A-904+rear end, HP ratings

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i dont know what rear you are talking about.
As far as the 904 if it is stock. I'd guess around 300 hp is all I would feel safe pushing through it. (flywheel HP that is). The 904 needs help to handle HP.
 
it needs help, how? and the rear end is just stock, I dunno, lol, never did figure out what kind it was... but it's smallish.
 
Properly built the 904 will handle anything you throw at it in a a-body...if you've got a 7 1/4 rear its time to step up to a 8 3/4,which if properly built also can handle just about anything in front of it..
 
what can I get a 8-3/4 out of? I have a 72' dart thats sort of a parts car and it has a rear end with a large bolt hole pattern, and the man said it was a cuda rear end.. is that a 8-3/4?
 
my 65 904 is built to go up to 500hp, my old 66 was similarly built after it got used up at track. Car at that time had 300hp and was going up as I had money and time. Beyond 500hp big help is needed or a different trans. JMO
 
Here's how to identify what rear you have

Mopar_axle.jpg
 
Just about any '65-74 model that has one if you're willing to narrow it.....'66-72 A-body if you want it to just bolt in. The A-body versions all have small bolt pattern wheels from the factory but aftermarket stuff is readily available to change it to the larger pattern. Stock, they're reliable up to about 500HP with an automatic trans. If you're going to bang gears, I'd cut it off at 450HP. With all the race goodies available they claim they will handle 1000HP now. Same with the 904....it just depends on how much money you want to sink into it to beef it up.
 
well this is what I need it to handle, I need them to handle a 318 build, bigger valves, higher comprestion, bigger cam, four barrel, high rise intake. I don't know how much HP that will make but it sounds like my 904 is safe, what rear end is best for it? (I really don't want to shorten an 8-3/4), thanks guys!
 
Wow, lol, what a thing to say! I'm just going to keep it, it's a stock dart rear end, maybe someday I'll want to do a total stock build! (Maybe)
 
swingingdart said:
Wow, lol, what a thing to say! I'm just going to keep it, it's a stock dart rear end, maybe someday I'll want to do a total stock build! (Maybe)
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Good thinking! I don't see the point in deliberately ruining a good part. Is it just me or doesn't anybody else cringe when they see a demolition derby? Must be the collector/ hoarder in me that wants to save/fix stuff.
 
I learned the hard way, raced my 66 cuda with 318 and 71/4 rear. Was ok until I made motor go faster and ran more rounds (got better). I made it to final round one day and sure enough, on the line right after semi round it went clunk. I took advice of many and found a good 83/4 rear had it narrowed and built for my needs. This cost me about 3k total, but I could not hurt it with 318, even as I improved Hp going into the 400Hp range. Car ran low 13's and was consistant and never had mechanical issues! I was good racer at that point and made many rounds and finals with no more issues except opponent! Spend some money now and you will be happy and never left on side of road or track. My current 65 is going to go through same process once paint and body are done. 318 built and when ready I will find 83/4 rear to go in along with my already built up 904 trans. Good Luck and enjoy the ride!
 
thanks!, the guy didn't have a 8-1/4 or anything for that matter, but he knew a guy who hoards up shortened 8-3/4s and 8-1/4s... so I'm in luck!
 
cudamark said:
Good thinking! I don't see the point in deliberately ruining a good part. Is it just me or doesn't anybody else cringe when they see a demolition derby? Must be the collector/ hoarder in me that wants to save/fix stuff.
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I love demolition derbies but prefer my 92 and up Crown Vics for that
 
hey I was looking through a junk yard and found a wagon, dodge or plymouth, (I know it's a 74 up model) will that have a good rear? and will it fit without narrowing? thanks guys!
 
8 3/4 came in 67-72 A-bodies Duster/Dart/Demon/Cuda 4inch bolt pattern SBP
8 1/4 came in 73-76 Dart Sport/Duster basically anything with V8 4 1/2 inch bolt pattern..LBP

I don,t think a wagon rear will bolt in an a-body unless it was from an Early-A v8 car,which would be rare.Hope this helps
 
Is it an F-body wagon? If so, I think I read something that said that an F-body rear is the same width as or really close to a '68-'70 B-body which means all you need to do is cut the spring perches and move them a .5 inch inward. If it's a V-8 car it should have an 8 1/4 rear.
 
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