Ellison and Supercarb-type throttle body units will work, but are spendy. But the stock carbs are definitely not the approach of choice, and will most likely give anyone fits in an airplane application.>Anyone care to share experience with Wynne's cam?The top choice right now is the OT-10 cam, and this is the one that William has in his engine. This cam is/was an aftermarket product by "Otto", and is one in a series (there is an OT-20, which is a warmer cam but of no benefit in our application). This cam is available through Larry's Corvair Parts.There has been lots and lots of testing and discussion, but William has gone through lots of different ones and the OT-10 is the best. I am getting a reground cam from Delta Camshafts (http://www.deltacam.com), a lower-cost alternative to the OT-10 with similar performance. Depends on if you care for reground or not. But either way- you can stick with the stock cam that comes right out of the 164 CID, 110 HP engine and get honest decent power and torque, or go with the OT-10 or Delta and get a bit better. In a Piet, all it means is better climb-out and the ability to cruise "in the yellow" and well past Vne at max power. William says his Piet was normally flown quite a bit throttled-back at cruise. Really, BHP had it right when he recommended not hopping up the Corvair... it's got plenty of HP in stock form. Neither the OT-10 nor the Delta are race cams... they are street cams with a profile that moves the curve to give better power lower down... which is exactly where we operate the engine in our application.There is much more information about all of this "frequently asked question" stuff at http://www.flycorvair.com/corvair.htmlOscar ZunigaMedford, Oregonmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.netJoin the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com________________________________________________________________________________
Larry wrote:>It sounds to me that at aviating rpm four carbs would not do much>other than add weight.Yep. One carb can do it all, at our RPMs. If you want to use 4 carbs, don't hook up the other three- just use them to help your Wo)>Adding carb heat to them all or plumbing to single carb it would>also be a mess.Yep. No need; use the single-port heads, and mount the carb underneath.>Is anyone running stock carbs?I believe I've seen pictures of a Piet with a Corvair engine pretty much as it came out of the car... blower fan, ignition, carbs on top, fuel pump, everything. But if you have the Pietenpol manual from Don Pietenpol, there is info there from BHP's experience with the Corvair when he first fitted it to the airplane. Carburetion was one of the things that he fiddled and diddled with, and he did not stay with the stock carbs. There are better options. Dave Stroud up in Canada is running a Zenith off a motorcycle on his Corvair in a Christavia, with good results. Many others are using the Stromberg (as used in Cessna 120/140's, or other C-85 engines), and it's well supported and can offer mixture control. The Ellison and Supercarb-type throttle body units will work, but are spendy. But the stock carbs are definitely not the approach of choice, and will most likely give anyone fits in an airplane application.>Anyone care to share experience with Wynne's cam?The top choice right now is the OT-10 cam, and this is the one that William has in his engine. This cam is/was an aftermarket product by "Otto", and is one in a series (there is an OT-20, which is a warmer cam but of no benefit in our application). This cam is available through Larry's Corvair Parts.There has been lots and lots of testing and discussion, but William has gone through lots of different ones and the OT-10 is the best. I am getting a reground cam from Delta Camshafts (http://www.deltacam.com), a lower-cost alternative to the OT-10 with similar performance. Depends on if you care for reground or not. But either way- you can stick with the stock cam that comes right out of the 164 CID, 110 HP engine and get honest decent power and torque, or go with the OT-10 or Delta and get a bit better. In a Piet, all it means is better climb-out and the ability to cruise "in the yellow" and well past Vne at max power. William says his Piet was normally flown quite a bit throttled-back at cruise. Really, BHP had it right when he recommended not hopping up the Corvair... it's got plenty of HP in stock form. Neither the OT-10 nor the Delta are race cams... they are street cams with a profile that moves the curve to give better power lower down... which is exactly where we operate the engine in our application.There is much more information about all of this "frequently asked question" stuff at http://www.flycorvair.com/corvair.htmlOscar ZunigaMedford, Oregonmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.netJoin the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com________________________________________________________________________________