Cox International

My Feedback: (10)

tubebass

Is it necessary to drill the tank and backplate?

Cox International

My Feedback: (10)

... ummmm .... no.

Why would you want to drill any parts?

Bernie
www.coxinternational.ca

forsakenrider

Because the vemom was .082" which is what Paul states in his other write-up. I recommend it, its super easy and add a little performance.

Why NOT do it?

Cox International

My Feedback: (10)

Ok, but what part(s) exactly are you referring to?

Backplate venturi hole?
Tank venturi hole (where it meets the backplate)?

Bernie
www.coxinternational.ca

forsakenrider

Both of those parts Bernie. As paul states in his other article, you hold the tank and back plate together without the reed installed and drill it out in one shot. there is very little material to remove, but enough to make the difference.

Cox International

My Feedback: (10)

I see and that makes sense. We will experiment and may do this on the Venom II that were are planning to assemble.

Thanks for pointing this out.

Bernie
www.coxinternational.ca

Mr Cox

I thought one of the major things with the Venom was a wafer thin piston?

You might not want to copy that (understandably) but what else is it that would make an engine a "Venom" engine, compared to e.g. a "Black Widow" or a "killer bee", I believe they also have the larger intake and the TD cylinder/pistons?

combatpigg

My Feedback: (3)

I've never had any problems with the wafer thin piston. Something else will break [ball socket or crankpin] if you run the engine above 26,000 [in the air rpm] for extended periods.
The wafer thin piston is what takes the strain away from the rest of the moving parts. If I could figure out a way to make it even lighter, I would.
Years ago Ptulmer sent me a never run KillerBee to see if I could prep it for pylon racing and to make his "Blink" as fast as possible. I'd never seen a KillerBee before.
After taking it apart, it was pretty obvious that there wasn't anything I could do to improve it. The piston could have been thinned a tiny bit more, but it wasn't worth the risk. All I did was detail the crank fit in the case, bolted a 4.2x4 prop up to it and ran it on 45% nitro.
It easily tached 28,000 on the first "pull", so I shut it down and sent it back to him basically untouched.

Mr Cox

So the piston was thinned on the killer bee too, didn't realize that. Yes a lightweight piston is preferable but I've understood the stock Venom piston (not cylinder) was made too thin in the top though, and they brake due to that.

Taking a stock Sure-start cylinder and piston, albeit with the exhaust slit removed, will not make it a high performance engine though, unless the piston is reworked together with the other modifications that are needed.

combatpigg

My Feedback: (3)

I didn't know the Venom had a thinner cylinder. I'd like to see a tach reading before and after the OD of the cylinder is altered.

I would guess that a thicker cylinder would help control expansion and help keep the ball socket and the rest of the engine cool.

skaliwag

My Feedback: (1)

What would the point of thinning the cylinder?

combatpigg

My Feedback: (3)

Eye Candy, coolness factor, marketability.

fit90

I thought the original Venom had a tapered cylinder.  I am not positive, though.

Bernie,

When you make the Venom II will it use standard height, lightened pistons?  If so, will you also sell them seperately or with cylinders?  I bet a lot of tinkerers would go nuts for those.

Bob

Mr Cox

Sorry my misstake, it was meant to read thinner piston not cylinder. I guess they made the pistons too lightweight and the conrod would come out through the top of the piston, I have never had one of these myself though.

My questions is then simply why an engine with a stock sure start piston and cylinder would qualify as a Venom II engine...?

Cox International

My Feedback: (10)

Bob,

We have not yet decided if we will make them with the "TD" cylinder/pistons (Surestart cylinder with bar in exhaust removed) or with our SPI set. The tendency is to make them with our SPI set as they seem to achieve best results with reed valve engines.

The reason we don't sell our SPI pistons separetaely is because they only work well in te Surestart cylinders with the bar is the slits. They actually produce lower RPM when used in open port cylinders (too much SPI).

Bernie