Overated BOSS Mustangs?

Sac68 · 02-20-2001, 01:25 AM

Everything I read and everyone I talk to says that the BOSS Mustangs, particularly the BOSS 429, were the pinacle of vintage Mustang performance.

Upon discovering some numbers in a recently purchased book, it seems that the 428 SCJ Mach 1 and the GT500 both outperform any of the Boss Mustangs acclelartion wise. The fastest BOSS (according to the book MUSTANG, 35th ANNIVERSARY) was the 351 which ran 5.8 seconds 0-60 and the 1/4 mile in 14.1. Meanwhile, the 428 Mach ran 5.5 0-60 and the 1/4 in 14.0, and the 69 GT500 ran 0-60 in 5.5 and the 1/4 in 13.8. Furthermore the vaunted BOSS 429 was running 6.2 0-60 and 14.09...

Why then, are BOSS's considered by most people to be the "racers choice" of vintage 'Stangs? Just common misperception?

------------------
98 Mustang coupe 3.8L V6
87 Mustang GT hatchback 5.0L V8
87 Bronco XLT 4bbl 351W

My mom drives a 99 Mustang GT convertable.

DemonGT · 02-20-2001, 02:11 AM

i remember my dad telling me about how he wasted a 1970 Boss mustang cobra jet with his 1971 and a half Dodge Charger R/T with a 440 Magnum slap stick auto. gotta give those mopars credit...they had some b***s

------------------
1991 GT,T-5,air silencer removed,racing clutch(previous owner put in so dont know what kind),K&N air filter,Aiwa deck,power acoustic amp,2 12" pianeers,UPDATE: Just got my Mac long tube headers and Cat-back

Future Mods:3.73's,Pro 5.0,Shifter knob,FMS 9mm wires

mustangII460 · 02-20-2001, 02:17 AM

Without writing two pages on why, I will say this.
Ford did not put a cam in the motor.

lx mike · 02-20-2001, 06:41 AM

They had to detune it for the street, the Boss 429 engine was a racing engine and they had to have 500 made for street use so they could use it for stock car racing, they used smaller cam and small carb that choked that engine.

------------------
93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

dinomite · 02-20-2001, 08:05 AM

What separates a BOSS mustang from another one? Specifically, what is the difference between say a BOSS 302 and a normal one?

Try Me · 02-20-2001, 09:29 AM

It's all in the name.
"BOSS 302", it sounds pretty tough to me!

lyonsd · 02-20-2001, 10:11 AM

Change the carb, cam and exhaust in the Boss 429 and then tell me how slow it is.

FoxBuilder · 02-20-2001, 12:25 PM

I'm going with lyonsd on this one.

The difference between a normal 302 and a Boss302 is that a Boss302 is a much more stout casting, 4-bolt mains, and Cleveland heads (big ports), and screw-in freeze plugs.

------------------
1984 Mustang Top Fueler with Flowmaster's

[This message has been edited by FoxBuilder (edited 02-20-2001).]

Jaydee · 02-20-2001, 03:55 PM

lx mike is correct that the Boss 429 motors were detuned big time for the street, as the corporate mission for these cars was not to make them street terrors but to get enough of the motors built to satisfy the homologation requirement so that Ford could go nascar racing. The carb was changed to a smallish (for this engine)735 cfm Holly, the exhaust manifolds were very restrictive and a lot of the earlier cars had very mild hydraulic cams - later cars got a more aggressive soild lifter cam which routinely whacked a half second off of the ET's. The thermactor emissions system used by Ford was also not well suited to these motors. The 14.09 et you quoted was from a 1969 issue of car life magazine and this car had a trap speed of 103 mph (the solid lifter cars ran as fast as 107 mph), which is more than enough for a low to mid 13's - also, remember that these times were run on small (F-60-15) hard compound bias ply tires. With a decent cam, headers and tires this beast would wake up big time.

------------------
1965 K code coupe - numbers matching - restoration ongoing. 1987 LX notch, stock heads and intake, 3.55's and typical bolt on's 13.89@100.25

Unit 5302 · 02-20-2001, 04:19 PM

All BOSS Mustang's featured Semi-Hemispherical head designs. I believe that is where the Boss designation originates from.

The 302, 351C, and the 429SCJ were the motors offered in the Boss cars.

The Boss 302 was not a drag car in stock form. It was a Trans Am series racer, and it kicked the **** out of everything else on the track. They were conservatively rated at 290bhp (a joke). In reality those motors put out damn close to 400bhp stock. Not to mention you could get much more than that out of them pretty easy. They need gears, and they need hook. Due to the 2.21" intake valves on '69 models, and 2.19" valves on 70's they developed little power until after 4000rpm.

The Boss 351 is probably the least known of the Boss cars. The 351C Mach 1 came with the same motor as the Boss, it ripped off a 0-60 in 5.6, 1/4mile in 13.80@106mph according to Car Craft (I believe). The 351C is a monsterous motor. The early blocks can take 800hp from what I've read, and stock, I'd expect significantly beyond the 302's 400bhp. It was rated humerously at 335bhp.

The Boss 429 had a 60/40 weight distribution. It'll smoke the tires at 60mph. I'm not talking spin. I'm talking smoke. Laughably rated at 375bhp, estimates I've seen place it in the area of 500+. With horrible weight distribution because of the motor size, they ran slow in the 1/4 because of lack of traction. The motor was actually so huge they had to place the battery in the trunk. The heads alone weigh 120 lbs each. According to a couple articles I've read with an optional traction bar and full slicks they run 12's. Stock. Even though people may claim the cam hurt 'em, they didn't need any more power. They need more traction. I'm also pretty sure they came with a 780cfm carb.

Hethj7 · 02-20-2001, 08:55 PM

I think there is a Ford encyclopedia in Unit's head...he always has the info we are looking for!

mustang145 · 02-20-2001, 11:19 PM

Quote:

Originally posted by dinomite:
What separates a BOSS mustang from another one? Specifically, what is the difference between say a BOSS 302 and a normal one?

the motor is a high output motor bigger cam .
every thing else is the same other then decal

Mach 1 · 02-21-2001, 02:15 AM

It would be a better encyclopedia if the information was correct.

The only Boss with semi heads was the Boss 429. And there was never any Boss 351. There was Boss 302 and Boss 429 and only for two years, 69 and 70. The Mach 1 with the 351 was just that, a Mach 1, not a "boss"

------------------
1993 GT/AOD
'93 Mustang GT

69fastback · 02-21-2001, 05:59 AM

Not to sound like a dick but Wow this whole thing is really messed up.
This is the way it is and if u don't belive me look it up and prove me wrong.
69-70 boss 302 and 429 that is it.
71 boss 351 those are the only boss motors.

The boss is not a 351 clevland they are two toatly different motors. A boss 429 also has nothing to do with a 429scj they are also two totally differnt motors.

boss motors are semi hemi heads that is what makes them a boss. clevleands and cobra jets are not even close

------------------
69 428 cobra jet: tons of mods.
97 f-150 5.4 xlt mark III
BUCKLE UP. SUCK IT IN.
Objects in the mirror are about to disappear...
QUICKLY!!!!!!

lx mike · 02-21-2001, 09:10 AM

here's a site on boss 351 info.
http://www.boss351.org/

------------------
93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

Unit 5302 · 02-21-2001, 09:10 AM

Okay, so if the 302 and 351C were not semi-hemispherical you wouldn't mind telling me how they got 2.23" and 2.19" intake valves would you? Oh **** ! You can't. Why? You don't have any room on a 4" bore for 2.19" or 2.23" intake valve. You do the math. 2.19" is the same size used on the 427 (2.23" on the tunnel port), which had a much larger bore than the 4" used by the 302 and 351. The 427 had a 4.23" bore. The Boss 302 used 2.23" in 1969, 2.19" in 1970. The 351C used 2.19" on the 4V apps.

As far as the hotter cam, that is totally BS. They were totally different motors, except for the 351C.

I will admit I'm semi unfamiliar with the Boss 351; however, the other two I'm solid on. It's not like I've never read anything on them, thanks. However, I would like to point out that the Cleveland is semi-hemi, thank you very much. Again, can't fit 2.19" intake on a 4" bore, which is what comes on the 4V Cleveland heads. Damn, read your specs again!

The SCJ was a designation given to a engine, like the 428CJ or Boss 429 based on the internals. I believe forged crank had something to do with it. The Boss 429 motor had an SCJ designation from what I've read.

Please, if you don't at least have a somewhat solid base, keep your BS to yourself.

Jaydee · 02-21-2001, 09:31 AM

There is indeed a Boss 351. The car and the motor were built only in 1971 and only 1,806 were built. The Boss 351 was one of 5 versions of the Cleveland in 71. It used the same big valve heads that were used on the Boss 302, was factory rated at 330hp and the compression ratio was 11.7:1. Other features of this motor were forged pistons, forged crank, a solid lifter cam with special valve springs, 750cfm Autolite carb, dual point distributor, 1041-h forged steel rods, 4 bolt mains, oversized bearing caps and a factory aluminum intake. As far as the Boss 302, there are lots of differences between it and a "regular" 302. It used the big valve Cleveland heads, solid lifter cam with special valve springs, dual point distributor, 4 bolt mains with oversized bearing caps, 1041-h forged steel rods, forged aluminum pistons, and a 780 Holley on an aluminum intake. The vin on these cars carried a G indicating the unique Boss engine. Both cars used a rev limiter which randomly cut out one cylinder at 6150 rpm. BTW, this info comes from the best source I could find, 2 guys in my club who own an original Boss 302 and an original Boss 351 who let me copy some of the reference material they have collected on their cars.

------------------
1965 K code coupe - numbers matching - restoration ongoing. 1987 LX notch, stock heads and intake, 3.55's and typical bolt on's 13.89@100.25

Mach 1 · 02-21-2001, 11:34 AM

The boss 302 had cleveland style heads. If you consider these hemi heads, more power to you. Let me know when you hear the pop. They had "canted valves" thus allowing more room for the large valves.

Im not sure about the boss 351, maybe there was some version of this out there, but it is not as well known as the 302 and 429.

Unit - chill out man. Cant you have an intelligent debate without whining like a baby? And you cant believe everything you read.

------------------
1993 GT/AOD
'93 Mustang GT

[This message has been edited by Mach 1 (edited 02-21-2001).]

[This message has been edited by Mach 1 (edited 02-21-2001).]

Unit 5302 · 02-21-2001, 01:15 PM

I'm not whining at all. I merely targeting posts that say I'm full of BS when the posters appearently have no idea what they are talking about.

Did I not say "semi-hemi"? That's what canted valves are considered in head design. None of the Boss motors was a full "hemi", they were all "semi-hemi". You can try some half *** tail between your legs "sniff sniff... well you said it was a hemi, and it's not, it only had canted valves" BS retreat if you want

, but the info I gave, other than my hp being off by 5, the Boss 351 was rated at 330hp, not 335 was accurate.

Hehe, not that I didn't figure another little insult war wouldn't surface between you and me eventually.

Now let's see, what was I right about, and what were you wrong about?

#1 All Boss Mustangs had semi-hemi heads
#2 There is a Boss 351.
#3 I never said the Mach 1 was a Boss 351, just that the Boss 351 used the same engine as the Mach 1, with a little different tune of course. (I can accept that information being misinterpreted.)

Sac68 · 02-21-2001, 04:33 PM

Good grief, an innocent question asked by me and look what ensues...anyways, thanks for all the info.

Basically what I've learned is that the BOSS's, specifically the 429, were cars that needed a little wakening up to be STRONG performers and drag strip terrors, because they were detuned race engines.

Thanks again.

------------------
98 Mustang coupe 3.8L V6
87 Mustang GT hatchback 5.0L V8
87 Bronco XLT 4bbl 351W

My mom drives a 99 Mustang GT convertable.

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02-20-2001, 01:25 AM	#1
Sac68 Registered Member Join Date: Feb 2000 Location: Pgh, PA USA Posts: 281	Overated BOSS Mustangs? Everything I read and everyone I talk to says that the BOSS Mustangs, particularly the BOSS 429, were the pinacle of vintage Mustang performance. Upon discovering some numbers in a recently purchased book, it seems that the 428 SCJ Mach 1 and the GT500 both outperform any of the Boss Mustangs acclelartion wise. The fastest BOSS (according to the book MUSTANG, 35th ANNIVERSARY) was the 351 which ran 5.8 seconds 0-60 and the 1/4 mile in 14.1. Meanwhile, the 428 Mach ran 5.5 0-60 and the 1/4 in 14.0, and the 69 GT500 ran 0-60 in 5.5 and the 1/4 in 13.8. Furthermore the vaunted BOSS 429 was running 6.2 0-60 and 14.09... Why then, are BOSS's considered by most people to be the "racers choice" of vintage 'Stangs? Just common misperception? ------------------ 98 Mustang coupe 3.8L V6 87 Mustang GT hatchback 5.0L V8 87 Bronco XLT 4bbl 351W My mom drives a 99 Mustang GT convertable.

02-20-2001, 02:11 AM	#2
DemonGT Registered Member Join Date: Aug 2000 Location: Wisconsin Posts: 879	i remember my dad telling me about how he wasted a 1970 Boss mustang cobra jet with his 1971 and a half Dodge Charger R/T with a 440 Magnum slap stick auto. gotta give those mopars credit...they had some b***s ------------------ 1991 GT,T-5,air silencer removed,racing clutch(previous owner put in so dont know what kind),K&N air filter,Aiwa deck,power acoustic amp,2 12" pianeers,UPDATE: Just got my Mac long tube headers and Cat-back Future Mods:3.73's,Pro 5.0,Shifter knob,FMS 9mm wires

02-20-2001, 02:17 AM	#3
mustangII460 Factoy Five Roadster Join Date: May 2000 Location: Sevier Co,Tennessee Posts: 1,681	Without writing two pages on why, I will say this. Ford did not put a cam in the motor.

02-20-2001, 06:41 AM	#4
lx mike Undescribable Join Date: Sep 1998 Location: Ft Myers Fla Posts: 1,539	They had to detune it for the street, the Boss 429 engine was a racing engine and they had to have 500 made for street use so they could use it for stock car racing, they used smaller cam and small carb that choked that engine. ------------------ 93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

02-20-2001, 08:05 AM	#5
dinomite The Dude Join Date: Feb 2001 Location: Arlington, VA Posts: 1,262	What separates a BOSS mustang from another one? Specifically, what is the difference between say a BOSS 302 and a normal one?

02-20-2001, 09:29 AM	#6
Try Me Registered Member Join Date: Jul 2000 Location: Ottawa, Ontario, Canada Posts: 465	It's all in the name. "BOSS 302", it sounds pretty tough to me!

02-20-2001, 10:11 AM	#7
lyonsd Registered Member Join Date: Dec 1999 Location: Flowery Branch, GA Posts: 236	Change the carb, cam and exhaust in the Boss 429 and then tell me how slow it is.

02-20-2001, 12:25 PM	#8
FoxBuilder Registered Member Join Date: Sep 1999 Location: Columbus, Ohio Posts: 233	I'm going with lyonsd on this one. The difference between a normal 302 and a Boss302 is that a Boss302 is a much more stout casting, 4-bolt mains, and Cleveland heads (big ports), and screw-in freeze plugs. ------------------ 1984 Mustang Top Fueler with Flowmaster's [This message has been edited by FoxBuilder (edited 02-20-2001).]

02-20-2001, 03:55 PM	#9
Jaydee Registered Member Join Date: Sep 2000 Location: Conn. Posts: 220	lx mike is correct that the Boss 429 motors were detuned big time for the street, as the corporate mission for these cars was not to make them street terrors but to get enough of the motors built to satisfy the homologation requirement so that Ford could go nascar racing. The carb was changed to a smallish (for this engine)735 cfm Holly, the exhaust manifolds were very restrictive and a lot of the earlier cars had very mild hydraulic cams - later cars got a more aggressive soild lifter cam which routinely whacked a half second off of the ET's. The thermactor emissions system used by Ford was also not well suited to these motors. The 14.09 et you quoted was from a 1969 issue of car life magazine and this car had a trap speed of 103 mph (the solid lifter cars ran as fast as 107 mph), which is more than enough for a low to mid 13's - also, remember that these times were run on small (F-60-15) hard compound bias ply tires. With a decent cam, headers and tires this beast would wake up big time. ------------------ 1965 K code coupe - numbers matching - restoration ongoing. 1987 LX notch, stock heads and intake, 3.55's and typical bolt on's 13.89@100.25

02-20-2001, 04:19 PM	#10
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	All BOSS Mustang's featured Semi-Hemispherical head designs. I believe that is where the Boss designation originates from. The 302, 351C, and the 429SCJ were the motors offered in the Boss cars. The Boss 302 was not a drag car in stock form. It was a Trans Am series racer, and it kicked the **** out of everything else on the track. They were conservatively rated at 290bhp (a joke). In reality those motors put out damn close to 400bhp stock. Not to mention you could get much more than that out of them pretty easy. They need gears, and they need hook. Due to the 2.21" intake valves on '69 models, and 2.19" valves on 70's they developed little power until after 4000rpm. The Boss 351 is probably the least known of the Boss cars. The 351C Mach 1 came with the same motor as the Boss, it ripped off a 0-60 in 5.6, 1/4mile in 13.80@106mph according to Car Craft (I believe). The 351C is a monsterous motor. The early blocks can take 800hp from what I've read, and stock, I'd expect significantly beyond the 302's 400bhp. It was rated humerously at 335bhp. The Boss 429 had a 60/40 weight distribution. It'll smoke the tires at 60mph. I'm not talking spin. I'm talking smoke. Laughably rated at 375bhp, estimates I've seen place it in the area of 500+. With horrible weight distribution because of the motor size, they ran slow in the 1/4 because of lack of traction. The motor was actually so huge they had to place the battery in the trunk. The heads alone weigh 120 lbs each. According to a couple articles I've read with an optional traction bar and full slicks they run 12's. Stock. Even though people may claim the cam hurt 'em, they didn't need any more power. They need more traction. I'm also pretty sure they came with a 780cfm carb.

02-20-2001, 08:55 PM	#11
Hethj7 Mizzou Tigers Join Date: Apr 1999 Location: weston, MO United States Posts: 1,455	I think there is a Ford encyclopedia in Unit's head...he always has the info we are looking for!

02-21-2001, 02:15 AM	#13
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	It would be a better encyclopedia if the information was correct. The only Boss with semi heads was the Boss 429. And there was never any Boss 351. There was Boss 302 and Boss 429 and only for two years, 69 and 70. The Mach 1 with the 351 was just that, a Mach 1, not a "boss" ------------------ 1993 GT/AOD '93 Mustang GT

02-21-2001, 05:59 AM	#14
69fastback IRAQ VET Join Date: Feb 2000 Location: high desert California Posts: 1,480	Not to sound like a dick but Wow this whole thing is really messed up. This is the way it is and if u don't belive me look it up and prove me wrong. 69-70 boss 302 and 429 that is it. 71 boss 351 those are the only boss motors. The boss is not a 351 clevland they are two toatly different motors. A boss 429 also has nothing to do with a 429scj they are also two totally differnt motors. boss motors are semi hemi heads that is what makes them a boss. clevleands and cobra jets are not even close ------------------ 69 428 cobra jet: tons of mods. 97 f-150 5.4 xlt mark III BUCKLE UP. SUCK IT IN. Objects in the mirror are about to disappear... QUICKLY!!!!!!

02-21-2001, 09:10 AM	#15
lx mike Undescribable Join Date: Sep 1998 Location: Ft Myers Fla Posts: 1,539	here's a site on boss 351 info. http://www.boss351.org/ ------------------ 93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

02-21-2001, 09:31 AM	#17
Jaydee Registered Member Join Date: Sep 2000 Location: Conn. Posts: 220	There is indeed a Boss 351. The car and the motor were built only in 1971 and only 1,806 were built. The Boss 351 was one of 5 versions of the Cleveland in 71. It used the same big valve heads that were used on the Boss 302, was factory rated at 330hp and the compression ratio was 11.7:1. Other features of this motor were forged pistons, forged crank, a solid lifter cam with special valve springs, 750cfm Autolite carb, dual point distributor, 1041-h forged steel rods, 4 bolt mains, oversized bearing caps and a factory aluminum intake. As far as the Boss 302, there are lots of differences between it and a "regular" 302. It used the big valve Cleveland heads, solid lifter cam with special valve springs, dual point distributor, 4 bolt mains with oversized bearing caps, 1041-h forged steel rods, forged aluminum pistons, and a 780 Holley on an aluminum intake. The vin on these cars carried a G indicating the unique Boss engine. Both cars used a rev limiter which randomly cut out one cylinder at 6150 rpm. BTW, this info comes from the best source I could find, 2 guys in my club who own an original Boss 302 and an original Boss 351 who let me copy some of the reference material they have collected on their cars. ------------------ 1965 K code coupe - numbers matching - restoration ongoing. 1987 LX notch, stock heads and intake, 3.55's and typical bolt on's 13.89@100.25

02-21-2001, 11:34 AM	#18
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	The boss 302 had cleveland style heads. If you consider these hemi heads, more power to you. Let me know when you hear the pop. They had "canted valves" thus allowing more room for the large valves. Im not sure about the boss 351, maybe there was some version of this out there, but it is not as well known as the 302 and 429. Unit - chill out man. Cant you have an intelligent debate without whining like a baby? And you cant believe everything you read. ------------------ 1993 GT/AOD '93 Mustang GT [This message has been edited by Mach 1 (edited 02-21-2001).] [This message has been edited by Mach 1 (edited 02-21-2001).]

02-21-2001, 01:15 PM	#19
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	I'm not whining at all. I merely targeting posts that say I'm full of BS when the posters appearently have no idea what they are talking about. Did I not say "semi-hemi"? That's what canted valves are considered in head design. None of the Boss motors was a full "hemi", they were all "semi-hemi". You can try some half *** tail between your legs "sniff sniff... well you said it was a hemi, and it's not, it only had canted valves" BS retreat if you want , but the info I gave, other than my hp being off by 5, the Boss 351 was rated at 330hp, not 335 was accurate. Hehe, not that I didn't figure another little insult war wouldn't surface between you and me eventually. Now let's see, what was I right about, and what were you wrong about? #1 All Boss Mustangs had semi-hemi heads #2 There is a Boss 351. #3 I never said the Mach 1 was a Boss 351, just that the Boss 351 used the same engine as the Mach 1, with a little different tune of course. (I can accept that information being misinterpreted.)

02-21-2001, 04:33 PM	#20
Sac68 Registered Member Join Date: Feb 2000 Location: Pgh, PA USA Posts: 281	Good grief, an innocent question asked by me and look what ensues...anyways, thanks for all the info. Basically what I've learned is that the BOSS's, specifically the 429, were cars that needed a little wakening up to be STRONG performers and drag strip terrors, because they were detuned race engines. Thanks again. ------------------ 98 Mustang coupe 3.8L V6 87 Mustang GT hatchback 5.0L V8 87 Bronco XLT 4bbl 351W My mom drives a 99 Mustang GT convertable.