Rear end options? Best bet?

[68plymouth383]

10 bolt cover is the 8 1/4. The 9 1/4 rear axle is a 12 bolt cover. I'd be interested in the 8 1/4 axle guts if the sure grip, and gears are good. I'd also be interested in the front disc brakes.

Yeah it looks like a 73 and he said it was a 73. I have not laid eyes on it yet in person but he said the rearend drops out the back and has 10 bolts on the cover. Here is a pic of the car.
I also picked up a 73 polara last week that was a 400 2 barrel that has the same 9.25 rearend in it.

 

[1969vert500]

He might be miscounting the bolts too. I will check it out. It is a disk brake car.Would they put an 8.25 in a C body behind a 400? Seems like a disaster waiting to happen.

 

[68plymouth383]

Yes they would. The 10 bolt is a stout axle, and often underrated.

 

[70bigblockdodge]

Yeah it looks like a 73 and he said it was a 73. I have not laid eyes on it yet in person but he said the rearend drops out the back and has 10 bolts on the cover. Here is a pic of the car.
I also picked up a 73 polara last week that was a 400 2 barrel that has the same 9.25 rearend in it.

400-2bbl most likely has a 8.25. If it has a single bolt at the bottom and cover is oval/round its a 8.25. A 9.25 has two bolts at the bottom and the cover has a flat spot at the bottom. The disc brakes on both those cars are worth the 300
As Moper said if you start building that kind of power you are going to push all the stock stuff over the top. 550 ft lbs.× 2.45 first gear = 1347.5 ft lbs. in the driveshaft × 4.10 rear gear = 5524.75 ÷ two axels = 2762.375 Axel twisting ft lbs.

 

[68plymouth383]

Hey 300 is full retail disc brake prices.... frugal sell em quick I'll pay a 3rd....

400-2bbl most likely has a 8.25. If it has a single bolt at the bottom and cover is oval/round its a 8.25. A 9.25 has two bolts at the bottom and the cover has a flat spot at the bottom. The disc brakes on both those cars are worth the 300

 

[1969vert500]

Is it just the rotors that everyone wants on those or is it the booster unit too? the polara I picked up had them too. I am pretty darn sure that one is a 9.25 as it had the flat spot on the bottom of the rear as I looked at that while I winched it up on the trailer.

 

[commando1]

Here. Print this out.

 

[Landyacht]

Well I agree that it could be a large issue with axle strength, but note I was looking at replacing them with a pair from strange. Also, curb weight of a 440 Fury on 1966 was closer to 3700 lbs. Vacuum for ancillaries is being ran by a hysroboost unit.

What I meant by manifold vacuum issues is when you're cruising along and decide to stomp on the gas pedal your manifold pressure is going to drop resulting in weak throttle response and poor acceleration. There's only so much timing adjustments and carb tuning you can do to remedy the problem. If you were worried about maintaining a tolerable cruising RPM you should have built a milder engine. By running too low of a gear ratio you're not allowing your motor to live up to its full potential. You will end up with a 600 + hp Plymouth Fury that performs like it has 350 hp

 

[70bigblockdodge]

Is it just the rotors that everyone wants on those or is it the booster unit too? the polara I picked up had them too. I am pretty darn sure that one is a 9.25 as it had the flat spot on the bottom of the rear as I looked at that while I winched it up on the trailer.

Nope it spindle, caliper bracket, one piece rotor, fits the same lower ball joint as 65-73. 74 up cars have a different balljoint layout. 73s are a one off year.

 

[mrkt09]

so would a set of 3.55 work? or would I have to go 3.73?

 

[moper]

Some ratios are notavailable in some rear axles. The 3.73s are one example - I think they are the 741 case only in terms of 8 3/4. They should be available in the Dana 60 ofr FAB9, possibly the 9 1/4. In terms of ratio choice - I think higher ratio is better for a cruiser with a big motor. Meaning the lower gear number: 3.55 or 3.23 would be fine.

 

[Landyacht]

so would a set of 3.55 work? or would I have to go 3.73?

I would go with a 3.73 minimum but preferably higher something like a 4.10 would be much better. Another alternative depending on how far you are into the build is going with a much smaller cam and running the Performer RPM intake instead of the Victor. A stock magnum cam with your setup should easily produce over 400 hp. and you could get away with running a 3.23 and have excellent throttle response. Horsepower numbers alone are not going to determine how fast you accelerate. A mild 400 hp build with a 3.23 gear may very well out perform a 600 hp build also running a 3.23 gear.

 

[twostick]

I would go with a 3.73 minimum but preferably higher something like a 4.10 would be much better. Another alternative depending on how far you are into the build is going with a much smaller cam and running the Performer RPM intake instead of the Victor. A stock magnum cam with your setup should easily produce over 400 hp. and you could get away with running a 3.23 and have excellent throttle response. Horsepower numbers alone are not going to determine how fast you accelerate. A mild 400 hp build with a 3.23 gear may very well out perform a 600 hp build also running a 3.23 gear.

With the correct converter that 512 will be a tire roaster even with 2.76's. It will have 500 ft/lbs of torque from basically idle and it likely peaks 625ish perhaps more if the heads are well done at or just under 4000 RPM. With those kind of numbers you don't need steep gears to multiply torque to the wheels.

My 9:1 493 with an MP509 pulled fine with 2.76's. What it didn't do well with 292 duration and 76 deg of overlap, was cruise in the 2100 range. 3.23's solved that problem.

What are you planning to do with the car? If it is mostly street the 8.75 should survive just fine with with good axles. If you add a lot of track duty with slicks and a trans brake then the 8.75 is a grenade with the pin pulled.

A 9 inch in stock form is really no stronger than an 8.75 and once you put enough aftermarket parts in it to survive, it will cost as much as a Dana. The only real advantage to a 9 inch is gear selection and a housing that lends itself to being braced so it doesn't bend.

Kevin

 

[mrkt09]

Good to hear. I guess I'm going Dana unless a 9.25 gets anywhere near as beefy.

 

[Landyacht]

With the correct converter that 512 will be a tire roaster even with 2.76's. It will have 500 ft/lbs of torque from basically idle and it likely peaks 625ish perhaps more if the heads are well done at or just under 4000 RPM. With those kind of numbers you don't need steep gears to multiply torque to the wheels.

My 9:1 493 with an MP509 pulled fine with 2.76's. What it didn't do well with 292 duration and 76 deg of overlap, was cruise in the 2100 range. 3.23's solved that problem.

Kevin

I seriously doubt that motor is going to produce 500 ft lbs of torque at idle. The 3000 RPM range sounds more realistic.
I owned a 73 satellite with a 318 with a 2 bbl carb producing an advertised 155 hp and 265 lb ft of torque and would roast the tires quite well with a 2.73 gear but that didn't necessarily make it fast. The argument that I am making is that the motor he is building has the potential to possibly pull 11 seconds in a quarter mile given the right gear selection. Im sure the car will be fast no matter what gear he chooses but will he be taking full advantage of what the motor has to offer. If you're going to spend the money to build a 600 hp monster, wouldn't you want to get your moneys worth out of it?

 

[70bigblockdodge]

I would give up a second in the 1/4, for a car that would do a 400 mi trip with ease.

 

[Landyacht]

Dilemma solved !

 

[twostick]

I seriously doubt that motor is going to produce 500 ft lbs of torque at idle. The 3000 RPM range sounds more realistic.
I owned a 73 satellite with a 318 with a 2 bbl carb producing an advertised 155 hp and 265 lb ft of torque and would roast the tires quite well with a 2.73 gear but that didn't necessarily make it fast. The argument that I am making is that the motor he is building has the potential to possibly pull 11 seconds in a quarter mile given the right gear selection. Im sure the car will be fast no matter what gear he chooses but will he be taking full advantage of what the motor has to offer. If you're going to spend the money to build a 600 hp monster, wouldn't you want to get your moneys worth out of it?

The stroker is a 512 Stroker, 10.3:1 comp, .574 lift Comp cam 110 lobe sep, 284/284 duration, Max ported super stealth heads, edelbrock performer RPM (ported) also have a victor intake. The reason behind the 3.23 is a semblance of highway ability while not revving to the moon. I have a second 742 casing as well that I could flip in and out. Called strange about axles and they have a set for the 8.75.

Slight exaggeration.

My 9:1 493 was making over 500 ft/lbs by 2000 RPM, 600 @ 4000 and still had 500 @ 5000 where it quickly ran out of cylinder head. This is on 87 fuel. It idles at 1100. IMHO 2000 with my cam, is just off idle.

He has 19 more cubes and 1.3 more compression. He has .065" more lift but 8 deg less duration than mine plus 2 deg more lobe separation. I would just about guarantee he is making more of everything sooner albeit slightly than my combo.

Everybody gets hung up on horsepower numbers. Torque is what moves the car and 512 cubes makes a boatload of it right away. When you have LOTS of torque at low relative RPM, you can make big HP numbers relative to RPM pretty much by accident.

Kevin

 

[commando1]

I researched the torque figures of every 440 available from Mopar to try and find the cam grind for the engine that brought in the most torque at the lowest RPM.
68, 69 lo-po model. Pulled like a freight train.

 

[moper]

I would go with a 3.73 minimum but preferably higher something like a 4.10 would be much better. Another alternative depending on how far you are into the build is going with a much smaller cam and running the Performer RPM intake instead of the Victor. A stock magnum cam with your setup should easily produce over 400 hp. and you could get away with running a 3.23 and have excellent throttle response. Horsepower numbers alone are not going to determine how fast you accelerate. A mild 400 hp build with a 3.23 gear may very well out perform a 600 hp build also running a 3.23 gear.

The difference between a factory 3.75 and your 3.91 is about 4%. The difference between the 3.75 and a 4.25 stroke is almost 12%. There is no loss for low end in the 4.25 stroke build, and honestly the cam listed is smaller given the total package. It will make huge torque right off idle, and as in most other cars runing them, the milder gearing will let the engione pull. They are similar to boosted engines in that regard. Gear them mild and let them pull.