I'm breaking in a rebuilt ST-V60 for my new Shark 45, and the tank I built is 5 oz. Spigot type Venturi size is .203 ST NVA.  The engine has lots of power (12-6 prop) and very good 4-2-4 run with 20 min. run time so far on test stand.  At this time the engine will run about 5 min. on a tank.  The engine has a hemi head, shimmed to .0035.  So my question is:  will the fuel consumption get better?  Will a smaller spigot Venturi, say .190, get better fuel consumption or lower compression?  Oh yes, I am running 10% 11-11 Power Master fuel.  I'm not saying the spigot makes it use more fuel.  Just need to get better fuel economy because it's the biggest tank I can fit in my Shark.

Jimmy Jacobs

Dropping from 10% nitro to 5% nitro will help, as you know, also.

You may need to take a page out of Brother Al Rabe's book and build a special tank.  Getting the ST 60 to do the pattern on 5 oz. will be a challenge.

Typically I have found that the spigot venturi atmoizes the fuel better and the run duration goes up accordingly.  You may run slightly hotter with the spigotted ST60 than with a peripheral jet or spraybar venturi.  However, the spigot venturi does draw better than either.

Frank,

Are there any tricks to getting a ST 60 through the pattern on 5 oz. of fuel like Jimmy needs to do??  He's using it in a Shark 45 so there is plenty of power available.

I'm breaking in a rebuilt ST-V60 for my new Shark 45, and the tank I built is 5 oz. Spigot type Venturi size is .203 ST NVA.  The engine has lots of power (12-6 prop) and very good 4-2-4 run with 20 min. run time so far on test stand.  At this time the engine will run about 5 min. on a tank.  The engine has a hemi head, shimmed to .0035.  So my question is:  will the fuel consumption get better?  Will a smaller spigot Venturi, say .190, get better fuel consumption or lower compression?  Oh yes, I am running 10% 11-11 Power Master fuel.  I'm not saying the spigot makes it use more fuel.  Just need to get better fuel economy because it's the biggest tank I can fit in my Shark.

Jimmy Jacobs

HI Jimmy

I setup over 700 of the ST 60s, I think you are going to have a very hard time getting a full pattern from 5 ounces, regardless of any type of fuel delivery system. The best way to do this is with a .175 true venturie or any other of the same area. I setup many that used a .181 venturie and ran either a 13 x 6 Bolly or a 12.5 x 5.5  Bolly, both used 6 ounces to just make a pattern.

Do you have any idea around when this 60 was made, The biggest fuel gain would be made using the latest piston with the tall baffle. Many of the much older 60s had shorter baffles on the piston top and used more fuel.Even when you used the same piston in a late model ST 60. The taller baffle deflected the fuel up into the chamber, Shorter ones let it just go across the piston and out of the exhaust.  Also a few engine tuners used to file or machine the top of the baffle shorter as one of their *trick* setups.... (this is how you get them to use 7 1\2 ounces)

If you have to you can always add 10 to 15 thou head shims and increase the prop pitch to get more time.
I have seen a couple of people use a Bolly 11 x 7 4 blade or 12.5 x 8 3 blade and get by on  5 1\4 ounces of fuel
try to set the motor up on 5% nitro to start, as the hotter weather gets here you will naturally get better fuel milage

Regards
Randy

Dave Royer brought an old Merco trick back to light of day. Add (up to) 5% unleaded gasoline to your fuel, and your fuel economy will increase noticeably. I'd sure try it. Also would put a few layers of pantyhose material on the venturi to reduce the effective throat area and keep bees out.    Steve

Well, I guess I'll just bite the bullet and cut the nose ring off so I can get a 7+oz. tank in.  I also made a spigot Venturi .190 size.  Oh, I always break them in with extra head gaskets.  Thanks for all your help!

There  is another easier  option, you  can add a sump to the tank back-bottom if it is a metal tank, by soldering on a large metal cap or make a sump out of tin stock, its not very hard to do...or  you can find a short plastic tank and plumb it up as a stunt tank


Regards

Randy

    Guy's could someone post a picture of the "spigot" set up ?  I can't seem to get an idea as to what it looks like in my  ? "Mind"?  .   
  " Of all the things that I have lost, I miss my mind the most"...

  Spigot venturi is not a sprinkler . NVA. in same place, but spigot venturi has only one hole with tube from hole in needle valve to just in side venturi hole about .020 or so inside .  Hope this helps

                                     Jimmy

""Note also that there is an extra o-ring below the annular manifold. That was the best thing I ever did for ST46 run consistency - maybe the only worthwhile modification I ever used or saw to an ST.""


There are many mods to the ST 46 and ST engines in general that are worthwhile, Putting in higher quality bearings is one since most ALL  ST 46s  came with open front bearing, the did leak , some much more than others, I have also seen many rear steel bearings that had corrosion in them new.

Getting rid of the Spinkler venturie and going with a true venturie is a very worthwhile endeavor, They draw fuel better, and do not burp over and over and over again at the end of the flight like the ones with all the little holes. The standard Sprinkler system had a wide deep groove cut all the way around The venturie, when you would run low on fuel and suck air into the line this would let the bubbles also go around the inside groove, letting the air in with fuel, making the lean burps at the end of the flight.

Balancing the crank back to the T crank shape helps much.

Taking the aluminum band off of the new stuffed cranks sometimes saved the engine from being totaled when it came apart.

cutting fins and a heat dam on the head did help the engine run cleaner when the glow  plug wasn't perfect and you ran a deep 4 cycle. It aslo helped it transistion a little better 4-2

using the early light round rods or using an I beam  rods was better than using the much heavier flat beefy rods that came from the Pylon racing 40, this really help most when you had the stuffed full circle unbalanced  crank.

There are many more  mods  that are  helpful to ST and many other engines.  I know many supposed  engine gurus    screwed up a lot of these and other engines  making some worse has  tainted  some views ,but remember  there are a lot with improved runs because of some of the above  mods.

I have modified literally 100s and 100s of Super Tiger motors  and  ran test on  this and  much more  for years and years. I also used the engines  with   ST stock venturies,   Restrictors, True venturies, fuel post venturies, and a couple of hybrid types. with many HP  plots of the exact same engine, and suction test, not to mention  in flight test same plane same engine with differant configurations.


Regards

Randy

HI BRETT

I never adddress 1984 vs. 2008, but I agree 1000% the quality and quantity of great stunt engines and products are far better today,  And YES  many people still use ST 46s and many more old motors, I am settting up 4 right now for people. I just finished 6 of them and have other 60s HP 40s  OLD 35S engines that I am setting up for flyers, most of them are  ..new...
I am continually amazed at the brand new in box engines that show up at my shop. And the ST 46 was discontinued back in the 1970s
In regards to ring seal, that applies to any engine that uses a ring, not just a ST46. If You don't have a good ring seal, you don't have an engine.
Although there was a big problem with the ST 46 that most people never recognized, more often than not the engine came with a ring in it that had zero or just barley one thousands gap.
 This was disaster, the motors would be very critical to break in ,and most would just heat up ,the end gaps of the ring would touch.  Then the ring would get even hotter..heat up more, and quickly wear a out of round, flat spot on the ring.
Setting  ring gap is one of the parts of  "blueprinting "and engine, another worthwhile item to do. unfortunately your are right that there are not many that do that properly.
When the ring flat spots,The engine was ruined on the spot, Most of the replacement rings also had zero gap , unless you had a cylinder that was worn at the top, I have even seen many that were   "bell" shaped" after  running.
To compound all of this  some  ST 46s came with chromed sleeves, some with steel non chromed sleeves, The ring end gap needed to be set differant on each. You could glaze a ST  sleeve with the wrong gap or if too much have the ring not seal properly. The best thing that happened to CL was ABC  AAC technology.
Another big problem was if the ST 46 had a chromed sleeve, when rebuilding many of these that had a good bit of run time had a mirror surface on the sleeve, the chrome was very hard and most people either couldn't, didn't know how, or didn't have equipment to hone a new "cross hatch" onto the sleeve surface, without this it was almost impossible to ever seat  a new ring. Needles to say the engine was never as good after that

I made fuel post venturies for the ST 46 and ran and tested them many years ago, along with ones for the OS , HP  and OPS.  There was no advantage in power or quality of run over a properly made venturie, however we used them a good bit in HP and OS engines. And they run much better than the restrictors most used then.
 The best thing about them in those engines ,as the ability to instantly change the size of the  venturie, with precision, by screwing the post in and out.  And in the OS motors case ,it fit the engine better since there was no case material to install a true venturie. This was particularlly helpful to me when developing the later schunrule and then piped engines to get the proper size the venturie needed to be.

Regards

Randy

  Guy's could someone post a picture of the "spigot" set up ?  I can't seem to get an idea as to what it looks like in my  ? "Mind"?  .   
  " Of all the things that I have lost, I miss my mind the most"...

Hi Gil

This a a fuel post or spigot  venturie, the fuel pickup and needle is on the same side. the only thing that goes into the venturie  is just a small part of the spray bar, and it goes in only from 1 side, the first ones are for the OS 35 S  and just screws onto the side of the case.
This version for the  OS like the ones for the  ST46 below are all tuneable  for the  exact size you need by screwing the post in deeper or backing it out with precision, you then just lock it back down with the  jam/seal nut

In looking down the center I think you can clearly  see this.   one of those  picture is worth a 1000 words  deal..

Randy