First attempt at port and polish

[CarGuy7a]

This is my first attempt at a port and polish job on the sleeve and crank. This motor is a wore out 3.3 I used for practice so I wouldn't destroy a good running motor. I still need to do a little work on getting the grind marks smoothed out a little more but I think even what I have now would run pretty good.

Let me know what you think.

Transfer ports



Boost port


Crank. I did a little knife edging on the closing side of the port and scalloping on the journal end of the crank.

[westoakmech]

Looks nice, good job. It takes a steady hand, and a little patience. I have done a few, if you get the little cotton tips, and the polishing compound you can smooth out some more. Now just do one up and run it. My 3.3 runs great, it even sounds different, and I have a 2.5r in my rusty that just shredds drive shafts.

[RC-Fan]

great job, looks pretty good

[CarGuy7a]

Looks nice, good job. It takes a steady hand, and a little patience. I have done a few, if you get the little cotton tips, and the polishing compound you can smooth out some more. Now just do one up and run it. My 3.3 runs great, it even sounds different, and I have a 2.5r in my rusty that just shredds drive shafts.

I used the felt polishing wheels and dremel polishing compound on that sleeve. I didn't quite like the dremel polishing compound as it only gave it a semi chrome type finish. I found some actual chrome polish in my garage today which provided some awesome results. Here's what I came up with on my OS 21TM parts. I can't wait to run this thing. It should be an absolute screamer. Now if it will just warm up outside.

Transfer ports. The left fang in the first pic I had a little bit chatter due to my cheapo $8 dremel from harbor freight the shaft isn't very straight and it wobbles a bit. I switched to my Campbell Hausfeld air pencil die grinder to finish the job up. I also noticed that the material the OS sleeve is made from is quite a bit harder than the 3.3. I used a tungsten carbide bit to cut it and the crankshaft.



Boost port


Crank pics. The crank already had a scallop in it from OS I just took and made it a little deeper and rounded the edges off.

[westoakmech]

Nice work. Hope it runs good, and last for twenty gallons.

Is my phone smarter than me?

[77dvl19]

I am new to the rc game but long time hotrod guy and always lookin for more power where can I find more info on port & polish for my 3.3 thank you

[CarGuy7a]

http://www.rcuniverse.com/forum/m_52...tm.htm#5235716

This write up has some good info. First you need to identify which ports are what. The exhaust port is the obvious one also on the exhaust port side of the sleeve is a notch at the top to keep the sleeve from rotating inside the block. On the Traxxas 3.3 and OS 21TM motor, 90° on each side of the exhaust port are the transfer ports. 180° from the exhaust is the boost port. The boost port is also usually the lowest port on the sleeve.

One thing you never want to do (if you are doing a simple fang job like I've done) is touch or change the port openings in the sleeve or crank. It will change the timing and ruin the motor if you don't know what you are doing.

[77dvl19]

Wht is the groove on the counterweight for ? And will it throw the crank out of balance

[Nitronaught]

Wht is the groove on the counterweight for ? And will it throw the crank out of balance

The crank is balanced to the piston,,, well supposed to be..

If you look at the crank it's hollow, there's a big cutout where it is under the carb throat, the fuel tavles though it to the back of the crank and then it is picked up at the sleeve area... The fang helps to "sling" the fuel around the back end of the crank and that get's more fuel up into the sleeve which has been bullet nosed (rounded) and also fanged.....

I am looking at the cut of the crank and don't understand why the edges of the cutting of the counterbalance are not rounded. The sharp edges will cause a lot of (turbulance) of the fuel flow at 30,000 + rpms... But, I'm not an expert at it.... For serious racing I go with a pro job... Still, suspension and tires, and driveline, wihtout adding weight but getting lighter,,, and driving,,, that's going to get you where you want to go IMHO...

[Wildman4910]

For getting the small areas smoothed out Dremel #462, Rubber Polishing Cone Point.
A rounded tip polishing accessory made with blue rubber and abrasives for removing small burs and scratchmarks on ferrous metals.
http://www.dremel.com/en-us/Accessor...lishing+Points

[johnzillia54]

I built a 3.3 that had that mod done to the crank, and I was breaking it in to day and on the first tank all u can say is wow there is a difference!!!!

[CarGuy7a]

I am looking at the cut of the crank and don't understand why the edges of the cutting of the counterbalance are not rounded. The sharp edges will cause a lot of (turbulance) of the fuel flow at 30,000 + rpms... But, I'm not an expert at it.... For serious racing I go with a pro job... Still, suspension and tires, and driveline, wihtout adding weight but getting lighter,,, and driving,,, that's going to get you where you want to go IMHO...

The cuts on my crank? Well on my OS crank I didn't touch the sides (the cut out areas to the right and left of the rod journal) that's OS factory. If you look on the left side of the journal it's actually scooped since the motor's rotation is clockwise from looking in at the rear of the motor. Me I would think knife edging on that side of the crank would be better than just a blunt square edge. Aerodynamics, it would cut through the air faster and I would think allow the motor to spool rpm's up faster. The cut on the right side of the journal would hardly matter since it would be in the trailing wake of the air being moved.

Really all I changed on the crank was made the original fang at 6 o clock a little deeper and added one at 3 o clock. Then I knife edged the closing side of the port in the crank and polished it all. I can't wait to see how it runs. I already have a good idea how it ran before, this motor was just broken in and has about a 3/4 gallon on it before I did the mods.

I agree though with the racing aspect you pointed out and I've seen it first hand numerous times. I used to race go carts for about 10+ years and used to run a blueprinted motor in the open class every once in a while and win with it. You can give one guy a huge horsepower motor, but if he can't setup the vehicle or drive good, he won't go anywhere. Give a good driver a motor that is half the HP but knows how to drive and setup his vehicle and he's the one to look out for on the track.

[JustynKace]

Hi I have been modding the TRX engines for a few years now. One of the best mods I have done to them is open the crank up and cut the sides near the rod pin like the OS crank you show. By cutting the crank, more oil can get to the bearing and they last longer. And a single piston motor can't be balanced 100%, because the load of the piston changes to often. With two pistons you can balance them by off setting the fire pattern. The way I balance the crank is, if I make a cut on one side of the crank I cut some from the other side. And I don't find that polishing the fangs help. I leave the fangs rough and polish the rest of sleeve.