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Permalink Reply by John Austin on September 20, 2026 at 2:15pm

There is one significant difference in the Gen 4 vs the Rotec cylinders for Gen 1-3.  The Rotec cylinder has a steel liner, same as the OEM Gen 1-3 cylinders.  The Gen 4 cylinder is all-aluminum with a Nikasil cylinder plating.  Not being critical of Rotec, just saying there is a difference!

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Permalink Reply by Mark Hanson on September 20, 2026 at 5:15pm

Absolutly correct, the original were steel as well. I guess when I said similar I meant that the cooling jacket and head "looked " similar as well as how they bolt to the case halves. I have maintained continentals and lycoming most of my career and have been very happy with thier steel cylinders. Just be careful not to let them sit for very long, but never had an issue breaking them in. 

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Permalink Reply by shaun wheeler 20 hours ago

I've been watching Rotec's news on the Gen4eva for a while. Their blurbs clearly refer to a steel liner in the kit, which of course doesn't bring parity with a true Jab gen 4. 

Like you, I'm not knocking Rotec. I just question what the advantage is of a kit that doesn't offer parity with a Gen4. 

Arion quoted me a little over 6K for pieces/parts plus cylinder honing on a Gen2 just a couple weeks ago. With an added 1000 hours its a pretty decent price. 

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Permalink Reply by Mark Hanson 9 hours ago

I think the greatest advantage over the original cylinder and heads is it's cooling fin design. One of the biggest advantages of going to the Gen 4 in my eyes is the Gen 4 doesn't seem to have the cooling issues that the earlier models have. I would like to have an engine that has good cooling properties without adding the complexity of liquid cooling. BTW I am still on the fence on which way to go. I have a GEN 1 with only break-in time on it but the cylinders are severly corroded. Everything else looks great.     

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Permalink Reply by John Austin 9 hours ago

Any improvement in cooling fin design would obviously be a good thing, but my late Gen 2 (with the steel lined cylinders) cooled OK after some tweaks.  I think the reason the Gen 4's cool so well is not so much the fin design as that they are all-aluminum cylinders with no steel liner.  Aluminum conducts heat more than 5 times better than steel!  When I went to the Gen 4, there was simply no comparison (vs the Gen 2) as to either how quickly the cylinders would warm up and how easily they cooled - I didn't even touch the ram air ducts internal vanes that direct cooling air nor did I do any sealing - it was "plug and play" right of the box ... er, crate!  :)

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Permalink Reply by shaun wheeler 7 hours ago

Mahle pioneered nikasil cylinders and pistons. Limbach was one of the earliest to adopt them for their modified Type 1 engines. I'm not sure why Rotec is still sticking with the original liners. The process for nikasil isn't really all that expensive when you compare the costs. 

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Permalink Reply by Mark Hanson 4 hours ago

Cost is the only thing I can think of. Rotec has 1 cylinder right now on a 3300 GEN 4., so we should be able to see how well it cools compared to a GEN 4 cylinder in the same enviroment.

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