Boss 429 motor swap

automart · Jan 25, 2007

I may have the oportunity to purchase a used boss 429. It was used in an alcohol funny car back in the day. The car i currently own is a 70 Mach I with 351C 4speed.

Does anyone know if this is a bolt in motor? I know the springs, shocks, etc will have to be changed. My current transmission is the small spline (28 I think) 4 speed toploader.

If it does come available I want to be able to jump on it if it will work in my car. If not, well, what is a complete motor worth?

Thanks,

Ronnie

amorrow · Jan 25, 2007

A swap will require modifications to the car itself, specifically the shock towers. Boss 429s had unique shock towers to accommodate the wider engine.

Wrt the engine's value, it depends how complete and original the engine is. Also, I know there were several variations of the semi-hemis. Maybe someone with more knowledge can chime in. Another good place to check would be www.boss302.com...this site has a Boss 429-specific forum (http://www.boss302.com/board/forumdisplay.php3?FID=12).

ratio411 · Jan 25, 2007

Yeah, you would need to do some pretty major surgery to your car.
Not a bolt in.
Your tranny will not work either.
The big engines used the big shaft toploaders and a fairly hard to find (nowadays) bellhousing.
Good luck
Dave

brianj5600 · Jan 26, 2007

Back in the day? Early 70s or mid 80s? Two different animals.

zookeeper · Jan 26, 2007

If it were me, I'd simply do a Mustang II front suspension swap to eliminate the towers and that motor will fit right in with room to spare. No, it won't look like an original Boss 429, but it will be better in every way. BTW, what's a motor like that going for? I've seen them on ebay for between $20K and $30K.

Pbum5 · Jan 26, 2007

Your Mach 1 sounds like a nice car w a 4spd and 351C.

I would leave that alone.

If you can get a deal on that BOSS 429 get another car for it and make it a clone. A real one just sold for $489,500 at BJ. OR build a killer street car with the MII front and the rest of the body mods to handle the power. As you know it won’t be cheap but what a motor to start with.

The stock versions were not as fast as people think. They had great potential but were detuned and had smog crap on them. Build it up and let that motor breath.

68RCodeConv · Jan 26, 2007

automart said:
It was used in an alcohol funny car back in the day.

That motor is going to be so radical that it will be useless for the street. And you will find that the parts you need to make it streetable (cam, valve springs, intake) are very, very expensive. And it probably has a 13:1 compression ratio that will require aviation fuel if converted to gasoline.

Anything that is Boss 429 specific is expensive.

As to the value, it depends on how heavily the Boss 429 parts (like the heads) were modified. A reasonable complete stock Boss 429 motor (block, heads, valve covers, intake, exhaust manifolds) with a rebuildable block would probably be worth about $10-15K. That is not a typo.

Hack · Jan 26, 2007

zookeeper said:
If it were me, I'd simply do a Mustang II front suspension swap to eliminate the towers and that motor will fit right in with room to spare. No, it won't look like an original Boss 429, but it will be better in every way. BTW, what's a motor like that going for? I've seen them on ebay for between $20K and $30K.

Better in every way?

I strongly disagree and I think you'll find a good percentage of others do, too. I really dislike the MII front suspension. It is decent for show cars that are rarely driven around corners/babied or cheap 4 cylinder cars from the late 70s, though.

BlueBossS197 · Jan 26, 2007

The shock towers shouldn't be a problem. The way Kar-Kraft got the motor to fit was with a hammer to the original shock towers. Kinda screwy to me.

automart · Jan 26, 2007

Thanks, I sure didn't know that it wasn't a bolt in. I haven't even finished restoration when I found a old friend who has one. As I said, he used it in an alcohol funny car. I don't know what parts he has. I don't really want to pursue the engine until I know for sure what I want to do.
I'm thinking around 5k for the complete engine, I'll let you know what happens.

zookeeper · Jan 26, 2007

If you find a saveable Boss 429 for $5K, you better jump on it.

zookeeper · Jan 26, 2007

BlueBossS197 said:
The shock towers shouldn't be a problem. The way Kar-Kraft got the motor to fit was with a hammer to the original shock towers. Kinda screwy to me.

I always thought they moved the entire tower outward, and notched it to boot. Where'd you hear they just beat on them?

Sicarius428 · Jan 26, 2007

Supposidly Kar Kraft moved each shock tower out by hand an inch... Not sure what that entails.
kevin

65up2d8 · Jan 26, 2007

I'm somewhat with Blueboss S197 in that I've also read that they only "massaged" the shock towers with a BFH, but I can't recall my sources at this time. However, I've also read articles that made it sound like Karcraft recreated the wheel to make it work. The truth would be interesting if anyone on here truly knows it.

brianj5600 · Jan 26, 2007

I think it is an Alan Root motor. Heck, leave the blower on it and all, JK. If it is an AR Boss, I don't know if it is dimensionally the same as the factory B429. I have a BFH if you need it. I'm just down the road. All aluminum hemi would be about as cool as it gets.

fvike · Jan 27, 2007

I say do it! If I could get my hands on a Boss 429 engine, my 351W wouldn't last a second before I ripped it out of there! The shock towers can be moved, and reinforced. They are e big part of the front ends strength, so I wouldn't cut them away for a MII setup. Then you would have no place to put the Export brace, which by the way is also Boss 429 spesific. I'm not sure if a Monte Carlo bar will fit over the engine.

GNN60GT500 · Jan 27, 2007

I say save the motor and buy a plain fast back and turn the fast back into a bOSS 429 clone-

bnickel · Jan 27, 2007

Kar Kraft completely removed the stock mustang shock towers and replaced them with a different tower, either stamped specifically for the boss or robbed from another car, like maybe an earlier Fairlane. the factory mustang towers were not used and would require an extreme amount of fabrication to make them work.

alternatively to using a 69/70 mustang you could use a 71-73 mustang or a 68-71 torino/fairlane since the motor should fit with very little if any modifications to the shock towers. the 71 mustang was designed to fit the boss '9 with no mods and is based on the torino/fairlane architecture, the engine bay was changed very little from it's original configuration in the torino, so therefore the boss motor should be a virtual bolt-in into the torino/fairlane as well.

i've been wanting to a mod motor swap into a big body stang vert for quite a while now and i think it will fit just fine by only making motor mounts and no mods to the shock towers, especially if i use a SOHC or 3-valve motor.

ratio411 · Jan 27, 2007

Going by part numbers, the towers, spindles, and several other suspension related parts are unique to the Boss 429 cars.
They definately weren't hit with hammers!
If you have ever seen a concours or original car, you wouldn't say that for a minute.
See a Boss and non-Boss side by side and you will know they are totally different.
I don't know about using Torino parts exactly.
I do know that a 68 Torino/Fairlane uses the same spindles as a 69 Stang, as the 69 Torino uses 70-73 Stang spindles, and neither is Boss 429 correct.
So maybe the sheet metal is Fairlane/Torino, but weight bearing parts like spindles are not.
Dave

bnickel · Jan 27, 2007

ratio411 said:
Going by part numbers, the towers, spindles, and several other suspension related parts are unique to the Boss 429 cars.
They definately weren't hit with hammers!
If you have ever seen a concours or original car, you wouldn't say that for a minute.
See a Boss and non-Boss side by side and you will know they are totally different.
I don't know about using Torino parts exactly.
I do know that a 68 Torino/Fairlane uses the same spindles as a 69 Stang, as the 69 Torino uses 70-73 Stang spindles, and neither is Boss 429 correct.
So maybe the sheet metal is Fairlane/Torino, but weight bearing parts like spindles are not.
Dave

hey Dave, i was only talking about the big body stangs 71-73 using torino/fairlane sheet metal in the engine bay basically the entire unibody was based on the torino/fairlane architecture. none of that appplies to the boss '9. what i was saying about the 429 is that i think the shock towers were from an early fairlane, like a 65 or earlier, but still modified. guess i wasn't as clear as thought i was. anyway, i did read somewhere that the boss '9 towers were early fairlane units modified to work in the mustang with the boss 429 engine.

Boss 429 motor swap

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