Six Ap­peal: Part 1

WE OUT­LINE THE SHORT-BLOCK DE­TAILS FOR A 200ci IN­LINE-SIX EN­GINE BUILD FOR TO­DAY’S DRIV­ING

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Build­ing a 200ci in­line-six en­gine for to­day’s driv­ing—in Part 1, we out­line the short­block de­tails

THE DAY BE­FORE I SAT DOWN TO WRITE THIS AR­TI­CLE, A FRIEND OF MINE PUR­CHASED A VERY NICE SIX­CYLIN­DER 1965 MUS­TANG HARD­TOP FOR HIS WIFE TO DRIVE—A VERY GOOD, SOLID CAR. His first ques­tion to me was, “Do you have an ex­tra 289 or 302 ly­ing around?” Ugh. The curse of the lowly

six-cylin­der Mus­tang. More so in the Mus­tang world than in the Fal­con/Fair­lane and other realms, the six­cylin­der Mus­tang has al­ways been a tar­get for an en­gine swap for more horse­power. Granted, the four-lug wheels and light­weight driv­e­line com­po­nents weren’t very ro­bust, but the six-cylin­der it­self was not a ter­ri­ble com­bi­na­tion in the small Mus­tang plat­form. In the six­ties, with 1960s driv­ing, roads, traf­fic, and econ­omy, the six was a good choice for a daily driver. Al­ways over­shad­owed by the V-8 en­gine, Ford had to make a spe­cial pro­mo­tion in 1966 with the Sprint 200 pack­age to sell more straight-six en­gines. Even with no over­drive gears, the six was ca­pa­ble of de­liv­er­ing mid-20s mpg num­bers in stock form. V-8 con­ver­sions started al­most im­me­di­ately with the Mus­tang and con­tinue to this day. But the cost of con­vert­ing to a V-8 is start­ing to get pretty high, and some own­ers are still in love with the econ­omy that the six-cylin­der pro­vides over the heav­ier, gas-guz­zling V-8. So we de­cided to look at an en­gine build that would pro­vide us with more horse­power for to­day’s driv­ing with­out sac­ri­fic­ing the econ­omy and torque ad­van­tages that the straight-six pro­vides.

Prior to this story, we out­lined the one manda­tory part needed to build a bet­ter-than-stock six: the Vin­tage In­lines cylin­der head (mus­tang-360. com/how-to/en­gine/1804-fi­nallya-per­for­mance-cylin­der-head-for­ford-six-cylin­ders). After that, we con­tacted Vin­tage In­lines in Michi­gan and told them what we wanted to do—build a six with power for to­day and the torque and econ­omy the six is tra­di­tion­ally known for. We didn’t want to build a high-horse­power, finicky-in-traf­fic over­build you so of­ten see in mag­a­zine builds; we wanted a build that made the straight-six an ex­cel­lent choice for a car that is driven reg­u­larly. As a bonus, we were also look­ing for one-stop shop­ping to get the build done.

After think­ing it over, we came up with an en­gine that we feel should get us into the 200-205hp range. That may not sound like much, but our tar­get is one horse­power per cu­bic inch, which is more than the 205225hp en­gine of the Fox-body 5.0L era—with the torque of the straight­six en­gine to boot. As the project un­folded, we started look­ing at in­duc­tion sys­tems. We de­cided that what we built would be used as the test mule to shake­down sev­eral dif­fer­ent fuel in­duc­tion sys­tems: The two- and four-bar­rel car­bu­re­tors and a cou­ple of fuel in­jec­tion op­tions, which we are build­ing for an up­com­ing project. Our plan is to dyno all these dif­fer­ent in­duc­tion sys­tems so you can de­cide which one is best suited for your driv­ing. But for now, let’s look at our en­gine and how we plan to reach our goals.

The Ba­sics

The Ford Thrift­power Six was in­tro­duced in 1960 in the form of a 144ci ver­sion. Early 1964 Mus­tangs were fit­ted with the 170 Spe­cial Six, and this was up­dated to the 200 in 1965. The 200 was used through 1969, when it was re­placed by the 250, which was used through­out 1973. Ford re-in­tro­duced the 200 back into

the Mus­tang in 1979, when the 2.8L V-6 was not avail­able in quan­tity, so the straight-six was back as a re­place­ment mid-1979. The last year of pro­duc­tion for the 170 was 1972; the last year for the 200 was 1983; and the 250 ended pro­duc­tion in 1980.

Be­sides the ob­vi­ous bore and stroke dif­fer­ences, the big dif­fer­ence came in the 200 with the seven main bear­ings in­stead of the 170’s four. This helped with not only mak­ing the bot­tom end more durable, but re­duced some of the har­monic vi­bra­tions in the en­gine. The 170 had three core plugs on the pas­sen­ger side, and some of the early 200s also had three. Ford be­gan putting five core plugs in the block mid-1965. The 250 is about 1.66 inches taller than the 200 and around an inch wider.

The Good

The in­line-six was not only used as a re­li­able base pow­er­plant in the Ford econ­omy line, it was also known for the one thing all in­line en­gines are known for—torque. “V” en­gines at­tach two rods to the same point, which drives the crank with two pis­tons at that point, in­creas­ing horse­power. In­lines con­nect each rod to a sin­gle point, and the push-pull char­ac­ter­is­tics in­crease ro­ta­tional torque. So for the size, in­line en­gines pro­duce more torque than V en­gines.

The bot­tom end of the six was very good; the seven main bear­ings in the 200 and 250 help make the en­gine very durable. In most street builds, no real spe­cial work needs to be done to the bot­tom end—the rods and crank are very good and can han­dle a mild build with no prob-

lems. The oil­ing sys­tem is also very good and does not re­quire any spe­cial al­ter­ations on most en­gine builds. Ac­cord­ing to my Bronco friends, the six is much bet­ter with cool­ing as well—where the V-8s over­heat (ac­cord­ing to them), the sixes re­main calm, even with a good build.

The Bad

With the ex­cep­tion of the weight, most of the prob­lems with the six are from the deck up. The cylin­der head was orig­i­nally de­signed with an in­te­gral in­take man­i­fold, which was de­signed as a sim­ple tube run­ning the length of the cylin­der head. With a sin­gle one-bar­rel car­bu­re­tor, the cen­ter cylin­der had a much shorter run­ner length than the outer two cylin­ders, which re­sulted in un­even fuel flow. The in­com­ing air charge had to make 90-de­gree an­gles to get into the cylin­der head, which was also not good for per­for­mance. The car­bu­re­tor was lo­cated right over the cen­ter ex­haust port, which meant it was sus­cep­ti­ble to heat from the

en­gine and va­por­lock­ing is­sues.

Speak­ing of heat, the cen­tral port on the cylin­der head com­bines the No. 3 and No. 4 cylin­ders to­gether to make one big port. This, of course, made the ex­haust out­put un­even, and worse, it heated up the cylin­der head more in the most in­op­por­tune place— right un­der the car­bu­re­tor. The af­ter­mar­ket came up with a spacer to in­sert to try and solve some of the prob­lems, but it is still a con­tin­u­ing prob­lem on all builds with the orig­i­nal head. The orig­i­nal ex­haust man­i­fold was very con­stricted, not in­tended for any real horse­power us­age, and of­ten cracked.

The head is cast for one car­bu­re­tor—a one-bar­rel. Per­for­mance en­thu­si­asts have made con­vert­ers and ma­chined for mul­ti­ple carbs and big­ger carbs for years, but com­bined with the three 90-de­gree turns, more car­bu­re­tor is not al­ways enough to help a bad sit­u­a­tion. The Au­to­lite 1100 one-bar­rel car­bu­re­tor was used in most ap­pli­ca­tions (some Hol­ley and Carters were also used), and the Au­to­lite had some hes­i­ta­tion is­sues that some car­bu­re­tor builders were able to en­gi­neer out.

The block it­self is heavy, in terms of cu­bic inches. Ford wasn’t too wor­ried about weight like they were with the V-8s, and the block was made for re­li­a­bil­ity, not per­for­mance.

Ford Aus­tralia

Ford Aus­tralia was deeply com­mit­ted to the in­line-six de­sign, and in the 1970s they de­vel­oped a two-bar­rel head with a re­mov­able in­take made to mount a Bendix-Stromberg 2V carb. (Now we are get­ting some­where.) They also made im­prove­ments to the ex­haust, and this al­lowed for in­creased horse­power in the six and re­tained the torque num­bers. Their work is where most of the en­gi­neer­ing for our build comes from.

Con­clu­sion, For Now

Part 1 of the en­gine build has shown what went into the bot­tom end

(short-block) of the 200. Come back next month for Part 2 to get de­tails about the camshaft, cylin­der head, and all the other parts re­quired. We’ll fin­ish up with Part 3 when we put this puppy on the dyno and see how much power it makes. But be­fore we take it to the dyno, we are go­ing to step back and at­tempt to de­sign and build a se­quen­tial fuel in­jec­tion sys­tem for the straight-six. There have been sev­eral at­tempts to use junk­yard parts, but we are go­ing for the whole pack­age, brand new. We may try to talk some other ven­dors into let­ting us test their ex­ist­ing EFI sys­tems as well. Stay tuned!

“Part 1 of the en­gine build has shown what went into the bot­tom end (short-block) of the 200. Come back next month for Part 2 to get de­tails about the camshaft, cylin­der head, and all the other parts re­quired.”

The fu­ture of the Ford six-cylin­der is here. You can now build a six-cylin­der that will per­form for to­day’s driv­ing with­out sac­ri­fic­ing the econ­omy and torque the straight-six was known for—pos­si­bly for cheaper than what you would spend con­vert­ing to a V-8.

The bot­tom end of our 1967 200 is very rugged with its seven main caps, so we only did the stan­dard ma­chine work— we bored it 0.020 inch and had the ma­chine shop check the align hone and deck; then they in­stalled our camshaft bear­ings and core plugs.

The ARP studs torque more than the stock main cap bolts. ARP prefers the bolt-stretch method over a torque wrench, but most of us don’t own a stretch gauge. ARP in­structs to torque them three times, which gets you clos­est to the true torque num­ber.

Noth­ing spe­cial was needed for the stock crank, which was turned 0.020 inch on the rods and mains. It’s a solid piece and will hold up fine on our mild build.

We are us­ing ARP main studs for the added strength needed for the dyno runs. Al­ways use ARP as­sem­bly lube on all ARP studs and bolts.

We’re check­ing our gaps on our Sealed Power moly rings used with the Silv-O-Lite flat-top pis­tons. These pis­tons should yield around 9.6:1 com­pres­sion with the 55cc cham­ber heads. If you don’t bore the block, check the ring gap at the bot­tom of the pis­ton travel.

We chose a Clay Smith hy­draulic camshaft with .450-inch lift and 224 ad­ver­tised du­ra­tion on 112-de­gree lobe cen­ters. This high-lift, short-du­ra­tion cam should give a good idle and still have good mid- to high-rpm re­sponse.

A com­par­i­son of an early camshaft thrust plate and our new af­ter­mar­ket thrust plate. The 1965 plate does not have the small oil-feed groove, and the af­ter­mar­ket plate has it on both sides and up­side down, so you can’t get it wrong.

Don’t lose this small beveled spacer that is in­stalled be­hind the cam thrust plate. It is not re­pro­duced!

It is rec­om­mended that you do not use a high-vol­ume oil pump, and that the stan­dard pump works fine. We chose a qual­ity Melling pump for our build. Don’t for­get your dis­trib­u­tor drive­shaft.

Our oil pan was beat up, so we opted for a new one from Vin­tage In­lines. The stain­less dress-up kit is also be­ing used on this build.

With our bot­tom end as­sem­bled, we went ahead and painted the block and oil pan with a coat of Ford Cor­po­rate Blue (Omni # 13358). This will re­ally set off all the pol­ished alu­minum planned in the build.

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