Die-cast Crank Case on a stunt tank... issue

WingingIt74 Sun 20 Jan 2013 - 15:09

So I built this engine for my wife as a gag gift, and called it Suz's Pink Panther. Well, I've been trying to get it to start. It will run on prime, but it causes backpresure into the tank and the fuel shoots out of the tank like a nice fountain. Any ideas why?

The other thing that surprised me is that the pink paint isn't fuel proof, I just figured it would be.

Cox International Sun 20 Jan 2013 - 15:29

Never tried it with a stunt tank but DC engines (non SPI) did run well with a conventional 5cc tank.

The metal tanks are not a good match for the DC crankcases. For one you need to use 2 CC gaskets, one DC and one extruded. The other issue is increased CC volume because the DC reed retainer is not in place. That, together with SPI may cause the issues. It is not a combination we have ever tried.

The powder coating should be fuel-proof, at least to some degree.

WingingIt74 Sun 20 Jan 2013 - 15:45

I have the dual gaskets on this one. Not sure why the crank case has pressure instead of a vacuum. Also not sure why the reed is allowing back pressure into the tank.

My first runs with the Killer Widow was on a 5cc tank and it has SPI. I wonder if it has something to do with the tubes on the stunt tank. Where are the vent holes on them compared to a babe bee back plate?

Surfer_kris Sun 20 Jan 2013 - 15:48

WingingIt74 wrote: It will run on prime, but it causes backpresure into the tank and the fuel shoots out of the tank like a nice fountain. Any ideas why?

I've had that a long time ago, turned out the front of the tank was made too thin. It will then split when tighten up against the case, and the crankcase pressure goes into the tank.

WingingIt74 Sun 20 Jan 2013 - 15:51

I'm going to try that tank on another engine, just curious....

WingingIt74 Sun 20 Jan 2013 - 16:33

I swapped the tank to another engine and it ran. It was a non-SPI engine, ran fine. Looked and Brandon's BW and it's SPI. I don't get it....

pkrankow Sun 20 Jan 2013 - 18:05

Planning on trying this with a cast crankcase (diesel) that I ordered. I would like to know what is up too. One of the 5cc stunt tanks I ordered is going on it with a Tygon pickup.

I wonder if crankcase air is entering the screw holes and pressurizing the tank. The gaskets for the DC cases do not surround the screws.

Phil

WingingIt74 Sun 20 Jan 2013 - 18:12

pkrankow wrote:I wonder if crankcase air is entering the screw holes and pressurizing the tank. The gaskets for the DC cases do not surround the screws.

Phil, that is an excellent point. Even with 2 gaskets, it may not be seating/sealing correctly.

pkrankow Sun 20 Jan 2013 - 18:21

I was going to say make a metal shim gasket to go between the two gaskets, but I don't know if that will work.

Can the plastic reed retainer be used with the metal tank?

Guess I'll find out in a week or so when my stuff arrives.

Phil

WingingIt74 Sun 20 Jan 2013 - 18:24

Here is a pic of how the gaskets interact.
Die-cast Crank Case on a stunt tank... issue Img_3311

WingingIt74 Sun 20 Jan 2013 - 18:33

pkrankow wrote:Can the plastic reed retainer be used with the metal tank?

It does and doesn't, as only the tip of the tank venturi will fit. I was thinking the same thing. I think if you trim one down, just for the plastic gasket, it may work.

Die-cast Crank Case on a stunt tank... issue IMG_2410

Die-cast Crank Case on a stunt tank... issue IMG_2410

pkrankow Sun 20 Jan 2013 - 19:10

What does the back of the DC case look like?

Phil

WingingIt74 Sun 20 Jan 2013 - 21:09

the same shape as the top gasket shown below.

Die-cast Crank Case on a stunt tank... issue Img_3311

**RknRusty** Sun 20 Jan 2013 - 21:14

I think Pkrankow is right, that it's blowing through the screw holes. Silicone sealer will fix that if that's what is happening.

Surfer_kris Mon 21 Jan 2013 - 0:29

Yes those gaskets are no good. Can't you use a regular one?

Die-cast Crank Case on a stunt tank... issue Cox%20049%20Babe%20Bee%20Engine%20Venturi%20Gasket%20Reed%20Tune%20Up%20Kit%201

Die-cast Crank Case on a stunt tank... issue Cox%20049%20Babe%20Bee%20Engine%20Venturi%20Gasket%20Reed%20Tune%20Up%20Kit%201

WingingIt74 Mon 21 Jan 2013 - 7:39

They won't work by themselves, no.

pkrankow Mon 21 Jan 2013 - 8:41

Wild and crazy idea, cut a gasket that is the combination of both.

I have had an extruded case engine that a tiny crumb of an old gasket made the engine not run well, and vibrate like nothing else.

I would LOVE it if you got this working before my engine shows up.

Phil

tru168 Mon 21 Jan 2013 - 8:52

Hi,

Normally when I have gasket problem, I will use high temperature RTV silicon rubber gasket, don't tighten the screws too tight, wait until silicon cured and tighten the screws , it works for me.

Surfer_kris Mon 21 Jan 2013 - 11:04

I must be thick, but I still cannot see why one couldn't use the regular gasket with the regular tanks...

WingingIt74 Mon 21 Jan 2013 - 11:21

The DC case is about 3/4 of the wall thickness of the extruded case larger. You can see how much different the diameters are of the gaskets in the pic above.

Surfer_kris Mon 21 Jan 2013 - 12:02

I had to have a look for myself, and yes the regular gasket is a little too small around the outer rim (it might still seal though if perfectly centered). One can easily cut a new gasket, the outer size and shape doesn't matter. I cut the right-hand one below some 30 years ago, and meant to trim off the edges once I disassemble the engine the next time...

Die-cast Crank Case on a stunt tank... issue Img_0611

WingingIt74 Mon 21 Jan 2013 - 12:09

I'll have to see if the depths are different between the tank and the backplate also.

pkrankow Wed 23 Jan 2013 - 16:17

My diesel bomber is here. The plan is to put it on a bee tank, just haven't decided which tank to use!

Actually the plan is to put a glow head on it, run about 2 oz of glow through it, then try it on diesel the way it is. Bad mojo might be caused by making too many changes at once ( lol ).

The plan is to make a square gasket that the round corners match the existing gasket designs, the inside hole will be to fit the tank. I and not going to consider crankcase stuffing, or lack of stuffing, at this time.

Phil

WingingIt74 Sat 26 Jan 2013 - 12:50

I cut a reed retainer and I don't have the pumping issue any more. Now I just can't get the stupid thing to run...... I give up. Last nigh I could get it to oscillate with maybe a brief run then it would die. I think I'm just going to swear off of DC cases, it's not worth my time.

Cox International Sat 26 Jan 2013 - 12:56

WingingIt74 wrote:I cut a reed retainer and I don't have the pumping issue any more. Now I just can't get the stupid thing to run...... I give up. Last nigh I could get it to oscillate with maybe a brief run then it would die. I think I'm just going to swear off of DC cases, it's not worth my time.

The DC case is not the issue - we sell loads of them every month and our Pink Panther placed close to top in a previous tach race.

Try taking the tank bowl, with reed and retainer installed, attach a piece of fuel tubing to the veturi side and do the blow/suck test. If the reed does not seal on the suction part, carefully grind around the hole where the reed sits.

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Die-cast Crank Case on a stunt tank... issue

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