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"Cox Tee Dee .010"



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Cylinder Shims

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Cylinder Shims

Post  Mark Boesen on Thu Jan 15, 2015 9:24 pm

There seems to be some confusion on what a cylinder shim does, so i thought i'd start a new thread. Here's a note from Kustom Kraftmanship that might clear it up.

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Re: Cylinder Shims

Post  TDbandit on Thu Jan 15, 2015 11:43 pm

Cool I've done something similar with my TD's what it is is a go no go gauge used to adjust piston crown to deck (shoulder) height the only difference between my way and theirs is I use a stop screw with no gasket while they use the copper disk which would be easier to do. (Bandit)
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Re: Cylinder Shims

Post  Ken Cook on Fri Jan 16, 2015 4:34 am

The last part of KK's instructions is the suggestion to have approx .012" sub induction. From my experiences I have found that .012's was too much sub induction . I've had better results in raising the cylinder even higher. I was using the TD on foamies so I was also using the shims to orientate the cylinder to prevent my wing from melting. However I was keeping all of the above in mind. In order to benefit from sub induction, my results were far better when I had only a tiny bit of light showing under the skirt of the piston. Ken
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Re: Cylinder Shims

Post  balogh on Fri Jan 16, 2015 7:41 am

I think the COX Int'l description on the purpose of the shims is self-explanatory. My only comment would be that shims can be used for all 049/050/051 engines and not fot TeeDee-s only.

http://coxengines.ca/cox-.049-tee-dee-timing-shims.html
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Re: Cylinder Shims

Post  TDbandit on Fri Jan 16, 2015 10:42 am

balogh wrote:I think the COX Int'l description on the purpose of the shims is self-explanatory. My only comment would be that shims can be used for all 049/050/051 engines and not fot TeeDee-s only.

http://coxengines.ca/cox-.049-tee-dee-timing-shims.html
Yup they can, there just not quite as effective on reedies as they are on engines with rotary valves (TD, Medallion and RR1)
As far as SPI goes, I agree with ken .012 is a bit much. Mine has about .008.
(Bandit)
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Re: Cylinder Shims

Post  roddie on Fri Jan 16, 2015 10:48 am

Ken Cook wrote:             The last part of KK's instructions is the suggestion to have approx .012" sub induction. From my experiences I have found that .012's was too  much sub induction . I've had better results in raising the cylinder even higher. I was using the TD on foamies so I was also using the shims to orientate the cylinder to prevent my wing from melting. However I was keeping all of the above in mind. In order to benefit from sub induction, my results were far better when I had only a tiny bit of light showing under the skirt of the piston. Ken

I'm now wondering if this may be contributing to the trouble I am having with my Reed Speed engine. The engine is a "Bear" to start... hot or cold.

Here's a couple TDC shots.




The focus is off on this photo (below).. but it really shows the extreme..



It's a brand new repro Tee Dee .049 cylinder/piston set and Killer-Bee style backplate/needle from Cox International. I was using a standard glowhead, single head-gasket and Sig Champion "25" fuel. I figured that one head gasket and a standard compression head on 25% nitro would put me in the ballpark. I don't possess any cylinder shims.

Does the SPI gap under the piston-skirt look like it's too much; given the top-end components?

As far as the erratic running I'm experiencing.. I also suspect the backplate to case seal. I'm using the flanged (black) plastic reed-retainer without any other gasket(s). This was a subject of debate back when I was getting the engine ready for the first Speed contest. Some people said they didn't use a gasket with the retainer.. and some said they did.. or it didn't matter much. I had a flanged-retainer already.. so I didn't buy a new one. I suppose if the flange is bad.. (hairline crack or scratch that I didn't notice) it may not be sealing the crankcase completely.

I notice now.. that Cox international shows that backplate "assembly" with a gasket forward of the retainer.  

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Re: Cylinder Shims

Post  crankbndr on Fri Jan 16, 2015 11:08 am

roddie wrote:
Ken Cook wrote:             The last part of KK's instructions is the suggestion to have approx .012" sub induction. From my experiences I have found that .012's was too  much sub induction . I've had better results in raising the cylinder even higher. I was using the TD on foamies so I was also using the shims to orientate the cylinder to prevent my wing from melting. However I was keeping all of the above in mind. In order to benefit from sub induction, my results were far better when I had only a tiny bit of light showing under the skirt of the piston. Ken

I'm now wondering if this may be contributing to the trouble I am having with my Reed Speed engine. The engine is a "Bear" to start... hot or cold.

Here's a couple TDC shots.




The focus is off on this photo (below).. but it really shows the extreme..



It's a brand new repro Tee Dee .049 cylinder/piston set and Killer-Bee style backplate/needle from Cox International. I was using a standard glowhead, single head-gasket and Sig Champion "25" fuel. I figured that one head gasket and a standard compression head on 25% nitro would put me in the ballpark. I don't possess any cylinder shims.

Does the SPI gap under the piston-skirt look like it's too much; given the top-end components?

As far as the erratic running I'm experiencing.. I also suspect the backplate to case seal. I'm using the flanged (black) plastic reed-retainer without any other gasket(s). This was a subject of debate back when I was getting the engine ready for the first Speed contest. Some people said they didn't use a gasket with the retainer.. and some said they did.. or it didn't matter much. I had a flanged-retainer already.. so I didn't buy a new one. I suppose if the flange is bad.. (hairline crack or scratch that I didn't notice) it may not be sealing the crankcase completely.

I notice now.. that Cox international shows that backplate "assembly" with a gasket forward of the retainer.  




Its been my experience the cylinders you speak of have too much SPI, but I only tested one.
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Re: Cylinder Shims

Post  TDbandit on Fri Jan 16, 2015 11:32 am

Same here my tach race engine has too much and I'm out of shims Sad my TD however has around .008 One way to find out is to take a feeler gauge used for adjusting points gap or valve tappets and with the crank at TDC measure the gap keep in mind any ball/socket slop you might have to remove the head and while holding the prop insert your finger and lightly press down on the piston while you take the measurement to keep the piston from lifting any as to keep from spoiling the reading. (Bandit)
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