Up­grad­ing your carbureted en­gine to EFI


The lowly car­bu­re­tor has been feed­ing in­ter­nal com­bus­tion en­gines since their in­ven­tion. As a re­ac­tionary de­vice just try­ing to feed the mo­tor they were strapped to, they worked well, un­til said mo­tor started mov­ing… like in a truck. Slosh­ing fu­els and dif­fer­ing al­ti­tudes caused man­u­fac­tur­ers to place

ad­di­tional re­ac­tionary de­vices to keep the air/fuel ra­tio on a level play­ing field and driv­ers from pulling their hair out. These worked about as well as any band-aid and we, the peo­ple, suf­fered through it un­til a pro-ac­tive fuel de­liv­ery sys­tem came around… and elec­tronic fuel in­fec­tion (EFI) was born!

For the mod­ern gear­head, the ad­vent of an af­ford­able, easy to in­stall fuel in­jec­tion sys­tem changed the au­to­mo­tive af­ter­mar­ket land­scape. Al­go­rithms ca­pa­ble of self-learn­ing and on-the-fly tun­ing are what re­ally brought leadingedge tech­nolo­gies used by the OEM’s into the garages of DIY’ers like us.

With the mass in­flux of these sys­tems avail­able, it can be hard to wade through the op­tions and know which is best for your ap­pli­ca­tion. We’re go­ing to try and clear some of this mess up, and give you a base­line of what to look for when you are think­ing of step­ping into the mod­ern cen­tury with your old school off-road rig.

For our pur­poses, we se­lected two pieces of yard art that would do noth­ing but kill off mos­qui­toes with plumes of black smoke when off cam­ber, on a bumpy road, or try­ing to make it over a high mountain pass; our trail rig Stinky Jeep has a high com­pres­sion 407 ci V8 with a Nitrous Ex­press di­rect port nitrous sys­tem set to slaugh­ter any hill or snow bank, and Ian’s Jeep J10 pick-up with what is essen­tially, a bone stock AMC 360.

We made a call to Sum­mit Rac­ing for two com­pletely dif­fer­ent Throt­tle Body EFI sys­tems and se­lected them specif­i­cally for their in­tended ve­hi­cles; a Hol­ley Ter­mi­na­tor PN 550-406 and a Sum­mit Rac­ing Max EFI500 PN SUM-240505 throt­tle body in­jec­tion sys­tem. We also scooped the proper fuel lines and fit­tings re­quired to feed these sys­tems stick­ing with Earl’s Va­por Guard prod­ucts. We don’t want to deal with fu­ture leaks and wanted a hose and fit­ting sys­tem that could hand the abuse and chem­i­cals.

Speak­ing of fuel sys­tems, Stinky Jeep al­ready has a stout Ra­dium En­gi­neer­ing fuel sump sys­tem ca­pa­ble of feed­ing many more horses then we can af­ford, but Ian’s J-10 does not. We have used Edel­brock’s Fuel Sump sys­tems in the past with great suc­cess and or­dered an­other when we had Sum­mit Rac­ing on the line. We won’t go into great de­tail, but the fac­tory, low pres­sure me­chan­i­cal pump feeds the Edel­brock Sump and a built-in, and in­ter­nally reg­u­lated fuel pump feeds high pres­sure ga­so­line to the EFI throt­tle body. No noisy ex­ter­nal pump, no cus­tom tank, no fuel re­turn lines, no ex­ter­nal reg­u­la­tor. Just a sim­ple fuel de­liv­ery sys­tem that uses the ex­ist­ing lines and pump.

Sum­mit Rac­ings Max EFI500:

The Sum­mit Max EFI500 unit is de­signed to be an all-in-one, easy to use self­learn­ing sys­tem for en­gines pro­duc­ing less than 500 Hp and can have you up and run­ning within a few hours af­ter an­swer­ing a few ques­tions. The J-10 with a stock smog era V8 would have a hard time giv­ing up over 200 hp at the tires on a good day. The goal of this en­deavor was to pro­vide a re­li­able base line for a truck that is driven daily back and forth to work. Easy start­ing, lim­ited warm up time, and a dou­ble digit mpg fuel econ­omy were our pri­mary goals, and we were not dis­ap­pointed.

The 4150 style mount­ing flange is a typ­i­cal stan­dard for al­most all throt­tle body in­jec­tion units and re­quires an adapter or new in­take man­i­fold to mount the EFI500 unit to the 360. Ian had scooped a new alu­minum in­take for the old AMC mo­tor, which was lighter, more ef­fi­cient and al­lowed for an easy bolt on. SCORE! The wiring harness is well made and only re­quires a few ex­tra con­nec­tions such as an O2 sen­sor, water tem­per­a­ture sen­sor, ig­ni­tion trig­ger source, along with con­stant and switched 12 VDC power sources. All sen­sors are in­cluded in the kit along with the small ECM (elec­tronic con­trol mod­ule). A small hand­held touch screen is used for the ini­tial setup but can then be used for mon­i­tor­ing the sys­tem or re­moved com­pletely.

A con­stant feed of 58PSI fuel is re­quired to sup­ply the unit’s -6 AN fit­ting on the fuel rail. This is not a feed through style sys­tem, so a re­turn line is not re­quired, and with our Edel­brock Sump pump, we didn’t have one. The unit is not ca­pa­ble of E85 Ethanol, but we are sure that with the pop­u­lar­ity of the fuel, a tune and setup will be avail­able in the fu­ture.

There are pro­vi­sions on the throt­tle body for con­nec­tions to mul­ti­ple ac­cel­er­a­tor ca­ble types as well as con­nec­tions for au­to­matic trans­mis­sions. If you have an elec­tron­i­cally con­trolled au­to­matic trans­mis­sion, you will have to pur­chase a sep­a­rate con­troller for that. Vac­uum con­nec­tions for dis­trib­u­tor ad­vance, power brakes and PCV valves are built into the unit as well.

Af­ter fi­nal con­nec­tions were made and some quick ques­tions by the pre­loaded soft­ware an­swered, we were very happy to hear the once prob­lem­atic V8 eas­ily come to life and roll into an idle so smooth we had to make sure the truck was run­ning. Once up to tem­per­a­ture, we set the idle and cal­i­brated the throt­tle po­si­tion sen­sor. The in­cluded in­struc­tions don’t say just how long it will take for the sys­tem to learn your par­tic­u­lar ve­hi­cle, but from our ex­pe­ri­ence, plan on two tanks of fuel of nor­mal driv­ing. This means take it easy… No run­ning from the cops or en­ter­ing an ul­tra 4 race the morn­ing af­ter you in­stall the unit. Con­sider it “bond­ing time”, and you will be re­warded with all the on- and off-road ben­e­fits that fuel in­jec­tion can of­fer.

Hol­ley Ter­mi­na­tor:

Sim­i­lar to the Sum­mit Rac­ing Max EFI500 from the out­side, the Ter­mi­na­tor of­fers all the ben­e­fits of the EFI500 as well as many more… hence al­most dou­ble the price tag. We chose the Hol­ley for the nasty rol­ler­ized mo­tor in Stinky Jeep over the Sum­mit brand for a number of rea­sons that we will touch on a lit­tle later.

The in­stal­la­tion is ba­si­cally the same as be­fore; a 4150 style carb flange is needed and a fuel sys­tem ca­pa­ble of feed­ing the 600 hp unit is re­quired at 45 PSI. An O2 sen­sor, water tem­per­a­ture sen­sor, and the usual power and ig­ni­tion con­nec­tions all plug into the nicely made harness. The ECM (which also eas­ily plugs into the harness with a wa­ter­tight con­nec­tion) is where the two sys­tems di­verge. The Ter­mi­na­tor comes with a very in­tu­itive self-learn­ing pro­gram but can also be man­u­ally al­tered for free with Hol­ley HP con­trol soft­ware from a lap­top with a USB port. Mul­ti­ple in­puts and out­put can be con­fig­ured for any­thing from cool­ing fans, to fuel and oil pres­sure feed­back and even ana­log nitrous con­trol. Have a com­plex pulse width mod­u­lated fuel sys­tem? Have a turbo charger or su­per­charger at­tached to your en­gine? Want to ad­just ig­ni­tion tim­ing? Use the sys­tem water tem­per­a­ture sen­sor to con­trol elec­tric fans? Want a switch to raise the idle by 500 RPM for an air com­pres­sor? The Ter­mi­na­tor can do all of these with ease.

Our 408 V8 was ini­tially con­fig­ured and wired to con­trol the two fuel pumps and elec­tric fans con­nected to the mo­tor. The nasty, high lift cam, high dy­namic com­pres­sion, and lumpy idle pro­vided very few is­sues with the ini­tial run­ning of the sys­tem but did re­quire some minor man­ual tweaks that could not be done with the EFI500 plat­form. Start­ing the mo­tor is sim­ple and re­quires lit­tle to no warm up be­fore tak­ing it out driv­ing, the same as a new school ve­hi­cle with mod­ern EFI.

Al­though we run a stan­dard trans­mis­sion, the Ter­mi­na­tor is ca­pa­ble of op­er­at­ing both ca­ble, vac­uum and with the proper pro­vi­sions, elec­tron­i­cally con­trolled trans­mis­sions.

Our min­i­mal ex­pe­ri­ence with the Nitrous Ex­press sys­tem on the rig was an­other ma­jor draw for the Ter­mi­na­tor as the sys­tem can be used to turn the sys­tem on only when the ac­cel­er­a­tor is at wide open throt­tle (WOT) and above a pre-de­ter­mined RPM (3000 in our case). This negates hav­ing a sep­a­rate nitrous con­troller AND we can have the Ter­mi­na­tor en­rich the air/fuel ra­tio when the sys­tem is on, just to keep our high dol­lar en­gine in­tact. We’re al­ways chang­ing things and ex­per­i­ment­ing as well, so the abil­ity to use the same EFI sys­tem and con­troller for mul­ti­ple uses ap­peals to us greatly.


The con­ve­nience and driv­abil­ity of mod­ern EFI can­not be ar­gued and if you are in the mar­ket to up­grade your old of­froad truck with a new in­duc­tion sys­tem and car­bu­re­tor, you owe it to your­self to look into the mul­ti­tude of self-learn­ing EFI sys­tems avail­able. Ad­mit­tedly we chose from two al­ter­nate ends of the spec­trum of throt­tle body in­jec­tion sys­tem in terms of price, but like your favourite pair of un­der­wear, this is not a “one size fits all” sit­u­a­tion.

Sum­mit Rac­ings Max EFI500

sys­tem is a ba­sic unit, per­fectly suited for a sim­ple car­bu­re­tor swap to im­prove the off road prow­ess of any sim­plis­tic, carbureted rig. Ian’s J10 Truck fit the bill to a “T”.


Af­ford­able Easy to in­stall Ex­cel­lent self learn­ing al­go­rithms Sim­ple setup


Un­able to op­er­ate with power adders (Boost, NOS, Methanol, etc.) Can­not op­er­ate with low en­gine vac­uum/large over­lap cam shafts Not man­u­ally tun­able No pro­vi­sions for aux­il­iary equip­ment

The Hol­ley Ter­mi­na­tor was brought to mar­ket for the per­for­mance crowd and the av­er­age gear­heads in­abil­ity to leave well enough alone, we and our axle snap­ping V8 fit in this cat­e­gory like bog­gers in mud.


Adapt­able to mul­ti­ple en­gine, trans­mis­sion, fuel and ig­ni­tion sys­tems Can be up­graded to Hol­ley HP for ad­di­tional tun­ing with a lap­top Works well with power adders Able to ac­cu­rately feed 600 hp en­gines


Al­most 2X the price of an en­try level sys­tem In­stal­la­tion re­quires slightly more wiring Many more pa­ram­e­ters to take care of Needs to make a min­i­mum of 250 HP

No mat­ter the sys­tem you choose, we have yet to run into a sys­tem on the mar­ket that was not light years ahead of the old gas dumper sit­ting atop the en­gine it re­placed. Our fi­nal ad­vice is to look at the pro and cons listed above and stick with a name brand you know and trust. Like many things in life, it’s bet­ter to have more op­tions and not need them, than need them and not have them, and these have the min­i­mum re­quired and more. Fol­low along as we high­light the in­stal­la­tion and run­ning of these two sys­tems and get ready to hit the trail.

Sum­mit Rac­ing Equip­ment – www.sum­mi­trac­ing.com

Hol­ley Equip­ment – www.hol­ley.com

Edel­brock – www.edel­brock.com

Four Func­tion Au­tosport – www.four­func­tion.ca

We were not re­ally ex­pect­ing an in­crease in power by swap­ping the old carb for EFI, but were pre­sented with it any­way. The ad­di­tional air and fuel the mo­tor could now eat pushed the av­er­age power up by roughly 20 hp. Throt­tle re­sponse and over­all driv­abil­ity were the real win­ner as well as be­ing able to drive at al­most any an­gle. We haven’t had a chance to cold start the Sum­mit Rac­ing unit yet, but can at­test that the Hol­ley sparked up and bur­bled into an idle, ready to hit the snow ev­ery morn­ing we tried.

1. Two boxes from Sum­mit Rac­ing are all that we need for the week­end shenani­gans of swap­ping the old car­bu­re­tor out of Ian’s rusty J10 pickup truck.

11. Watch­ing a set of un­bal­anced Su­per Swampers howl on a chas­sis dyno is an amaz­ing ex­pe­ri­ence and we fully rec­om­mend it…. from a dis­tance… with a hel­met on… and maybe a mouth guard. 11

10. To get some ac­tual num­bers, we headed down to Four Func­tion motorsport to leak oil and purge grease all over their fancy dy­namome­ter. We first ran a few tanks of fuel though the truck driv­ing on the street so that the com­puter could learn the en­gine it was now at­tached to. 10

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