Stan Tyler is using the crankshaft timing on two Tee Dees on his twin Flite Streak.  Now that he has de-varnished the cylinders, tightened the ball joint in the piston and reduced the compression a bit while using 35% Nitro fuel, he is getting dynamite runs on both engines (at the same time, even!)  He is using stock venturis and Master Airscrew 6x3 props.  I have pretty much the same setup, and also get reliable runs, though on a single, not twin model.

I really prefer the port timed pressure to backplate pressure.  It is more gentile and does not allow any backflow.  Another local 1/2A flyer who shall remain nameless (but loves hats) is using backplate pressure and having a hard time getting consistent runs.

If you want to seal the hole in the crankcase, I do think JB weld is the way to go.  Be sure to clean everything well with a killer solvent like Acetone or MEK. I really think that just putting a cap over the nipple will do the job, since, if there were leaks, the pressure fitting wouldn't work in the first place.

Of course I have no idea what the geometry of your tank setup is, but I would bet that is the real problem.

Note that with any pressure setup, the stock needle is totally inadequate.  You need the fine thread needle from Texas Timers.  Do a search on varnish and rod/ball joint tightening.

      I went out today and tried my hand at running the tee dee again. This engine is in a mouser and its using a rectangular perfect tank 3/4 oz. The pick up was re plumbed to the outside  but no other vents other than the stock ones. Engine is very difficult to start and I needed to pinch off the pressure line and run the prime then release the line. At that point needling was a bit touchy. Just as the engine was coming up on rpm's it would just fall off. I launched plane and it may have flown 2-3 laps and just when it sounded like it was going to unload it would quit. Venturi is now at 5/32 inlet and stock needle valve assembly. I richened it up a good bit figuring it was just going over lean and it ran the tank but not as fast as I wanted it to be. I was using a stock black Cox 5x3 not the safety tip version. I switched to a Tornado 5x4 black and got a bit more speed. I then switched to a KK needle assembly and found I could lean it a bit more and also start it easier. I just still couldn't get the rpm's out of the engine. I then capped the backplate line and ran it standard suction and it seemed to be a bit more perky. One problem though was trying to needle the engine. At first it ran on the setting I was using with pressure then I had to open the needle almost 1 1/2 turns while it was running . I got it to settle in at a rich setting and launched. The plane snagged a line I suppose a weed or something and off it went skyward right over the top and almost did a loop. Plane hit the ground breaking one of my last Tornado's which was more upsetting than anything and other than dirt everywhere its ok. I really don't know what to try next. After a bit of throwing a tantrum I listened to my son for a few minutes. I haven't had in my opinion good luck at all with ANY tee dee I've ever owned. A lot of this was lack of listening to others and some of it was just some simple mods needed for more effective runs. I can get these engines to run and thats not the problem its just getting it to run the full flight and without hesitation. My son commented about speed guys never probably got the runs they wanted the first time without experimentation. With that being said I had to agree and therefore I surely don't want to quit. The fellow above posted about using a one way valve. I think this is something to try its simple and inexpensive. While I was trying to start it the engine showed some signs of overcompression. I suppose a gasket or two might resolve this? My concern is that I don't want to lose compression in my quest for speed. I purchased this engine used so I'm not sure what kind of time is on the engine. My first tee dee I purchased new came with 3 glow head gaskets. It clearly stated to use the 3 for break in then remove them one by one. I was wondering if this engine is suffering from trying to be pushed to hard without being broken in all the way. How much time is generally required ? I probably have myself about 15 flights on the engine. Ken

      I decided to run the tee dee without pressure by plugging the backplate tap and use regular suction. The engine starts and needles better. I added a few shims to the glow plug a total of four. The plane flew out the tank but still not as fast as I think it should be going. I'm making this comparison based on a fellow member with the same plane and set up. His plane flies much faster than mine. I'm using 42' lines and I know he's using  a shorter length possibly 35'. I know this will make a big difference if I shorten them. My pilot whipped it for a few laps and it surely unloaded and was sounding much better. I wish it would hold that setting. I then went back to the engine with drilled crankcase. I had only one shim under the plug but I had high hopes for the timed crank pressure set up. I was using a venturi with a .128 inlet. I started it and after a few seconds had to back the needle out due to it going lean and launched. The plane took off nice unloaded then started to go over lean but it flew the entire tank out. I noticed that the engine was surging a bit. I was wondering if this is due to the crank pressure. It was mentioned that this is a positive pressure and that the one way valve really shouldn't be needed. I started it once again and set it a bit richer in hopes it would lean up which it did but went overlean again. While trying for the third flight it wiped the plug out due to the overlean runs. I installed another high compression plug realizing that this is getting to be an expensive day. I then added 3 more gaskets started and launched it. It would run the entire flight but it was overheating and not maintaining a steady run. It sounded like it was sagging the majority of the flight. When it landed I noticed the plug was loose and I'm sure that was cause for a lot of the problems but it smoked the new plug I just installed. I was a bit upset with this. I put it aside and flew the stuff that was working. I looked at it when I got home. There is no crankshaft binding or piston fit binding. The top of the cylinder for approx 3/32 is blued. I never have seen this in any Cox engine I've run. I'm sure its due to some of the high r's it was making then the sag. The top of the piston is blackened and I don't know why. The fit seems good which puzzles me. I'm using the same fuel I always run which is Sig 25%- 35%.  This engine is in a small combat wing with the tank installed within the wing. When trying to run suction it just coughs and hesitates due to the running away from the fuel. It makes me wonder what did people do to get these kind of set ups to work years back. Is bladder the only solution to this problem? I recall in the eighties a friend of mine flying a Baby Flite Streak like there was no tomorrow and he surely didn't have any whiz bang set up.  Ken Cook

        I was at it again today. Due to the high comp heads that I keep destroying I switched to a used Glo Bee I had. I'm glad Xenalook is carrying high comp plugs now. The Glo Bee added serious compression to this engine. I already had 4 glow plug washers installed and I had to install another 2. I think it could of used one more actually. It was if the engine was idling everytime I flipped. I guess its actually running forwards and backwards. If I could flip it real hard and fast with a fat needle setting I could get it to run then quickly lean it up. I actually got pretty good at this. When launched this engine was sounding real good and fast. This would only last about 10 laps then it would overheat and sag. I tried several runs to launch it rich so that it wouldn't go lean but it kept sagging. This plug launched so I had to switch to the Galbreath set up. I didn't want to harm the plug so I kept the six washers and it fired right up. This time it kept the rich setting all through the run. I then leaned it up a bit but the engine wouldn't come alive like it did with the Glo Bee head. I guess I could've dropped a washer or two but I elected to run the backplate pressure once again. When I launched I thought it was semi -rich but apparently it wasn't , the engine leaned sounded good then died. I restarted opened the needle then launched again. This time it was running but it was obvious that it was running rich. It was fast but from the burbling crackle you could tell it was rich. If I close the needle anymore it just quits half way around. My thoughts are is the hole in the venturi large enough for this run? Is there a possibility the tank is at suspect here. I thought maybe the pickup isn't in the dead corner of the tank. I can't help to wonder if the fuel is getting delivered by pressure it obviously needs more air to accomodate it. Initially my first test from above rendered pressure useless until I opened the venturi hole slightly. Now that its running on pressure do I have a large enough opening? I'm going to eventually get this engine to run like I want it. I just get a bit frustrated with failed attempts. Ken

        Jim, I did switch to a finer needle. This took a bit to find the sweet spot for starting. In no way I'm doubting what you've stated,  for me it just allowed a finer adj., it didn't solve my problems. I tried to stick with the stock unit based on Larry Renger's version using a stock needle with timed crank pressure. I'm not using the timed pressure nipple but am using a backplate version. I did try the pressure nipple with another engine and it suffered from poor runs such as incapable needling and also surging. The whole reason I'm trying to use pressure is due to the venturi opened up for a bit more power. My initial test with the stock venturi wouldn't allow a run at all with pressure until I opened the hole to .128. I'm not sure what the stock hole was but I didn't open the venturi all that much. I tried to switch to the 5/32 version I had that was on bladder and this was the most inconsistent run to date. I believe I'm dealing with several factors here. I strongly believe that based on my experiences the older versions weren't always better due to the fact they're older. My eighties version engines Tee Dee's, Black Widows, Babe Bee versions etc. are my best runners to date. I'm assuming the engines I'm using are the earlier 60's-70's version due to the thin cylinder walls and no tool flats on the cylinders. I want to experiment next by using the "80" version engines and see what the outcome is. My issues could truly be in my tank. I just want to explore some other avenues prior to opening it up. I may have some difficulties in getting the tank off of the one plane due to the fact it was epoxied in. Ken

HI Ken,

After reading all the above. The BIG problem is indeed your TANK!  It is going from rich to overlean in the air.
Recalling what you said, a std vented tank does just that, go rich to overlean. The faster the model goes the greater the rich to lean spread is.
This is why speed models are MOST FINICKY with tank venting & position & stunt models are most forgiving.
Two things are required for a mouse racer. A thin tank & proper location of pipes. Any normal WIDE tank ALWAYS runs rich to lean in the air.
The proper fix is to find or make a narrow tank. What do I mean? Looking down at your model from the top. With a straight edge lined up on your
needle valve fuel nipple, the outside corner where the fuel pick-up is should be in line with the straight edge. I can almost guarantee that your
pick up point is outboard of the straight edge. Am I right?  One fix is to shim the engine out with metal plates under the engine lugs, or move the tank
inboard by cutting into the fuse, OR by making a new thin tank. I have had people tell me that when they have done this (engine shimmed more O/B)
that their engine took on a whole different attitude & ran like never before.  I'm off on vacation, but might be able send you a photo if there's time.
And of course....LEAKS make everything run terrible for sure, as has been pointed out.

The good news is your engines probably allright....

Cheers, Paul