I needs to know ST G/21 40

Was recently told that the ST G/21 40 is a racing engine. The examples I have of this engine don't appear to be for that application. All of them have about a 176 intake hole in the venturi. I had always thought that for racing you would want that 1/4" hole so that it could be run on pressure? When I have run these engines they certainly weren't the 46 but they were still not bad and didn't give the feeling that someone else should be in the circle racing me.

>Was recently told that the ST G/21 40 is a racing engine.
>The examples I have of this engine don't appear to be for
>that application. All of them have about a 176 intake hole
>in the venturi. I had always thought that for racing you
>would want that 1/4" hole so that it could be run on
>pressure? When I have run these engines they certainly
>weren't the 46 but they were still not bad and didn't give
>the feeling that someone else should be in the circle racing
>me.
>
>Bill

The rear rotor version was the racing engine. Formula one Pylon,boats,etc.You have the front rotor version? We used them in boats back in the seventies until the K&B (Knock and Bangem)or (Krank and Broke'em) came in.

>We used them in boats back in the seventies until the K&B (Knock and
>Bangem)or (Krank and Broke'em) came in.

My dad and I used Knuckle Buster.

Here's the racing version - rear rotor, single ring & deeply finned head.

Eggy

You know, I had read on a forum, the same thing: that the ST G/21 40 is a (rat) racing engine. There were some pre-Sig Chipmunks built around the Chicago area in the 1970's which used the G/ 21 40's (front intake) for power.

Some of these still turn out at fabled Ned Brown flying field, and seem to provide good stunt power even with mufflers eliminating some of the power gain from the sub-piston induction.

The ST engine that has captured my imagination is the rear intake, side exhaust .51 which turned up this summer. Mike Schmitt now uses it on the front of one of his Magnums, quite successfully.

LAST EDITED ON Dec-15-03 AT 04:57 PM (CST)
 
I have seen several FISE ST 40's that had an excellent stunt run.
The Man flew the USA-1 on them at first.
Randy Smith had several for sale at the Huntersville meet.
Bill <><

The version I am refering to is the FISE. I also have the RR 40 but its intented use is quite obvious. None of these engines have ever ran like a Rat Race engine nor acted like they were starved for more nitro.

I have had a lot of ST40-46's and the later single ring 40 has the same timing as the 46. I have been told the 46 is a lot more powerful than the 40 but I found this not to be true. The old double ring ST40 was a lot weaker than the 46. I have used the rear intake 40 on a profile and it ran fine for stunt. I used a .270 intake with the needle through the intake center.
Ed

The original G21/40's FISE were used for US Rat Race and Australian open combat when they were first released in the mid 60's. They came with a suction venturie and a big pressure venturie as well as a pressure nipple. They were the equivalent of the Fox .40 BB otherwise known as the Goldem .40, and had equivalent performance. Stuart Sherlock (aka Joe Supercool) of propeller fame used one to win open combat in the 1965 (or so) Australian Mentone nats. I know because I was in his pitcrew!

So your informant was partly right. The timing etc may have been modified in subsquent models to make them more suitable for stunt.

Hello There

This is an interesting theme. I have two st40's FI both have sub piston induction.

The 40 rr photo is different to the 40 rr that I once fitted a carby to for pylon.

The one I worked on had the carby at an angle upwards.

Were there any 40's wothout sub piston induction?

I have believed stories that mufflers and sub piston induction do not go together.

Must try it one day to test for my self.

There are sooooo many ST variations.

on occasion we discuss where I am in Aussie land who had the most variation in engines Gordon Burford or S/tiger.

John Quigley

Bill,

Sprinkler venturii are misleading. The hole looks very small, but the net area is closer to a larger hole with a spraybar across it. The sprinkler is also cleaner for the air to flow through...

For a better comparison, though a bit crude, Figure the area of the sprinkler min diameter: D squared x pi/4.

Then figure how much area a 5/32" diameter spraybar would take out of that if it were the same length as the hole diameter. 5/32 is 0.1563, so there'd be nearly NO air clearance! Compare the usual choke diameters with net area figured the same way, and you'll be surprised at how big a hole you need (with spraybar) to natch that 0.176 sprinkler!