Ford’s incredible 1969-70 Trans Am BOSS 302. Not the 2012-13 Coyote DOHC BOSS, but instead the genuine pushrod original from an era when Ford did the unthinkable repeatedly—and won! Ford’s classic 1969-70 BOSS 302 engine was a bold step forward after a miserable season in 1968.
The odds of you building a vintage Ford BOSS 302 engine are slim because Ford built so few and so many are already spoken for. However, it’s always fun to think about building one or even erecting one from scratch, which you can do with a Ford Performance BOSS block (M-6010-BOSS302) and Cleveland heads. You may also cruise the online auctions for a vintage 5.0L roller block (F1AZ-6010-B). There are plenty of them lying around used and new-old-stock.
Ford has always been a car company that dared to go where no automaker had ever gone before. That tradition dates back to the company’s founding in 1903. Think of Ford as a free-spirited car company with a rich history, driven by ego, that took big risks much as it is doing today with electric vehicles.
In the 1960s, Ford was an outspoken car company, much as Pontiac Division was within General Motors. Pontiac was the outlaw division. It didn’t conform to corporate protocol and invented the muscle car in its 1964 GTO. It had to sneak the GTO in under the radar of upper management. Ford took on the world with the GT40 supercar. Ford went to Le Mans and beat Ferrari not once, but four times, settling an age-old dispute over who had had the fastest cars in the world. Henry Ford II wasn’t going to have it any other way. Enzo Ferrari, and others, were handed their backsides.
Ford’s great success with its powerful V8 engines is legendary. The brute 427 FE Series big block that won Le Mans also reigned supreme in limited production 1964 Thunderbolt Fairlanes in NHRA competition. The darned thing was rabid dog fast. The 306-horse 289 cubic inch High Performance small-block V-8 in Shelby GT350s took on Corvette and the rest and managed to spank America’s sports car in SCCA competition.
With such great success under its seat belt, Ford decided to dabble with the 289 and stroked 302 to see what could be done to further its performance image. For the 1968 Trans Am season, Ford took the 302 cubic inch “Tunnel Port” out there in search of victory. Because the 302 Tunnel Port called for high revs in the 9,000 rpm range to make real power, racers scattered these engines all over racetracks across the country and left feeling defeated. The 1968 Trans Am season was a disaster.
Enter Ford’s development of an all-new 351ci engine with poly-angle valve heads and tight-fisted wedge heads destined for a 1970 introduction. Because the new 351 engine had the same bore spacing as the 289/302, it seemed logical for Ford to adapt this high-performance cylinder head to the small-block Ford V8. The 302 Tunnel Port already had a terrific four-bolt main block and steel crank along with beefed up “C3AE” 289 rods and special pistons designed for the Tunnel Port heads. Ford engineers took the new 351 cylinder head and modified it to work with the Tunnel Port block.
The result of this engineering effort was the BOSS 302 engine, which became the Trans Am mill of choice for 1969-70 and beyond in SCCA competition. To conceive the BOSS 302, Ford had to develop a special forged piston with a significant dome that would reach deep into the 351C head’s 64 – 67cc chambers. TRW developed these pistons and suppled Ford with them for both racing and production engines.
Because the BOSS 302’s heads sported monster-sized intake ports, these engines had a high-revving demeanor with peak torque and horsepower coming in around 7,000 rpm instead of the Tunnel Port’s outrageous nine grand. The result was a powerful 290-horse factory screamer with peak street power coming in around 6,000 rpm. These elements made the BOSS 302 a unique mill compared to what the rest of Detroit had to offer at the time.
We will admit to you our results on the dyno were disappointing—304 horsepower and 288 lb.-ft. of torque. We learned on the first few pulls that we had too much carburetor with our 750 cfm Holley 4160 and too little camshaft. Those of you who understand the BOSS 302 know Ford fitted these engines with a 780 cfm Holley but not necessarily because that’s what they needed. It was what the SCCA mandated for street homologation. Truth is, a factory original Boss 302 is happiest with a 600 to 650 cfm Holley. The BOSS 302’s biggest shortcoming is port sizing, which is something Ford has rarely been able to get right. The BOSS 302 engine could use better cylinder heads with right-size port and valve sizing in a set of Trick Flow cylinder heads and a more compatible roller mechanical camshaft. We tried this formula to see what our basically stock BOSS 302 would do. We got our answer.
Jim Smart is a veteran automotive journalist, technical editor, and historian with hundreds of how-to and feature articles to his credit. Jim's also an enthusiast, and has owned and restored many classic vehicles, including an impressive mix of vintage Ford Mustangs.
Wait… 1.6 rockers? Did you get them at a Chevy garage sale? Factory was1.73 IIRC. What cam specs and static CR? Something is very wrong with this, a blueprinted stocker should be in the 375-400 HP range.
[…] Here’s a close up of the head Marvin is using on our 351C build. We discovered this was a 1969-70 BOSS 302 head modified for use on a 351C. (Image/Jim Smart) Although these are 1969-70 BOSS 302 heads, they […]
Boss 302 is a Windsor engine; uses Windsor cam lobe profile & 1.6 Windsor rockers.
The factory Boss 302 did not have a deep sump pan although it did have a baffle in the sump, and yes it has 1.73 ratio rockers from Ford.
the 1970 Boss 302 had a 6 quart pan factory with a baffle in the bottom and a special pickup tube . the heads were different on the 1969 Boss 302 the valves were even bigger and the 69 had a hydraulic cam shaft . in 1970 they used slightly smaller valves and a solid cam shaft you had to set your valves manually with feeler gauges
Hate to tell you this but a BOSS 302 has Cleveland type heads. So your wrong. . If you used windsor heads it’s not a BOSS.
All Cleveland style heads including the BOSS has 1.73 to 1 ratio rockers.
Australian car enthusiast with 30 years experience in the high performance industry.
Great article is there a video available ?
Boss 302’s did indeed have 1.73 ratio rockers from the factory. But there is absolutely something else wrong. Even the stock cam should peek higher than 5500 rpm.
Both 1969 and 1970 302 BOSS engines will run great with a properly tuned 750 Holley. The less you know the more you need vacuum secondarys. 1.73:1 rockers, 522 lift 292 duration nets 420 HP at 6300. Index your plugs on these engines. There is no flat spot and these engines will pull from 2000 against any rival including a Windsor.
I’m looking for three Ford Cleveland 4V engines. (BOSS)
Can you further help me with where to buy this?
Condition does not matter!
Have a 70 351 4v stored 25 yrs 50 k miles complete minus carb dist has manifolds 1800
never lube the seal lip ? good luck with that.
Depends on material… old school rubber gets lube, the “Polytetrafluoroethylene rubber” go’s on dry.
Not too much carb for this engine. I had 90 runs on an original Boss 302 in a 70 Mustang. Every time I put a bigger carb on it, it ran faster. Typical rebuild, headers, Competition solid lifter cam, 1.73 Crane roller rockers. Was running 850 dbl pump Holley with 4:56 gears, and I was running 12:20’s at over 112 mph in the quarter. More than 400 horses easy
I’m sure you had over 400. In my 70 years of fooling with cars, we always had a formula. It took about 500 honest HP to break into the 11’s with a little bit heavier car than your mustang. I really liked my 69 428 CJ.
I have a 1969 Boss 302 original however I need to reassemble it I originally bought ARIES 10:1 forged pistons I believe 30 over . I might like to put it back together this summer with your fluid damper a 600 holley carb and maybe your electronic distributor .
Why would you build a 302. The heads were to big for a 351CLEVELAND. Stroke that thing. I never did own a Boss 302, but I was around them when they were new.I have had lots of 351C. From new ones to the aluminum headed one I have in my fairlane now.
I’m sorry guys but you somehow missed something there are boss 302’s out there cranking out way more than what you guys are claiming. Tell ya what ,leave the ford enginrs to the ford guys, and you keep playing with that some ole cookie cutter bowtie garbage you’re so used to. Evidently you’re research people are either misinformed, or just don’t really care about building anything ford. We’ve got 302 fords with gt40 3 bar heads making over 500 hp. I simply can’t believe this is all you’ve got. Perhaps you should do a YouTube search for Ford 302 boss vs 302 Chevrolet…perhaps it could wake you up on how much you DONT know about ford racing . Im extremely disappointed in this blog….. 10 years????? What? Building LS garbage? Junk ass Chevrolet stroker engines….puleeeeeze. I was building that garbage in 2nd grade.
I am presently installing a 302 clevor into a 83 mustang GT.
This engine was built in the 80’s by someone with way to much money. He stated he spent over $10,000 back then.
What I have found out so far, the engine runs.
The block is a 1980 302 Winsor.
The heads are Cleveland heads. I have not been able to specifically identify because the stamp on corner does not mach up with what it should be.
The intake is off a 1965 Shellby. That would probably have been the only intake available to work , at that time.
This 302 was in a F250 so I have to find the proper oil pan to fit the 83 foxbody, and proper fit for the oil dipstick entering the oil pan. No stick hole up top.
I’m trying to leave this pretty much as is, until I get a few good drives in. Then I’ll be looking for upgrades.
Any advice would be greatly appreciated.
Raced and owned quite a few Boss 302’s. We started FORD Drag Club at Horn-Williams Ford in Dallas,Tx. in 1969 with Doug Durham and me ,TED FORDMAN EHRHARDT who took a new Boss 302 short block apart and checked all specs. Plus we used cam dial-in and it was only off a half degree. Ford had and did a great job with Ford Motorsports programs which we were in . Also; I had Carroll Shelby/SAAC racing program in several other FORD dealerships . We got more than 450 HP on Ford’s dyno when we blew right rear tire and it took out Ford training board. No more dyno there. Our FDC has over 150 racing members and FORD promised us Hubert Platt’s Drag Mustang after series which disappeared. Bob Perkins(WI) located it and restored it to original shape and build special plexiglass trailer for it to display. Marvin Shaw built us some nice HP heads for our later 1989 Super Stock Mustang driven by Charlie Ford who set 1/8th mile record under 6 seconds in 89/90 . I have certificate for it. Still have lots of racing Boss and Hipo parts. Thanks to all who helped us get here.
I’ve had the same 1970 BOSS 302 for over 50 years. Technically, BOSS 302 is one of the trim levels of those Mustangs. The engine was a 302 HO or a 302 Special, but now every one calls the engine a BOSS 302. It is a very special engine with many advances over the standard 302 SBFs.
– The harmonic dampener is about 50% thicker for the wide-open-throttle jabs and the hard braking that occurs when racing at a road course.
– The flywheel was made with a high nodular iron content for running over 7,000 RPMs without grenading.
– The alternator pulley is twice the size (like a 289 HiPo) to reduce its RPMs when the engine is spinning at 7,000 RPMs.
– The water pump uses a better impeller which uses 17 less horse power than the regular water pumps.
– The rods are forged steel and are the same as the 289-HiPo but the BOSS used better rod bolts.
– The heads were better than any other small block, and the ’69 heads used larger valves than a 427 BB Chevy.
– The block is stronger and it has casting plugs instead of freeze plugs, so drain the block in cold climates.
– The 3 center main caps have 4 bolts instead of 2and the crank shaft is forged steel.
– The radiator, brakes, U-joints, bearings, are the same ones used in the 428 CJ cars.
– The rear end is a 9-inch Nodular Iron (N) housing. Mine also has a 1965 “Daytona” pinion support with the large bearings, but I’m not sure if all BOSSes came with that pinion support.
– The front and rear springs are much stiffer than a regular Mustang: 420 lbs/in at the front instead of 240 lbs, and 250 lbs/in at the rear instead of 150 lbs.
– The fenders lips are rolled for the bigger 15 inch wheels and tires.
– This is a little known fact; the US-DOT allowed manufacturers to use thinner sheet metal in 1970, so the 1970 BOSSes are about 300 lbs lighter than the ’69 BOSSes. Mine weighed 3032 lbs from the factory.
– The engines do use the Cleveland “sled” style rocker arms with a 1.73:1 ratio.
– I love the exhaust note of all three BOSSes. They must use the same mufflers.
– And I love the manual choke.
– The original TRW forged aluminum piston skirts would crack. Use a modern racing piston instead.
– Although dual-point distributors reduce point bounce, they don’t eliminate it. Use an electronic distributor.
– Valve spring seats were hardened cast iron for ’69 and stamped steel for ’70, but they won’t hold up over 7,000 RPMs.
– The cast iron exhaust manifolds are OK for 6,000 RPMs, so switch to Hooker Headers if you want to go faster.
– Disconnect (but don’t throw away) the electronic RPM limiter because it stretches the dwell above 6,250 RPMs.
– The manual choke because I often forget it.
I used a DuraSpark II ignition module and distributor which would keep the dwell at exactly 34 degrees, and I used a 40,000 volt coil. That engine would spin all the way to 9,000 RPMs with NO point bounce. I used a Ford 289-HiPo cam and solid lifters which greatly improved the throttle response. I set the valve lash at 0.022 ” instead of 0.025″ and I gaped the plugs at 0.025″ instead of 0.035″ so there were NO miss-fires. I jetted the Holley two sizes up in the primaries and 1 size up in the secondaries. I always figured that Autolite intended for people to index the spark plugs because they sold 10 plugs in a box, which is perfect amount the for indexing.
The first time out it ran 12.28s at 98 mph. At the end of the season it was running 12:00 sec. flat in the quarter.
– After driving a Fox body with the T-5 tranny, the BOSS’s T&C Top Loader 4-spd seems like the shifter linkage has fallen off because it is so easy and smooth to shift.
– 9,000 RPMs will crack the cast iron spring seats and flatten out the stamped steel spring seats. Keep it under 7,000 or use titanium spring seats.
– At the stock compression ration of 10.5:1, spark plugs will only last 6 weeks of city driving.
– When you change the plugs, go ahead and adjust the valve lash because it will be a little bit loose.
– Don’t use the vacuum advance diaphragm. Set the mechanical advance for 20 degrees to come in before 2,500 RPMs. Set the initial timing at 16 degrees BTDC. The total advance should be 36 degrees by 2,500 RPMs. This is because of the compression ratio. Higher compression ratios require far less total advance.
– Although the oil pan is the same as a regular 302W, the BOSS dip stick is shorter (and chromed) so the engine takes about two extra quarts of (7 instead of 5) to show it’s full. That’s OK because there is a windage tray which prevents the crank shaft from frothing up the oil.
– The BOSS 302 suspension was designed for “bias belted” tires, not “radial belted” tires. If you want to improve your road course lap times, switch to “bias belted” tires OR tune your suspension for the radial tires.
– The original Holley 780 CFM carbs are OK, but the Autolite 4100 is superior because it atomizes the fuel better and it doesn’t leak externally like the Holley does.
– The Autolite power valve does leak internally after a shot time, but, you can replace it with a Holley power valve because it has the same threads and the Holley power valve is made to resist the effects of ethanol. I’ve been using a Holley power valve in the Autolite carb for 3 years now with no internal leaks.
Symptoms of a leaking power valve:
– hard to start when cold because the carb is actually flooded,
– stalling when you come to a stop,
– rough idle,
– Very poor fuel economy.
The BOSS 302s are hot and noisy and stiff, and a lot of fun to drive.
Lots of great information. I just received delivery of my first Boss 302 today. Wanted one all my life. Your comment answered my question about the oil level as I changed oil tonight. Wondered why it did not come up to the full line at 5 quarts.