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                   1964-1966 Mustang Engine Swaps FYI



Below, I've put together some information relative to 351W and 351C engine

swaps into 64-66 Mustangs.  Since the shock towers of these Mustangs are

quite narrow, engine swap choices are restricted to the mid-sized 351's.

You can forget about big blocks, modular motors, or even a 351M/400, unless

you are willing to do major surgery (i.e. shock tower removal).  Of the Ford

351's, the 351W is the most popular.   Less popular, but still possible with

special headers and a little tower massaging, are 351C swaps.


Essentially a taller deck version of the 289/302, the 351W is the most

straightforward of the mid-size blocks to swap in.  The 351W is taller and

wider, but fits within the general V envelope of the 289/302 engine. The

351W (and 351C) share the 289/302 motor mounts and bellhousing bolt patterns

(64-65 5 bolt 260/289 blocks excluded).  Unfortunately, there isn't enough

clearance between the heads and the shock towers to fit the stock 351W

exhaust manifolds.  The shock towers could be notched to provide the

necessary clearance, but the usual approach is to replace the cast iron

exhaust manifolds with a set of steel tubing headers, preferably ones made

specifically for the swap.


In some cases, the companies listed below have a specific swap header for

64-66 Mustangs with 351W's.  In other cases, they show a generic header for

64-73 Mustangs with 289/302/351W engines.  Your best bet is to stick with the

specific swap headers.  There's an outside chance the generic headers will

fit but most likely they will require mods to the shock towers and/or header



A while ago, I did some checking into 64-66 Mustang 351W swap headers for one

of the list members who suffered sticker shock over the JBA swap header price

($699 for his case).  I was suprised to see so few places making headers

64-66 Mustang 351W swap headers.  This is a fairly common swap, so I expected

to see a wide variety of vendors supplying these headers.  I actually ran

across more places with Pinto 351W swap headers.  The first three vendors

listed below also carry 351C swap headers.


1. Mustangs Unlimited (from their 1995 catalog)

   800-243-7278 order

   203-647-1965 tech and local


   MU carries a specific 64-66 Mustang 351W header (1 1/2" primaries

   with 3 1/2" collectors).  Part number is ES9 and price is $289.95.


   They list the JBA 1606 header for $699.95 (1 3/4" primaries, 3 1/2"

   collector) but note that it will not fit power steering cars and

   that the equalizer bar from a 1967 standard 289 engine must be used.


   Their catalog claims that power steering brackets ($14.95) are

   required for any 64-70 Mustang using any style header and power



   They show a Hedman Header (P/N 88300) for $109.00 with a generic

   fits 64-73 Mustangs with 289/302/351W notation.  I checked the Hedman

   listing in the PAW catalog and it shows this part number fitting

   several different applications, but not specifically a 65-66 351W.

   I'd call Hedman and check:


                        Hedman Manufacturing

                        9599 West Jefferson Boulevard

                        Culver City CA 90232-2126



   Mustangs Unlimited also lists 64-66 Mustang 351C swap headers in

   their 1995 catalog.  For the 2V heads, they have part number ES7

   (1 3/4" primaries with 3 1/2" collectors).  For the 4V heads, they

   have part number ES7A (1 7/8" primaries with 3 1/2" collectors).

   Price for either set is $289.95.


2. Sacramento Mustangs

   order 800-442-8333

   info 916 334-0190


   Note: This info is from an old (1989) performance catalog supplement.


   They list a custom header for $259.00 for 64-66 Mustang, Comet, Falcon,

   and 70-76 Maverick and Comet applications.  They might be sourcing the

   headers from Total Performance (or their suppliers) since they show

   several other swap headers that TP sell (like the 64-66 351C headers).


   They also have a generic listing for 64-70 289/302/351W Tri-Y headers

   for $109.95 and list a power steering adapter.


3. Total Performance

   44050 N. Groesbeck Hwy.

   Clinton Township, MI 48036-1108


   313-468-7434 fax


   Note: This is from a 1989 price sheet.


   Part number 8009 is listed as fitting 60-66 Mustang, Comet, Falcon,

   70-78 Maverick and Comet applications with 351W's, 1 1/2' primaries.

   Price is $269.


4. Summit Racing (216-630-0200) shows the same part number (SUM-G9031) for

   64-73 260-302 Mustangs and 69-73 351W Mustangs.  Price is $77.50.


One list member was able to make a set of generic Hedman Hedders work in his

'66 fastback ('69 351W with C4).  He notched the shock towers in 3 places and

modified the end of the headers where they exit.  The job was time consuming

as it involved several iterations of dropping the engine in (without tranny),

putting the headers on, marking where they touched the shock towers, pulling

the engine out, heating up the area with a torch, and notching it in with a

round buck and a hammer.   He reported the end result was very professional



A member in the local (St. Louis) Ford club had good luck with the 351W swap

headers from Total Performance (much better than my own experience with TP's

351C swap headers).  His swap consisted of a 351W with T5 manual transmission

and air conditioning into a 1966 Shelby GT350.


In all cases, you'll need to verify fit for your specific combination of

transmission (automatic or manual), power steering, air conditioning, etc.


In most cases, early Mustangs with power steering will need to have the power

steering slave cylinder relocated using a swap bracket.  One list member

reported the bracket is inadequate to take the load from the power steering

system.  His fix was to weld the bracket to the frame with a pair of 1/4"

plate gussets behind it.


Many times headers for Fords are listed as being incompatible with automatic

transmissions but often this applies only to the large bellhousing C4, C6,

and FMX.  In those cases, switching to a small bellhousing C4 (and matching

blockplate) and a 157 tooth flywheel (50.0 oz-in balance factor) will provide

the required clearance.  When doing this, you may need to roll the lip of the

oil pan back a bit to get proper starter placement.  With a 64-66 Mustang,

the C4 (or an AOD if you want overdrive) is definitely the way to go if you

want an automatic transmission.  The C6 is much larger and will require

transmission tunnel work to fit.


You may also want to consider switching to the small diameter, late model,

permanent magnet starter that came on some Lincolns.  Once your headers are

in place, you may find it impossible to remove or install the starter (I did),

without removing the headers or disassembling part of the suspension.  The

lightweight starter is much smaller and slipped right into place.  SVO sells

them new with a wiring harness and instructions.  These can be had for less

than $150.  My favorite approach is to find a core and get it rebuilt with a

lifetime warranty.  If you go this route, remember these starters are wired

differently.  I should have a copy of the wiring diagram (it's very simple),

if you need it.


Aftermarket bellhousings and heads, suspension modifications, steering

modifications (like the Shelby quick-steer kit with longer idler and pitman

arms) can complicate matters as well.  In many cases, oil filter relocation

(using a 90 degree elbow or remote filter), will be required or will make

things easier.


Another tip is to intall a torque strap to limit engine rock under

acceleration.  This can keep the headers and air filter case from making

contact with inner fenders or hood.  I also suggest you wait until you've

made a trial fit and any needed modifications before you have any sort of

coating applied to the headers.


Over the years, the shock towers on early Mustangs tend to sag towards each

other.  This can complicate a 351W or 351C engine swap.  The proper dimension

for 64-70 Mustangs is 40" from inner fender to inner fender (at the Monte

Carlo bar mounting points).  You may need to use a port-a-power to spread

them apart.  Once you have the engine in, install a Monte Carlo bar to keep

the shock towers from flexing under load and causing clearance problems.


Hood clearance will be tight.  If I remember correctly, the '65 motor mounts

lower the engine farther than the '66 mounts.  They are better for hood

clearance, but worse for ground clearance.  Low profile intake manifolds and

air cleaners are generally required if you don't use a hood scoop.  Remember

to leave enough clearance to account for the engine rocking in its mounts.

I use an Edelbrock F-351 intake and 14"x3" drop base air cleaner on my 351C

with room to spare.  The local club member with the 351W in his Shelby GT350

used both Performer and Torker II intakes with a low profile Mopar open

element air cleaner.


In many cases, sparkplug access can be tight, so some general sparkplug tips

are in order.  The first tip is obvious but easy to overlook.  Many sparkplug

sockets have flats on them so they can be used with an open end wrench,

instead of a ratchet handle.  Sometimes the wrench will need to bent to get

the proper clearance.  The second tip is handy when it's difficult to get a

socket on the plug.  Cut a U-shaped opening into the side of the socket. This

opening can be aligned with the plug to gain clearance.  Since the opening

will weaken the socket, try to remove the minimum amount required for

clearance.  In some cases, you can also trim the overall length of the socket

for additional clearance.  Also, Accel makes plugs that are approximately 3/8"

shorter than standard plugs.  If you still can't get a socket on, try heating

and bending a box-end wrench to fit.  The final tip can help get the plug

started in tight spaces.  Push a piece of rubber hose over the end of the

sparkplug and use it to position the the sparkplug at the hole.  Simply spin

the hose to start the plug.


Specially modified tools can also come in handy elsewhere.  I bent and

trimmed some box wrenches to make it easier to do home alignments.


If you're still running points, you may want to switch over to a high energy

electronic ignition to extend sparkplug life.  However, I'd stay away from

platinum plugs.  Under the right circumstances, platinum plugs can have

remarkably long (100,000+ miles) service lives, but they seem to be

susceptible to rich mixtures and can foul easily.


The 351W is approximately 65 to 75 lbs heavier than a comparable 289/302.

A 351C is another 25 lbs more (see the engine weights and dimensions chart

below).  You can compensate for the increased front end weight by installing

stiffer and/or taller springs in front.  You may also want to increase rear

spring rate or add a traction device to handle the increased torque.  See

the Early Mustang Suspension FYI for details.


Of course, you can also lighten the load by using aluminum heads, an aluminum

water pump, a lightweight starter, tube headers, a fiberglass hood, relocated

battery or by deleting heavy accessories like air conditioning and power

steering.  On the 351C in my '66 fastback,  I have no power accessories, an

aluminum intake, tube headers, a lightweight starter, and a relocated battery

(trunk mounted).  I expect my front end weight isn't that much different than

a '66 289 Mustang with cast iron intake and exhaust manifolds and maybe a few



The magazines have featured 351W swaps a number of times:


1. "Windsor of Change", Mustang and Fords, September 1993.


This article details a 351W swap performed by Dyno Don Nicholson into a

friend's 1966 GT fastback.  JBA swap headers were used.  The shock towers

on this car had sagged and had to be port-a-powered apart.  The 351W was

dyno tested with both Torker II and Performer intake manifolds.  The Torker

II, with a one inch spacer, made the most power but would not fit under the

hood so the Performer intake was used instead.  The car was fitted with power

steering and a C4 automatic, both of which are not supposed to work with the

JBA headers.  Power steering bracket lengthening was required.  A four core

radiator was used.


2. "Old Favorite", Super Ford, November 1991.


This article covers a 351W swap into a 1966 fastback using JBA headers and

a T-5 transmission.


3. "'Stang With Sting", Hot Rod, date unknown.


Another 1966 fastback with 351W, this time with Doug Nash 5 speed tranny.


The 351W swap is, for the most part, straightforward.  The 351C swap, on

the other hand, is more involved.  The Cleveland heads are wider than their

Windsor counterparts, making the shock tower clearance problem more

difficult.  Special swap headers or extensive shock tower modifications

are required.  Sparkplug access and adequate cooling will be more difficult.

The 351C is also generally more expensive to modify these days and is about

25 lbs heavier than the 351W, which is already 65 to 75 lbs heavier than a



On the plus side, the 351C has a lower deck height, so hood clearance will

be a bit better.  The 351C also has better flowing factory heads and strong

crank, rods, and main caps.  It will take more work than a 351 swap, but the

results can be impressive.


Three list members have voiced their experience with 351C into 64-66 Mustang

swaps.  Here's what Darius Rudis had to say:


"My best friend stuffed a 351C (yes Cleveland 4V) into his 1966 coupe.

This I would say physically fits, but not really.  By the time the shock

towers were sludge hammered out it looked pretty sad.  The car is fast as

hell, and a real sleeper.  The hardest part of driving it is not switching

lanes as you shift the toploader cause of all the torque and tire spin it

is difficult to drive hard.  The 351W, I am not sure how hard it would be

to stick that in, but I know it is a lot less difficult than the 351C.

Plus there are companies who sell headers for the swap."


Here's how Dave Williams responded:


"-> My best friend stuffed a 351C (yes Cleveland 4V) into his 1966 coupe.

-> This I would say physically fits, but not really.  By the time the

-> shock towers were sludge hammered out it looked pretty sad.


When the front end finally gave out in my '70 Torino I yanked the

11.2:1 351CJ and put it in a 1966 notchback.  It was *not* a happy swap.

I had to sledgehammer the shock towers, grind the A-arm bolts, and grind

on the manifolds.  A couple of places sell headers which are supposed to

work with that swap, but I don't know how they'd run them.  The engine

had about 1/16 inch clearance on each side, and I got rid of it before I

had to worry about changing spark plugs.  The only practical way (short

of pulling the motor) would have been to cut holes through the



-> > exhaust system.  I've been told that the only headers available are

-> custom > made by JBA and have a list price of $899.


Cyclone used to sell some, Hooker still does.  They're substantially

cheaper too.


If you really, *really* want the Cleveland in there, check into the

Crites big block conversion.  They sell modified A-arms and shock tower

plates.  You carve out the stock towers and weld in new suspension

pickups, a'la the Fairlane Thunderbolts.  The Crites kit was, as I

remember, in the neigborhood of $300 a couple of years ago.  It would

give you plenty of working room around the engine."


My results were much better than either of these.  I used special swap

headers (from Total Performance) which ended up requiring a lot of re-work,

but the final product is very strong.  The headers are individually flanged

and slip-fit into the header collectors, with two of the tubes passing under

the engine and into the opposite side collector.  The swap headers are a bit

big (1 7/8" diameter primaries, 3 1/2" collectors) but they are the only size

available for the 4V heads (1 3/4" primaries are available for the 2V heads).

Initially the headers were bolted to a spare block for a trial assembly.

The fit was pathetic.  Bolted to the engine, the primaries were not even

close to fitting into the collectors.  There was steering linkage and oil

pan interference, as well.  After several trial fits, all the tubes were

re-bent and a couple of sections grafted on.  Still, the shock towers had

to be slightly massaged (heated with a torch and rapped with a body hammer,

repainted and undetectable) to get everything to fit.  When I called Total

Performance to express my displeasure, I was informed that 5 out 10 people

get them to go together without too much trouble, 3 out 10 have trouble but

eventually get them to fit, while the last 2 just give up!  Besides Total

Performance, Mustangs Unlimited and Sacramento Mustang also carry 351C swap

headers.  Their telephone numbers are listed above.


A re-located oil filter was necessary, as was a larger radiator.  I used a

larger 3 core unit from a V8 Maverick with A/C.  This radiator has different

mounting points so I had to move the pick-up points.  This set-up provided

adequate cooling for a previous 351W powered '66, but has proven to be

inadequate for my 351C.  It worked okay when I had the stock converter, but

when I installed a high stall speed converter, it was immediately apparent the

heat load had increased.  I added an auxiliary tranny cooler but it hasn't

helped much.  It sits in front of the radiator and just seems to super-heat

the air flowing past the radiator, reducing its effectiveness.


There are several manufacturers of replacement 3 and 4 core radiators for

64-66 Mustangs, but they are all constrained by the physical size of the

radiator support opening.  One of the vendors also makes a late model style

cross flow unit which requires cutting the radiator support opening to match

the (much larger) radiator dimensions.  I've not pursued this much since I

plan to switch to a Tremec 5 speed manual, which should reduce the heat load

considerably.  If, after the tranny swap, I still have cooling problems, I

plan on opening up the radiator support and and fitting a late model style

cross flow radiator.   Wrapping the headers with Thermo-Tec might also help,

but that would be a real chore with my swap headers.


One other radiator note.  The stock 289 radiator has both the inlet and the

outlet on the same (passenger) side.  351C, 351W, and late model 5.0 engines

all have water pumps inlets that require the bottom hose to be on the

driver's side.  Any competent radiator shop can move the lower radiator hose

neck to the driver's side to match the water pump inlet.


I've re-worked the suspension to match the increased power of the 351C-4V,

so I don't have any of the traction problems Darius Rudis described.


The 351C really fills the engine bay, but the layout is quite clean.  There

are no messy emissions hoses or accessories to clutter up the bay.  With a

few customized sparkplug wrenches, the sparkplugs can be changed *without*

loosening the motor mounts and jacking up the engine (unlike my Dad's 428CJ).

I can also remove and install the starter without removing the headers or

disturbing the suspension.



               Engine Weight and Dimension Comparison



The following numbers come from an early Ford SVO catalog and are for

"typical" engines.  The dimensions include such things as air cleaners, oil

filters, water pump fan, etc., but not bellhousings.


               Engine    Width Length Height Weight


               289-302W  24.0  29.0   27.5   460

               302 Boss  24.5  29.0   28.5   500

               351W      25.0  29.0   29.0   525

               351C      25.5  29.0   29.0   550

               351M-400  26.0  29.0   29.0   575


This is consistent with my experience (and other published numbers).  As a

check, I weighed several sets of heads and got the following weights:


       50.0 lbs  289/302 - complete including rockers

       56.5 lbs  351C 2bbl open chamber - bare

       58.0 lbs  351C 2bbl open chamber - complete except for rockers

       60.0 lbs  351C 4bbl closed chamber - bare


Adding 2 to 3 lbs for valvetrain weight to the 4bbl closed chamber heads,

yields 12 to 13 lbs more per head than a smallblock Windsor.  For the

pair of heads, figure on 25 lbs extra for Cleveland heads.  A Cleveland

block may actually be a bit lighter than a Windsor block, since they have

a lower deck and thinner cylinder walls.  Thus a 351C should be about 25

lbs more than a 351W (525 lbs vs 550 lbs).  The 302 Boss weight estimate

seems high compared to a 302W, especially considering it's aluminum intake.


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