71/4 How Strong Really

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Mopardeacon

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I am thinking about driving to the street legal drags to watch, but have been thinking about making a pass or two with my very slightly modified 318 powered duster....(wife, kids and other matters have kept me away from bracket racing for nearly 30 years but am feeling like it may be time to try it again). I know these rear ends are very weak, but the car makes very little horse power, so just was wondering what you guys think.
 
Theres a reason they came in slant 6 and 318 cars,they can't handle any real power..
 
It Should Handle 90 Horse Power Or Less. It Took Me One Weekend To Break One On The Street. A 1969 Dart, 273-2v, & 3-speed Manual. That Is The Weakest Mopar Part That I Have Ever Seen.
 
Ask confusedecuda that? His lasted exactly one hard hit off a red light with his mild 340.

I would do a raffle and have numbers from 0-100.

I'll take 3 with a 318.....but you gotta hit it hard out of the hole!:toothy10:

Cheap fix is the 8-1/4 so the say.

"Good luck were all counting on you"

Mop
 
I've broke them (seven of 'em) with a stock 273 4spd. Broke another six with a stock 225 and an automatic. (then I ran out of spares and had to upgrade to 8-3/4s) It seems that if you seriously spin one wheel the pinions rip out during the pass or very shortly therafter. I wouldn't count on a serious application of power from a Briggs & Stratton and expect to drive a 7-1/4 home. Of course, your results may vary.........
 
yep the sg ones are a lot stronger.

I've busted a few non sg ones in my few short years
 
The sure grip units will take more abuse but like my dads you will probably shear the ring gear bolts on one of those.
 
Who here actually has a sure grip 7 1/4?
and have you had it apart to look at the ring gear bolts?

I'm trying to find something out, I'd appreciate it.
 
I know red scampy has one it's under his red '72 with a 360, I doubt it has ever been apart though
 
1wild&crazyguy said:
Who here actually has a sure grip 7 1/4?
and have you had it apart to look at the ring gear bolts?

I'm trying to find something out, I'd appreciate it.
Click to expand...

I have one.I had it in my 65 Barracuda 318 4 speed car and pulled it out the day before I sold the car to keep for a slant 6 project.They are good as long as you don't beat the **** out of your car.
 
I have a 7 1/4 SG 3.91 in my 66 Valiant, that turns mid 13's. Had that same rear in my 13,sec Cuda that weighes 3200 lbs, and my 65 Valiant, before that. Also have a 5.13 SG 7 1/4 on the "rack, and the parts to build a 4.56SG 7 1/4. The early Clutch type SG are much stronger then the later cone type, or an open rear. The clutch SG's have 4 spider gears, where the other units only have two spiders. I would not use a 7 1/4 with a stick, but a SG one with no "slop" and a 904 should be OK.

PS: my cars 60 foot about 1.79-1.80 and my 170 nitrous motor makes 358 foot lbs 2950 rpm at the rear wheels
 
Here's a 7 1/4 3.55:1 ring/pinion from a sure grip out of a 1963 4 spd dart.
I got rid of the sure grip, it was missing a few things along with 2 of those special/weird 3/8 shouldered 5/16 bolts.

Photo 531.jpg


Photo 535.jpg
 
Yikes....I knew they were weak, won't be making any passes with these kind of odds, the track is almost 90 miles away and I don't think wife would be amused if we had to hitch a ride home and pay a large tow bill. I have a 81/4 bbp but it needs every thing...I have heard these are much stronger...I think I will just spend the money on it and then try it. Thanks for all the info.
 
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