Welcome to…………..


The Rat Patrol’s Mopar Skunkwerks is  dedicated to the retro conversion of  The Rat Patrol – my 1971 Valiant Charger – to a Generation 3  Hemi 6.1 litre engine.

This will include the retro-mod from EFI to carb induction.


It will detail all the steps and modifications  necessary to achieve the conversion..including a comprehensive “to do” list and parts list to assist those who may want to try the same ……..


1st iteration – single carb on Modman intake – woeful tuning issues with intake



2nd iteration – dual quads and plenum divider on Modman – improved peak HP but still terrible bottom end signal



3rd iteration – Edelbrock dual plane dual quad – far superior signal strength – Improved peak HP by 20 rwhp – Improved TQ across range by significant amount – Did show some shortage of plenum volume at track, slightly taller than the Modman requires some skimming for engine bay clearance.





11.7 – a win in my book…

Three Years ago I was talked into replacing my broken LA stroker with a Gen 3 hemi.

I figured why not? Easy I assumed.. Run 11s easy I assumed….

Well if you’ve been following…you’ll know it ain’t been easy – but I succeeded through trial, error, bloody pigheadedness and some light bulb moments!


If I had my time again…id have gone straight to a hood scoop and a drag pack intake – not because its the best way to make HP with a carb….BUT three years ago it was pretty much the only efficient way. Other intakes on the market were inefficient, or needed more than one carb.


If I had my time again…Id know to try to replicate the factory EFI intake….looong runners…and a decent plenum.

So instead…I used stacked spacers


Now thanks to Joe O’Cone’s OCP intake, the resto mod is a lot easier… But that wasn’t around when I started.

For me..I had to take the long path  – running dual carbs, a 5.7 intake and a retarded camshaft – it was all about finding the right balance…and I’m still only 3/4 the way there – I’m not made of $$ .

Cam calibration is still a thorn in the side of those doing this mod.  Unless you use custom slugs..it’ll bite you on the backside!

I plan on contacting Modern Muscle next year to see what can be done to defeat Piston/Valve issues without swapping slugs.


And then there’s port matching..but now the Eddy dual quad is available with 6.1 ports…for a mere $700 US…..

Until then..I have my 11.7 timeslip to keep me warm 🙂


Dyno Data is IN!

Hi all

A while back I promised that Id do a genuine comparison between the Modman intake and the Edekbrock 5.7 dual quad dual plane.

I experienced significant tuning issues with the Modman running both single and dual carbs – (333 RWHP) and it only really worked half way decent when I installed a full height divider (346 RWHP)

Below is the dyno chart ( same dyno..similar atmospherics) showing three (3) runs – 


Dyno Dynamics Dyno Chart

The BLUE line was the Modman with divider – this netted a 11.9@ 114mph

The MIDDLE RED is the EDDY – same carbs – 360 rwhp

The Upper RED is the Eddy with twin 1″ 4 hole spacers. – 368RWHP


Dyno Dynamics Dyno Chart

The Eddy had a home port match to the 6.1 heads.

I think this proves conclusively that the Modman is a JUNK NA intake.

My guess is that the carbs are losing about 15 rwhp to the EFI….

Going steady with Mopar and EDDY!!


after much testing and trialling of the INDYtm intake which yielded only moderate improvements, I bit the bullet and purchased the EDELBROCK  / MOPAR PERFORMANCE Dual Quad Dual Plane AIRGAPtm. 

Only a moderate change in tuning was needed, the mid range and WOT needed leaning by one step on the step-up rods, and the pump shot set back one step.

The difference has been staggering…with an enormous amount more mid range and far more responsiveness.

Ive found it impossible to get an accurate GTech 0-60 time because the car just smokes the bags all the way through 1st and well into 2nd gear.

I wont be able to provide any statistical comparison until I get it to the track…but Im confident my 60ft issue is no longer going to be induction related……Hooking up may be snother challenge!!!!


Eddy dual quad


Indy Modman MISERY!!

To speak plainly, Indy Cylinder Heads should be ashamed in releasing such an ill-thought out product on the market, without comprehensive testing including track time.

Peak HP on engine dynos maybe one thing, but its highly doubtful even Indy are aware of what an average performer this piece is in carburreted format.

If you plan on buying a Modman…I’d recommend you use it in an EFI or Forced Induction role.

Single 800 AVS - second best MPH but appalling lean out off the mark - shooter drilled to .040th helped a little

Single 800 AVS – second best MPH but appalling lean out off the mark – shooter drilled to .040th helped a little

The following is a detailed chronology of my efforts to get the Indy Modman intake to work efficiently on my Gen 3 HEMI.

 All tuning changes were validated both on the same dyno and at the track in similar DA.

 I have been tuning Carter and Edelbrock carbs for thirty years and am fully aware of the processes required in re-calibration and enhancements.

1st tune – Single 800CFM AVS Thunder carb

333 RWHP – 110.8 MPH – 12.4 sec qtr – 1.94 60ft

Comment – Lean bog very apparent on launch


2nd tune –  Drilled pump shooter to .040th – 1.91 60ft

Comment – No bog if I rolled on the throttle, but sluggish response


3rd tune – Pro Systems 830 cfm – 50cc Primary pump shot, 30cc secondary

No dyno – 109.8 mph – 12.4 sec – 1.84 60ft

Comment – No bog but sluggish 60 ft


4th tune – Twin Edlebrock 500cfm Performer carbs – drilled shooters to .040th

No dyno – 111.1 mph – 12.39 sec – 1.91 60ft

Comment– Slight bog unless I rolled in the throttle


5th tune – Twin Edelbrocks with twin Brodix turtles inserted in plenum

Comment – No change


6th tune – Twin Edelbrocks with full height divider along length of plenum – increased initial timing from 15 to 21 deg .  Converted linkage from progressive to 1:1.

348.7 RWHP – 114.3 MPH – 11.9 sec – 1.82 60ft


This has been the best result achieved. The 60 ft is still woeful for the mph and HP.

Dual quads 1:1 linkage

Dual quads 1:1 linkage


  – Traction not a factor in any testing.

  –  No modification of air bleeds with Holley, just jetting.

  –  The Modman plenum volume results in a significant loss of signal and requires a MAMMOTH pump shot to overcome the overall plenum volume requirements.

  – The full height divider I ran was also ½” wide, serving to occupy some plenum space as well as improve the signal.

 – The car 60 footed better when I rolled on the throttle than when I rugged it in every scenario.

 – Stalling up had a negative effect – often resulting in a bigger bog.  I have determined this was because stalling uses up some of the ‘tip in’ travel hence a smaller pump shot.

 – The cam I ran was a HR with 219@.50 – It does not require a big converter , nor really high gears, so this was not contributing to the issue .

The divider that showed biggest gains. Hard to believe this lump of metal improved MPH by 3 mph!

The divider that showed biggest gains.
Hard to believe this lump of metal improved MPH by 3 mph!


On the street, no one would ever guess that these issues were to arise at the track..until I did some street tuning on drag radials.  It was only then I noticed the car struggled to turn the tyres on the street until tune #6.

 This problem manifested even worse at the track.



  • NO intake should perform better with a plank of metal inserted into the plenum.


The Modman is a show/supercharger intake – pure and simple.

It may function better with a large cube motor – but as it runs a plenum that is 5x the volume of a normal single plane M1, I would still recommend experimenting with a divider.

25 Mar 13 – TRAPS FOR THE RAT!

So here’s a summary of the issues I’ve confronted. 

I’ve linked the problem to the page where I’ve covered it in my blog


ENGINE POSITION –Using these adapter mounts you can expect an extreme pinion angle, a crooked engine and very little valve cover clearance on the right side inner guard (as viewed from the driving position) with an A body installation.

The problem lies with the left side mount – the pedestal is too high – pushing the motor up at the front and across .

FIX – In Australia you can use the Hemi 6 cylinder K frame and mounts devised by Elko/Valiant spares, OR

FIX – Have the left side TTI mount modified, OR

FIX – Centre the engine,

Left side mount - pedestal stands too high for a level motor.

Left side mount – pedestal stands too high for a level motor.


STEERING BOX CLEARANCE –  Thought I’d  found a solution with Street and Performance shorty headers.  These work a peach on the left side…but foul on the aussie steering box and are probably NOT going to work on a R&P  conversion.

 FIX – In Australia / NZ  – Simple answer..budget for custom headers or expect to re-fabricate the right side shorty.

FIX –  In the US – Use TTI headers and the Dodge RAM truck Hemi manual trans starter motor.


Fabricated right side header


 DIPSTICK – Milodon are discovering that their 6.1 dipstick is the wrong length.

 FIX – ATM they are modifying them on a “return” basis….hopefully they’ll wise up and fix the issue.

 MILODON PAN GASKET – Variety of issues – Stud hole not large enough, splash trough not deep enough, etc

FIX – Do what I did…use the FACTORY splash tray/gasket and trim the ears off it and drill two extra holes to match the Milodon pan.


If it leaks – then COMBINE with the Milodon cork rail gasket for a happy marriage between the tin pan and pan rail.

 OIL FILTER – The TTI adapter mounts foul on the TTI block off plate.

 FIX – Some small grinding required.


FIX – Run a Dakota angled filter mount – a shorty filter and some grinding is required.

 In any case, clearance for remote oil hoses is tight between the auxiliary oil ports and the Alt. 





 CLEARANCE – 6.1 Car Alt sits too low and fouls the A body frame rail

 FIX – Provided the engine mount problems are fixed…the Jeep Cherokee 6.1 Alt provides more clearance to the inner guard.


 FIX – Buy a March pulley kit system


FIX – Clearance the inner fender fold.

 REGULATOR CONNECTOR – The modern G3 Alt. has a twin post external regulator socket. 

 FIX – Connect one to the F(-) and one to 12V switched.

 CURRENT – The G3 Hemi Alts can make 150 or 160 amps – This will fry the old factory ammeters at full load. 

 FIX – Fit an extra “shunt” wire that runs from the Alt. post to the starter relay – this “splits” the current and makes it highly unlikely your car will ever draw enough load through the existing Alt wire to cook your ammeter.   Use 10 or 12 gauge wire.


COMPATIBILITY –  The 6.1 runs non-compatible senders to the later MSD Hemi 6 ECU harness.

 FIX – Buy later 5.7 Cam and Crank sensors.


BRAKE BOOSTER (Aussie only)

 COIL PACK INTERFERENCE – The aussie  V8 brake booster is not a happy marriage with the coil on plug valve covers. Basically any re- positioning of the booster in the bay, or cutting of the booster bracket, will still not allow enough room to be able to remove either the #6 or #8 coil packs for plug removal.

 FIX – Relocate the booster to a remote system, The MC will also need to be re-positioned on a off set bracket as coil pack clearance is necessary, OR

–  Use the offset bracket from Elko / Valiant Spares and a Hemi 6 booster


Off set brake booster bracket available from Elko / Valiant spares – includes new dust boot, all linkages and bushings.



CLEARANCE – The two rear most pan bolt lugs on the left side interfere with the body of the Mopar mini-starter.

 FIX – The two left rear-most oil pan bolt lugs cast into the block must be trimmed back to allow clearance for the starter when using the Mopar mini starter.


 Use a 2005 Ram starter. (This may interfere with  TTI headers)


 INLET/OUTLET – LOCATION AND DIAMETER – There is no direct compatible radiator for the A Body / G3 6.1 conversion.

FIX – Champion makes a “B Body 6.1 radiator”  P# CC1643 – however although on the correct side – the inlet / outlet pipe diameters are reversed.

 They ARE on the correct side however– so ………… 

Fix – Use Gates universal hoses – 1 x p# 25526 (13″), 1x p#25527 (15″) 


14 Jan 13 – Wired…

Got stuck into the wiring – figured I may as well do something positive.


MSD – 6013 HEMI6 ECU

MSD – 88864 – Harness (2005-2008 5.7)

The MSD Harness was a snap to connect up – Fortunately I hadn’t bolted down the intake as it was much easier to install with the intake off.

Wiring on the firewall still needs “stowing” properly – can’t do that until the mounts are re-fabricated and there’s a bit more clearance.

Before we installed the engine, I installed the MSD Hemi6 ECU on the passenger side kick panel in the cabin – dremelled a hole through the firewall and got a suitable grommet.

(Ignore the white wire, its the alternator shunt – the shunt splits the load so I can run the factory ammeter) – I haven’t inserted into conduit yet. I’m leaving it un-enclosed until I’m certain how much length will be required.)

You could lose a small car down those intake ports!




Remember – if you’re running a 6.1, you MUST swap the cam and crank sensors to a 2005 or later 5.7 sensor for it to fit the later MSD 6013 harness.

(Next – we discuss Indy Cylinder heads INSANE concept of what reasonable bolt clearance IS…Stay tuned Folks!!)