FYI: Dutra Duals and Starter Clearance

[69DartDave]

Hi folks. Just wanted to share, so that others could possibly use this information.

I recall a few months back trying to learn more about what starter motor to select for my son's /6 build. We purchased Doug Dutra's latest version of his cast iron exhaust manifolds, and obviously the factory starter motor was waaaay too big to be a contender. This forum helped me select the starter motor from a late-90's V8-powered Dodge Dakota, which was much more compact. It dropped right in.

Now that we've got the motor up and running, I thought I'd post pictures to show that the starter motor and the Dutra Duals work just fine. At the closest point, the rear exhaust pipe (1.75" OD) comes within about 9/16" of the starter motor. I've started fabricating a heat shield for it for longevity reasons, but I wonder if one is really needed.

Here's a photo of the stock '69 Dart starter versus V8 Dakota starter, plus a look under the intake manifold (AussieSpeed long-runner 2bbl) showing the aft pipe routing for the aft manifold. Local shop here in Seattle fabbed the exhaust.

 

[kesteb]

Shield not needed, I run 2 1/8 pipe over the starter with out any starter problems.

 

[Brandon Weaver]

It almost looks like you stole my pics! Haha I ran dual dutras with the aussiespeed 2v on my last build, now I'm trying to figure if I want to run my Aussie or the Offy!

Whats some info on the lovely engine this is strapped to?

 

[69DartDave]

Yeah, I was really glad to see everything fit great under there. This forum has helped SO much on making this a reality.

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 torque 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

Camshaft:
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

Intake
AussieSpeed 2bbl Long-Runner intake
Holley Avenger EFI

Exhaust
Dutra Dual cast manifolds into custom exhaust

Ignition
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.

 

[slantsixdan]

To be clear, that's actually Dual Dutra Duals, using two of what was originally designed by Dutra as the front-3 exhaust manifold. The setup known as Dutra Duals uses one of those, up front, and the rear half of a cut-and-capped stock exhaust manifold for the rear three cylinders, which keeps intake heat and automatic choke capabilities. Obviously not usable with intakes that (like yours) that don't have a hot spot, but the point is that any starter works with Dutra Duals. You need a compact one only with Dual Dutra Duals.

 

[Brandon Weaver]

Ah... Let us know how it runs once you get it together, and if you get some dyno/drag results!

 

[69DartDave]

Thanks for the clarification, Dan (as well as all the other 'indirect' help you've given our project via your participation and advice on this board). The need for that 'lil starter was indeed a by-product of the dual Dutra dual setup. We were really glad to learn that Mr. Dutra still makes those.

Brandon, I'll certainly ensure that when, the time comes, I report out on how the motor runs. My son wants to get it on a chassis dyno once the motor is broken in a bit, just for curiousity's sake. I was mildly surprised it started up on the first turn of the key after dropping it in the car. The miracles of EFI, I guess.

We did the 20-minute cam break-in process, holding at at 2000 RPM, but have not driven it yet (still waiting on getting the seats back from the upholstery guy). 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).

 

[armyofchuckness]

Cool! I'm doing dual Dutra Duals with the Offy 4bbl intake and using an electric choke on an Eddy 500cfm. Other than that, my build is very similar to yours. Eager to see how it turns out!