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  1. #1
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    Slayer Pro Rebuild Recommendations

    Hey whats up guys, I just blew up my 3.3 in my Slayer Pro and I need outside opinions on my next move. Send my engine to traxxas through the Power Up Program and get a stock replacement or go aftermarket. I'm leaning towards a stock replacement due to already having the losi 3.4 carb, Robinson Racing 15T Bell and a THS pipe that works well. Other then that my truck is stock (except for the Proline SC wheels) so I am limited without upgrading the driveline which I'm not really looking to do. Also If I keep the stock 3.3, should I upgrade the clutch? I have been getting conflicting info on that subject, some state the stock clutch is almost as good as it gets and other say to upgrade? Hopefully I can get some unbiased feedback here from a honest enthusiast. I appreciate any help. Thank you.

  2. #2
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    I've run the 3.3 and the O.S. TM21 both. The O.S. is twice the money especially from what I understand about that Traxxas engine program. I wouldn't expect a major difference in performance between the two but other than the Losi carb (I'm not sure if that would work in the O.S.) everything else should bolt right up. That O.S. can put up with some abuse. I would see what your budget is. I don't think there is anything wrong with the 3.3 however if you have the extra money the O.S. is a decent upgrade. Since you said you blew you 3.3 the O.S. may be able to stand up to a little more bashing. This was just my experience with them.

  3. #3
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    Thanks Trev. I'm building an E Revo 2.0 at the moment so my budget is pretty much consumed with that. I took the cheaper route and went with the 3.3 again, $115 said and done through the power up program with Traxxas. I saw a website about someone porting and polishing the 3.3, do you know anything about that? It was another forum I was reading but I was getting conflicting info, some say 100% must do and others say the 3.3 is maxed out and can't handle any upgrades internally. The post was old so I didn't bother getting feedback from them. Just a thought. Thanks for your advice, I appreciate it.

  4. #4
    Marshal Double G's Avatar
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    There is a bit of a performance difference between the two - the OS is a bit stronger. No you don't want to put the LOSI carb on the OS as the 11K carb is a bigger and better one anyway.
    There is not much out there for performance with nitro and some accessories will be hard to come by now. THS makes good pipes (I run it on my .21TM and had it on my 3.3); Buku has been "Temporarily Unavailable" for more than a temporary time. Search for a large write-up and discussion here in the Slayer subforum regarding different carbs that fit on the 3.3. You can look at ABMods or RBMods for their porting and polishing services or read up on the magazine article on "How to Hot Rod Your Engine" from over 10 years ago from RC Car Action (referenced in a thread on RC Universe).
    As with any modification to any engine - RC or automotive - the more power it pushes out the less total run time you'll have on it.
    The Super Derecho

  5. #5
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    Port and polish sounds like either a fun experiment to try if you want but also a good way to ruin an engine if you do it wrong. Since you already have a 3.3 that's toast maybe read about the technique and try it on a bad sleeve? Let us know how it goes. Like the previous comment, there are some great articles on how to do it. Traxxas likely won't take that back though. My overall recommendation with this truck is learn what exactly you want it to start doing and tune components from there. I run 97% on asphalt. After tuning the suspension and buying some simple add on's, working on overall driving technique made the truck faster than any work you can do trying to get more power from the engine.

  6. #6
    RC Qualifier nebulous.cow's Avatar
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    Im a fan of doing light engine mods to all of my nitro motors I get. I can't stress the "lightness" of the mods I do enough, though.

    I usually break in all my motors, get a good at least 5-6 good full fun sessions in with a motor, then I'll open it up. That way, if it was gonna blow up, it probably would during break in or the first few sessions after leaning it out and tuning it up. So that your warranty would be intact with a new motor! After that initially high chance of failure (for any engine) then I would mod it. Just make sure its running good before you do.

    For the most part, I just remove burring/flashing and sharp edges. On the sleeve for the intake ports, I gently grind off the sharp edges under the intake ports, just so they are not sharp. I don't polish them when I am done, because personally I am on the side that says the roughness aids in fuel atomization over polished surfaces.

    If the crank has a really rough entrance for fuel pickup, I'll just get a round ball-shape dremel bit and smooth out the edges inside the hole.

    Again, Im basically just smoothing out edges. I have found mild improvements in every engine I have done it to. It usually wakes up the mid range in most engines, with little or no effect on WOT, but a very small increase in torque off the line. It does factually help, but it may not be worth your time. I did this to my 3D helicopter nitro engines, and man that made a big difference for flying, but that's way different than car nitro stuff. People even asked me "what I did to that engine to make it fly like that" and it's just the little things, sometimes they go a long way. The edge smoothing I described is a great way to get into engine modding, if you do what I mentioned, it's almost guaranteed that you won't damage your engine, but the payout is small. Just take your time and use a steady hand. I can post pictures of past mods I have done before and after, I've done it on numerous engines if you want to see the degree of modding I do.

    All that said, I have yet to do this to my brand new revo 3.3 engine. It's got maybe 10-12 tanks on it and its running okay, but I am bummed about the stock carb tuning difficulties and the power a bit. I want the OS21TM for sure, but I might try to milk some more power out of the 3.3 first. I also run 30% nitro in all my cars and trucks and it's awesome. Just bummed my Revo can't wheelie at all, but I live at almost 6000' altitude, so it's to be expected. The thin air here plus the high content nitro fuel seems to kinda work out. The thin air helps prevent detonation, so I can get similar cylinder pressure as I would say with 20% at sea level, so my stuff runs actually really nice on 30% up here, but to each their own. My nitros are monsters at sea level though too lol.

    I recommend trying these things in this order if you want to milk out that last couple HP:
    -smooth out the edges inside the engine on the intake ports and crank if needed. easy, cheap, and low risk.
    -try higher nitro fuel. Byrons RG2, Traxxas, or for me I use VP Race fuel, all in the 30/33% variant, and retune
    -try other temps/brand of glow plugs. I found in onroad nitro, they seem to make more apparent differences, but those are different than basher monster trucks/engines. Nonetheless, good plugs in the right temp ranges do make a difference. Maybe try a cooler plug for these engines, generally small motors like hotter and big motors like cooler plugs.
    -make sure your engine gets adequate cooling. Heat eventually robs you of power. Trim up the body or something. My revo suffered this bad without trimming the body, I think I will trim it even more around the engine head to allow more flow, on top of the nice hole I made in the windshield.

    That's what I'm gonna do to my 3.3 before getting the OS. Might as well. I think the 3.3 will go in another truck, so might as well make it run good. The 3.3 is a good cheap motor with a need for a better carb, but with some tweaking it does pretty good I bet.

    Stock clutch should be good for the 3.3 and OS21, just make sure your idle is low enough that it's not always rubbing and the spring is not worn out, should be alright.
    -Mike
    Last edited by nebulous.cow; 04-18-2020 at 03:49 PM.

  7. #7
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    Thanks for the feedback guys. I think the smart choice would be to leave the internals as is and just fine tune with what I have and enjoy the truck. Its fun to try and achieve more power and speed as long as its reliable. Spending tons of money and hours working takes the fun out quick.I'm still going to look into reading the articles you mentioned double, I'm fascinated on how much power can come from such a small engine. Thanks for the advice.

  8. #8
    RC Qualifier nebulous.cow's Avatar
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    I actually just did the mods I mentioned to my new 3.3 that's post break in, I'll report back the differences soon. Came out very nice.

    Sounds like you found the best route for your build. Sometimes simple is the best!

    -Mike

  9. #9
    RC Qualifier nebulous.cow's Avatar
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    Hmm, this engine came out a little different than most mods I do on my motors, I got a little more 'generous' with the dremel, but nothing crazy. Actually gained a little more in the mid/high range, as opposed to the mid/low gains I usually get from this mod. Seems to kick into 2nd gear with a little more authority than before, but nothing big. Glad I did it though. Tuning didn't change at all, temps are the same, perhaps starting was easier too but that's probably not due to the mods.

    Next up is my Kyosho GT2 big block touring engine on the cutting block.
    -Mike

  10. #10
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    But can a rookie with a Dremel cut that?
    Asking for a friend...
    Slayer Pro, Slash VXL 4x4, Jato 3.3, Rustler 2.5

  11. #11
    Marshal Double G's Avatar
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    Yes.

    Answering for a friend.
    The Super Derecho

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