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ideola
Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL
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 Posted: Fri Jun 26, 2020 11:42 pm Post subject: |
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I think it was Augidog who had a high CR NA made with S2 pistons + NA head.
Digging thru some of his old posts might be interesting:
http://www.924board.org/search.php?search_author=augidog
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition |
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ideola
Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL
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| Posted: Fri Jun 26, 2020 11:48 pm Post subject: |
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| safe wrote: | | Note that you need "spacers" to center the rods on the crank with those bmw rods. |
I'd be intereseted in how one would implement this solution.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition |
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safe
Joined: 18 Mar 2017
Posts: 166
Location: Sweden
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| Posted: Sat Jun 27, 2020 12:00 am Post subject: |
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| ideola wrote: | | safe wrote: | | Note that you need "spacers" to center the rods on the crank with those bmw rods. |
I'd be intereseted in how one would implement this solution. |
Me too, probably making spacers on the small end centering in the piston. |
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gegge
Joined: 27 Jul 2007
Posts: 1075
Location: Sweden
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| Posted: Sat Jun 27, 2020 12:09 am Post subject: |
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I made thick 22mm washers in aluminium in order to center the rod, nothing fancy. It is mportant that they are a tight fit to the wrist pin and doesn´t move. The inside of the piston was wedge shaped, two parallell surfaces to would be better thogh. But there are no horizontal forces on the rod so I guess it worked...
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
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TJC
Joined: 04 Apr 2010
Posts: 751
Location: Central-ish Arizona, USA
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| Posted: Sat Jun 27, 2020 12:21 am Post subject: |
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| ideola wrote: | | safe wrote: | | Note that you need "spacers" to center the rods on the crank with those bmw rods. |
I'd be intereseted in how one would implement this solution. |
Many moons ago I did my time at a high performance/race engine machine shop in Phoenix, Az. I don't remember the application right off the top of my head, (probably a open wheel sprint car Chevy V8 or midget 4 cylinder engine), but we took rods that were too narrow at the big end and machined spacers from chrome moly tubing and then tack welded them onto the rods. we split them at the parting line of course, resized the rods and made sure they had the proper chamfer on them to facilitate proper clearance and oiling. I think we were using Carillo rods at the time. It was over 30 years ago and actually may have been for the all aluminum Chevy V4 engines we built for midgets...a designed first conceived by my late friend Ron Trainor.
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'95 BMW 318i/5 ..."Pearl"
'80 Porsche 924 Turbo..."Pogo"
'81 Porsche 924 Turbo...Parting!
'87 Porsche 944 NA... "Liebchen"
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Still on the Prowl!
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ideola
Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL
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| Posted: Sat Jun 27, 2020 12:24 am Post subject: |
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Cool, thanks for that. Follow up questions:
1. So these washers are at the little end, placed over the pin bushing?
2. Rough estimate of the thickness of the washers?
3. Any thoughts on specific flavor of alu?
4. Why alu vs steel?
5. Any concerns about the alu deforming over time due to the harder metal of the rods and pin?
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition |
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