Hi guys,

I have an XTM Mammoth that just needs a new engine to get it up and running, but not knowing much about the XTM cars I was wondering if anybody here has run something different than the 24.7 engine they came with (or the .28 upgrade they recommended)? Is there anything that is a drop in upgrade?

I'd usually just try to buy another 24.7 engine to drop in but it looks like they are scarce.

Thanks!

You should be good with just about any .21-.30 engine. I did a quick search and saw some mammoths listed for sale that had lrp .30 engines in them.

Tower has that engine for around 160 and it would probably work very well.

I also saw that SH engines (from A-Main (can't post links yet)) makes what appears to be the exact same 24.7 engine that XTM used, I may go with one of those. A-Main also claims it will be a drop in upgrade. I might go with the LRP motor though, bigger is better right??!

Thanks!

Not always. Does the XTM have a 2-speed? If so, get the 30. If a single speed, get the LRP 28 Spec 3. The 28 will be awesome either way..

Yes it has a 2 speed. In that case, I'll get the LRP .30.

Don't know that truck. But the LRP ZR.30X is AWESOME in my LST2. IMO the truggy version with the closed backplate is worth the money. You then have to buy the pullstart backplate, and put a rotostart plate on it or whatever you want.

To be clear - there are two LRP 30 versions, one with a pullstart, one with a closed backplate. You want the latter, but with the pullstart backplate from the former. The truggy/closed backplate version has a better carb, and possibly even more power from different porting(Don't quote me on that - have heard different things.. The carb IS better though..) It's pretty crazy in my LST2..

It's also VERY user-friendly. Nice break-in, keeps a tune, not finicky, etc.

It costs a bit more in time, money, and hassle having to buy the extra backplate, but it's worth it IMHO.

Is there any issue with the LRP 30 with the pullstart (aside from less power)?

It has a standard - i.e. non-insulated - carb.

I have had the LRP Spec 28, the Losi 454(same engine), and a bunch of other engines from the same factory. They are all great. But...., they don't tend to idle perfectly. I learned to live with that by blipping it to clear it out. Oddly, my 454 purrs like a kitten... But a lot of how an engine tunes has to do with fuel, plug, pipe, and how the owner tunes it. I tend to like mine a bit rich on the safe side, but still with a screaming top end. Anyway, the standard engines are great for the money. The ZR.30X though has a much better carb. It'll just sit there and stay idling. It's very easy to tune, and keeps a tune. I've come back to mine after six months of sitting, and it runs just fine. To be fair, I can say the same about those other engines as well.

So I don't know. All I can say is, my ZR.30X has been an absolute BEAST in terms of power, and the tuning side of it is just really good, more like a Novarossi or other race engine, which will sit there and just idle steadily.

ps You can get those other engines to idle steadily too, but IMO you tend to have to use a hotter plug, and for me anyway when using a hotter plug (like an OS 8 instead of a 10), I notice a drop in top end power, revs, and speed. BTW, the Odonnell purple medium plug is the BEST non-turbo plug you can get for MT big blocks...

One of my co-workers just slapped an AE 28 pro down on my desk that apparently has low run time. It looks like it will work so I think I'll play with this first and see what happens. Hey it was free so no big loss right?

Yeah, go for it. Set up right I'm sure that engine can be fine. Just make sure the clutch is perfectly shimmed, the plug is good, the air filter clean, etc.

Was able to slap the AE .28 in after a little bit of work with the dremel on the stock Mammoth motor mounts, I'm glad just about everything is going to work perfectly. I have some shims I need to put in to get the stock 2 speed clutch bell to stop rubbing on the flywheel and then it should be perfect. Now onto replacing the stock HS-311 throttle and XTM 175 steering servo.

Picture of the truck. This is the first time the body has been on it in about 10 years. Excited to finally get to drive this thing.

i have an xtm mammoth st and i have a dynamite mach 26 and it runs great

i have an xtm mammoth st and i have a dynamite mach 26 and it runs great