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Discussion Starter #1
So last winter, I had many, many carb issues with that old 2bbl holley, I rebuilt it twice, and it would fail after a few months..

So I finally smartened up, I bought a 4 bbl Performer Intake, an Edelbrock 600 cfm, manual choke carb (I have a manual choke I installed), removed the A/C unit, and all of it's lines, and put an open element air cleaner..

It woke that 318 up like I could never believe, from 60-120km/h, she's a rocket, it starts up usually on the first turn of the key, and idles like a Cadillac.

My question, with the extra horsepower gains, should I be worried about damaging that 7 1/4" rear end? The transmission mount did break shortly after the modifications to the engine.

The other day I was able to break the back end loose coming around a corner, I'm running 225 wide snow tires....
 

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I'm glad that you have it running well.
I thought that the sixes had the 7 1/4 and the V8's had the 8 1/4 rear axles.
The 8 1/4 is a fairly robust axle and should be able to handle it, if you have this axle.
A rear axle fluid change for maintainance services with a Synthetic 75W-140 will help. This is what we suggested for heavy-duty, trailer-pulling V8 vehicles. Always check and clean the chip magnet.
Noise is usually the first indication of trouble.
 

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Discussion Starter #3
Thanks for the quick response!

Yeah, I've got to do that rear end dope one of these days, it doesn't make any noise, the transmission had a slight slip, but changing the transmission fluid seemed to remedy that issue..
 

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They put the 7 1/4 behind 318s in many F and M bodies and even some of the J bodies.
There are four general weak points:
1) The computerized ignition and carb Sounds like you addressed that.
2) The plastic gears on the timing chain
3) The lockup torque converter
4) The 7 1/4 rear axle.
Not every one will have all those problems. And a cop car didn't have the timing chain or rear axle problems.
Just as a precaution, I'd look for an 8 1/4 axle from an F/J/M body. You may find a deal on one easier before it breaks.
 

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Discussion Starter #5
I did buy a 1987 New Yorker from a buddy of mine, it's a rough low mileage parts car, it was $100, I was going to pull the motor, trans, and axle..

Plus, with how difficult it is to find those rear leaf springs around here, I'll definitely keep those!
 

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Make sure you keep the driveshaft too if the other car has an 8 1/4. The 8 1/4 driveshaft is a little shorter and finding one made to fit is cheaper than having yours shortened.
 
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