Builders,
Last week our piston manufacturer in California, the same one we have used for years to make 2,850 and 3,000 cc pistons, called to say that my order of 2,775 cc pistons will be done by the third week of October. I placed a very large order with them a while back, and these will be delivered in time to make their public debut at Corvair College #35 at Barnwell.
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These pistons are a large overbore on a stock 1965 Corvair cylinder. They are aimed at being able to run 89 octane auto fuel with 95 heads or 92 octane with 110 heads. Because they are a bored, the cylinder set is several pounds lighter than a smaller engine, and lighter than a 2,850 with it’s thicker wall full-fin cylinders. I already have several hundred original cylinders at Clark’s Corvairs, ready to be bored to match these new piston sets.
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These pistons are made with spiral locks, so they can have floating wrist pins, and be easier to assemble than stock pistons which need to heat the rods to install the wrist pins. The ring sets are .060″ over Hastings Chrome rings, the same ones we have put into Corvairs for more than 20 years. Because these pistons have floating pins, they can also use the new billet rods available from the Weseman’s at SPA/Panther.
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These will not appear on our products page until they are here, we are not selling them yet, we don’t need deposits, etc., but if you are interested, you can always send us a note with “2,775” in the subject line. we will let you know more in a few weeks.
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-ww.
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Above, a 2,850 piston made in the USA, specifically designed for flight engines. The “2,775 cc” looks identical, but is .045″ less in diameter and has a different chamber volume. I wrote a story about having these on the back burner of development 24 months ago, but the project will be done shortly, and they will be an option for builders. read more: Getting Started in 2013, Part #15, 2,775cc.
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I am interested in the 2775 system of piston, rod, cylinder. I will be attending Mexico MO. hope to get more info/advise there.
On other “floating pin” engines (like a VW), the rods are attached to the crank, THEN the case is closed. The pistons are installed into the cylinders and the assembly is slid down the studs to where the rod can be installed into the bottom of the protruding piston.
Given the tight confines of the Corvair case, could the floating pins on the 2775 engine be done in a similar manner, or am I overlooking something?
Thanks for your thoughts on this approach…
Carl,
Those engines have to be built that way because they do not have an ‘open top’ case like we do with the Corvair. Among aircraft engines, the most common design that is like a Corvair is the Franklin. While having floating pins you could put the rods on as if it were Lycoming, I think that working inside the case isn’t that bad compared to trying to assemble a spiral lock wrist pin retainer on a piston below the cylinder. Lycomings don’t have this because they commonly use wrist pin buttons (which have their own issues). The wrist pin locks on VWs are easier to install, but are not as positive as spiral locks. Taking the old rods out of a core Corvair is a lot harder than putting rebuilt ones back in. If you would like the easiest combination to work with, opt for SPA/Panther billet rods, as they have rod bolts, not rod nuts, they are much easier to work with, and the 2,775 pistons mate with them directly.
-ww.
Thanks, William; I was unfamiliar with the spiral-lock type of wrist pin clip until I looked them up this AM based on your statement above. Yeah, I can see that would be a bear to install if done with the rods already installed! Based on my experience with Nik-a-sil’s and a service bulletin about the wrist pin clips popping out, I was a bit concerned until I researched the spiral-lock type. Thanks for the recommendation about the SPA/Panther rods as well.
William,
I have read the .com and .net pages and the conversion manual with great appreciation of your work. I’m probably thick as a rock, but I know how to ask a question or two. The answers may be in what I have reviewed, but I’m just having a hard time drawing them out, Sometimes I see power reduction expressed in HP and sometimes expressed in percent and I am not sure if I could combine the two to get a bottom line HP expression.
I understand the 2700, 2850, 3000 engine sizes and 2 different head versions making 6 combinations. Safety from detonation is of utmost importance to me, and HP is important as well. I’m not worried about cheap fuel and will gladly use 100 LL routinely. However, I may need to buy auto fuel with ethanol, or marina boat fuel in a pinch and may want to be prepared too, so I am looking at benefit trade-offs, not safety trade-offs. Personally I’m shooting for the 3000. I’m trying to make a matrix for myself on the resulting HP I would have based on the 3000 sized engine and different heads, and achievable compression ratios that will keep detonation at bay. I would be using all of the parts you recommend on the rest of the engine.
Could you refer me to an earlier web page discussion or pages in the 2014 conversion manual?
Mike Kynett
Virginia Beach
Mike,
If you would like a 3,000 cc engine that has the ability to run on premium auto fuel (ethanol is only a factor on how long the gas lasts in the tank, not it’s ability to resist detonation ) than you can use 110 heads with a 3,000 kit because it has dished pistons and that is a proven combination.
Some very specific tests are planned for the near future which will give a very accurate comparison between 95 and 110 heads on a 3,000 cc engine, we will write a story about it when it is done.
-ww.
WW
I’m glad to here you have given the builder an option for dished pistons for the stock cyl. for
those of us that want to burn auto gas continually–I have a Q witch might be out of place here
but I’m wondering how Dan’s stroked crank can be used with this bore piston –can they be
made with the pin location higher or does Dan have his Billet rods made shorter—
I want to thank you for all your doing to make the corvair conversion a better choice for an A/C —
engine
George– on the west coast of this great country
George,
On Dan’s stroked motors the rod stays the same, but the pin location in the piston is changed. Give Dan a call in a week or write him an email about it, the stroked crank/stock cylinder combo is something he has spoken of before.
-ww, on the east coast of this great country.