I have a 65 comet with an 8" rear end, if i get a posi spool from e-bay and some gears from jegs, how much horsepower can I expect it to take? Will it be able to handle 500-600 horse power or am i better off just getting a 9"? And how much horse power can a stock rebuilt c4 take? Thank you very much.
X2 300-350hp is roughly the limit. I'm sure somebody has made more, but if you're building for reliability a 9" or 8.8" would be a better choice.
the 300-350hp number is a very general estimate on what it might handle. High torque numbers and hard launches with very good traction are usually what does the damage and the 8" with stock 28 spline axles are generally the limitations. all of this is what the Mustang guys have been saying for years. I say leave it until it breaks if it's already there, but if you have to spend a lot of money for a drag car I wouldn't do it on an 8".
Sounds right. I'm thinking of another engine that might get 300 RWHP so your comment got my attention. Poster didn't mention tires but I'm not expecting any problems with my 8" on street tires.
I'm still running an 8" with a detroit tru-trac and 3.50 gears and street tires, it's a little noisy because of the not-so-high quality gear, but it works. I'm only at 215rwhp but it makes 294ft/lbs of torque. If it breaks, I'll upgrade.
Back in the early 70's I had a very wicked 64 Comet (was an ole drag car) that I street'd.........289ci real deal HiPo with 69 351w heads, barely streetable cam and with cheaters it turned low 13.0's and the occassional 12.9's.............it had a top loader and 4:56 gears..........with the stock 8". I really punished that car both on the street and strip and never had a problem. But I know the car had a lot less than the HP figure you are talking about. My current race only Maverick is putting down around some serious HP to the 13" rear slicks................3300lbs and 9.9's in the 1/4............and it has a 9" with spool and 35 spline axles. If you are going to make that kind of HP I wouldn't wait for something to break and just bite the bullet now. Building a car for the track or street is thinking about realibilty and having fun....................breaking something is not having fun in my book. It's your car and your pocket book..................have fun and build what you can afford...........IMHO
an 8 inch should be fine to high 11's in the 1/4 with an automatic. I have went 7.40's in the 1/8 with a 9 inch with stock 28 spline axles
It's not the HP numbers, but the sudden application of torque, combined with good traction, that's going to break something in a rearend.Just for an example I had a V8 Ranger I sold recently, everyone advised against running the stock 2 piece driveline with it, but it was fine until I swapped in a built 331, then one day I decided to show off and tried a dry burnout on a rough asphalt parking lot. When I dumped the clutch, the stock middle cast yoke in the driveline turned out to be the weak link. Normal everyday driving isn't going to do anything.
So it definitely sounds like a 9" is the way to go. I just saw a 9" housing for a 65-66 mustang on e-bay for about $300. Will this bolt on to my 65 comet and is that a decent price? I have to wait until monday for the junk yards to open so i can start calling around now that I know I'm going this way.
$300 for a bare housing seems a bit on the high side, if that's what it is. I paid $150 for a loaded 9" from an 81 Bronco with 31 spline axles and trac-loc a couple years ago. Needed to be narrowed but the center section with 3.50's and trac-loc was well worth it.
Is there a significant difference in strength between the 28 and 31 spline carriers/axles? I just want to make sure I don't spend the money for a 28 spline and find out I should've gone with the 31.
