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Old 04-01-2007, 11:38 AM   #1
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Default Need help shimming RB engines for 30%

I have a C6bb and a new S3 I need to break in. Last summer I ran 20% in my C6 because my other class I used 20% and didn't want to risk grabbing the wrong fuel bottle in the heat of the action. This summer I am running .21 engines exclusively and want to run 30% nitro. What shims do I need in each engine to properly run the 30%? Both engines are shimmed as they came from the factory.

Also, anyone know which after-market head I can run on the S3?
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Old 04-01-2007, 05:22 PM   #2
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I don't think you have to shim a .21 engine for 30% Nitro. I have a RB W7 worlds and it run's great with 30%.
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Old 04-01-2007, 05:35 PM   #3
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RB engines need to be at 24 - 26 thousandths deck clearance. Usually you can just run it stock and it will be fine with 30%. Haven't had an RB that did not like race fuel and we sell a bunch of them.
RB does make a button (single dot on top) that fits the sport sleeves. You can then run and head that will fit Novarossi type engines.
The Works heads are awesome. I just run the S3 head on mine.
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Old 04-01-2007, 07:05 PM   #4
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you don't need to change the shims due to nitro %. the shims is only for the combustation chamber and piston clearence during runnig from the glow plug. different percentages will not change that. just a re-tune and maybe a different glow plug from what you were running.
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Old 04-01-2007, 07:10 PM   #5
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add a .1 mm shim. RB engines come prepared to run on 25% not 30%. People will argue but that is the word from Rody himself. Their forums are on www.rbproducts.com
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Old 04-01-2007, 07:31 PM   #6
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I've been running 30% in my S7 without additional shims, no problems at the 2 gallon mark.
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Old 04-01-2007, 07:52 PM   #7
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Quote:
Originally Posted by AzBobby
you don't need to change the shims due to nitro %. the shims is only for the combustation chamber and piston clearence during runnig from the glow plug. different percentages will not change that. just a re-tune and maybe a different glow plug from what you were running.

thanks for polluting these boards with more shitty information.

you must not run nitro, so why would you comment on something you have no experience with?

The shims are used when changing nitro percentages. When you jump from 20% to 30% you need more clearance because 30% brings in more air, which means a bigger explosion, hence the need for more room in the combustion chamber.

When you use glow plugs that have different heat ranges, then you need a slight re-tune on your motor. Every glow plug is the same length, unless you put yours in with a hammer, then I could see you needing to add a couple of shims.

Many european engines do need the addition of shims, for some reason they come prepped for 25%, even though they all run 30% across the pond too.
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Old 04-01-2007, 09:27 PM   #8
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O.S. actually he does run nitro. And thank YOU for being such a jerk
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Old 04-01-2007, 09:56 PM   #9
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"RB Products - Rody
Administrator


posted 21 February, 2007 10:35
--------------------------------------------------------------------------------
If you increase the % of nitro the combustion starts earlier, if the combustion starts too early(before TDC) then you will have détonation occuring which damages your engine. This is why you need to add a shim of 0.1mm to make the combustion start later again.

If you use less nitro the combustions starts a little later and so this will not have this problem.

--------------------
Do not forget to check out our FAQ section!"

he has alot of nice info too. he keeps it simple and gives the right answers.
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Old 04-02-2007, 05:33 PM   #10
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Quote:
Originally Posted by AZRCaddict
O.S. actually he does run nitro. And thank YOU for being such a jerk

glad I could be of service!
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Old 04-02-2007, 07:12 PM   #11
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is it true shimming can make the engine more relax and smooth.. and the engine can long lasting since less compression, less stress on conrod, crank shaft, bearing..

Last edited by arghh; 04-02-2007 at 07:24 PM.
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Old 04-02-2007, 08:09 PM   #12
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Thanks for the replies. Since Rody himself says to add a o.1mm shim, I'll do that. No need to take chances with apart that is cheap enough to buy. What is best plugs for 30%? I have been running MC59's with no problems. Should I continue or switch?

I think I'll stick with the S3 head for the time being. At least I know I have options if needed.
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