 Deck Height, using shims UNDER the cylinder |
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| IHHRA |
 Dec 11 2011, 09:14 PM
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#1
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Newbie  Group: Members Posts: 2 Joined: 11-December 11 From: Western NC Member No.: 13,888 Region Association: None  |
When calculating compression ratio, is it a no-no to use more than one shim under the cylinder to get the desired DH?
Thanks, Bill |
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| Mark Henry |
Dec 11 2011, 09:49 PM
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#2
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Three shims max, but I would get shims made by RIMCO to the correct thickness.
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| sean_v8_914 |
Dec 12 2011, 08:51 AM
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#3
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Chingon 601 Group: Members Posts: 4,011 Joined: 1-February 05 From: San Diego Member No.: 3,541 |
burnish the faces and de-burr teh edges.
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| IHHRA |
Dec 12 2011, 08:54 PM
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#4
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Newbie Group: Members Posts: 2 Joined: 11-December 11 From: Western NC Member No.: 13,888 Region Association: None |
QUOTE(Mark Henry @ Dec 11 2011, 11:49 PM)  Three shims max, but I would get shims made by RIMCO to the correct thickness. Even with good sealant, will I be adding additional opportunity for leaks with 2 shims vs. 1? |
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| 76-914 |
Dec 12 2011, 10:39 PM
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#5
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,698 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California 
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QUOTE(Mark Henry @ Dec 11 2011, 07:49 PM) Three shims max, but I would get shims made by RIMCO to the correct thickness. No disrespect to you Mark (especially if that is you in that avatar (IMG:style_emoticons/default/lol-2.gif) ) but I wouldn't piss on Rimco if they were on fire. Things changed there. Search my posts last spring. |
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| Mark Henry |
Dec 12 2011, 10:54 PM
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#6
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
QUOTE(76-914 @ Dec 12 2011, 11:39 PM) QUOTE(Mark Henry @ Dec 11 2011, 07:49 PM) Three shims max, but I would get shims made by RIMCO to the correct thickness. No disrespect to you Mark (especially if that is you in that avatar (IMG:style_emoticons/default/lol-2.gif) ) . That's an old pic, I wear glasses now (IMG:style_emoticons/default/shades.gif) |
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| sww914 |
Dec 13 2011, 11:31 AM
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#7
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Advanced Member Group: Members Posts: 2,439 Joined: 4-June 06 Member No.: 6,146 Region Association: None |
I can't recommend it, but I ran 5 shims in my 2056 for years with no problems and no leaks. Obviously one shim would be best but I ran out of time and money and I had plenty of shims. Used Curil's minty green stuff on all the sealing surfaces.
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| stugray |
Dec 13 2011, 12:07 PM
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#8
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
How about NO shims?
Any advice on that one? Stu |
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| '73-914kid |
Dec 13 2011, 12:32 PM
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#9
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California  |
On stroked motors, or motors that are not your "typical" combination, the only way to avoid shims is to either mill down the top of the piston, or just run astronomical compression ratio. Without shimming my cylinders, I would have had a compression ratio near 12:1. FAT performance can cut shims to any thickness you want IIRC.
Just make sure when you do get shims, or decide to stack the shims, deburr them like Sean said. Otherwise when you put things together, take them apart repeatedly during mock-up, you deck height will change throughout as things settle in. I don't have any experience in shim stacking to recomend or discern it though. I was lucky enough to find a little VW shop that had EMPI produced shims from the late 80's. They are out there, you just might have to call around. What size shim are you thinking you will need? |
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| wndsrfr |
Dec 13 2011, 12:39 PM
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#10
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Senior Member Group: Members Posts: 1,449 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region
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QUOTE(stugray @ Dec 13 2011, 10:07 AM) How about NO shims? Any advice on that one? Stu I'm re-doing my 2316 right now......shooting for 10:1. I'll get 9.9:1 at zero deck height with a .056" shim. Based on the CR calculator at CB's website, if I put in no shims, I'd have minus .056" deck height which would yield 11.6:1--too much for me on 93 octane and probably get valve interference as well with the 9560 cam. Be mighty careful if you go that close! Of course, your registers may be higher up or your piston pins as well, so you've got to measure your specific deck height carefully--here's the link to the CB calculator- http://www.cbperformance.com/enginecalc.html John |
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| bobhasissues |
Dec 13 2011, 01:07 PM
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#11
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seemingly endless issues with my 914 Group: Members Posts: 218 Joined: 13-February 07 From: Chicagoland Member No.: 7,532 Region Association: None |
Type IV shim sets available at DRD Racing approx $10 per set. Available in .010 increments.
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