LRP .28 or LRP .30?

[young.1192]

Hey everyone. I've got an extra Revo 3.3 that I want to make into a big block project car. I plan to attempt to make a new era styled mount but for now I already have the traxxas big block kit. I am fine with going the bump start route and I really don't want to move the transmission forward. I've got a hobby king eg sport .28 bolted in now just for mock up with a 3 shoe HPI clutch and only had to do some very light grinding to the engine mount and engine flange.
I want to go with a an LRP .28 or an LRP .30 but from reading online the .30 says it has a beefier crankcase so that makes me wonder if it will still fit the traxxas big block mount without severe grinding or mods.
Does anyone know if these two engines are pretty much the same exterior size in terms of crankcase and length from tip of front shaft to rear cover? Has anyone here bolted one of these in a trx big block mount and used bump start and an m2c 3 shoe clutch without moving the transmission? Also what gear ratios are possible with this mount?

 

[olds97_lss]

Honestly, the 28 would probably be better in the revo. It has a bit more RPM. I have the 30 S2 in my savage X and the 28S3 in my revo. I don't have them apart to measure stuff, but I do have a few photo's I think of them side by side. I have a spare 28 sitting out and need to change the CB in my savage, so could measure when I mess with that, but won't be doing that for a few days.

Here's the photo's I took before the install:

The fitment into the savage X seemed pretty much the same. I didn't add or take away any shims when installing it.

I can say that while the 30 may have a few less top RPM's, it has a brutal amount of torque. The 28 pulled 47/17 gearing fine and even handled 47/18 gearing ok, but the 30 pulls second gear wheelies with 47/18 and I'm about to install a 19T CB to hopefully make it a bit more controllable with the 30 in it.

I only went with the 30 because the 28 was being a pain. In the end, I'm pretty sure it was my fuel tank leaking air that was causing me tuning issues as I had the same issue with the new engine. After swapping tanks, the 30 settled down and I never tried the 28 again. I have ran 4 of the 28S3's over the years in various rigs. Has been a really good engine.

 

[young.1192]

Thanks for the reply, very helpful. The videos I've seen showing the low end torque and second gear wheelies are what put me on to the .30 in the first place. In your Revo did you use a new era mount? Also did you have to move the transmission? I've been looking on hobbytowns website and they have the .28 with pull start but the .30 comes with the bump start rear plate already on it so that's another reason I am debating.

 

[olds97_lss]

Yes. I used the new era mount. I didn't have to move the trans forward, but I did because the 1/10 style clutch/clutchbell couldn't get the power to the ground even back when I ran just an OS21RG in my first revo. So, I move the trans forward about 1/4" to fit in 1/8th scale clutch/bell. Even then I found that I had to run alloy shoes with the LRP28 or they slip a lot. It was fine running composite/teflon shoes with the XTM24.7 and OS21RG, but the LRP28 would just cook them, especially when I geared it up some to tame it down a bit. It's still a wheelie freak. But I run stock plastic center/outer axles without much issue. I change them out maybe every 3 gallons of use because the yokes get sloppy. I do have full RRP steel in the trans though as well.

Using the new era mount made it annoying to fit a rear pipe though, as well as a side pipe. To run a side pipe comfortably (so the pipe wasn't at a stupid angle or way too high), I had to use a long header so the pipe could sit pretty parrallel to the ground. I used an old duratrax warhead header that I cut, then used a silicone coupler.

Kind of surprised I don't have more photo's of my bb revo... That's not like me. lol
Side pipe setup as explained above:

Then I got the THS big block revo rear pipe and it fit very badly with the NE mount. It made the pipe stick way up in the air and there was no way a body was going on the thing like that. Pretty sure it was made for the TRX type mount that kept the engine down low. So, I mangled an LST2 header (since I had a couple laying around) and got it to work with the THS pipe. This was the result:

Notice though, the mount isn't New Era. It's a one piece mount. New era is a 3-piece I think. There was a guy on this forum that made a few mounts by using the New Era mount. I loaned him my NE mount so he could use it to make them. He gave me a prototype as a thank you gift. So, I've been using that mount while keeping the NE mount in case I wanted to install it on my other revo. NE mounts are like unicorns these days, so I don't want to sell it. You will also notice that I cut a few fins off the LRP28. I did this so the top of the cooling head was lower than the contact point between the wing and top of the NE 3 point roll bar. I raised the roll bar 1/2"-3/4" as well so it was taller, but still cut off a couple fins. Totally hack I know, but it works. Makes it way less likely that the engine ever makes contact with the ground to damage it or the chassis,since the engine bay on the revo isn't all that strong to begin with.

This is with a different engine, but shows the side pipe clearance with the tire:

Sorry for all the photo's. Thought they might help you out some.

 

[young.1192]

Thanks for another great reply! I was also looking at the THS exhaust which is another reason I thought I'd give the trx mount a try. Good to know about the clutches. I will probably try out one of the aftermarket 1/10 clutches before biting the bullet and moving the tranny to squeeze in the 1/8th which also worried me because I'm assuming that limits you options for steel center cvds... What did you use for center driveshafts after moving your transmission?

 

[olds97_lss]

Stock plastic center and outer axles. There's enough room in the front one to compress 1/4" and enough in the rear to extend. I just change them out as the yokes start to wear, which is every 3 gallons or so of use. Lately, that's every couple of years. Haven't burned a lot of fuel the past couple of years, plus I have a savage and OS21TM revo as well. The centers tend to wear faster than the outers, which is to be expected.

I bought my OS21TM revo used with a 3.3 chassis/engine in it. It had center MIP already, so instead of moving the trans, I'm running the dynamite max-life 2 shoes on the stock flywheel/cb. The 3.3 just didn't have enough power for me, even with the THS small block torque pipe, so instead of doing a second full blown BB revo, I got the 21TM. I had to upgrade it's trans to RRP as well because the 21TM was just enough torque to tear it up repeatedly. I'd get a tank or two through it before one of the gears would lose teeth.

On my first revo, many years ago when just the 18TM was available, I moved the trans in it to run 1/8 clutch setup on it too because the trx shoes just sucked. I ran the HPI savage flywheel with teflon shoes in it though and it was fine.

 

[young.1192]

Well I bit the bullet and ordered the .30! I have an m2c clutch on my old 3.3 and an hpi 3 shoe on my eg sport so I'll get the engine and see how it all fits up and maybe start with one of those clutches and go from there. Will have to look at the cb and spur ratio too. Thanks again for the helpful posts and I welcome any other feedback as well now that I'm starting down this path.

 

[Certified Mike]

Keep in mind that although you have a difference in rpm, the torque can likely make up for that with a larger pinion. The question becomes how big can you go before the bells start getting too big and require cutting and slotting etc... Just a thought.

 

[olds97_lss]

Keep in mind that although you have a difference in rpm, the torque can likely make up for that with a larger pinion. The question becomes how big can you go before the bells start getting too big and require cutting and slotting etc... Just a thought.

Yeah. I didn't really go that deep on it. Fuel consumption also comes into play. The 28 doesn't "sip" the fuel as it is. The 30 is just worse. The power it puts out is quite noticeably stronger though.

I tried shopping for a decent .21 for that reason. Not a real cheap engine, but a decent LRP quality. I had a hard time finding anything sub $200 and with a pull start. Kind of how I ended up with the LRP28. I had one in my aftershock and really liked it.

The revo doesn't need a stump pulling engine in it. Granted, you can gear it to the sky if you do, but for me, I just wanted something that would roll the revo effortlessly in the grass without overheating all the time, go reasonably fast, have enough power to pull wheelie's without much effort, last a long time/many gallons and be reliable. I suppose I could have just bought a dynamite 21 and been content, but all they offered were engines with that stupid spin/pull start on it that breaks after 5 uses...

Anyway, will be interested to see how you like the 30 on a revo.

 

[Certified Mike]

I have heard some less than satisfied reviews on the .21's I have always been fan of the OS engines so.... Not sure what to say. Stay with what you know is prob the best thing I can offer... Of course, no matter the choice... I would DEF love to see a vid of it running when they're done!

 

[Certified Mike]

I know it's WAY easier when you're spending someone else's money buy I have read that of a 250cc and tekno 250cc tanks will both work in the revo, I have not seen this in person so I don't know for sure. As long as the footprint for the tank is close, getting it in shouldn't be terribly difficult.

 

[olds97_lss]

Yeah, they used to make a kit to move the receiver/battery box combo around:
http://i139.photobucket.com/albums/q284/CHEEZBURGER_bucket/Revo002.jpg

It's discontinued though. Found a place I've never shopped at that appears to have it in stock:
http://www.activepowersports.com/tekno-rc-tkr1002-rx-box-fuel-tank-conv-revo-tkr1002/

I should buy that... then I can use the tank I tried to fit on my savage at least. Although, Traxxas made a 150cc tank that fit right in and I have that now anyway.

 

[young.1192]

Thanks for the links guys, I'll have to look into the tanks when I get this up and running. I got the .30 tonight and it seems like it will fit up as well as my .28 eg sport did after I grind the corner on the engine flange. The clutch and bell I was using on my .28 was from my hpi savage x and it fits very well without moving the transmission but it would really be nice to have a larger 40 mmm flywheel to use for bump starting on the Revo. Any suggestions for a flywheel to use with the 3 shoe hpi clutch or even an entire clutch and bell system that could be directly swapped to fit the same without moving the transmission? I have the m2c clutch on my stock 3.3 Revo with the 40 mm flywheel but I can't just swap flywheel as I dont believe the pins on the same diameter due to the traxxas clutch bell being smaller than the hpi.

 

[olds97_lss]

There are a few clutch/flywheel kits from Buku that I think work with stock clutch bells that are 40mm:
https://www.bukupower.com/ClutchTraxxas.aspx

That might be good enough for you.