William Wynne

"The Corvair Authority"
5000-18 HWY 17 #247
Orange Park, FL 32003

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January 19, 2005

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Subj: One more head stud question
Date: 1/19/05

Hi William, can you stand one more question about head studs? I need to replace the top studs due to thread corrosion (so far no case damage from removal). Your excellent posts on the subject have cleared everything up but one minor question. No mention is made of Clark's standard size replacement stud. Are they recommended? I know one of the selling points of the ARP stud was stretch similar to OEM or something like that. Would that be a concern with the Clark's studs? If these could be used (with Loctite 620) it would avoid the Helicoil/Timecert operation.

Thanks, Gunther Zion, Manual 5086, Greenfield, Indiana
Reply from WW:
We've put Clark's standard studs with Loctite 620 into Corvair cases which had no thread damage. With proper hole cleaning, they will perform as well as stock studs in excellent condition.

Subj: Bing carbs
Date: 1/17/05

I have been looking for an alternative to using the MA3 carb, mainly due to its cost. My question is: Would a Bing 64 carb with their new manual mixture control work for a 601XL Corvair application? I e-mailed http://www.greenskyadventures/ (in your neck of the woods - Florida). Jerry Olenik is the owner and he wasn't able to give me an answer since he is not familiar enough with the Corvair conversion.

Thanks, Ralph Young, Zenair 601, Emmet, ID

Reply from WW:
I have known Jerry for more than 10 years. He's an incredible expert on Rotax engines, and for a long time, was the oldest Rotax dealer in the country. I assume Jerry is certainly one of the leading experts in the country on Bing carburetors. Although the Corvair will run on a wide variety of carburetors, I don't know of anyone who's yet run it on a Bing or pair of Bings. To explore this option, you'd certainly need the guidance of an expert on the carb, and Jerry would be that person. Keep in mind, there are idiosynchracies to Bing type carburetors. They have the curious characteristic of shutting off if they're subjected to ram air pressure. In the end, I suspect that the engine would likely need two Bings to run, and the expense of these would approach the cost of an Ellison EFS-3A.
Subj: 1964 vs. 1965
Date: 1/17/05

I do not have your Manual yet. Just doing research at this time. I was given a YN motor, checked the crank and found out it is not the correct 164 cid motor. Have located another motor, ZF. Haven't checked the crank yet. My question: Are the 1964 110 motors as good as the 1965 and later motors. Heard there was a difference in the motors. Would like to replace the EA81 Subaru in my Zodiac with a Corvair. Have enjoyed reading about your Zenvair.

Regards, Dave New, CH601HDS, N928DN
Reply from WW:
Your ZF could be a 1964 long stroke engine with an 8409 crank, or a 1961-63 145cid engine with a short stroke 5607 crank. You should check that before purchasing it. The only difference between a 1964 and a 1965-69 engine is the width of the head gasket. In operation, we have never blown a head gasket on an engine that we've built. Thus, I have found the 1964s to be just as good as their later brethren. Keep in mind that we resurface the head gasket areas where necessary, and use solid copper head gaskets. Combined with using the correct torquing technique and pattern, you can expect the same perfect head gasket reliability we've experienced. All of this is covered in great detail in the Conversion Manual.
Subj: Turbo
Date: 1/17/05

Thanks for your last response. I noted your advice on setting up for the turbo when doing the conversion. I have a few questions before I decide on that approach. My primary use for the 601XL will be cross country flights to paved runways.

What do you expect as to the added performance with the turbo? Cruise speed, climb, additional fuel flow? I understand exact numbers will be available on your testing, but I would like an educated guess so that I can start ordering parts for the conversion. My thinking is that if the added performance is minimal, I will go with your standard conversion, but if I can expect significant improvement, the turbo mod would be my perference.

Also, you stated that you tested two turbo cams to make sure that the performance on a non-turbo engine does not adversely affect a non-turbo installation. I was not sure what your findings were.

Best Regards, John Butterfield, 601XL Corvair
Reply from WW:
I certainly want to emphasize that the standard Corvair engine and the XL are a good match and more than enough performance for virtually all 601 builders. Our takeoff roll at full gross is short, maybe 500 or 600 feet. On a standard day, the plane climbs about 700fpm, loaded. The additional power from the turbo would substantially increase the climb rate, but I've never really felt that the airplane needed it. Gus and Grace flew to Oshkosh at 9,500'. The plane was loaded to gross, and Gus reported that it still had a good rate of climb at altitude. The turbo would most likely be of interest to people with home field elevations in the 6000-8000' range. While most high altitude airports have long enough runways for a naturally aspirated engine, these airports are obviously in mountainous areas where sustained climbing ability is always a plus. My personal interest in the turbo is to see if the plane can deliver 165+mph TAS at 10,000' on 6 gallons per hour. These numbers are hard to predict, but I suspect they're possible.

Our tests on naturally aspirated engines with turbo cams installed showed that the engines were only slightly down in peak power, maybe 2 or 3% from the same engine equipped with the OT-10 cam. This is an acceptable reduction if you're interested in keeping turbocharging open as a later option.

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