Corvair College #23 – 2850cc Engine, Roger Grable, CH-750 Builder


Here is another builder’s story from Corvair College #23. Below is a sequence of photos of the 2850 cc 110hp engine we assembled for Zenith 750 builder Roger Grable from Missouri.  All of the action pictured took place at the College.  

We met with Roger and his wife Sarah at CC#22 in Texas a few months ago.  It didn’t take long to understand that he knew engines fairly well, and had considerable experience working on them. His questions were observant and thoughtful. He spent #22 carefully considering a plan that made sense for his project and timetable. By the end of #22, Roger made the decision that he wanted to have us assemble a 2850 for him, and this would keep his fast paced 750 project moving.  I have no problem building an engine for a guy with Roger’s approach. He still wanted to learn as much as possible, and that in my book is what makes him a good Corvair guy.



Above, Roger and I stand beside his engine on the run stand.  Every engine we run has the oil system primed for 20 minutes with an electric drill. The only oil we use for break in is Shell Rotella T 15w-40. In every engine we add ZDDP. You can get it from a lot of places, but Clark’s sends it with camshafts they sell. We run the engine for 25 or 30 minutes without stopping, at 1500-2000 rpm. This has proven over hundreds of engines to protect the cam and lifters, which are the primary thing you are concerned with during the first hour.


Above, a number of the builders at CC #23 admire the smooth power of Roger’s 2850. The engine is equipped with a billet Weseman bearing and a very nice set of Falcon heads. We configured the engine for a heavy-duty oil cooler. On aircraft like Zenith 750s, the slow climb speed capability and the high angle of attack challenge the stock oil cooler capacity in hot weather. Thus, we set the engine up with a cooler block off plate and a Gold Sandwich Adapter and a 20003 series aircraft oil cooler. The baffle kits the Wesemans offer are fitted for either the stock cooler or the 20002 or 20003 series. When complete, the oil system is contained on the engine, none of it is mounted on the firewall or cowling. This gives the engine installation a clean, organized appearance.


Above, Roger keeps an eye on the oil pressure. His engine is equipped with our new high volume pump. For these, I carefully  use the mill and expand the capacity of the oil pressure bypass, to prevent the engine from having a very high peak oil pressure on start up with cold oil.  When the engine is first started, several minutes of operation to warm the oil is a good idea, and we do this at 1000-1200 rpm.  In a few minutes the oil will regulate at 50 psi or so. When the engine is at full temp, this will settle down to 45 pounds of pressure. This slight reduction in regulated oil pressure between 140 and 205 degree oil is a Corvair characteristic. Beside Roger in the yellow shirt is his grandson Graham of Kansas. The young man proved to be very smart and good company. Many of the builders though Graham was 20 or 22 years old by his manner; it was a small surprise that he is far younger, still in high school. He is very interested in flying, and it is easy to guess that he will do very well. The kind of younger person who defies all the common media stories about youth.

We often get inquires about complete engines. Most of these are from people who only know about the low price of the engine. They have no other attraction, they know almost nothing of our development or support. Experience has taught me that any guy who decides to buy an engine he never heard of before after reading a one paragraph news release is not a guy who is in things for the long haul. Any guy who thinks you’re a genius in 1 minute is just as likely to decide you’re a fool without reason. Steady people who consider merits thoughtfully are typically the people who succeed in homebuilding. To understand an extreme case of people who are only interested in price shopping, I had a guy ask about a 3,000cc engine. He said it was priced at $50 more than his other choice, a four-cylinder, geared, tiny displacement computer controlled, imported car engine. I pointed out that philosophically these were radically different concepts in aircraft engines, and he needed to think his choice over a bit.

His response was to ask if I would sell him an engine but not the Conversion, Installation and Operations manuals, so it would reduce his cost and make up his mind. I calmly asked him why I would sell an engine to anyone who told me they didn’t want any instruction on how to operate it. I hope he is happy with the other engine, I don’t work with people who know the cost of everything but the value of nothing. Roger and his family impressed me as the perfect antithesis of such people. We have room in the Corvair movement for many types of people, but I can make a good argument that experimental aviation and flying in general has had quite enough of people who have no interest in learning anything.


Above, Roger and his grandson Graham. The picture provokes a thousand thoughts on where their adventure will lead. Will they both be there for the first flight? Will his grandson solo in the plane? Will Grandfather be the first passenger in his log book?  I watched the two of them at the College, they were having a very good time together. Roger, obviously proud of his grandson, and the young man accompanying his grandfather on an important and fun trip. Both of my grandfathers passed before I was born. Looking at these two made me think about it many times during the College. I have been very lucky in many ways, but as a young man I would have treasured having a grandfather. In person it was easy to tell that Roger’s grandson felt the same way about Roger.-ww



One Reply to “Corvair College #23 – 2850cc Engine, Roger Grable, CH-750 Builder”

  1. A CH-750 is what I’ve been most interested in. Reading your last blog entry about the featured owner built motor re its oil cooler, I figured the -750 would definitely need the increased capacity cooler due to its slow speed characteristics and high alpha. Confirmed here; thanks.

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