Machined cylinder

roddie wrote:

JPvelo wrote:I was going through some tee dees today I hadn't had a chance to mess with since purchase and came across this:
https://i.imgur.com/zP6zMCl.jpg
https://i.imgur.com/G7b7I0S.jpg
https://i.imgur.com/y93Fsjb.jpg
The top is machined flat. It was on an engine that had a glo-bee head and a pressure tapped backplate. Couldn't start the thing to save my life.

Jim

Jim, Did the engine have that head and back-plate "on it" when you tried to start it? Did you get it to even "pop" off an exhaust prime? How did the compression feel? Maybe temporarily "plugging" the pressure tap will get it to start... then you can decide whether or not to open it up for a pressure feed? What's the dia. hole on the pressure tap? I'm guessing that it probably shouldn't "exceed" a certain inside diameter, to work correctly with a bladder. I don't have experience with that... but plenty of people "here" do!

I installed a standard backplate and insert type head with 5 shims.Piston fit is TIGHT! A few pops and rich sputters but no action. I installed the piston/cylinder on a reedie and got a disappointing 15k.

Jim

JPvelo wrote:

roddie wrote:

JPvelo wrote:I was going through some tee dees today I hadn't had a chance to mess with since purchase and came across this:
https://i.imgur.com/zP6zMCl.jpg
https://i.imgur.com/G7b7I0S.jpg
https://i.imgur.com/y93Fsjb.jpg
The top is machined flat. It was on an engine that had a glo-bee head and a pressure tapped backplate. Couldn't start the thing to save my life.

Jim

Jim, Did the engine have that head and back-plate "on it" when you tried to start it? Did you get it to even "pop" off an exhaust prime? How did the compression feel? Maybe temporarily "plugging" the pressure tap will get it to start... then you can decide whether or not to open it up for a pressure feed? What's the dia. hole on the pressure tap? I'm guessing that it probably shouldn't "exceed" a certain inside diameter, to work correctly with a bladder. I don't have experience with that... but plenty of people "here" do!

I installed a standard backplate and insert type head with 5 shims.Piston fit is TIGHT! A few pops and rich sputters but no action. I installed the piston/cylinder on a reedie and got a disappointing 15k.

Jim

The run on the reedie was with the glo-bee head...? I personally have never had good results on a reedie with an adapter head/std. plug. I have heard that there are only a "few" of these heads that work well... one of which was (if you can find one...) a Kustom Kraftsmanship KK-1 head w/Nelson plug... "specifically designed" around the Henry Nelson plug and specifically designed for the Cox Tee-Dee .049/.051 engines running 20% nitro. KK's brochure states that a std. plug will not work. I am not sure why, but I assume that the "length" of a Nelson plug falls somewhere in between a "short" and "long" plug? Not sure.

KK also recommended the use of "cylinder-shims" that fit between the cylinder and crankcase... to adjust cylinder "height" for optimum performance.

There is a remote possibility that you "do" have one of the KK cylinder/head/Nelson plug combos... but lack the recommended cylinder shims... (you mentioned "tight piston fit") Who knows... maybe the guy who sold you the engine didn't know what he had?

The "Nelson" plug was possibly an "insert" type plug (like the head adapter and it's insert plugs that Bernie sells at Cox International) C.I. mentions add'l. "head gaskets" may be needed with the use of their insert style head... but does not mention "cylinder-shims". Maybe you're dealing with a "timing" issue...? (I'm presuming a previous owner may have swapped cylinders; not knowing what they were?)

I use the C.I. insert heads with 5 shims on all my runners. The more I think about it this cylinder was customised with timing shims in mind. Put a shim under the cylinder and intake starts sooner on the downstroke making for a longer intake and faster escape of the exhaust gasses. Machining the top keeps compression where it should be with the raised cylinder. I just need to find some timing shims.

Jim

I got some timing shims from Darrin Albert (combatalbert on eBay).

stevej wrote:I got some timing shims from Darrin Albert (combatalbert on eBay).

I ordered some from Matt at Exmodel Engines.

Jim