7 1/4 stock 400

-
Please... That rear would pop faster then a bunch of horny virgins in a di**o factory.
 
I put a stock 60's 383 in a '72 Valiant. I INTENDED to just leave the 7-1/4" in long enough to get it to and from the muffler shop. I ended up leaving it in for a couple weeks. It was still a 2.94 geared peg-leg, with stock 13" tires. Smoking the one skinny from 30+ mph was too fun, and it got done a bunch. Within the 2 weeks, it got REALLY noisy, and I swapped in the 8-3/4" before it was too late.
 
my 7.25 lasted three years behind my built slant before anything happened to it... and that smog 400 probably puts out about the same lol
 
I had one with a 383 for a while. No noises or anything. Lot sof abuse...lol. But it never hooked, and the engine was a 2bbl. It's all about how good a shape it's in, how much the car hooks, and how much power you have.
 
So....What's actually going to break??? The Axles? Will the gears strip out?? What needs to be done to make a 7 1/4 bullet proof?? Were they made with some inferior metal??? I just don't get why they're so hated. Makes me want to try to blow mine up.
 
OwdKasd said:
So....What's actually going to break??? The Axles? Will the gears strip out?? What needs to be done to make a 7 1/4 bullet proof?? Were they made with some inferior metal??? I just don't get why they're so hated. Makes me want to try to blow mine up.
Click to expand...

its the spider gears on a open diff...

ive never heard of any issues with the later sure gripped units of the later years...
 
OwdKasd said:
So....What's actually going to break??? The Axles? Will the gears strip out?? What needs to be done to make a 7 1/4 bullet proof?? Were they made with some inferior metal??? I just don't get why they're so hated. Makes me want to try to blow mine up.
Click to expand...


For every day granny driving they are OK. I have had several over the years and never broke one.

Put some power to it, and that's a whole different story.
 
OwdKasd said:
I see. Couldn't he just put some stronger Spider's in then?
Click to expand...


then the differential pin will snap, had it happen. the gears are just too weak to handle any sort of power if your going to abuse it, 8-1/4 will hold but to be sure a 8-3/4 will take lots of abuse. if you look at the inside of an 7-1/4 compared to a 8 1/4 you will see what we mean by weak.
 
a ford 8.8 will work and be cheap just move spring perches...i broke many and many 71/4 with my 273 in 1964
 
I broke my 3.55 SG 7.25 back in '86 after about 6 months of cruising around and a few high school burnouts. I bet the SG part really made is stronger than the peg leg version because that 340 I had would regularly beat a stockish 340 Duster that was down the street. I had 10 inch tires out back, but my car was pretty light and the 3.55 put less stress on the rear than a 2.76. When it let loose, the pinion stripped out the ring gear. Could have been a combination of spider gear failure or something else, all I know is it stunk to high he11 when I opened it up. I replaced it with another 7.25 with 2.76 gears. Car was an absolute dog after that, could not break the tires loose, but would fly on the freeway. Sold it shortly there after, Boot Camp was calling.
 
Let me add my .02...

It will last a while if....

1. You install temporary spares on the rear axle....(No traction= No load)

2. You install a throttle stop to never allow more than 1/8th throttle.... No throttle= No Load

3. Throw ignition key in nearest river..... No Run-No Break :scratch:
 
My Swinger had a 7 1/4 in it for a year behind a 400 horse 360. It had 205s on it and ran 12.90s with no traction. It had 3.23s in it and i eventually broke it. Total hamburger when i took the cover off, it look as though the carrier broke. My friends and I still laugh hysterically at the beating it took, I even ran it with some 245 hoosier Dirt Bozz tires on it at a Mopar race at Speedworld in Surprise Arizona. But I think that rear was the exception, I would say that it wont tolerate that 400 very long. :burnout:
 
pishta said:
I broke my 3.55 SG 7.25 back in '86 after about 6 months of cruising around and a few high school burnouts. I bet the SG part really made is stronger than the peg leg version because that 340 I had would regularly beat a stockish 340 Duster that was down the street. I had 10 inch tires out back, but my car was pretty light and the 3.55 put less stress on the rear than a 2.76. When it let loose, the pinion stripped out the ring gear. Could have been a combination of spider gear failure or something else, all I know is it stunk to high he11 when I opened it up. I replaced it with another 7.25 with 2.76 gears. Car was an absolute dog after that, could not break the tires loose, but would fly on the freeway. Sold it shortly there after, Boot Camp was calling.
Click to expand...

The SG 7.25 is quite a bit stronger than the peg leg. I drag raced with one for a couple of years.

The open 7.25 is a bomb waiting to go off. It's just a matter of time..
 
You must log in or register to reply here.
-

Back
Top