wondering what the best snowmobile engine you ever had in a 6x6

i am just wondering on input on what engines have a power band worked well at ashtabula or anny where else in the past for say an old 73 ish argo solid axle
i know possibilty is endless i am just unshure on how much mud these can sling
i have a freind that has a few argos.
he has a few engines ...
he uses a vangaurd or so as a main beater.
he has a rotax 640 that was in one that he got cheep and never unsiezed it . i have like 2 of em that turn freeley.and both were rebuilt at some point n time with tnt pistons .
they are 3 port skidoo engines used in the heavey sleds like the valmont nordic and alpine the caps are leaked so no sparkey ..
i did see that one thread on here somebody did buy a 540 yamaha fan engine ,i know the early 540 had smaller reed cages and had descent lowend .
i am unshure how anny of the water cooled rotary valve engines from doo would do in one of these like the 521 or 467 or so
anny input would be nice to see on what ppl have tried and had fun with ..
craigslist is a good place if you dont mind driving to newyork from pennsylvania where i live to scam a good deal , there is a 530 el tigre along with 2 72 ish panthers with low miles both 440's for like 350 bucks for all
thanxz in advance

I am a HUGE fan of and I'd highly recommend the 440 Cuyuna, which is basically a later version of the JLO. This is a 5 port engine, and also highly desirable in the ultralight aircraft crowd. Parts are pretty easy to get and with a little bit of top end work, they'll REALLY scream! Hydromike and I both ran them in our racers at Ashtabula. You can get them out of most late 70's and early 80's Scorpion snowmobiles. Also, the 484cc G50B Chaparral is a great motor that Attex used in the Superchief, but they're not that common. The 503 Rotax is another great option......this engine came in many 1980's Ski Doo snowmobiles.

I had a '71 Ski Doo TNT with the 640 and it was a good sled, but I know for a fact a newer Cuyuna 440 would run circles around it all day long.

Thanks jp..., nice reference on where to find those engines. I have always wondered where those engines came from!

i took some time to attempt a crash course in snowmobiles a wiseco catalog is plenty of hunt peck and reading then search on ebay and see what crap is going for etc atleast ya know where to look amd what hood has what underneath it
personally would like to hook myself and my freind up with a 540 fan from an excel-v vk540 or srv540 yamaha fan .
yeah the cuyuna engine is a popular piece and ez and cheep to rebuild
anny scorpion or massey will do what 76 up
i know make shure ya get the 5 port and the more then 4 head bolt 400/440
the 503 rotax came in the bizzard 5500 amd others up into the 90's very common piece coulda had 2 for 300bucks or best offer 1 needed a stator on c/l
i actyally preferr the yamaha reed motors the 433 looks like one of the best candidate
iz ez to find a 440 exciter 440 enticer it uses blaster size reed cages wich interchange with a bunch of Yamaha engine size and stock is about 50 hp bottom ends are somewhat the same for the 300 twin 340 twin 396 and 433 . you can bore a 340/300 fan to accept older non reed 433 pistons
and base gasket is the same as a 488 phazer so the phz cylinders will fit on the 433 340 bottom ends with some die grinding to the sleave area of the case so if size is an issue . that and with dual carbs and boost bottles lots mud can be tossed
the ss440 has the roof cutback to the exhaust port so it has some crappy bottom end
with a huge hit on the mids and is the same base as the 540 fan cooled so either reduce the gearing and change reed cages to the mx bike stule with 2 stage reeds
pr 540 it the 540 came in 2 reed cages small early that interchange with the ss440and the big/later models....
earlier has the small cages same as the yamaha dirtbikes from the late 70;s it yz mx 250/400 425. same as the kx 250 400 . and pwc 650-'s 300 from kawi 12 5 cagiva
the later 540has about a 10hp increase larger reed cages same as the early 80's 4 bolt ityz 250/465 490 and tri-z and late 80'sa early 90's yz 250 4 bolt reed cages
i
i ride a 440ss 100 dollar snowmobile find the cyl has some port work to em . 10 feet out goes annywhere but straight , needs the new track i got her
i also have a set of 540 cylinders from the junkyard that had a fresh wiseco topend on it and flried the ringland on one of the piston i guess first time out he shoulda checked his jetting before chernobling it . wiseco is doing some plating to stop that issue the new catalog states that
what i plan on doing on my 540 build is run a majick marker down the piston through the exhaust port then mark on top of piston while on bottom dead center where front of pri trans port is
pull pistons measure half way between the 2 points and chalk a line down the piston then 1/2 way between the rist pin and bottom ring drill a hole about 10 thousandth through the piston . do ing this kepps big bores from siezure 4 holes on the front skirt 2 hish 2 low .2 on the rear of piston rear are done half way between wristpin and compression ring end gaps /pins what it does is lets oil seep thropugh the piston to help cool the piston and transfer heat from piston to cyl wall . works well on yz250's and trx250r's as well as putting that small hole in back of piston for the reeds to breathe through
a freind of mine has an attex he wants to build
i will not rule out water cooling i have a exciter 570 water cooled sled .
and i aint ruling out a rotax water cooled rotary valve mid 80s 467 or 521
o wouldint mind turbo ing one either .....
this is where i stand on
id preferr your input of you have anny more bases to cover
thanxz
amc

hi how did you make out with engine swap ? I just got a 1980 8x8 gave to me for free and a ski-doo 503 for free so was thing about putting in the 8x8 just want to talk to someone how did it already ? is that to much power ? how is it to drive ?