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what size of head shims to run in a CMB.21RS redhead??

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what size of head shims to run in a CMB.21RS redhead??

Old 09-26-2008, 12:14 PM
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misshydro
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Default what size of head shims to run in a CMB.21RS redhead??

Well I'd poped acouple of glow plugs on my cmb.[:@] Was told to put another headshim in my motor.[>:] come to find out it doesnt have one...[X(] Do they come with one from factory and what size should be in it,or what size of shim should I run??[&:] I'm running 33%.[8D]
Old 09-26-2008, 07:21 PM
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wave waker
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Default RE: what size of head shims to run in a CMB.21RS redhead??


ORIGINAL: misshydro

Well I'd poped acouple of glow plugs on my cmb.[:@] Was told to put another headshim in my motor.[>:] come to find out it doesnt have one...[X(] Do they come with one from factory and what size should be in it,or what size of shim should I run??[&:] I'm running 33%.[8D]

side question, what glow plug ur using?..probably get cmb headshim..
Old 09-29-2008, 10:14 AM
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jetpack
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Default RE: what size of head shims to run in a CMB.21RS redhead??

I found most head shims are about the same size on bore diameters. You have a short stroke which most are, so any type in your displacement size should work, but its best if you can compare bore sizes before you buy. A little bit of homework will be needed to compare all the factory specs on that, but shouldn't be too bad.

Different manufactures have different thicknesses available, too...so there should be a pretty good variety.

Always start with more clearance than factory, and lower it as you tune your engine. If you start blowing glow plugs, and you know your mixture is correct, and happy with the plug your using, then add back a shim or lower your nitro percent.
Old 09-29-2008, 01:45 PM
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G.McClintic
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Default RE: what size of head shims to run in a CMB.21RS redhead??

Miss Hydro

You might try this

http://www.woodrcboatproducts.com/head_shims.htm

Glenn
Old 09-29-2008, 06:20 PM
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laedco58
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Default RE: what size of head shims to run in a CMB.21RS redhead??

.008 clearance works well with .21 motors
Old 09-30-2008, 09:30 AM
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Default RE: what size of head shims to run in a CMB.21RS redhead??

.008 is sometimes hard to tune on, .010 is where mine is set for 60%



Also the RS 21 has the same stroke as the LS motor, so its a long stroke.
Old 09-30-2008, 04:17 PM
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misshydro
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Default RE: what size of head shims to run in a CMB.21RS redhead??

A guy that my boyfriend talked to name Jack Iawbaugh who's used to race R/C boats for 30 years and has been out of it for 3 years. Now he drag races a R/C rail with a .21 nova in it.Jack was racing in Celina on sunday.Jack told my boyfriend that he shims his heads at .010 on his nova's.21 and run at 60% nitro..I'd wished I wouldve let my boyfriend takened my boat on sunday.[:@]He wanted to do some test runs on my boat.Plus I forgot that they were drag racing on sunday too.[X(] Jack wanted to take a look at it and see whats it should be set at and whats been done to the motor like timing and post work..[8D] Well As what I was told Jack could pass for Jerry Dunlap brother!!
Old 10-01-2008, 12:02 AM
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Ron Olson
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Default RE: what size of head shims to run in a CMB.21RS redhead??

It's not really the head shims but the head clearance that you want. You vary that by adding or subtracting shims.
I used to have a dial indicator for doing just that until I loaned it out and haven't seen the guy since. I used ot run mine at a comfortable .012".

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