What next?

[GideonBowles]

2.5 ish year after I first bought my 71 Monte Carlo. I have done a plethora of things, rebuilding the engine, sanding, and priming the car, replacing body panel panels, and I finally got my glass back in it so I can drive. What next? Well I’m doing body work the next 4-5 months, will be painting it after that.

 

But for the drive? I had my 454 rebuilt, to a 462, 781 heads, big cam, but still am running a stock intake manifold and exhaust manifolds. The car runs great. The only issues I’m having is one - the engine, not being as powerful as it could be, but that’s more of a personal thing, and two - having absolutely zero grip because I still have the stock differential, only one wheel grips and they’re very low gears.

 

What should my next big purchase be?

again, the car runs great. I just want to access the full potential.
 

Get a new differential so I can apply my current power better? Or get a new intake and headers to have more power….. which can’t be applied fully yet. 
 

Any advice?

I am aware that it comes down to what I want and what I think would be best, but that’s the issue. I don’t have enough experience to identify which would be better.

 Thank you!

[jft69z]

Rear Differential. 

[cny first gen 71]

 Joe is right most people overlook rear end thinking motor needs more. Gear it properly for the type of driving you'll be doing and set up.

[Michael Boyte]

I agree with Joe and Steve, get yourself a good posi unit and a set of gears and you should be good to go. I personally would look at gears between a 3:73 and the 3:31's , maybe even a set of 3:55's , as Steve pointed out, depending on the type of driving that you plan on doing 

[Dtret]

I agree with the diff but you’re probably under powered with the intake and carb as it’s stock. I’d skip the headers , you’re not going to gain much as a driver and they can be a PITA. 

[Scott S.]

Definitely the rear end.... I like my 3.31's, but it all depends on what you're want out of her.

I assume you're still running a TH 400. 

One thing you might also want to consider is the torque converter. If it's still a stock unit, it's not getting all that power to the rear either.

As for under the hood, an intake would probably help with the breathing, especially if you've up'd your cam shaft. 

Start with the rear... a good 12 bolt posi, and see what it does for you. Then you can go from there. 

 

[GideonBowles]

On 12/24/2024 at 3:34 PM, Scott S. said:

Definitely the rear end.... I like my 3.31's, but it all depends on what you're want out of her.

I assume you're still running a TH 400. 

One thing you might also want to consider is the torque converter. If it's still a stock unit, it's not getting all that power to the rear either.

As for under the hood, an intake would probably help with the breathing, especially if you've up'd your cam shaft. 

Start with the rear... a good 12 bolt posi, and see what it does for you. Then you can go from there. 

 

Thanks! I have been looking at 355s, would you advise buying the parts and installing myself? Or paying a shop to do it? I’m a mechanic which some old blood here that can help but a lot of people told me not to try and add a posi myself and to pay for it.

[GideonBowles]

On 12/24/2024 at 1:39 PM, Dtret said:

I agree with the diff but you’re probably under powered with the intake and carb as it’s stock. I’d skip the headers , you’re not going to gain much as a driver and they can be a PITA. 

Skip the headers! The intake is stock but my carb is a 750 cfm holly. 

[GideonBowles]

On 12/24/2024 at 1:28 PM, Michael Boyte said:

I agree with Joe and Steve, get yourself a good posi unit and a set of gears and you should be good to go. I personally would look at gears between a 3:73 and the 3:31's , maybe even a set of 3:55's , as Steve pointed out, depending on the type of driving that you plan on doing 

So far I have been looking at 3.55s if I do. Would you say a man could install said dif by himself? Most of my people told me to pay to have it done.

[cny first gen 71]

It does require some special tools and skills, I'd suggest if it's something you've never done before to have someone that knows how to do it properly. I did learn how to do them many years ago but I would definitely have it done for me now.

[Michael Boyte]

I would not advise it . You will come out ahead by paying someone to do it that has the knowledge and the correct tools to do the job. 

[Scott S.]

4 hours ago, GideonBowles said:

Thanks! I have been looking at 355s, would you advise buying the parts and installing myself? Or paying a shop to do it? I’m a mechanic which some old blood here that can help but a lot of people told me not to try and add a posi myself and to pay for it.

Considering that you're going to be changing the entire carrier assembly, it would depend on your confidence level.

If you're buying an assembled unit, then changing the pinion and bearings is the biggest job. 

That and setting the lash and shims. 

If you're thinking of building a whole new carrier, yeah, that's best left to someone who's done a few.

[John S]

Tightening the pinion nut to crush the sleeve for preload and getting the pinion depth, correct is a little tricky. Years ago back in the early 80s myself and some friends would take another set of pinion bearings and hone them out, yes it took a while. Pinion bearings are pressed on. We would hone them out so they would slide on the pinion so we could easily disassemble to get the pinion depth correct. I had Atlanta driveline set up my rear end when the Posi unit was replaced. I wasn’t gonna mess with that anymore.

John S

[GideonBowles]

You wouldn’t happen to know or have any advice on tutorials or information on how to do that Myself would ya?

[DragCat]

One thing I'd add to the mix is upgrading the axels while you're at it. Some of us installed new strange. 

Seems like you're leaning on doing it yourself, I'm sure there's tons of YouTube videos out there. 

When I did mine (disclaimer, I was the intern for my buddy) its a lot of work. And as mentioned, your going to need the right specific tools. Having done it once I wouldn't do it myself I the future.

Another note, be sure to add the rear gear oil additive.

[Scott S.]

It is much easier to do "out of car" as well.