I did this swap quite a few years ago.  If you already have a V8 in the car it's mostly painless and there is little extra weight (~50 lbs) that you will not notice at all.

The things that you need to worry about are swap headers (available from several good manufacturers), the T5 rear mount (also available from several good manufacturers) and the clutch setup.  A stock 4 row radiator should cool the engine just fine if you run a shroud and are not overbored more than .030.

I got my crossmember from Modern Driveline and it's perfect.  The one that Rosehill sells is also good but won't work if you have a convertible.  I've had the Hedman long-tube swap headers and they worked well but it was a major pain to get all the bolts into the head on the left (drivers) side.  I currently have the JBA shorties.  They're expensive but work well and have no issues so you get what you pay for.

The clutch is an area you will need to make a decision.  You can either get a cable clutch (Mustang Steve sells a kit) or alter your bellhousing and use the current bellcrank.  I bought and installed the cable clutch kit but wish I had not.  You have to cut new holes in your firewall and beat the crap out of the bottom of the cowl (which may be rusty and fragile) to make it fit.

Lastly, the T5 will require you to have your drive shaft shortened about an inch so you have adequate clearance between the transmission housing and the U-joint on the yoke.

About the only bad points of having the 351 are the reduced clearance between the engine and the shock towers (your alignment guy will hate you and it's a little harder to change spark plugs).  I've also found that the header being so close to the steering box will cause the grease inside the box to melt and leak out of the box, leaving you with little or no grease inside the box and very sloppy steering.  You might want to fab up a heat shield around the box if you keep the stock unit.

Last edited by John Ha (11/24/2015 6:37 AM)

Click on my web site address at bottom of my post to see my 351/393 stroker swap. I love it, fun to drive!

I had a 351W in my car for 17 years.  I used the long tube Hedman swap headers. (See my article on 351W buildup and on the FAQ page of my site).  I have since removed that engine and installed a 351W based 427 stroker.  This time I used the JBA shorty headers.  All the spark plug clearance issues went away.  I never had steering box issues with the 351 and hedman long tubes as John described, but I had rebuilt my box previously so maybe the gaskets and seals were in better shape.  The shorty headers are the way to go.  They will make your life SO MUCH BETTER whether you go with the 289/302/5.0 based engine OR the 351W engine.  I have never experienced any starter heat issues.  The hedmans and the JBAs give great access to the starter.  Back when I put the 351 in there, the hedmans were the only decent swap headers available.  Now there are much better choices.

The 351W does make it a royal pain to get to the upper control arm nuts when doing an alignment.  I trimmed a small amount off the shock tower humps so an open end wrench would have clearance to swing when I did the new engine.  I dealt with the hard-to-reach nuts on the old engine and it's not like you realign the car every week.. Not that big a deal.

If I was building just a normal driver type car, I would definitely go with a 5.0 roller block based engine and shorty headers, or more likely 289 HIPO manifolds.  You won't really notice the power difference on the street, if there is any difference.  What you WILL notice is ease of maintenance and easier spark plug access.

Pics show shock tower clearance with JBA shorties on 351W based 427 stroker in my 66.


  If budget is a factor and building a fairly stock engine is the plan, the stock 351W engine makes nearly 100 HP more than a stock 5.0, both with four barrel carbs.  Plus a bunch more torque.  Size is a tradeoff, but the only real difference there is the heads are 1/2" farther from the center of the crank on the 351W.  All the pulleys will work but the Alt, P/S and A/C brackets are a little different, based on the year.

As for the comments about beating the heck out of the cowl in order to install a cable clutch, there was not that much on my car.  I have sold over 2,000 of the cable clutch kits so far and only a handful have complained about the dent in the cowl.  Cars have dimensional differences built in just like mechanics have varied mechanical abilities.  That dent is a small compromise in order to have a properly functioning cable system for T5 installations.  If one KNEW they were never going to also want power brakes, the dent could be eliminated and the cable could come out of the firewall 1/2" lower.  But, my experience has been that my customers like power brakes for the most part, so the cable system is designed with that booster in mind.

After years of installing various engines and transmissions in these old Mustangs, unless you just HAVE TO HAVE a 351W based engine, the 5.0 based one is the way to go.  Your life will be easier when it comes to maintenance.  If I was doing it over, I would have built a 366 based on the Dart aluminum big bore 5.0 spec block rather than the big bore 351W based aluminum 427 that is in there now.  Once you get up to about 400 hp, you really cannot find a decent place to unleash more hp than that without getting into serious trouble.  Not to say there is ever enough HP, but in reality...  I can never "get on it" without drawing undue attention.

Thanks for all the good responses.  I guess I'm still on the fence about this.  I'll have to read and digest what ya'll said several more times and think some more.  I always wanted a real hot rod while driving this car in high school but never had more than a 289 with a choppy cam, four barrel, and a c4 with a shift kit.  I was actually leaning towards a 408 for the car with the go big or go home attitude for this last restoration, but a hot 302 based stroker realistically will be more power than the car needs.  Both motors will probably be very close in costs, since I will be starting from scratch, so not a big factor.  Having more power than I can use seems like a good problem to have but I'm just cautious about regretting my decision either way.  Any other thoughts are welcome, but thanks so far!

I have done both routes and more or less did them backwards, I have a 393/351 based in my 66 coupe, with Hedman long tubes, and have a 331/302(5.0) based in my 68 coupe with JBA shorty's which is 2" wider. At one point I actually considered swapping them. Both have T-5's. The 66 with 393 has a hydraulic clutch, and the 68 with 331 has a cable (MustangSteve, with barely a mark on the lower cowl).

The rest of the details,
The 66/393/T5, has a 8" rear with 3.80 and an Auburn diff and 245-60-15 tires, crazy torque and will NEVER hook up when playing and having fun.
The 68/331/T5, has a 8.8 rear with 3.73 and Trac loc and 275-40-17 tires, good torque, revs like crazy and will Never hook up when playing and having fun.
Without a doubt, you can feel the torque difference of the 393, but you are not able to take advantage of it in such a light car, yes I could put a much higher gear (3.00) behind the 393, but this is what I have.

With all that said, I am building a 63 Falcon right now, and am going with a STOCK 5.0, T-5 (MustangSteve cable clutch and power brakes), 8.8 with 3.73 & trac loc. shorty headers, and 275-40-17 rear tires, I am betting it will be fun to drive, easy to work on, get decent fuel economy, and run at what ever temp I choose it to run at. 275-300 horsepower in these light cars is a lot of fun on the street, and can be made easy and reliably, and with a T5, its a lot easier to add gear than horsepower.

Added note, if the Hi-po manifolds would work with my Falcon firewall and power steering box I would have went with them as MustangSteve stated, bolt them on and forget about them, you wont notice a power difference.

66 Coupe 393/351

Everyone always ask about the 275's on the Falcon, had to widened the wheel well a bit, but fits nicely.

MustangSteve wrote:

As for the comments about beating the heck out of the cowl in order to install a cable clutch, there was not that much on my car.  I have sold over 2,000 of the cable clutch kits so far and only a handful have complained about the dent in the cowl. 

I apologize - It was not my intent to disparage your product.  I meant only to convey my opinion/experience as requested in the original post.

MustangSteve wrote:

Radiator...  This is the 24" 70 radiator.  A three row core is plenty to cool a 400HP 351W with ac running in 100 degree stop and go traffic.
Since this was a stock radiator on a 70 Mustang it also appears "stock" on a 66.  You cannot tell the core support has been modified and most that see it think it is a pretty good way to do it and make it look stock to the casual observer.  Plus you can actually buy a decent fan shroud that fits it and actually works.

        Whats your thoughts on if you have 69 or 70 Mustang?  Would you still go with the 5.0 base or 351? 

 

lowercasesteve wrote:

Steve69 wrote:

MustangSteve wrote:

Radiator...  This is the 24" 70 radiator.  A three row core is plenty to cool a 400HP 351W with ac running in 100 degree stop and go traffic.
Since this was a stock radiator on a 70 Mustang it also appears "stock" on a 66.  You cannot tell the core support has been modified and most that see it think it is a pretty good way to do it and make it look stock to the casual observer.  Plus you can actually buy a decent fan shroud that fits it and actually works.

        Whats your thoughts on if you have 69 or 70 Mustang?  Would you still go with the 5.0 base or 351? 

 

No! No!

Install a 427 FE and put a 428 crank in it.  454 ci.  Then you will have bragging rights.  You can even change the plugs in it.;-)

Yeah!!!!!!.........One of these^^ will fit juuuuust fine!           https://www.youtube.com/watch?v=uzkEviShBUw
(go to the :59 sec. mark and watch!)
6s6

 

Last edited by 6sally6 (11/25/2015 6:26 PM)

Steve69 wrote:

MustangSteve wrote:

Radiator...  This is the 24" 70 radiator.  A three row core is plenty to cool a 400HP 351W with ac running in 100 degree stop and go traffic.
Since this was a stock radiator on a 70 Mustang it also appears "stock" on a 66.  You cannot tell the core support has been modified and most that see it think it is a pretty good way to do it and make it look stock to the casual observer.  Plus you can actually buy a decent fan shroud that fits it and actually works.

        Whats your thoughts on if you have 69 or 70 Mustang?  Would you still go with the 5.0 base or 351? 

 

A 351W in a 67-70 is similar fit as a 5.0 in a 65/66.  Plenty of shock tower clearance.  The car is bigger and heavier so more cubes is good in my book. 
 

Kar wrote:

I was asked if I was rebuilding the 5.0, well sort of, I went cheap. I actually drove the wrecked 89 mustang that the 5.0 and T5 were in before pulling and with 120k miles on it, it still ran well and the motor had good oil pressure and compression and sounded good. I went ahead and broke it down and checked all the clearances and threw in a set of new bearings and did a light hone job for a fresh set of rings. I had the rods checked and the crank checked, cleaned everything up really well, pu a new set of freeze plugs, cam bearings, timing set, and all seals. I did throw on a new set of valve springs, and seals, and had about 5 thousands taken off the heads to clean them up for a good seal. So no, I didn't do a true rebuild, just a garage fressioning. Truth be told, I could have done a good degreasing of the 5.0, put some new paint on it and it probably would have been fine for a long time. I decided that I would rather spend $1500 on AC, vs a set of heads, I bought a tilt steering column vs a cam, power brakes vs long tube headers. Can you see the direction I am going with this build.

I turn 50 in less than two months, and have been fooling with cars & trucks since I was 12, and I have always spent all my time, effort, and money building them for how I think or want to drive them which at best is about 5% of the time or less. So now I am going to build this little Falcon sedan/post car for how I drive them 95% of the time. I know, what a concept. Its going to sound good, stop good, idle good, run cool under the hood and in the drivers seat, have enough gear to be fun, and be as comfortable as a 53 y.ear old car can be.

    I to turn 50 next year and feeling the same way as you about the 5.0 in the garage.  Should I buy the AFR heads or go with AC.  Should I go with a bigger cam or leave the stock cam!  Should I sell the 5.0 and buy a 351.  Like you said I also want something dependable that's going to run good and get my where I want to go.   Thanks for the info! Steve69

 

Last edited by Steve69 (11/26/2015 10:17 AM)

6sally6,
I agree that a lumpy cam can be fun and who doesn't like the sound, my decision is also based on budget and where to spend the funds I have, no since camming it up without better heads and so on. I'm just getting to the point in life that AC and power steering have moved up the priority list ahead of the total horsepower I might make. Now if I had unlimited funds it would be a different story.

mustang66 wrote:

Thanks for all the great input guy's!  I've got some time to think about it, but it intrigues me about running a 351w because not everybody has one in these cars, although it looks like I've stumbled on a pretty fair share of them on this forum!  One other question I do have though...is it recommended to install subframe connectors on these cars when you run a healthy motor with plenty of torque?  I think some Shelby style traction devices will be installed in the rear also.  Hope ya'll are all having a happy Thanksgiving today.

Absolutely!

You should have as well as subframe connectors(get weld in's not bolt ins),  an export brace and Monte Carlo bar.  Those 3 are the basis of a properly handling car.  They will make alignments a thing of the past and will keep the shock towers at the proper distance.(Don't worry about what that is.  Just installing the bars will make the dimension correct.) 

Rear traction devices are goo too.  I use Traction Masters, but they are what Shelby used.  There are lots of other traction devices available.  But just installing the 3 things above is where to begin.