Printable Version of Topic

Posted by: IHHRA Dec 11 2011, 09:14 PM

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

Posted by: Mark Henry Dec 11 2011, 09:49 PM

Three shims max, but I would get shims made by RIMCO to the correct thickness.

Posted by: sean_v8_914 Dec 12 2011, 08:51 AM

burnish the faces and de-burr teh edges.

Posted by: IHHRA Dec 12 2011, 08:54 PM

Even with good sealant, will I be adding additional opportunity for leaks with 2 shims vs. 1?

Posted by: 76-914 Dec 12 2011, 10:39 PM

No disrespect to you Mark (especially if that is you in that avatar ) but I wouldn't piss on Rimco if they were on fire. Things changed there. Search my posts last spring.

Posted by: Mark Henry Dec 12 2011, 10:54 PM

That's an old pic, I wear glasses now

Posted by: sww914 Dec 13 2011, 11:31 AM

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.

Posted by: stugray Dec 13 2011, 12:07 PM

How about NO shims?

Any advice on that one?

Stu

Posted by: '73-914kid Dec 13 2011, 12:32 PM

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?

Posted by: wndsrfr Dec 13 2011, 12:39 PM

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

Posted by: bobhasissues Dec 13 2011, 01:07 PM

Type IV shim sets available at DRD Racing approx $10 per set. Available in .010 increments.