i hear good and bad about axial .28's go with the RR instead of the 1s
but if you want to go with a mach .28 go with the mach .28 platinum, because that engine, is in every detail the exact same as the LRP Z.28 Spec 3, personally, stay with the .25, or just get a mach 427, the savages are not really meant for powerful engines unless you are ready to go buy a whole new high end drive-line out of steel or titanium
but if you are looking for power go with a mach .28 platinum or the lrp z.28 spec 3, they both last hella long more than 4 gallons, i have heard of a few lasting for 9 gallons, they also can heat up to about 270 or 280 with is more than most engines, which means longer run time and longer engine life
i say they are a good deal!
+ both have like 3.81 or 3.91 HP
i have an lrp z.28 spec 3 in my aftershock and i love it to death