Hi all,

I have 1968 Dodge Polara Convertible with a 383 2BBL Dual exhaust. I am thinking I want to change that 383 to be ALOT more horse power but still have the option to drive down the road. I know I need to do something to the rear end probably (guess), and the tranny (It's all original right now) and I drive to work every now and then in it. I've converted the radio so it looks stock (shows AM only) but has FM, bluetooth, sirius xm) so I don't know if either (tranny or rear end) will support the increased engine power. I've been looking at 383 stroker kits but have no idea what to go with. Any Advice? In the end I want a sleeper that has been converted to todays safety standards, sounds nice with the dual exhaust, but will also sling rubber ... any help would be appreciated.

For the money it takes to make a 383 into an hot motor you could go with a 440. Trans being a 727 should be able to handle plenty of horse power. For cheaper fun stick a cam, 4bbl intake and carb and a good set of headers on the motor you got. Depending on what gear ratio in the rear end and if it's a sure grip 8.75 or not you may want to upgrade.

So the current trans will handle the horse power ? so to recap... you are suggesting stick a diffrent cam in 4bbl intake with Holley (750?) carb some hooker? headers and how do I find out the gear ratio on the rearend?

Hey oldfart. Yes, I think that's what stumpy is saying.

If you don't have any bolts on the center of the rear end when you look at it from the back (no cover with bolts) , then you have an 8-3/4" and it will handle quite a bit of horsepower.

For gear ratio in the rear end, you have a couple ways to go.
1. There may be a little, thin metal tag on one of the rear end bolts with a number on it (the gear ratio). Sometimes they're missing.
2. If you believe the rear end is original, you can check the fender tag for a "rear end code" (D-something I think? D for differential?) Somebody who's sure chime in please. No code = "standard" rear end gear & you have to check online to see what's standard.
3. Lift up the rear of the car on jack stands, place a mark on the tire & ground, turn driveshaft by hand one revolution & count how many revolutions you got at the tire. Compare that number vs. possible gear ratios for that rear end & you can figure out what you have.

stroke the 383 .

The basic TF727 and 8.75" rear end you very likely have can hold a lot of power if in decent shape. If the transmission is a high mileage original a moderate performance rebuild may be in order. Otherwise should be good to 400-500 HP. The rear end should be fine with any engine and street tires. If you start running drag slicks and pushing 500-600 HP with hard launches, the rear could become an issue.

You have lots of choices. You can warm up the 383. It is kinda a tough engine to build for performance due to short stroke and low compression but can be done.

Much better results can be obtained by stroking and increasing displacement. There are lots of well proven streetable combinations up to around 500 cubic inches. With cam, compression and carburation chosen for street use they can be easy to drive and reliable.

A nicely built engine would use a quench style head and piston combination to allow good compression on pump gas. Also a moderate cam. Starting with a 383 block, around 438 cubic inches with 3.75" 440 stroke, around 440 or 450 cubic inches with 3.9 stroke on up to around 500 cubic inches with 4.25" stroke. Or you could change to a 400 or 440 block if readily available... though I do not think that is necessary with your goals.

The stroker option does best with aluminum heads... 440 source stealth, Edelbrock RPM or Trick Flow. Also does best with careful blue printed rebuild to dial in piston height, quench and compression.

It really comes down to how far you want to go and resources available.

On your deal you need to decide on how much more HP and torque you want as well as the budget
Being a C body convertible I wouldn't want to risk tearing up the original numbers matching block by hopping it up
If you where my customer I would advise you to find a good 400 junk yard motor that had no holes in the block or cracks in it and use it to build good pump gas 505 to 512 C.I. low deck motor with a good set of new aluminum high flowing heads, intake manifold, bigger carb, cam and kit and the other parts you want to use like a good set of headers and larger exhaust system from the headers back, if your good with using headers
The only bad things about doing a motor like that like I want you to do is it might scare the BeeJesus out of you the first time you hit the loud peddle to wide open throttle
AKA aside, those motor make a hoop of power
PM me on here if you want more help on this

Do not change anything. Your 383 2BBL Dual exhaust is just fine for that type of car. Do not trade reliability for performance. Nothing wrong with a 383 stock big block.

X2 (keeps your numbers matching block). & Welcome aboard. Keep the heads/top end everything the same (& just enjoy the increased torque from the stroking). EDIT or get a 400 block & stroke it with an offset ground 440 crank (470 cubes) which wouldn't be prohibitively expensive & obviously keep your 383 stashed (this would minimize your down time). You'll feel the extra 100 cubes. with a B block (400) your exhaust system & ps/alt fitment on the front of the block would be the same. You could even keep the 383 pan/pickup.

Im guessing as to what youre after , based on your post. Trans wise, a rebuild with the red (rv and plow , heavy duty style) clutches and bands , along with a trans go shift kit make the 'flite happy. Assuming local cruising , a 3.23 sure grip does all you need, maybe 3.55. Engine wise, for the money and expected power return , Id go cheap cast crank emissions era 440. Cast or forged pistons (hyperuetectics are a no-no in my book), 440 source aluminum heads with a going over by a good engine builder, and a lopey cam that falls short of needing a converter any more than 2,500 stall speed.Keeps your small inch matching number on the stand (even though im apparently one of the few 383 fans),and takes advantage of cheap easy cubic inch.

In my experience you can do both.

Nice car, any pictures?
I had a '68 4-door hardtop back in the 1980's.
The car should have a 8-3/4" rear end and 727 transmission. Both can take alot of power. If in good shape, with a shift kit, can handle around 500 HP and even more with a few modifications.
You can stroke the 383 to around 496" (actual size depends on bore oversize.) That is a 4.25" stroke crank.
The 440 source stroker kits are good for the price.
I haven't priced any of the fancier cranks, rods, pistons in 10 years, so not sure how the prices stack up?
There are a bunch of aftermarket heads to choose from. For something not to crazy (Hydraulic Flat tappet cam?) I would look at heads that accept stock style rocker arms.

On the Milider and maybe easier side of things, there is a guy in Centennial, CO. who is selling a freshly rebuilt 440. I don't know anything about it, but it might be worth checking out?

i'd just bolt in a 440 and save the 383.

Check out your rear end and figure out what gear ratio it is by seeing how many times the driveshaft turns for one full revolution of a rear tire. If you have something like a 2.76 or 2.94 you may find just a gear change may be enough to give you the extra jam you are looking for. If it's not enough, it's ok because with a hotter engine build you would probably be looking at doing a gear swap anyway.

Try changing gear to a 3.55 and adding a good shift kit and see where you are. If your not happy with that then stroke it.

I drove my Dads 67 and also a 68 Polara through High School and it had a 383 2bbl, and let say, that that thing would fry the tires and I could wind it to 65 mph in first gear, so I wouldn't change a thing. 383s love rpm.

First off, "today's safety standards" have nothing to do with what you are proposing. My advice would be to not get in completely over your head (and budget) trying to make a Ferrari out of a Polara. I would basically copy the factory 383 used in the roadrunner - mildly hotter cam (degree'd in), 4bbl intake and carb, some gears and a ~2400/2500 stall torque converter. You should already have pistons rated around 9:1 compression which is fine with today's gas.

Honestly, I know what your post says, but reading between the lines it sounds like you would be more than happy with a warmed 383. The 727 can easily be built to handle 500HP with no issues (you will be nowhere near that) and you should have an 8 3/4 rear which is also bulletproof for your combo. Factory HP exhaust manifolds will work nearly as well as headers at that power level and will be less problematic.

For a kick in the pants on a budget I would either

1. put in a 440, or

2. heads, intake, cam, headers on the 383 if compression checks out on your motor

Either would be a significant upgrade from what you now have. You don't always have to spend 7-8k on a new mill to improve performance and have fun. Spend the other money on brakes, and holley sniper fuel injection to get the modern performance aspect you mentioned.

how much highway driving vs in town cruising? If you're rarely out on the interstate, I would agree gearing it is by far the easiest thing to do to make you giggle around town.

Don't build for horsepower, build for torque.
Building an engine for horsepower comes with all kind of 'issues' that need to be tackled/improved/upgraded as well like valve springs, pistons, intake, carb, torque convertor, rear axle.

With an engine built for torque you leave the rest of the drivetrain pretty much stock.
2.94 to 3.23:1 gears? They are perfectly OK to burn rubber if you have torque under the hood.