302 compression ?? External fuel tank??

[bill boyes]

Ok Cut them to fit or you be sorry. Trust me on this.

[me-otch]

Will do. I'd rather not burn up a piston. But thats not the only reason i would think you would have to cut them off.
If they were sticking out would that not affect the cc's?
Possibly a very small ammount. but for those who are already at the min it might?

[Ron Hill]

The only thing I would worry about is that the two cylinders are not reading similar compression. The OSY motor that I run has much less than 100 lbs in each cylinder....

Guedo, you are supposed to tighted the compression guage all the way in the hole, then crank the motor...

I will agree, both should be close to the same no matter what the pressure is.

[Ron Hill]

Yes I was going to make my CMH a floatless carb and add a tank to nice question lol

Steve A

What is the height of the "DUMP TUBE" on a floatless 302 carb?

[blueskyracer]

I gather from what I am hearing you don't use the regular factory float system with a fuel pump and seperate tank?

[Ron Hill]

FLOATLESS Worked Great With Alky

In the OLD STOCK OUTBOARD DAYS Carter carbs worked great if the brass float seat held. Which it didn't hold very often and as a result Mercury made a "KIT" for the 20-H and 55-H. Part of the "Kit" was a Tilson carb.

What Quincy did, for ALKY RACING, and I'm not sure they did it first, was machine the bowl and a few other things out in a Carter carb, throw away the float and float seat and make a dump tube or over flow tube at the height or close to the height of a closed float.

Thew dump tube was attached to the carb bowl by a 1/4 pipe fitting that drained the bowl back into the fuel tank. This worked flawlessly as long as the return line was lower than the float over flow dump tube.

The main thing to worry in making floatless carbs was how high to make the dump tube or overflow tube. A carb and a toilet are basically the same. A floatless carb never stops running, but it doesn't matter as it has an over flow back to your tank.

This worked great for Alcohol motors as they need more fuel than gas and you never had to worry about the float seat holding in rough water.

Not sure I have this completely right, I'm sure someone will tell me the rest of the story!

[crfabbro2F]

I gather from what I am hearing you don't use the regular factory float system with a fuel pump and seperate tank?

I've been using the BTM system for 2 years, and it has worked perfectly.
No changes to the carb needed.

[crfabbro2F]

I can make pretty much any kinda aluminum tank you want. I can even put it on the steering bar if you want. I'm Daves Dad

What would charge for a tank similar to the top one?

[bill boyes]

Why do you want to go with a floatless Carb? Many racers have gone to a fuel pump and left the carb alone.

[Aussie Steve]

Why do you want to go with a floatless Carb? Many racers have gone to a fuel pump and left the carb alone.

Yes this I what I will do now I have better info on the subject .
No need the change with the pump on.

Steve A

[blueskyracer]

I would like to say that I wet down both cylinders over night and did another compression test and both read 118.

As for the fuel pump I guess I will have to decide if I want to add it and also add another thing that could possible break? With the short tower coming it would be nice to even get the CG lower with no tank up in the air.

[bh/]

I've been using the BTM system for 2 years, and it has worked perfectly.
No changes to the carb needed.

If one fits a pump, electric or pulse, and runs it straight into a float type carb, the pressure may overcome the float valve, and pressurise the float bowl, causing rich mixtures.
The OEM M20H came with a regulator to prevent this.
The 80/102/302 tank sits about 6" above the carb float,
and creates about a 1/2 psi pressure on the float valve.
The BTM system pumps fuel up to the heigth of the OEM tank,
creating the same pressure on the carb, and overflows the excess.
If a floatless carb is used, there is no need to restrict pump pressure,
as the dump tube in the float bowl overflows the excess back to the tank.
This 'overflow' approach is dead simple and fool proof.
It is only legal in mod.
The BTM system works good too, but has many more parts to contend with.

[propnuts]

One mans opinion on external tanks

I have seen fuel pumps fail, gravity has never let me down

[me-otch]

I have seen fuel pumps fail, gravity has never let me down

True enough. But it does help lower your CG when you have the tank in the boat instead of way up high.

[blueskyracer]

True enough. But it does help lower your CG when you have the tank in the boat instead of way up high.

I think that the little bit of weight I was trying to get lower for a better CG is not worth giving up reliability. The newer short tower will be good enough. Now if it increased power that would be another story.