Mopar Muscle - - Contents - TEXT AND PHO­TOS: CHRIS HOL­LEY

Test­ing a radiator and SPAL fan from U.S. Radiator

For the last four decades, auto man­u­fac­tur­ers have em­braced the use of elec­tric fans. Elec­tric fans first ap­peared on low­pow­ered, emis­sions-laden front-wheeldrive cars that were in dire need of re­duced par­a­sitic power losses when­ever pos­si­ble. While re­duc­ing par­a­sitic loads on the en­gine at cruis­ing speeds, these elec­tric fans still pro­vided ex­cel­lent lowrpm cool­ing when idling or at low ve­hi­cle speeds. Our orig­i­nal in­tent was a dyno test com­par­i­son of the factory-fixed four­blade fan and an elec­tric fan setup on our ’67 six-cylin­der Dart GT, but as luck would have it, the 51-year-old radiator sprang a leak just as we com­pleted our base­line dyno runs, so we were on the search for a radiator and elec­tric fan setup. We con­tacted Don Arm­strong of U.S. Radiator, and he set us up with a radiator, SPAL fan, and cus­tom shroud for our Dart. U.S. Radiator has been in busi­ness for more than 40 years, and the staff has plenty of cool­ing sys­tem ex­pe­ri­ence with all types of ve­hi­cles and man­u­fac­tur­ers.

The test ve­hi­cle was Penn­syl­va­nia Col­lege of Tech­nol­ogy’s (PCT) “dyno” Dart. The orig­i­nal 22K-mile Dart was do­nated to the col­lege in 2012 and has be­come a test mule for var­i­ous bolt-on com­po­nents in the col­lege’s dyno classes. The Dart has a re­built Slant Six (ma­chined and as­sem­bled in the col­lege’s ma­chine shop with an in­creased com­pres­sion ra­tio of 9.37:1, a re­sult of a com­bi­na­tion of deck­ing the block and milling the head. To ig­nite the air/fuel, an elec­tronic ignition has been in­stalled to re­place the sin­gle-point ignition. A 2.25-inch Ac­cu­rate Ex­haust Prod­ucts full ex­haust han­dles re­mov­ing the spent hy­dro­car­bons. The rest of the driv­e­train re­mains as the factory in­stalled it in late 1966.

To es­tab­lish our base­line, we tested the per­for­mance of the radiator and the factory four-blade fixed fan. The Dart was run on the PCT Mus­tang dyno in an rpm range of 2,200 to 4,000 rpm. The en­gine could’ve been run a few hun­dred rpm higher than 4,000 rpm, but the horse­power peak was al­ready trend­ing down­ward at four grand, so there was no need to beat the Slant Six. We made a series of three base­line runs within 1 per­cent of each other, and the 225 spun the rollers to a peak of 149 lb-ft of torque at 3,100 rpm and 95 hp at 3,800 rpm. Upon com­ple­tion of our third run of the series, we no­ticed a small pool of coolant on the shop floor un­der the Dart. We knew what that meant; we were now in search of a new radiator to com­plete the test­ing. We were just thank­ful to com­plete our base­line test­ing.

U.S. Radiator sup­plied a high-ef­fi­ciency radiator (20 per­cent more heat trans­fer points over orig­i­nal equip­ment), and the use of a 22-inch (width) re­place­ment radiator rather than the 19-inch factory radiator was sug­gested. The 22-inch radiator would fit in the factory radiator sup­port open­ing with­out any mod­i­fi­ca­tions, so we agreed to the big­ger radiator for our test­ing. The fan se­lected was a 16-inch SPAL puller fan that would pro­vide more than enough air­flow across the radiator. We made all the mea­sure­ments we could to de­ter­mine the fan fit­ment, and U.S. Radiator took our mea­sure­ments and fab­ri­cated a fan shroud with a fan open­ing to the max­i­mum right (pas­sen­ger side) of the radiator to clear the factory wa­ter pump pul­ley.

When the radiator ar­rived, the radiator, fan, and shroud were com­pletely as­sem­bled and ready to drop in to the en­gine bay. Even with all our mea­sure­ments, the fit be­tween the fan and the wa­ter pump pul­ley was tight. The fan depth caused some con­cern. We pushed the radiator to the right (pas­sen­ger) side as far as the bracket bolt slots would al­low to pro­vide enough clear­ance be­tween the wa­ter pump pul­ley and the SPAL fan mo­tor. Once we had the clear­ance we de­sired, we loos­ened the driver-side en­gine mount and jacked up the en­gine to see how much en­gine move­ment could oc­cur be­fore any con­tact be­tween the pump pul­ley and the fan mo­tor oc­curred. We still had clear­ance at a point well be­yond any en­gine mount de­flec­tion un­der ac­cel­er­a­tion.

The SPAL fan comes with an in­stal­la­tion kit that re­quires a temp send­ing unit to be in­stalled in the cool­ing sys­tem, near the en­gine’s ther­mo­stat. This would’ve been straight­for­ward on a V-8 en­gine,

be­cause the in­take man­i­fold has one (or more) pro­vi­sions for the temp send­ing unit to be in­serted, but a Slant Six en­gine doesn’t pro­vide such ac­cess. U.S. Radiator could’ve put a bung in the up­per radiator tank for us (if we had asked), but we ended up mod­i­fy­ing a piece of 1½-inch out­side di­am­e­ter (od) ex­haust pipe, which we drilled, tapped, and then in­stalled the send­ing unit bung. We used cold weld (two-part epoxy) to af­fix and seal the bung to the pipe. Once cured, the temp send­ing unit was threaded into the bung. We

in­stalled the send­ing unit hous­ing into the up­per hose with the temp send­ing unit point­ing down­ward. A pair of hose clamps se­cured the hous­ing into the hose.

With the radiator as­sem­bly and temp send­ing unit in­stalled, we had to wire the fan. The SPAL in­stal­la­tion kit pro­vided a 30-amp Bosch re­lay and har­ness to wire the fan. We mounted the re­lay next to the radiator and the bat­tery at the driver-side cor­ner of the en­gine bay. Fol­low­ing the in­struc­tions, we sup­plied a fused 12-volt source to pin 30 (power side) of the re­lay, and a switched (ignition) 12-volt source to pin 86 (con­trol side) of the re­lay. Pin 85 (con­trol side) was run to the temp send­ing

unit that we had in­stalled into the up­per radiator hose. We ran pin 87 (power side) of the re­lay to the fan 12-volt wire and grounded the other wire from the fan. Af­ter com­plet­ing the wiring, we added the coolant to the radiator and checked the up­per hose sev­eral times for any leaks.

The ’67 factory cool­ing sys­tem didn’t have an over­flow tank, which meant there was no reser­voir for the over­flow coolant from the radiator. In this sys­tem, the up­per tank is de­signed to be the ex­pan­sion tank. The coolant is filled to the top of the core not the top of the tank. The tank acts as the over­flow area when the en­gine warms. The prob­lem with this de­sign is coolant loss onto the ground and de­bris en­ter­ing the radiator lead­ing to con­tam­i­na­tion and re­duced cool­ing sys­tem ef­fi­ciency. We elected to in­stall a generic over­flow tank to the Dart. We could now com­pletely fill the radiator’s top tank, and the over­flow tank could be filled to the fill cold line. When the en­gine was run, the coolant would push out of the radiator into the over­flow tank, and when the en­gine cooled the coolant would be drawn (pushed back into) the radiator. This de­sign would end any coolant leak­age onto the ground and limit con­tam­i­nants from en­ter­ing the cool­ing sys­tem. We in­stalled our over­flow

tank in­side the pas­sen­ger-side fend­er­well. For now, we zip-tied the over­flow tank to the bumper bracket and will de­ter­mine a per­ma­nent po­si­tion for it in the fu­ture.

With the radiator’s top tank filled with coolant, we topped off the over­flow tank and warmed up the Slant Six. We con­stantly checked the temp send­ing unit hous­ing in the up­per hose for leaks and found none. The en­gine’s tem­per­a­ture con­tin­ued to rise, and just about the time we thought some­thing might be wrong with the fan’s wiring, the fan spun to life. The fan was de­signed to turn on at 180 de­grees F and turn off at 165 de­grees F. In con­junc­tion with the 160 de­grees F en­gine ther­mo­stat, the fan op­er­ated prop­erly, cy­cling sev­eral times while the slant idled. We used an anemome­ter to mea­sure the elec­tric fan’s abil­ity to pull air across the radiator and com­pared it to the four-blade fan mea­sure­ments. The elec­tric fan pulled

a con­stant 3.5 mph of air across the radiator re­gard­less of the area of the radiator tested. The factory four-blade fan could match the 3.5 mph speed of the elec­tric fan in the cen­ter of the radiator, but the speed fell off greatly as the anemome­ter was moved to the edges of the radiator.

Back on the dyno, the Slant Six was run through the same pa­ram­e­ters as the base­line runs. We made each run with the elec­tric fan in op­er­a­tion to com­pare the per­for­mance dif­fer­ence be­tween the fixed fan and the elec­tric fan. Af­ter the series of runs, the elec­tric fan showed a mild in­crease in torque and horse­power, and most of the im­prove­ment was in the higher rpm of the run. The peak torque was up to 151 lb-ft at 3,100 rpm, and the peak horse­power rose to 99 hp at 3,900 rpm. The torque climbed 2 lb-ft, and the horse­power in­creased by 4 hp.

Was the elec­tric fan worth the ef­fort? Well, 4 hp at the wheels is an in­crease. For the sake of sim­plic­ity, Arm­strong sug­gested we add a U.S. Radiator cus­tom shroud, radiator, and flex fan, while fore­go­ing the elec­tric fan idea for the slant. We — now — agree, as we had con­cerns with the elec­tric fan (a 7-amp ad­di­tional draw with an 11-amp ramp up draw) tax­ing our 35-amp al­ter­na­tor and worse adding ad­di­tional loads to the 51-year-old wiring har­ness. If an elec­tric fan is in your fu­ture, con­sider up­grad­ing your en­tire charg­ing sys­tem to meet the needs of the new elec­tri­cal re­quire­ment (For in­for­ma­tion about up­grad­ing your charg­ing sys­tem, re­view “Elec­tric Av­enue Charg­ing Sys­tem Up­grade with a Tuff Stuff Al­ter­na­tor” from our July 2018 is­sue.)

U.S. Radiator pro­vided us with ev­ery­thing we needed to up­grade the cool­ing sys­tem of our Dart. Would this in­stal­la­tion have been eas­ier and more suit­able on a mod­i­fied V-8? Yes, but U.S. Radiator de­liv­ered a per­fect pack­age for our Slant Six Dart. In the case of the Slant Six, we shouldn’t have been so de­ter­mined to have the elec­tric fan and lis­tened to Arm­strong’s sugges­tion about the flex fan op­tion, which would’ve saved us time (temp send­ing unit hous­ing mods and radiator fit­ment). It wouldn’t have al­tered our charg­ing sys­tem re­quire­ments, and the per­for­mance gains would have most likely, in the case of the Slant Six, been sim­i­lar. If you need a radiator, shroud, fan, or even guid­ance as to what to do with your cool­ing sys­tem, con­tact the rep­re­sen­ta­tives at U.S. Radiator. They’ll pro­vide you with 40-plus years of ex­pe­ri­ence and knowl­edge, and point you in the right di­rec­tion. It’s up to you to heed their ad­vice.

The ra­di­a­tors are sim­i­lar in de­sign; how­ever, the U.S. Radiator is a high-ef­fi­ciency radiator (20 per­cent more heat trans­fer points over orig­i­nal equip­ment) that’ll meet the cool­ing needs of the re­built 225 Slant Six. Ad­di­tion­ally, the radiator from U.S. Radiator is all-new, so it’s void of 51 years of con­tam­i­na­tion and de­bris.

The Dart was run on the Penn­syl­va­nia Col­lege of Tech­nol­ogy’s Mus­tang dyno in an rpm range of 2,200 to 4,000 rpm. The 225 Slant Six with the fixed factory four-blade fan and 19-inch radiator es­tab­lished a base­line of 149 lb-ft of torque at 3,100 rpm and 95 hp at 3,800 rpm. At the com­ple­tion of the third run of the base­line runs, coolant was no­ticed on the floor un­der the radiator sup­port.

The 51-year-old radiator looks dry at the top tank, but just above the bot­tom tank, the core had some pre­vi­ous da­m­age that fi­nally split open and be­gan leak­ing dur­ing the test­ing. The Dart came from the factory with a fixed fan and no shroud.

The factory 19-inch radiator (left) pro­vided 51 years of ser­vice, but dur­ing our lat­est test­ing it fi­nally started leak­ing. The so­lu­tion was a radiator, cus­tom shroud, and SPAL elec­tric fan from U.S. Radiator. The radiator is a 22-inch de­sign, which fits into the factory radiator sup­port open­ing at the front of the ’67 Dart GT test car.

The up­per and lower radiator hoses were re­moved, and the trans­mis­sion lines were dis­con­nected from the cooler in the bot­tom tank. The two up­per radiator re­tain­ing bolts were re­moved, and the two lower bolts were loos­ened but not re­moved. With a lit­tle tilt­ing of the radiator to­ward the fan, the radiator was pulled out of the Dart’s en­gine bay.

With the radiator out of the way, the fixed fan bolts were eas­ily re­moved. The four bolts, the fan, and a fan spacer were re­moved. We left the wa­ter pump pul­ley in place, so the pul­ley and the wa­ter pump flange re­mained lined up for the in­stal­la­tion of new wa­ter pump pul­ley bolts.

Coolant leaked onto the lower radiator sup­port, down the sup­port strut to the K-frame and onto the trans­mis­sion line. The radiator could’ve been re-cored, but U.S. Radiator sup­plied a bet­ter-thanfac­tory new radiator for our test­ing.

We found suit­able (shorter) bolts to at­tach the wa­ter pump pul­ley to the wa­ter pump flange. We used lock wash­ers on the bolts to min­i­mize any con­cerns of the bolts back­ing off. When se­lect­ing new bolts, check the back side of the wa­ter pump flange to make sure the bolts aren’t too long, re­sult­ing in in­ter­fer­ence with the wa­ter pump cast­ing.

Both trans­mis­sion line flare fit­tings were re­moved from the 19-inch radiator and trans­ferred to the new 22-inch radiator. If new fit­tings had been re­quired, they’re a male con­nec­tor 1/8 NPT on the cooler end and AN-05 (5/16) flare on the trans­mis­sion line end (PN Edel­mann 148520, Everco 48D, or Weather­head 48x5).

For the radiator drain, a new plug was picked up at a lo­cal auto parts store. The factory pet­cock in the 19-inch radiator was phys­i­cally dam­aged and too cor­roded to trans­fer to the new radiator.

With the radiator drain plug and trans­mis­sion cooler fit­tings in­stalled into the lower tank, the radiator was dropped onto the lower radiator bolts that had been left in the radiator sup­port. The radiator was pushed to the right (pas­sen­ger side) as far as the radiator bracket slots would al­low, so max­i­mum clear­ance be­tween the SPAL fan mo­tor and the wa­ter pump pul­ley could be at­tained. With the radiator in place, the four radiator bolts were tight­ened.

While at the auto parts store, we picked up a bung (left) and short­ened it to the length we de­sired. The SPAL temp send­ing unit threaded into the bung. We en­sured the send­ing unit would be in the flow of coolant at all times to pro­vide an ac­cu­rate tem­per­a­ture mea­sure­ment. U.S. Radiator could’ve pro­vided a bung in the up­per tank if we had asked, but our mod­i­fi­ca­tion did the job.

A piece of 1½-inch out­side di­am­e­ter (od) ex­haust pipe was used for a place to in­stall the temp send­ing unit bung. The pipe was drilled and tapped, and the bung was in­stalled. This pipe would be short­ened and fit­ted into the up­per radiator hose.

The bung was threaded into the pipe and then glued into place with a twopart cold weld epoxy. The pipe was short­ened to the de­sired length, and when the epoxy dried, the as­sem­bly was sanded and painted black.

The up­per radiator hose was cut to ac­com­mo­date the new tem­per­a­ture send­ing unit as­sem­bly. A pair of hose clamps held the ex­haust pipe in place. The temp send­ing unit was threaded into the bung.

The Bosch re­lay was mounted on the up­per radiator bracket bolt on the driver-side up­per radiator sup­port. The wiring har­ness uses weather-pack (blue) seals to re­duce any wa­ter or de­bris from con­tam­i­nat­ing the cir­cuits. A fused 12-volt source was sup­plied to the yel­low wire, and a switched (ignition) 12-volt source was ap­plied to the or­ange wire of the re­lay. The gray wire was run to the temp send­ing unit in­stalled into the up­per radiator hose, and the red wire was the 12-volt wire to the mo­tor.

The SPAL elec­tric fan wiring har­ness in­cluded a 30-amp Bosch re­lay, sev­eral fuses and wire ends, shrink-wrap butt con­nec­tor, fan con­nec­tor har­ness, in­line fuse holder, and wiring in­struc­tions. We wired the fan as out­lined in the in­struc­tions.

The heavy-gauge red wire was con­nected to the fan con­nec­tor har­ness’ red wire. The pro­vided shrink-wrap butt con­nec­tor was used. The shrink wrap pro­tects the wires from con­tam­i­na­tion. The gray wire was run to the temp send­ing unit, and the black wire (un­der left hand) was run from the fan to a chas­sis ground. When the wiring in­stal­la­tion was com­plete, the wires were all tucked be­hind the factory har­ness on the radiator sup­port.

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