1969 Dodge Dart Custom Sedan Slant Six, Father-Son Project



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Aug 1, 2015
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An unexpected father-son project kicked off this summer, fueled by my 18-year-old son’s purchase of his first car: a 1969 Dart Custom Sedan with a slant six.

He had been eyeing a neighbor’s ’66 Dart 270 sedan for many months, and just simply loved the clean, classic looks. He also wanted a sedan to better haul around his friends with eventally, and didn’t want a fuel-thirsty V8 motor to tap into his budget.

A Craigslist browse one night back in June revealed what was to become his car. We drove to Renton, WA to check it out and test drive it (his first experience driving a vehicle that had neither power brakes nor power steering), taking some photos as well. After some talks about the scope of this project, costs, and how long it would take us to restore it, my son slept on it for two nights, and then he bought it.

The previous owner was a nice older gentleman who had owned the car for decades, and gave us a fine price for the condition it was in. He had a small collection of cars, and this Dart had not seen much attention in a while, so it was time for him to let it go. A great choice for us to serve as a starting point for a restoration project.


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Wanting to drive it around a bit before tackling the project, there was a short list of things to go at immediately.

The right rear door’s latch mechanism was failed in the unlatched position, and some McGyver –level of engineering (a rope) had gone into keeping the door from swinging open when taking left turns. This was the first repair we did - we disassembled the entire door’s innards, cleaned and lubed everything, and reassembled. Fixed! (Also, a good confidence boost that we knew what we were doing ;-)

Vapor Lock
The prior owner forewarned us about the car stalling on hot days, and summer in Seattle was unusually hot this year. We wrapped the steel fuel line in fiberglass insulation and wired some aluminum foil around that in order to limp the car home, and that did the trick – no stalls. The fuel line was then modified to replace most of the hard-line with a (properly rated) flexible fuel hose that simply arced over the valve cover straight to the 1-bbl carb.

Electrical Issues
No dashboard lights. No right turn signal. No emergency flashers. Fuel and engine coolant temperature gauge inoperative. This forum was instrumental in teaching what needed to be done to remedy all this. Including the purchase of the 1969 Dart Shop Manual as a starting point.

Ammeter – what a crappy, fault-intolerant design. Same as my 1977 Dodge Aspen had (my first car I bought back in 1988 ). Bypassed per the MadElectrical article, with the alternator feeding the battery directly.

Bulkhead connectors, fuse panel, parking lamps, headlamps, most accessible electrical connectors got inspected and cleaned. New turn signal flasher (wow is that hidden well). All new bulbs for the instrument panel. The right turn signal/parking lamp resurrected, but that’s it.


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Thanks to this forum, the Instrumental panel Voltage Regulator (IVR) was the likely culprit. Wow, those are expensive, and what a weird design in the first place! Apparently it provides a 5V RMS to the fuel and coolant temp gauge, with a capacitor thrown into the circuit for good measure. Good luck testing the old IVR output with a digital voltmeter (signal bounces too much to be read).

Our cheaper way of fixing this required a little bit of extra time, compared to just swapping out the IVR with a new one.

At the auto parts store we bought a $12 generic USB charging port. It puts out a steady 5.1 volts DC given an input voltage of 9 to 16 volts DC. We had an old USB charging cable laying around that we repurposed. Grab a solder iron, crimp and solder on some male spade connectors, and there you have it: 12VDC input to 5VDC output, which plug right into the back of the instrument panel.

We did need to feed it a switched power source, so there is some additional wiring work needed to feed it. In our case, it came from a new fuse panel that we added above the existing fuse panel (provisions for future circuits).

Plugged it in, and...... still no gauges! :???:


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The interior of this car looked its 46-year age. This is an area my son wanted to spend a lot of time making it as new (and fresh smelling) as possible, which meant a complete strip-down. So far we’ve :

- Replaced the carpeting (after removing all rust from floor pan, then priming and painting it)

- Removed the old headliner and ceiling insulation

- Removed both bench seats, stripped down to their wireframes (fyi, 90% of that “old car smell” is the mildew colony residing in all the seat cushions, we learned. The other 10% is apparently the carpeting and insulation above the headliner)

- Removed all plastic and vinyl trim and mouldings, scrubbed, prepped, and paint/dyed with Colorbond LVP (I am duly impressed with this product!)

- Scraped/wirebrushed rust from all interior door cavities, then sprayed with rust-converter paint. (lubed all the door internals while we were in there, too)


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Okay, restoring a sedan has its challenges. Good luck finding replacements for headliners and seat upholstery. Especially seat upholstery. The market is driven by coupe restorations, and after purchasing and returning the ‘wrong’ parts more than once, we needed a break from the interior. ( I did finally find a headliner, and it’s on its way.)

Prior to purchasing it from him, the original owner disclosed that the #2 cylinder was dead due to a burnt exhaust valve. And the exhaust sure made pretty clouds of blue smoke when you stomped on the gas during our initial test-drive, so we knew that we were getting into a car that needed a full-up engine rebuild. I’ve pulled and rebuilt a few motors in the past, and my son was looking forward to learning how it was done.

What an easy motor to pull out! I love these older cars for their simplicity. Sure enough, the #2 cylinder exhaust valve was toast. The crank mic’d in 0.009 to 0.0014” past the wear limits (con rod and main journals both), so it’ll get a 0.010” undersize machining done along with a +0.030” cylinder bore. We found a machine shop near us that can do the work, and a rebuilt kit is on the way.


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great to see a family project! you guys are really doing some good basic work getting it back to life and clean too!!! keep us posted on your progress.
This (excellent) forum taught how to pull the instrument panel, so out it came, as we were determined to get the gauges working and the back-lighting functioning! I was disappointed that my USB-powered IVR replacement didn’t do the job.

I grabbed an ohmmeter and measured the dark blue wire for the fuel tank sending unit down near the kick panel, and it read 21 ohms (near half-full), so I knew at least the sending unit worked. Likewise, the temperature sending unit measured around 240 ohms (cold un-running engine). Are the gauges themselves bad?? I can’t help but worry now that I’ll only be able to find gauges for 2-door Darts, not 4-door Darts. (only half-kidding when I say that, but geez! Even the rear package tray shelf is different for sedans, and impossible to find! :banghead:)

But it became quickly obvious what was going on. Those riveted-on pin connectors on the instrument panel circuit boards are feeble, and the one pin feeding the fuel gauge was simply broken off. Plus, two others broke off while being ham-handedly disconnected during removal (by someone who shall remain unnamed). Craaaaap!:eek:ops:

Okay, fine, with an engineer on our team, we figured out a way to fix this. Very small machine screws, lock washers, and nuts to the rescue. Drill out those crappy pins, go to Frye’s Electronics, buy more shrink-tubing and generic wire harness connectors, and spend all evening at the dining room table carefully modifying the circuit board connectors.

Note the job of heat-shrink tubing to provide electrical insulation, as well as having to stack washers in order to gain clearances. It's hard to tell from the photo, but there was full-coverage of heat-shrink tubing between screw posts.

Also, we replaced the headlight control switch to rule out a bad rheostat causing failure of the dashboard lights.

Of course, since the ammeter had been bypassed a few weeks prior, and the instrument panel was already out, why not go ahead and cleverly install a voltage gauge in its place? It required some fitting because we ignored the advice on which exact Sunpro model number fits right in. Some swearing may have occurred during its installation. All the gauges' needles were painted the same orange color too, for good measure.

End result: SUCCESS! : Dash lights work, fuel gauge reads, temperature gauge reads (we did this before pulling the motor, and as the motor warmed up the gauge was reading it), new voltmeter showed the battery voltage. :cheers:


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Thank you, eBay, for helping me find a remanufactured cylinder head for cheaper than what it would’ve cost to have the stock one machined! It came with new bronze liners, hardened valve seats, and a single-angle valve job.

After many, many careful measurements, I concluded that the remanufactured head was milled somewhere between 0.021” and 0.026”. This was consistent with the shop I bought it from saying that it was the second time this head had been worked.

It has the same casting number as the original head, which I was glad for, since 1969 heads had a more efficient combustion chamber shape compared to earlier heads.

The rotary tool got a workout doing “clean up” to the valve bowls and passageways leading to them (yes, a respirator was worn). Mostly this consisted of blending out machining marks, matching the valve seat insert diameters to the bowls below them (they were quite a bit different, leaving a ledge), and contouring the valve stem casting bump-out. Some of the runners had really horrible casting blemishes resembling mini-stalactites!

On the exhaust side, I did an extra step of smoothing everything. On the intake side I didn’t bother; a little bit of roughness can help keep fuel atomized a bit better, especially at low RPM / low throttle settings (when intake port velocities are low enough to not “care” how clean and big the port sizes are).

I also removed casting roughness from the combustion chambers, as well as blended a bit off of the sides of combustion chambers along the outboard edges of the valve seat areas.
No hogging-out, just simple, conservative machining work.

My poor-man’s flow bench (think shop vac and kill-a-watt meter) resulted in a small but noticeable amount of flow increase, which was good enough for me!

With all that done, the head was cleaned and painted, and the stiffer valve springs that match the Erson camshaft were installed. Assembly lube on the valve stems and rocker arm shaft. Lookin’ good.


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The engine machine work and rebuild are complete, with the exception of bolting on the intake and exhaust (which will wait until the motor is back in the car). It’s been pretty straightforward, with a few do-overs as minor issues have cropped up.

Oh gawd, the degreasing and scrubbing and wire-brushing and solvent-cleaning of every big and small part. But we were determined to paint everything properly with engine enamel, and wanted it to adhere for good. Run a die over each scrubbed-clean fastener, and a tap through each threaded hole, and you learn that you really are anally-retentive, after all.

Pushrods: Since the head was shaved 0.020” and the block was decked 0.050”, I was figuring that there would be no problems with rocker arm/pushrod geometries. I “read on the Internet” that less than 0.100” of milling keeps the geometry in the range of normal pushrod cup adjustability.

It turns out that using a remanufactured cylinder head from a different /6 motor ended up adding enough variability to cause two of the pushrods to contact the side of the cylinder head (see photo below).

So the head came back off, and both spots were grinded to provide clearance (plus 4 other spots that were too close for comfort; these things flex under load, you know). At least the lash was easily set within the amount of adjustability that the rocker arms offer (see, the Internet was right!). Erson said .020" intake lash and 0.020" exhaust lash for my cam, which seems big but, hey, they're the experts!

I was glad that I hadn’t done the final torque step on the head bolts before noticing that; I was able to re-use the head gasket


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That body looks clean, it will make your son a nice first car.
One thing about buying a working, driving car for $2180 is that you can't help but compare all the rest of the money you spend on it to that initial cost. "Wow, the EFI conversion kit will cost almost as much as the car did!" "The wheels and tires will cost more than a third of what the car was!" and so on. One thing that helps put it in perspective is to look at the savings for doing the bulk of the labor your self!

And so far, our favorite 'labor' by far has been the assembly process of the motor. There's something really cool about bolting together squeaky-clean parts, wearing your normal day clothes. You get so used to perpetual grime on your hands & fingernails, that it's almost weird to wrench in the garage for 4 hours and ... not be stinky and grimy.

Color-wise, there's the original sky blue, then there's Chrysler International Red, or what about Hemi Orange? We decided to keep it simple and see what engine enamel they had on the shelf at the local parts store. It ended up being (I understand this may be considered somewhat blashphemous to some Mopar purists) Chevy Red-Orange.


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Putting on non-factory intake and exhaust manifolds means that, well, things probably won't fit right away. Time to do some fit-checking!

The Dutra Dual exhaust manifolds are excellent castings, and the only thing needed to accommodate them was to slightly grind off a triangular (or rather, tetrahedral) wedge off the rear top of the block (circled in blue). Easy. (We were really glad to hear that those are still available to buy!)

This motor is going to be a low/mid RPM torque-monster, so the research led to the AussieSpeed long-runner, 2-barrel manifold. With EFI on the way, we don't care about warming up the intake and carburetor any more, so this was a pretty easy choice (although I'll be curious to see how well the power brake retrofit kit works with this - I hope there's room!). Plus, buying it off eBay provided the latitude of the 'make an offer' option, which allowed us to get this at a deep discount.

Bolting the two, er, three manifolds to the block was very revealing. The casting seam of the intake manifold showed interference with the Dutra manifolds in 3 places. One such place is circled in yellow. Out comes the grinder again.

Also, the central top hole of the intake manifold needed material removed to be able to fully seat the washer that goes on top of that top center stud.

No big deal. But glad we checked this out while it was still on an engine stand.


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This car came with no radio, no antenna, and only one raggedy speaker in the center of the dashboard. Eventually there's gotta be music, and with the interior stripped, now it's easy to get up under the dashboard.

First is replacing that center 4x10 factory speaker with two 4" rockford speakers, re-purposing the mounting flange to mount them in. These 4" speakers were the perfect depth to not interfere with the vent control cables. 6x9 rockfords went in the existing holes in the rear package shelf.

Add check out the fancy radio knobs - ha! Just a USB charging port, a headphone-in jack, and a toggle switch to turn on the hidden amp. Simple. What more do you need, with the entire music collection and streaming capability of a smart phone?


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This is one of those jobs that you underestimate how long it'll take. Suffice it to say that by the time the underhood grime was scraped, brushed, wiped, degreased, sanded, primed, basecoated, and clearcoated, over 30 hours had been spent in that engine bay.

We're redoing the car in the original B7 medium metallic blue, which I was able to find on-line in custom-order spray cans, as well as spray cans of two-part high-gloss clearcoat.

At least now the engine bay looks as clean and new as the engine does. That orange motor in the blue engine bay should really stand out. Big milestone for the day.

Now, back to that headliner....


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Since it's close to time to put the engine back in the car, the time has come to add the fuel system that the EFI kit requires.

We've gotten pretty good at mocking up tube runs with a thick solid wire bent to shape, and then using the tubing bender to reproduce it. Man, the tools you end up accumulating when restoring a car. I'm going to need a bigger garage by the end of this.

The new electric fuel pump is mounted in the inboard part of the frame rail just forward of the axle, at about the same height as the bottom of the fuel tank. That's the closest place we could figure to install it. A new 3/8" line will feed the EFI, and we'll re-purpose the existing 5/16 line as the return line. We did need a new tank sending until that includes two outlets in those sizes (stock one just had a single, 5/16 outlet, of course).

The low-pressure filter goes between it and the tank. I attached the tubing with rubber-lined clamps and short stainless sheet-metal screws up through the floor pan, going so far as to dab the pre-drilled pilot holes with primer before sinking the screws in.

For routing the new feed line, we paralleled the existing line as much as possible, but had to make two exceptions, where we ended up drilling holes through frame members. Primered up those new holes and added rubber grommets to buffer the tube from chafing on the edge of the holes.


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This past weekend we took the motor off the engine stand and finally dropped it back into the car. This was a big milestone for us! O:) This project has really come a long way in the five months that my son has owned it.

The only hitch was my fault – I had bolted-in the passenger-side motor mount upside down, which my son noticed as we were lowering it into the engine bay. Easy enough to flip over, and then the motor went in pretty easily.

Bolting on the intake and exhaust revealed one more spot where there’s a minor interference with getting a socket or wrench on one of the lower exhaust manifold nuts.

Also, given the hood clearance issues we now have (the adaptor plate between the intake and TBI body eat up an inch), we quickly learned that the 3.5" tall K&N filter element we had ordered previously was WAY too tall; we ended up getting the shortest one they make (1.75" tall), and it just barely fits.


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This past weekend we took the motor off the engine stand and finally dropped it back into the car. This was a big milestone for us! O:) This project has really come a long way in the five months that my son has owned it.

The only hitch was my fault – I had bolted-in the passenger-side motor mount upside down, which my son noticed as we were lowering it into the engine bay. Easy enough to flip over, and then the motor went in pretty easily.

Bolting on the intake and exhaust revealed one more spot where there’s a minor interference with getting a socket or wrench on one of the lower exhaust manifold nuts.

Also, given the hood clearance issues we now have (the adaptor plate between the intake and TBI body eat up an inch), we quickly learned that the 3.5" tall K&N filter element we had ordered previously was WAY too tall; we ended up getting the shortest one they make (1.75" tall), and it just barely fits.

Wow that looks awesome! Great work.
This is a revised repost of a thread I started in the Fuel and Air Systems sub-forum, but for the sake of this project page's completeness, I'm including some of it here

Retrofitting EFI into a slant6-powered '69 Dart has been mostly fun, but also a little frustrating. Frustrating due to some unintended consequences, but I hope that others can use this information to learn from and maybe apply to their own projects.

The biggest change (other than the 2" hole you gotta drill in the firewall to route the new wiring harness through) is the fuel system, and my son and I knew that before making the decision:
- You need a bigger feed line diameter, a 3/8".
- And you need to add a new fuel return line.

The fuel no longer will just dead-head at a carburetor inlet; now it is pressure-regulated to stay at 22psi (for the Holley Avenger kit, at least). Excess fuel not needed to maintain 22psi is sent back to the fuel tank.

The car came with a 5/16" diameter fuel feed line. Which is great, since you can re-use that as the return line.

The rub is: the fuel tank sending unit. If you want to re-use it, you technically could for a slant-six powered Mopar. Just put an 5/16-to-3/8 adaptor just outside of the tank to neck upsize the original line before the fuel filter. The fuel flow rates for a slant six are low enough to be fed by a 5/16 line, so long as the entire run isn't 5/16. Then, add a new return line that terminates at, say, the fuel tank fill tube (there are aftermarket fittings to help do just that).

But that's not what we did. We bought the only off-the-shelf sending unit I could find that has both a 3/8 feed and 5/16 return line built-in to the bulkhead. Which I thought was great. But the Ohm range is advertised as being different than stock, which I didn't know enough at the time to pay attention to and compare against.

Bottom line: The fuel gauge is now going to be WAY off. When the gauge first reads empty, there's still going to be about 7 gallons present.

Luckily, forum member 68gtxman pointed this out to me:

It will match the sender to the gauge. Problem solved.O:)

The plot I made below shows how 'off' the new sender is compared with the stock one, for reference.


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I should include some information on what our homework led to for building this particular motor.

The motor has been a fun build; we took a comprehensive look at the car's gearing (A904 + 7 1/4 rear with 2.76:1) and daily-driver status to build it up as a low/mid-RPM torquer motor that ensures this 2800 pound Dart can get out of its own way.

Here's some of the high points:
Rebuilt Heads:
Stock Valves
Hardened valve seats
Moderate amount of conservative port cleaning/smoothing work
Head shaved 0.020"
Erson dual valve springs
Stock rocker arms

Engine Block, Reconditioned stock 1969 :
Polished & Balanced stock forged '69 crankshaft
Cylinders Bored +0.030"
Block decked 0.050", which with the head shave probably gives ~ 9.4:1 compression ratio
New bearings, oil pump, etc, plus some smoothing on the oil pump inlet/outlet areas

Erson Cams Custom Grind: Intake per 'RV10M', Exhaust per 'RV15M'
254 / 266 Advertised Duration, 110 deg LSA, +4 deg adv
0.435" / 0.435" Theoretical Lift
210 / 218 Duration at 0.050" Tappet Rise

AussieSpeed 2bbl Long-Runner intake
Holley Avenger EFI

Dual Dutra Dual cast manifolds into custom exhaust

Pertronix Ignitor II module in stock distributor
Coil: Pertronix Flame Thrower II, 0.6 Ohm, 45kV
(deleted ballast resistor accordingly)
Wires: Magnecor KV85 Competition 8.5mm
Plugs: NGK Spark Plugs ZFR5N, gapped at 0.044"
(removed crush washers before installation)

Should give about 190hp peak before 5000 RPM, with a torque peak of about 235 ft-lbf in the mid-range.

The motor started on the very first turn of the key, thanks to the wonders of EFI. We did the 20-minute cam break-in process, holding at at 2000 RPM, but have not driven it yet. It has a fairly quiet muffler set-up, but at higher revs I gotta admit it sounds pretty good for an in-line six.

I suspect it'll never do burn-outs off the line, not with the 'granny gear' 2.76:1 rear axle ratio. But it should be peppy enough at speeds. In fact, part of the cam choice had to do with ensuring it was in a fat torque band doing a 3-to-2 downshift at highway speeds (i.e. passing power).


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