71 Coronet Project (Stock Gear Ratios, 318 capabilities, etc.)

[CyBeRdEmOn12345]

So last year I got stationed in California and I went ahead and bought my first car, a 1971 Coronet Base. Save for an MSD electric ignition box, the car is pretty much as stock as stock gets. So needless to say, I'm trying to get this car up to date performance wise without changing the overall apperance of the car that I fell in love with. Problem is, it's not a very popular model year so getting information isn't easy. I think for the year, the Charger and Coronet were pretty much the same car, except one was a coupe and one a sedan, but I'm still not sure if I should go off the Charger specs when it comes to stock gear ratios. The reason I ask is because it's got a 318, which I'm told can put up some good numbers HP-wise if you know what you're doing (which opens up more questions, but I'll get to those). So basically my question is this: what is the stock gear ratio for my car and can it (if I'd guess, probably not) handle around 400HP? If not, what gears do I need for numbers like those? Are those numbers even possible with a 318? If so, could i do it with bolt on parts or will i need to stroke it? Also, my buddy tells me the 727 TorqueFlight auto tranny in the car can handle 400HP and he knows more about cars than me so I tend to take his word for it, but is it true? I know it's a lot of questions, but if anyone has the answers, they'd be greatly appreciated.


My name is Gary, by the way. Rather new to FBBO, being this my first post, but I'm looking forward to schmoozing with you guys on various things and hopefully learning some valuable knowledge along the way. Thanks again for any responses.

 

[Darter6]

Anything can be done if you are willing to throw enough money to it. A 71 318 is a good starting point.Just remember"There is no substitution for cubic inches".This is with a normal aspiration and no turbos, blowers,etc.Your car may or may not have a 8 3/4'' rear axle. If the rear cover is removable with bolts it should be a 8 1/4''. You will be looking at a rear ratio of 2.45- 2.76 as most common.Either can handle 400 hp with a ratio change(say 3.55 for street) and a suregrip differential installed.Your car may have a 727 or 904 torqueflite and either will handle 400hp with ease.Getting back to the 318, a stroker kit to 390 CI with other parts,cam, intake, carb, headers and a good exhaust you can reach your goal.
Sounds like you have some learning to do and you will find it here over time. Have fun with your 71 !

 

[DWilbur]

Hello Gary and welcome the FBBO. I'm going to be installing new engine and trans in my 73 Satellite next week end. I spent about $6,000 on my 318 stroked it to 390 CID. I bought a 904 replacement trans from ATI for $1,100. the engine should put out about 450 hp. the trans was built to handle 575 hp. I bought most of my engine parts from Hughes Engines and Summit Racing. Check out Hughes Engines they have several options and they are very helpful on the phone. I will be starting a build thread next week end after most of the work installing the engine and trans is complete.

 

[CyBeRdEmOn12345]

Sounds like you have some learning to do

If that's not an understatement, I don't know what is. I'm a little bit behind the curve knowledge-wise, being that my dad pretty much never taught me jack about cars and I was never really interested in cars period until I moved to California last year and saw my first Challenger :icon_lol: So now, I have a few friends who are pretty knowledgeable about cars so whenever I have a general question I usually ask them and if I have a question specific to my car I usually seek info on google or here now that I actually have an account. I'm learning though, slowly but surly, reading manuals and others pubs and doing a lot of hands on scheduled maintenance. Thanks for the advice btw!

P.s: What would be the difference between a 3.55 and a 3.90 gear? The whole gear thing is still kinda confusing.