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Valve timing for model engines along with Compression ratio's vary significantly from full size practice. Generally lower CR's and much less overlap on cams to make them much easier to start, tune and run. As I understand it, a much milder cam timing is required to make a good running MODEL engine. Valve timing and events such as those published by Westbury are generally to be preferred.
Dave - I misspoke... its not ASME, it was the Proceedings of the Institute of Mechanical Engineers Vol 186 2/72 - "The development of the Porsche Type 917 car"https://journals.sagepub.com/doi/pdf/10.1243/PIME_PROC_1972_186_005_02RegardsJohnEDIT - trying to fix the URL link.
also buried in this doc...https://porschecarshistory.com/wp-content/old/biblio/17/Porsche-917.PDF
Dunno, Ask Steamer, the 917 is his projectMike
Quote from: Vixen on January 25, 2023, 11:07:11 AMDunno, Ask Steamer, the 917 is his projectMikeSorry about that Mike, I actually knew that LOL. Late night typing & getting my exotic engines crossed. Anyways I continue to tinker with my cam spreadsheet tools & its been somewhat revealing (to me). I've also been working on a kind of cookbook cam phasing/orientation procedure... well lets just call them personal scribbles & kind of a symbol matrix for now. This came about because I as suspicions of a certain cam & getting it wrong in real life seemed like a lot of work to be avoided. There are quite a few variables that enter the picture. Anyways, it was good to work through the problem on my own. So I look forward to whenever the topic comes up in discussion.
Hello Dave,You seem to want/need to avoid the use of 1144SP steel for the cylinders because of potential fin cutting issues. Instead you are considering aluminum finned cylinders with cast iron liners. What is the objection to making the whole finned cylinder from cast iron? I am sure that's what Craig did on his big 'Le Craig' rotary engine.Just thinkingMike
Hope this is useful for you DaveTop left spiral gear is the tacho drive on the inlet cam.Notches at either end of the exhaust cam (lower) drive the scavenge pumps at front and rear.Thrust bearing in the center (flanges), and drive gears attached via vernier plate integral to the shaft. Gear is located with standard bearing nut KM series.RegardsJohnEDIT - timing as per typ.906 Mezger details the lift and accelerations in the ASME paperINLET 12.1 mmEXHAUST 10.5 mmAmax 0.0143 mm/°/°Dmax 0.0056 mm/°/°typ.906 cam timimgINLET OPEN 104 °BTC INLET CLOSE 104 °ABC EXHAUST OPEN 100 °BDC EXHAUST CLOSE 80 °ATC
lets call it 120 grooves 1mm wide x 5mm deepNicole thin bits .043 wide by .236 depth of cut. Best price so far is $21 EACH. ( I have a holder for them.) I'll keep looking, but Bubba! (Steve Huck ) if you know a cheaper place to buy...let me know.