To Mod, or Not to Mod, that is the question. What will break at 500hp?

[Project Sketchy]

The car is a mostly original 1967 Newport, 2dr, 383 4-barrel, 727. Body is in good shape, interior is a little rough with rips in the front seat and a missing headliner. Engine runs okay, but is down on power and smokes a little on startup. It needs more power. 450-500hp at the crank would be a reasonable start.

Option 1. Rebuild the 383 with 500hp as minimum goal, bore it out, stroker kit, aluminum heads, aggressive roller-cam, gapless rings, EFI
Option 2. Mothball the 383 and install fresh 440
Option 3. Sell 383 and go with an LS or Late Gen Hemi 5.7 hemi (going with EFI and modern, 6sp automatic with OD).
Option 4. Sell the 383, throw caution to the wind, stick in an LS with a twin turbo EBAY kit or electric turbos, 4l80, and invest in a tire company
Option 5. Freshen up the 383, cleaned up cylinders, new rings, knurled pistons, hardened valve seats and keep it as original as possible. 325hp.
It doesn't feel right doing something to a survivor that can't be undone relatively easily by the next owner.
Still, 500hp seems like a good number. I have great faith in the 727 and Chrysler rear ends, but it is a big, heavy car. What is most likely to break at the drag strip?

 

[furious70]

Stuff only breaks if you have traction. 500 isn't a big deal for OEM parts.

 

[RemCharger]

A strong 440 will get you there, don't worry about going wackadilly on goofy ideas.
Rear springs might be weak for it, otherwise should hold up well

 

[CBODY67]

ALL that horsepower ONLY happens past 5000rpm, NOT at 2500rpm. Easiest to do a 383 stroker with a good cam (almost all B/RB roller cams I've seen are too wild from daily normal street use, but Lunati has a "modern performance" B/RB HP cam that seems to work well in normal 383s. Check threads in here, Summit sells it under their brand, too.) Do online searches for aluminum head videos on YouTube, PLUS David Vizard's YouTube videos on effective porting and such.

There is a video at Nick's Garage on a later 1950s Chrysler 2x4bbl intake that made almost 500 lbs/ft of torque. The original B-engine Plymouth Fury 350s used such an intake. Iron heads, too, IIRC.

The guts of the TF727 can hold up, but the frictions probably need to be upgraded for more "grab" and such. Best would be a ZF 8-speed upgrade (with a low gear ratio of about 4.75:1), but that can get expensive. Check threads on here about using pressure switches to regulate the shifting. With an OD automatic and carburetor(s), plan on a 3.91 or 3.55 rear axle ratio.

TTI dual exh system. 2.5" pipe diameter.

Knurled pistons? Does ANYBODY still do that? A band-aid way to not buy new pistons, when needed. BUT you want a round cyl bore for any high-power engine, so that means a .030" overbore and new pistons in that same size.

On your last inquiry, get solid u-joints and make sure they have grease in them when they are installed! With a driveshaft loop for good measure.

THAT gets the engine/transmission items. Next would be the chassis upgrades, like stouter rear springs and such, even some "Traction Master" bars. Then the brake upgrades to better lining materials, complete 11x3 brakes at all wheels, or even a complete 4-whl power disc brake set-up.

FORGET all of the "LS" STUFF, PERIOD!!! Late model Gen III Hemis are plenty good enough. NO tissue rejection issues, either. Check the Holley website for information on B-body conversion kits and see if some of those things might also work in a C-body. Then you just have to worry about making the electronics work or putting a normal distributor and carb on it.

Still, probably the easiest thing would be a stroker 383. Just don't tell anybody about the different crank and such.

Enjoy!
CBODY67

 

[twostick]

Put the original engine under the bench.

Pick out a 4.25" stroker kit and the best cylinder heads you can afford and a compression ratio compatible with the fuel you're willing to pay for. NO REPLACEMENT FOR DISPLACEMENT!!!

400 blocks are becoming scarce but you can use all your existing accessories as is. 440s are more plentiful which means they should be cheaper but you will want one that is complete with all the accessories and brackets. If you have all the doodads in stock a bare block will be the cheapest way to go because that's all you're going to use anyway. The 400 gets you a few more cubes than a 440 will 510ish vs 505ish, no big advantage.

Don't get hung up on horsepower numbers and big roller cams. 500 cubes with good heads will make 500 horsepower falling out of a tree with a very mild hydraulic flat tappet. What will hurl a 4500 lb C Body through an intersection with authority and not a lot of throttle input is torque and a mild cam will make boatloads of it in the off idle to 3000 rpm range that this engine will spend 90% of its time in. Peak should be a bit north of 600 ft/lbs before it hits 4000 rpm. It also eliminates the need for steep gears and high stall torque converters. 3.23 gear will be the steepest you will want or need and you could probably get away with a 2.94 assuming a 28" tall tire.

Dwayne Porter is a Comp Cams distributor and is your go to guy to get the right cam for your application. He covers all the bases, lift, duration LSA and lobe profiles. There are lots of shelf cams in the catalog for a Mopar but for your specific application there will probably be something wrong with all of them. Headers vs manifolds will require very different camshafts so Dwayne would be a huge help there depending on your choice of exhaust.

Find a good machinist and I wish you luck with that. The only thing a good machinist needs to specialize in is making things round, flat and straight to within 4 decimal places minimum so be wary of those that claim to possess some kind of black magic when it comes to Mopars. It's BS. The guy that does my stuff and built my 493 is non denominational. Everything from 1 lung St Lawrence engines from the beginning of the 20th century to Rolls Royce Griffon marinized aircraft engines for a vintage unlimited hydroplane and other exotica nobody's ever heard of. The machine work in mine is no less than what went into that Rolls.

The transmission is more than up to the task with a few minor upgrades. Don't waste time or money looking for 4 pinion planetaries. The splines in the aluminum hubs fail long before the pinions do. Extra frictions and steels if they'll fit or aftermarket or modified parts so they will fit is money well spent. If you upgrade the sprag, go with the Super Sprag with the extra elements in it. The regular bolt in one is no better than a stock one is as far as a potential failure point is concerned. If there is going to be drag racing in your future, a billet front drum is a safety item that should be considered. Google 727 explosion to see what can happen with a stock drum after a sprag failure if you don't follow the never ever do this to a 727 rules.

EFI is a nice to have and if you're starting from scratch for an induction system, not that much of an upcharge.

That got a little long winded... lol

Kevin

 

[70bigblockdodge]

I agree with^^^^^, big gears suck period, that's a "back in the day" modification. Nowadays just make sure it will roll along at 75-80 mph in the low to mid 2k rpm (nobody likes being passed by granny in her Hyundai on the way to church), you'll give up like 2 tenths in the quarter 3.23 vs 3.91, and 3.55's are good for nothing. 4.25 stroke in the stock 383 block with some aluminum heads, I would use a solid flat tappet but that's just personal preference, hydraulic will work fine also. Lose the power brakes and a carburetor will trap speed faster in quarter mile than EFI, if you have crappy vacuum it will still be temperamental with anything but sequential port injection. Just my thoughts/opinions.

 

[bigmoparjeff]

What will break at 500hp?​

The left side motor mount.

Jeff

 

[Project Sketchy]

Some great ideas and suggestions!
Anybody have any experience with 440source.com? They have some inspiring stuff on their website.

Now I just need to find a good 383 block. Hmmm...think Santa could get one down the chimney?

 

[livininharrow]

I agree with^^^^^, big gears suck period, that's a "back in the day" modification. Nowadays just make sure it will roll along at 75-80 mph in the low to mid 2k rpm (nobody likes being passed by granny in her Hyundai on the way to church), you'll give up like 2 tenths in the quarter 3.23 vs 3.91, and 3.55's are good for nothing. 4.25 stroke in the stock 383 block with some aluminum heads, I would use a solid flat tappet but that's just personal preference, hydraulic will work fine also. Lose the power brakes and a carburetor will trap speed faster in quarter mile than EFI, if you have crappy vacuum it will still be temperamental with anything but sequential port injection. Just my thoughts/opinions.

bigblock what is your reasoning behind a 3.55 gear being good for nothing? just curious. thanks in advance.

 

[70bigblockdodge]

bigblock what is your reasoning behind a 3.55 gear being good for nothing? just curious. thanks in advance.

Mostly just personal opinion. The one thing I like about modern cars is the effortless cruise on the highway at a low lumbering rpm. My Challenger has 3.23 rear and at 70-75 mph it's turning 32-3400 rpm, that is not really a issue, but it really makes you tired after a 6-10 hour ride. I did a 11 hour ride to and from S. Carolina in my Charger with 3.23 rear and a overdrive, mid 2k rpm and 70-80 mph. When I arrived I was not worn out. On the flip side I swapped the gear in my Challenger to a 4.10 and only gained 3 tenths in the quarter, so what is a 3.55 going to do for me, the 21% increase gained 3 tenths. A 9% increase to 3.55 will result in almost no et reduction, but a more tiring road car on the highway. I think it is just too much compromise. Some people love them I guess it just does not fit my acceptable range.

 

[furious70]

I don't like 3.55 either. 3.23 or 3.91 - pick one that'll do what you want, not the one in the middle that does neither.

 

[LocuMob]

My Challenger has 3.23 rear and at 70-75 mph it's turning 32-3400 rpm

What size tires are you using out back? My Polara 500 with 3.23 and 235/70/15 cruises at 70-75 1k rpm lower.

 

[70bigblockdodge]

What size tires are you using out back? My Polara 500 with 3.23 and 235/70/15 cruises at 70-75 1k rpm lower.

My tire size is part of the problem, 225/70/14, the converter is another. If I had a big 12" converter it would surely be less (less slip). If I use a calculator my car at 3300 rpm and 5% converter slip (low) it puts me at ~75 mph, if I increase the tire size it lowers it but still does not get me in the low to mid 2k rpm. 3.55:1 just makes it all worse.

 

[LocuMob]

My tire size is part of the problem, 225/70/14, the converter is another. If I had a big 12" converter it would surely be less (less slip). If I use a calculator my car at 3300 rpm and 5% converter slip (low) it puts me at ~75 mph, if I increase the tire size it lowers it but still does not get me in the low to mid 2k rpm. 3.55:1 just makes it all worse.

My Polara with the higher stall converter (2500?), 3.55 and 275/60/14 is at 2800 at 75. That tire is 2.2% shorter than the 225.

 

[twostick]

Some great ideas and suggestions!
Anybody have any experience with 440source.com? They have some inspiring stuff on their website.

Now I just need to find a good 383 block. Hmmm...think Santa could get one down the chimney?

I have a 440Source kit in my 493. Mine is from early days when Brandon was working out of his house. Above and beyond customer service.

If I was to spend any time searching for a block, I'd be looking for a 400. Same block with a 4.342 bore vs 4.250 for the 383. 15 cubes extra for free.

Kevin

 

[Project Sketchy]

Anyone ever try mating a 383 up to a modern, OD transmission? Recently, I spent some time working on a Doug Nash 4+3 in an 84 Vette (the original Project Sketchy). When we got the car, the overdrive wasn't working (a combination of mouse-modified wiring, corroded contacts, and stuff plugged into the wrong connectors.) Without OD, the car was tiresome to drive long distances at 70mph---engine drone, transmission whine, heat---it was just unpleasant. MPG according to the car's computer was around 18.
It was a revelation once the OD was fixed. The engine rpm is radically lower---its just loping along. MPG hovers in the high 20's. Long, high-speed trips don't end in feeling dazed, tired, and slightly deaf.

Anyone interested in odd mechanical stuff can find lots of articles about the Doug Nash 4+3 on the web. Essentially, it is just a T-10 manual 4-speed with a hydraulic overdrive grafted on to the back (some articles compare the OD unit to a powerglide.) Apparently there is a version of the 727 with an overdrive on the rear---called the 518 or 46RH.

 

[RemCharger]

I have a 440Source kit in my 493. Mine is from early days when Brandon was working out of his house. Above and beyond customer service.

If I was to spend any time searching for a block, I'd be looking for a 400. Same block with a 4.342 bore vs 4.250 for the 383. 15 cubes extra for free.

Kevin

I agree, but more importantly than the extra cubes, is the lack of valve shrouding.

 

[furious70]

I have an a500 behind my turbo 383 in the fury

 

[SuperDave]

First few things that come to mind are motor mounts, trans upgrades, U-joints, driveshaft, ring & pinion, axles & leaf springs. The 8.25 axle can only "safely" handle 400 hp in stock form, any more and either the internals need serious upgrades, OR replacing it with an 8.75" or better. Caltrac traction bars if you're going racing or prone to showing off. A 727 is mandatory minimum, a 904 will die in short order, red line clutches and a super sprag is a must. Again, if you're racing, I'd strongly recommend Strange axles for survivability.

I'm surprised no one mentioned brakes. Stopping is equally important as going, and power/speed upgrades require brake upgrades. Front disk is a must, preferably with slotted/drilled rotors.

 

[Mr357M]

The car is a mostly original 1967 Newport, 2dr, 383 4-barrel, 727. Body is in good shape, interior is a little rough with rips in the front seat and a missing headliner. Engine runs okay, but is down on power and smokes a little on startup. It needs more power. 450-500hp at the crank would be a reasonable start.

Option 1. Rebuild the 383 with 500hp as minimum goal, bore it out, stroker kit, aluminum heads, aggressive roller-cam, gapless rings, EFI
Option 2. Mothball the 383 and install fresh 440
Option 3. Sell 383 and go with an LS or Late Gen Hemi 5.7 hemi (going with EFI and modern, 6sp automatic with OD).
Option 4. Sell the 383, throw caution to the wind, stick in an LS with a twin turbo EBAY kit or electric turbos, 4l80, and invest in a tire company
Option 5. Freshen up the 383, cleaned up cylinders, new rings, knurled pistons, hardened valve seats and keep it as original as possible. 325hp.
It doesn't feel right doing something to a survivor that can't be undone relatively easily by the next owner.
Still, 500hp seems like a good number. I have great faith in the 727 and Chrysler rear ends, but it is a big, heavy car. What is most likely to break at the drag strip?

Definitely a stroker is the way to go with a good pair of heads and a cam with around 240@050 will give you between 450hp to 500hp with street manners. Keep it simple. I’d go for 3.73 gears and a 2800 rpm stall and have fun.