Mopar Muscle - - Contents - TEXT AND PHO­TOS: DAN FO­LEY

Bolt-ons will help your Slant Six go with the flow of to­day’s traf­fic.

Hey, it’s sad to say, but the old-re­li­able Slant Six in bone-stock form isn’t any­where near the per­for­mance stan­dards of a mod­ern six- or four-cylin­der en­gine. When we put our ’66 Dart GT on the road two and half years ago after a 20-year hi­ber­na­tion, we came to re­al­ize just how slug­gish the old lean­ing tower of power is in this day and age. Foot to the floor and not go­ing any­where is a scary ex­pe­ri­ence with to­day’s tail­gaters want­ing to run you off the road. Most new­fan­gled econoboxes have a large per­for­mance ad­van­tage over our un­der­pow­ered ’66 Slant Six Dart. We des­per­ately needed to do some­thing to add per­for­mance and ef­fi­ciency to our slow-go­ing six to be com­pat­i­ble on to­day’s roads, which are jammed with im­pa­tient driv­ers.

We con­sid­ered adding the ’73-’80 Mopar elec­tronic dis­trib­u­tor with the vac­uum ad­vance unit and the re­quired

wiring, plus volt­age reg­u­la­tor to run it. Per­son­ally, I don’t care for the look of the ’70s-style volt­age reg­u­la­tor on a vin­tage ’60s Mopar. On oc­ca­sion we speak with Steve Davis of Per­for­mance Dis­trib­u­tors, well known for its Davis Uni­fied Ig­ni­tion sys­tems. We men­tioned to Steve there’s a need for a Tri-power ig­ni­tion for all of those slug­gish Slant Sixes out there with points-type dis­trib­u­tors. Through the years, we’ve used and tested PD’S re­li­able Tripower and/or DUI ig­ni­tion on smal­land big-block en­gine alike, with great re­sults over points and other elec­tronic dis­trib­u­tors. Now for the good news: Per­for­mance Dis­trib­u­tors is now pro­duc­ing a Tri-power ig­ni­tion for the Slant 6. We couldn’t wait to try out this new ig­ni­tion and ditch our points-type dis­trib­u­tor for­ever!

Also re­leased at the same time from PD were Slant 6 Livewires ig­ni­tion wire sets. Th­ese 8mm spi­ral core, low-re­sis­tance, high-temp wires will de­liver the ad­di­tional volt­age from the Tri-power Ig­ni­tion to the spark plugs. Stock sup­pres­sortype wires wouldn’t be able to han­dle the ex­tra fire­power com­ing from the high-volt­age In­ferno coil. After in­stalling this new elec­tronic ig­ni­tion, amaz­ingly, the idle in­creased by 600 rpm (from 700 to 1,300 rpm) at the same 10 de­grees of ini­tial tim­ing. We read­justed both the idle set and fuel mix­ture screws on the stock 1-bar­rel Hol­ley car­bu­re­tor for 600 rpm. Right away we no­ticed a smoother idle, and blip­ping the car­bu­re­tor lever showed much quicker throt­tle re­sponse. Our test­drive re­vealed a big-time im­prove­ment in ac­cel­er­a­tion and drive­abil­ity. Also, there’s no more hes­i­ta­tion, dead spot, or fear of stalling while driv­ing and warm­ing up the en­gine to reg­u­lar op­er­at­ing tem­per­a­ture. This Tri-power ig­ni­tion is a hands­down win­ner over the an­ti­quated points-type ig­ni­tion.

We also spoke with Sam Davis at TTI Ex­haust about a high­flow 2½-inch ex­haust for an early A-body (’63-’66). Our cob­bled-up 1¾- to 2-inch ex­haust was chok­ing our poky six-cylin­der. On all Slant 6 engines, the ex­haust man­i­fold out­let is 2¼ inches. On our en­gine the ex­haust flange had a small 1 7/8 hole with a 1¾-inch pipe in­side of the flange. Be­sides the ma­jor

re­stric­tion at the man­i­fold to ex­haust pipe flange, the stock-type, low-flow muf­fler is also chok­ing the lean­ing six-cylin­der from ex­hal­ing. We knew a high-flow 2½-inch ex­haust would show a ma­jor im­prove­ment in per­for­mance. In just a cou­ple of month’s time, TTI came to the res­cue for the Slant Six-pow­ered, early A-body en­thu­si­ast.

Be­fore in­stalling the new TTI high-flow ex­haust, we de­cided to take a 45-minute high­way ride to Tune Time Per­for­mance in Lake­wood, New Jersey, for base­line dyno test­ing. With the new Tri-power ig­ni­tion, the Dart was able to fear­lessly cruise with the high­way traf­fic at 70 to 75 mph — no thanks to the 2.94 gearing in the 7¼ rearend. Prior per­for­mance with the points-type ig­ni­tion was so ane­mic we were afraid to take the Dart onto the high­way. The ’66 Slant Six A-body was strapped-down to TTP’S Mus­tang Dy­namome­ter. After spin­ning the rollers, we all laughed at the piti­ful num­bers the silly six pro­duced: 63 rwhp at 2,900 rpm and 110 lb-ft at 2,900 rpm. More pulls were made at dif­fer­ent tim­ing set­tings. It seemed our lean­ing pow­er­house ran best with the base­line tim­ing set­ting of 10 de­grees ini­tial and 35 de­grees to­tal. We saw power drop with ei­ther re­tard­ing or ad­vanc­ing the tim­ing from the base­line set­ting.

In our home garage we in­stalled the new TTI high-flow man­drel-bent 2½-inch ex­haust. The TTI Ex­haust pack­age in­cludes all the hard­ware, gas­kets, clamps, and hang­ers for an easy DIY in­stal­la­tion. As al­ways, we were im­pressed how well TTI Ex­haust fits with good clear­ance for a rat­tle-free ex­haust sys­tem. Test­driv­ing demon­strated how re­lieved the en­gine be­came with the new ex­haust. The power­band im­proved re­mark­ably right from low-speed to high-speed driv­ing con­di­tions. Now, with it run­ning so much stronger and smoother, we couldn’t wait to drive the now Lean­ing-tower-of­power back to the chas­sis dyno.

Back on the Tune Time Per­for­mance dyno re­vealed we picked up 9 rwhp and 10 lb-ft at peak. Max­i­mum peak horse­power moved up from 2,900 to 3,500 rpm. Peak torque stayed at 2,900 to 3,000 rpm. Each pull was made from

2,500 to 4,200 rpm. At 4,000 rpm the TTI Ex­haust helped the six pro­duce over 22 more horse­power (see the dyno graph). That ex­tra high-rpm power is felt out on the high­way right where it was needed. Now that our Slant Six-pow­ered Dart can keep up with to­day’s traf­fic, next time we’ll try port­ing the cylin­der head and shav­ing it .080 inch. We’re hop­ing to get an­other 20-plus rwhp out of the “buzzin’-half-dozen.”

Our sub­ject Slant Six re­sides in a ’66 Dart GT with fac­tory A/C. After a 20-year hi­ber­na­tion, we put it on the road in 2015. Per­for­mance was so slug­gish by to­day’s stan­dards; we des­per­ately needed to im­prove its get-up-and-go. Per­for­mance Dis­trib­u­tors juiced up the ig­ni­tion, and TTI’S un­re­stric­tive ex­haust teamed up to de­liver a big-time per­for­mance im­prove­ment to our lean­ing six-cylin­der.

With the ro­tor fac­ing the 7 o’clock po­si­tion we swapped out the points for the PD Tri-power elec­tronic dis­trib­u­tor. No­tice the Dyna Mod mod­ule in place of the vac­uum ad­vance unit. This strong-spark ig­ni­tion im­proves re­sponse so much that the vac­uum ad­vance unit isn’t needed any­more. PD uses a tried-and-true Sun dis­trib­u­tor ma­chine to dial-in a smooth ad­vance curve for your com­bi­na­tion.

The weak-spark, points-type dis­trib­u­tor had to go. Re­cently, Per­for­mance Dis­trib­u­tors de­vel­oped this Tri-power ig­ni­tion for the Slant Six. This elec­tronic dis­trib­u­tor fea­tures a Dyna Mod (Heistyle, four-pin mod­ule) with higher dwell for in­creased spark du­ra­tion and volt­age. It’s teamed with a high-volt­age In­ferno coil to jolt the Slant Six’s per­for­mance sig­nif­i­cantly (PN 70620, $309). The Livewires are spi­ral wound core sup­pres­sor wires for low re­sis­tance and max­i­mum volt­age to the plugs (PN C9082, $95).

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