Anyone know what kind of power (torque, hp) an 8 inch rear can handle? Been searching online and have been unable to find anything. I have a mildly modified 289 - Edelbrock performer cam, intake and 600 cfm carb. Stock heads and pistons (9.3 compression?) JBA short headers with 2 1/2 pipes. Of course without putting it on a dyno I don't know what kind of power it's making, but how far can I go before I should seriously consider a 9 inch rear? Appreciate any knowledgeable replies. Thanks guys and Happy Mustanging!

 

That 8 incher will handle that much power and more. I seriously doubt you are putting out 400 rwhp. You could spend your money on some gears for that 8 incher. Which gears will depend on how to plan to drive the car.

 

Thanks Soaring: It is a brand new 8 inch center unit, 3.25 gears. Guerss I will spend my money on a T-5, need the overdrive as this setup runs at 2800 rpm @60mph in high gear (Toploader 4 spd).

 

Yeah, with the price of gas nowadays, 2800 RPM at 60 ain't good for the freeway. The 325's are a great compromise for all-around performance situations.

 

If you are not using real sticky tires your 8" will be fine. However, if you plan to use slicks and launch the car hard, your 289 (with a std. trans.) makes enough HP/torque to break that rear. They usually break the case at the small pilot bearing boss. That's why the "K" code cars with 271 BHP got the 9" rears.

 

well i have the 8 inch 3.25 posi that origianlly came with my car. This rear end set up is kinda hard to find info on, mainly because not ver y many had posi rear ends in them, a lot more came in the larger and stronger carrier. However i can tell you that my rear end holds up quite nicely against whatever it is i throw at it, and imo really no strong diff from the 9 inch

 

I absolutely agree that it's a strong rear. But if you try to use it with slicks or real sticky street tires, even a moderately warmed over 289 or 302 has the power to break it, especially with a manual transmission. The later 8" cases were stronger than the earlier ones but they still have a tendancy to crack at the pinon pilot bearing boss. I broke two of them many years ago running a warmed over 302 in a 66 coupe with a top loader and 4.62 gears. For moderate performance use they are excelllent.

 

Well, I am running Dunlop GT Qualifier's (225x50x15's) but the bottom line is I don't plan on dumping the clutch at 2500 rpm or anything. It is basically a street cruiser/show car. But was wondering if I do get on it fairly hard, if the 8 incher will do me right. So I guess that opening the four barrels while rolling, this rear end is gonna do just fine. Planning on more engine mods in the future, maybe a set of aluminum heads eventually. But doubt I will ever exceed 300 hp... Thanks guys.