new engine for a old 25

[oldschoolsavage25]

Hey guys. i have a old 25 and I'm looking at getting a new engine for it. I'm looking at the lrp line, I'm thinking .30 or .32. I'm wondering if i will be able to just drop one of those beast engines into my rig?

 

[Jam Racing 1]

Sure it will drop right in, but the torque of something like that is going to for sure STRESS everything from the clutch out to the tires, so it is possible you should do some upgrades before doing that.....
things like the differentials need to have good well shimmed gears in them and for sure the 4 spider and alloy diff cups to keep them alive..
also the spur and bell should be of the hardened variety and the slipper pad,spring, washers and nut should be in good shape also... also the transmission should be all metal gears because plastics just fail under the loads that engine can produce...
Read thru some of the other threads here before you make a final decision as to what to go with.....

 

[olds97_lss]

I run an LRP28 in my X and it chewed through the stock diffs before I got it broken in fully. I bought the truck used, but from previous savage's, I know even the machined gear diffs require really good shimming and alloy diff cases/gear box to work the best. On my X, I just went straight to the BP diffs off ebay. Haven't had an issue since and that was easily 2+ gallons ago.

I also upgraded the output axles/cups/dog bones to the larger HD ones around the same time since the XL diffs came with the larger cups.

A few years ago prior to my X, I had a normal Hot bodies lengthened savage and I put BP diffs in it too, but it required that I used the old diff cups because the new ones wouldn't fit through the old diff case/box, so I was stuck using the original output cups and the smaller dogbones. It held up fine though, would twist a dogbone off on occasion, so I made sure to have a couple spares with me.

I just said all that because your thinking on going with an engine with even more torque than mine and I wanted to let you know the things you should do before you even fire the thing up.

With the LRP28, I'm also running an HPI steel 47T spur because I kept having the center of the spur melt out on me even with a fully compressed spring. I recently went to a 17T bell to see how it did and it can easily take an 18T bell. Depending on the tires you run, gearing up may be a necessity too or you will just cook the engine or break more stuff due to the torque it has. I run traxxas 3.8" rims and chevron tires. They weigh about the same as the old savage GT2 tires and are similar diameter.

 

[oldschoolsavage25]

sooooooo, basiclly you are telling me upgrade everything!!!!!!! I run pro-line Big joe tires on some basic pro-line rims. of course i have the 17 mm hub adapters to run those big tires and rims. can you give me a couple of links for some upgrades i should pick up. I'm going to get some BP diffs

 

[oldschoolsavage25]

i found some savage x ss whole diff assyies , cases and everything. are they any good?

 

[oldschoolsavage25]

HPI Savage X 4.6 BULLETPROOF DIFFERENTIAL Diff 29/9 Ring Gear Bevel Case. i also found these? will they work? i know the stock ones have a different gear ratio

 

[olds97_lss]

The BP diffs are the ones you want, but, if you don't have savage X diff cases/gear boxes (whatever HPI calls them), basically one piece diff case/bulkhead where the diff can slide out the front, odds are they have the larger cups that won't fit through your bulkheads.

 

[olds97_lss]

i found some savage x ss whole diff assyies , cases and everything. are they any good?

Those just have alloy cups in them for the spider gears. Or they probably are.

These are what I bought off ebay (for my old savage):

Then I used hot racing (I think) alloy diff halves and had to use my original smaller output cups in the new diffs because they have holes for the diff cups to go through:

The alloy case halves weren't a necessity, but did add strength and shimming accuracy. I never had a diff issue after doing all this. I suppose I could have dremeled out the case so the big cups would pass through, but I can't recall if the bearing was the same OD as the large diff cups or not.

My current savage though is an X, and I bought the same diffs as above, then just transplanted the diff/pinion as it was (after cleaning out the grease and adding 50K oil) and bought the HD dogbones to the wheels with the HD diff cup/axles for the wheels. I have no photo's of that build though. Figured if you had an X or XL, photo's are irrelevant.

 

[Jam Racing 1]

You do not "need" the BP gears to have a good stout differential, I am running the 43/13 stock savage X differential gears in my rig and if they are shimmed right they will be fine..... My a stout axial .32 is making plenty of low end power and in a year of running I have not broken anything in the differential yet......

 

[oldschoolsavage25]

is it possible to upgrade the diffs in my truck to something close to the BP ones? like with new spider gears and new cups. ive seen 4 spider gear upgrades

 

[oldschoolsavage25]

can i put the easy access diff bulkheads from a 4.6 x in a 25?

 

[Jam Racing 1]

sooooooo, basiclly you are telling me upgrade everything!!!!!!! I run pro-line Big joe tires on some basic pro-line rims. of course i have the 17 mm hub adapters to run those big tires and rims. can you give me a couple of links for some upgrades i should pick up. I'm going to get some BP diffs

well you could always just put in that torque monster and blow stuff up and repair/replace as things fail....

 

[olds97_lss]

can i put the easy access diff bulkheads from a 4.6 x in a 25?

I never did it, so I don't know what all you would need to replace. Guessing the towers, skids alloy post that the top bolts go to, skid/bumper mounts, not sure if the alloy parts under the skids need replaced.

From what I've read, the front/rear assembly off the X/XL will bolt on, so where the TVP's mount should be the same.

Still, it's a lot of stuff.

2 of these gets the case, diffs, towers:
http://www.ebay.com/itm/NEW-HPI-SAV...978378?hash=item48864f224a:g:~GIAAOxyuR5TYZ73

Still leaves you needing the HD dog bones, outer axles, skids, bumper/skid mounts.

Or find a guy that is selling the entire front/rear clip off an XL:
http://www.ebay.com/itm/HPI-Rear-Ax...947594?hash=item33ab5726ca:g:NIEAAOSw9mFWJSA6

Just double check that they have the BP diffs. That will have the extended outer axles though, not sure if you want those. I didn't, but was mostly because the truck wouldn't fit in my bag with those and 3/4" offset wheels I had bought for it. And it would really strain the bearings to run those wheels with those extended axles.


Again, this is a lot to do right off the bat. If you want, just get the engine and start breaking it in with what you have. For what it's worth though, just replacing with non-BP diffs will end up with you replacing them more than once. So, it's totally worth doing whatever to get the BP diffs in there when things start failing so your not wasting money on parts that will fail again.

 

[oldschoolsavage25]

http://www.hpiracing.com/en/part/1403 so i have one of these laying around and i decided to put it in the 25 for the hell of it. i have a bunch of clutch bells and spur gears and none of them seen to fit right. its like the engine is 1/16 of a inch to long. the gears mesh together but the front of the bell hits the side of the spur gear.... any ideas?
this is just a place holder engine till i get a new one.

 

[Jam Racing 1]

only thing I can think of is to break out the measuring tape and see if both engines are same length crank end to backplate...

 

[olds97_lss]

You do not "need" the BP gears to have a good stout differential, I am running the 43/13 stock savage X differential gears in my rig and if they are shimmed right they will be fine..... My a stout axial .32 is making plenty of low end power and in a year of running I have not broken anything in the differential yet......

Give it time. I went through 4 or 5 of HPI machined ring gear diffs over the course of a couple summers (prior to BP diffs existing).

I'm not saying it's required, but if you blow a diff, might as well skip a minor upgrade and go for the better upgrade.

 

[olds97_lss]

http://www.hpiracing.com/en/part/1403 so i have one of these laying around and i decided to put it in the 25 for the hell of it. i have a bunch of clutch bells and spur gears and none of them seen to fit right. its like the engine is 1/16 of a inch to long. the gears mesh together but the front of the bell hits the side of the spur gear.... any ideas?
this is just a place holder engine till i get a new one.

Not all engines are the same. How big of a gap do you have between the flywheel and crank case? I've had to grind the collet down (the side towards the engine) to get a CB closer to the engine for clearance reasons. Some collets are shorter than others, some flywheels are deeper than others. Odds are, you can make some space by grinding down the collet.

 

[oldschoolsavage25]

So I never even looked at the flywheel. I feel dumb. It had a big collet on and the flywheel had a big lip on it, cause of those 2 things it didn't have the clearance to fit right. So I took the flywheel of the old stock engine and put it on the hot bodies 3.5 and everything is fine and dandy.