How to clone a Cox Venom

Not much different from what I have made. My friend has a mini lathe and I'll be trying to lighten a piston by removing some from the inside skirt. I have had so many complaints about the plans I have on my site. I think people were using your td/surestart cylinders and not real #4 cylinders.

With all the parts (assuming the black stunt tank is 29.99), it would be around $90... Seems like a fair price for a Venom

ideeman1994 wrote:With all the parts (assuming the black stunt tank is 29.99), it would be around $90... Seems like a fair price for a Venom

Not bad as long as it looks like and preforms like (or better then) a real venom.

Good thing! I'll buy one as soon as they're ready

20,000 rpm is not bad at all! I was only getting at the most of about 19,500 with a 5x3 black prop on 25% sig. On the other hand, others were reporting only 10,000-13,000 from their own builds. The problem with people building their own engines is some people just buy the parts and throw it together. They may use loose fitting cylinder/piston sets and maybe a loose crankshaft/crankcase assembly. I do find the plastic retainers seem to boost the performance. Are the new stunt tanks going to use a "e" circlip or the plastic slip-on flanged retainers?

Admin wrote:20,000 rpm is not bad at all! I was only getting at the most of about 19,500 with a 5x3 black prop on 25% sig. On the other hand, others were reporting only 10,000-13,000 from their own builds. The problem with people building their own engines is some people just buy the parts and throw it together. They may use loose fitting cylinder/piston sets and maybe a loose crankshaft/crankcase assembly. I do find the plastic retainers seem to boost the performance. Are the new stunt tanks going to use a "e" circlip or the plastic slip-on flanged retainers?

Did any cox tanks use a plastic slip on?

For me, the Venom used a flanged retainer, just as the lasts Texaco engines...

nitroairplane wrote:

Did any cox tanks use a plastic slip on?

My 1990 Black Widow has a slip on retainer.

Admin wrote:

nitroairplane wrote:

Did any cox tanks use a plastic slip on?

My 1990 Black Widow has a slip on retainer.

OK wow i never knew that,
I have only seen "e" retainers.

Paul didnt mention how many head shims he ended up with... As mentioned previously these are not just thrown together engines. How many head shims needed for optimum performance (correct compression ratio) is determined by a quite few different factors, ie fuel (nitro content), initial head space, glow plug/head type, altitude, ambient temp and humidity.

In the OEM Venom, Cox supplied 3 extra head shims with a note mentioning their purpose and how to use them in the engine instructions.

Paul briefly mentions head shims in his Revised 2011 Mouse Race Program document. (Which by the way has been revised to include photos now.) On one of my engines that had a Galbreath/Nelson head, I needed 6 shims to get it to run right

Cheers

nitroairplane wrote:

Admin wrote:

nitroairplane wrote:

Did any cox tanks use a plastic slip on?

My 1990 Black Widow has a slip on retainer.

OK wow i never knew that,
I have only seen "e" retainers.

Was it NIB? Somebody might have just thrown it on there.

They can't be just thrown on there. On a tank that requires the use of a slide-on retainer has a smaller diameter reed valve intake surface while the circlip "e" has a larger diameter surface to be able to hold that "e" clip and the reed. I may have to post some pictures, this is hard to describe at this moment.

Admin wrote:They can't be just thrown on there. On a tank that requires the use of a slide-on retainer has a smaller diameter reed valve intake surface while the circlip "e" has a larger diameter surface to be able to hold that "e" clip and the reed. I may have to post some pictures, this is hard to describe at this moment.

Ah, I see. I've never owned one before.

Admin wrote:They can't be just thrown on there. On a tank that requires the use of a slide-on retainer has a smaller diameter reed valve intake surface while the circlip "e" has a larger diameter surface to be able to hold that "e" clip and the reed. I may have to post some pictures, this is hard to describe at this moment.

Correct. Would be good to have some exploded views! I think this change occurred sometime in the early 1990s after Cox moved to Corona.

There are several different versions too. 1. On the Surestart engines the reed retainer clips on / press fit, no flange. 2. The Killer bees, Venom etc have a reed retainer that is flanged, held in place by the 4 backplate screws. 3. There is also a larger size (ie diameter) flanged retainer for the die cast crankcase version. Have a look at Bernie's or Matt's "Back End Parts" and you will see the different versions available.

They really started making things hard for themselves when they did this... ie so many different versions. From 1956 to 1990 it was easy, there was only one type! The star reed with e-clip.

warrenlead wrote:

Admin wrote:They can't be just thrown on there. On a tank that requires the use of a slide-on retainer has a smaller diameter reed valve intake surface while the circlip "e" has a larger diameter surface to be able to hold that "e" clip and the reed. I may have to post some pictures, this is hard to describe at this moment.

Correct. Would be good to have some exploded views! I think this change occurred sometime in the early 1990s after Cox moved to Corona.

There are several different versions too. 1. On the Surestart engines the reed retainer clips on / press fit, no flange. 2. The Killer bees, Venom etc have a reed retainer that is flanged, held in place by the 4 backplate screws. 3. There is also a larger size (ie diameter) flanged retainer for the die cast crankcase version. Have a look at Bernie's or Matt's "Back End Parts" and you will see the different versions available.

They really started making things hard for themselves when they did this... ie so many different versions. From 1956 to 1990 it was easy, there was only one type! The star reed with e-clip.

I have also seen a version where there is no retainer at all! The reed is just slightly bent to be inserted into a grove machined right on the tank! I wish I could find that picture! I'll go look for that picture.

Admin wrote:

warrenlead wrote:

Admin wrote:They can't be just thrown on there. On a tank that requires the use of a slide-on retainer has a smaller diameter reed valve intake surface while the circlip "e" has a larger diameter surface to be able to hold that "e" clip and the reed. I may have to post some pictures, this is hard to describe at this moment.

Correct. Would be good to have some exploded views! I think this change occurred sometime in the early 1990s after Cox moved to Corona.

There are several different versions too. 1. On the Surestart engines the reed retainer clips on / press fit, no flange. 2. The Killer bees, Venom etc have a reed retainer that is flanged, held in place by the 4 backplate screws. 3. There is also a larger size (ie diameter) flanged retainer for the die cast crankcase version. Have a look at Bernie's or Matt's "Back End Parts" and you will see the different versions available.

They really started making things hard for themselves when they did this... ie so many different versions. From 1956 to 1990 it was easy, there was only one type! The star reed with e-clip.

I have also seen a version where there is no retainer at all! The reed is just slightly bent to be inserted into a grove machined right on the tank! I wish I could find that picture! I'll go look for that picture.

I've got testors motor that's like that.

"I have also seen a version where there is no retainer at all! The reed is just slightly bent to be inserted into a grove machined right on the tank! I wish I could find that picture! I'll go look for that picture."

Here's one.
I have no idea where I got it.
Hope this works(image).
Bob

dckrsn wrote:"I have also seen a version where there is no retainer at all! The reed is just slightly bent to be inserted into a grove machined right on the tank! I wish I could find that picture! I'll go look for that picture."

Here's one.
I have no idea where I got it.
Hope this works(image).
Bob

It didnt work
If you like you can email it to me and ill upload it for you.

Here it is(I hope)