69 FB 351w to 428 conversion tech questions

[Seandavis333]

Say guys, I bought a 69 fastback that was a 351w originally and have decided to replace it with a 428. My research so far indicates that I have to replace the sway bar with at least 1 to 1 1\8 inch one, heavier coil springs, an export brace, reinforcement plates welded in, a 428 transmission brace, larger radiator. I am running easel rock heads so they clear the shock towers and an aluminium intake for weight. Any advice or input welcome. The car will be a weekend cruiser not used for racing. I also am using a top loader 4 speed with the small spline...will it hold up to the engine? Thanks, sean

[jayb]

I don't think you need to do all of that stuff.  I have a 68 fastback, originally a 302 car, and I'm just plunking in the 428.  Not all FE Mustangs had the  shock tower reinforcement plates, the 68s didn't as far as I know.  The big swaybar and export brace are Shelby items; my 69 R Code Mach 1 didn't come with either of those.  You will definitely need the bigger radiator though.  Not sure what you mean by a 428 transmission brace; do you mean the trans mount?

I think whether the small input toploader will hold up will depend on which one it is.  I ran a 351C toploader with the small input shaft behind a 428CJ for many years with success, but I broke a 289 toploader in about 5 miles with the same engine.  As long as you aren't running slicks, I don't think that the small input shaft itself will be the problem, but other internal toploader parts might be...

[ScotiaFE]

Not sure why Jay's TL failed? Info Jay?

But if you have a small in small out wide ratio TL and using street tires that can fit in the stock wheel wells
you are pretty safe you won't grenade it if it is in good shape.
You will need the proper tail shaft to line up with the hole in the floor.
The trans mount is an easy fab.

Now as for a full upgrade to FE from small blk.
I would get the export brace for street action.
The Addco front sway bar and rear bar are really nice upgrades.
You will need a new driveshaft.
Well the engine is out do the Shelby drop on the a arms and put in the cam locks on the lower bolts.
Springs will be hit or miss.
Full up grade on the fuel line from tank to carb. 3/8" min.
There are LOTS of little things that you will come across as you do the swap.
Sure they came from the factory like that, but you're doing in the shed almost 50 years since the day.
It is a very satisfying swap though.
I've done it a few times over the past 40 years.

You have just about finished when there is not one stock part or bolt left in the drive train.

[jayb]

On further reflection, I'm going to amend my original post to say that the 289 trans only lasted about 200 yards LOL!  Here's what happened.  When I first bought my 68 Shelby convertible (1978!), it had a 428CJ from a 69 Torino, but no transmission or exhaust.  The guy I bought it from had an old toploader sitting there, and I had heard what good transmissions they were, so I bought that too.  Installed the bellhousing, trans, headers and exhaust over a period of a couple months (as I could afford it).  I did the work where the car was sitting because I had not fully paid for it yet, but the guy I bought it from was a Shelby racer, and very understanding of a kid like me, so he let me continue to pay for the car while I worked on it.  Once I had the car all together, I confess I was a little nervous about driving it, so the seller agreed to take it for its first cruise with me in the passenger seat.  We got out of the driveway, and about 100 yards down the road when he hit the 2-3 shift.  Suddenly, the car stopped accelerating despite the fact that the engine was running, and we coasted to the side of the road.  We were both trying to figure out what had happened, when the seller looked down through the shifter hole (I had not yet installed the boot), and said, "There's your problem, you have a hole in the transmission!".  Sure enough, the tailshaft housing had a hole in it; the output shaft of the transmission had sheared and grenaded through the tailshaft housing.

We pushed the car back to the shop, and if I recall correctly I bought a different toploader from the seller, that had come out of a 351C car.  It needed a different transmission yoke, because the output shaft was bigger on the 351C transmission.  Think I had to cut and re-balance the driveshaft too, because the transmission was longer.  But that transmission lasted as long as I used it, before I eventually replaced it with a Doug Nash 5 speed in 1982. 

That's my toploader story, and I'm sticking to it 

[bn69stang]

Diddo on what Jay and Howie said , you would nt hook the car hard enough with street tires to hurt  the top loader , and as far as shock towers go i have nt done anything to mine , mine are small block towers but i run a export brace . If i were you i would also put sub frame connectors on to limit twisting and flexing , a 1 inch sway bar at least and remember with alum heads , intake , water pump , headers your 428 will have the weight of a small block . and if you use the stock cross over shaft , you will have to move the frame side mount to the rear a bit , and you will need a clutch fork for a 67-69 390 mustang .. Happy converting Bud

[Nightmist66]

I'll agree also with the toploader. I like them. We have abused the small in/out toploaders for some time without any major problems. This includes hard launches at the track with slicks in a 37-3800lb car. Even with a solid hub clutch. I plan on running mine pretty hard at the track this year, but my car only makes a little over 400hp probably(for now). I'll see if I can find another weak link in the driveline, I've already found a couple.

[cjshaker]

Plus 7, or is it 8, on the small input toploader being up to the task for street duty. 390's came with small inputs from the factory. And I'd agree on the export brace also, but I think you'd be fine on the street without subframe connectors. My car's been fine without them for over 30 years, although I may be putting some on this year to have some strip fun with it.

I'd have to disagree on the no tower braces though. Over the years, I've seen several small blocks that ripped the center out from the tower. Ford used those braces for a reason (they even became standard in '70)...they knew it was an area prone to stress fracture. Especially when there were just a dozen or so heavy spotwelds holding all the braces together. If you didn't use them, I'd at least weld those braces up, including the outer "wing" to the tower itself. That will tie everything together and at least help.

I had a 351 Mach 1 many years ago. I ran it with a 351 for about a year before I just had to yank it out and put in a 390. That smallblock  just didn't cut it.

[Seandavis333]

I have a choice between a 72 428 with an A casting or a 68 428 with a C casting on block rear. The guys says it's a cobra jet motor but I have not measures it yet. Will both fit and is there a preference?

[TorinoBP88]

Get the one with the stock bore, if you can.  Don't over pay, they are prob both fine. I'd take the 72 if it were me.

You can cut 1/2 or one coil off the 302 springs in the suspension in front to rake car and make it 10% stiffer, or not.  Some small block sway bars may hit the oil filter, but you can use a half size filter if you don't want to change the sway bar.

I got a nice 3/4" bar for $100 from Verginia Classics. I think you need motor plated.  You can drill the holes in the perches 3/4 up to lower them.  If you have an mx trans it may work with a TL.  If you have a small in out TL trans, run it.

I also put on a manual adapter on the steering to delete the power junk.  If you keep poise and use headers instead of manifolds, you may need to put a drop bracket on the power ram.  Some valve covers hit some power break boosters.