1964-1966 Mustang Engine Swaps FYI
Below, I've put together some information relative to 351W and 351C
swaps into 64-66 Mustangs. Since the shock towers of these Mustangs
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,
you are willing to do major surgery (i.e. shock tower removal). Of the
351's, the 351W is the most popular. Less popular, but still
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
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
(64-65 5 bolt 260/289 blocks excluded). Unfortunately, there isn't
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
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
64-73 Mustangs with 289/302/351W engines. Your best bet is to stick
specific swap headers. There's an outside chance the generic headers
fit but most likely they will require mods to the shock towers and/or
A while ago, I did some checking into 64-66 Mustang 351W swap headers for
of the list members who suffered sticker shock over the JBA swap header
($699 for his case). I was suprised to see so few places making
64-66 Mustang 351W swap headers. This is a fairly common swap, so I
to see a wide variety of vendors supplying these headers. I actually
across more places with Pinto 351W swap headers. The first three
listed below also carry 351C swap headers.
1. Mustangs Unlimited (from their 1995 catalog)
203-647-1965 tech and local
MU carries a specific 64-66 Mustang 351W header (1 1/2"
with 3 1/2" collectors). Part number is ES9 and price is
They list the JBA 1606 header for $699.95 (1 3/4" primaries, 3
collector) but note that it will not fit power steering cars
that the equalizer bar from a 1967 standard 289 engine must be
Their catalog claims that power steering brackets ($14.95)
required for any 64-70 Mustang using any style header and
They show a Hedman Header (P/N 88300) for $109.00 with a
fits 64-73 Mustangs with 289/302/351W notation. I checked
listing in the PAW catalog and it shows this part number
several different applications, but not specifically a 65-66
I'd call Hedman and check:
9599 West Jefferson Boulevard
Culver City CA 90232-2126
Mustangs Unlimited also lists 64-66 Mustang 351C swap headers
their 1995 catalog. For the 2V heads, they have part
(1 3/4" primaries with 3 1/2" collectors). For the 4V
have part number ES7A (1 7/8" primaries with 3 1/2"
Price for either set is $289.95.
2. Sacramento Mustangs
info 916 334-0190
Note: This info is from an old (1989) performance catalog
They list a custom header for $259.00 for 64-66 Mustang, Comet,
and 70-76 Maverick and Comet applications. They might be
headers from Total Performance (or their suppliers) since they
several other swap headers that TP sell (like the 64-66 351C
They also have a generic listing for 64-70 289/302/351W Tri-Y
for $109.95 and list a power steering adapter.
3. Total Performance
44050 N. Groesbeck Hwy.
Clinton Township, MI 48036-1108
Note: This is from a 1989 price sheet.
Part number 8009 is listed as fitting 60-66 Mustang, Comet,
70-78 Maverick and Comet applications with 351W's, 1 1/2'
Price is $269.
4. Summit Racing (216-630-0200) shows the same part number (SUM-G9031)
64-73 260-302 Mustangs and 69-73 351W Mustangs. Price is
One list member was able to make a set of generic Hedman Hedders work in
'66 fastback ('69 351W with C4). He notched the shock towers in 3
modified the end of the headers where they exit. The job was time
as it involved several iterations of dropping the engine in (without
putting the headers on, marking where they touched the shock towers,
the engine out, heating up the area with a torch, and notching it in with
round buck and a hammer. He reported the end result was very
A member in the local (St. Louis) Ford club had good luck with the 351W
headers from Total Performance (much better than my own experience with
351C swap headers). His swap consisted of a 351W with T5 manual
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,
In most cases, early Mustangs with power steering will need to have the
steering slave cylinder relocated using a swap bracket. One list
reported the bracket is inadequate to take the load from the power
system. His fix was to weld the bracket to the frame with a pair of
plate gussets behind it.
Many times headers for Fords are listed as being incompatible with
transmissions but often this applies only to the large bellhousing C4,
and FMX. In those cases, switching to a small bellhousing C4 (and
blockplate) and a 157 tooth flywheel (50.0 oz-in balance factor) will
the required clearance. When doing this, you may need to roll the lip
oil pan back a bit to get proper starter placement. With a 64-66
the C4 (or an AOD if you want overdrive) is definitely the way to go if
want an automatic transmission. The C6 is much larger and will
transmission tunnel work to fit.
You may also want to consider switching to the small diameter, late
permanent magnet starter that came on some Lincolns. Once your headers
in place, you may find it impossible to remove or install the starter (I
without removing the headers or disassembling part of the suspension.
lightweight starter is much smaller and slipped right into place. SVO
them new with a wiring harness and instructions. These can be had for
than $150. My favorite approach is to find a core and get it rebuilt
lifetime warranty. If you go this route, remember these starters are
differently. I should have a copy of the wiring diagram (it's very
if you need it.
Aftermarket bellhousings and heads, suspension modifications, steering
modifications (like the Shelby quick-steer kit with longer idler and
arms) can complicate matters as well. In many cases, oil filter
(using a 90 degree elbow or remote filter), will be required or will make
Another tip is to intall a torque strap to limit engine rock under
acceleration. This can keep the headers and air filter case from
contact with inner fenders or hood. I also suggest you wait until
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
other. This can complicate a 351W or 351C engine swap. The proper
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
them apart. Once you have the engine in, install a Monte Carlo bar to
the shock towers from flexing under load and causing clearance problems.
Hood clearance will be tight. If I remember correctly, the '65 motor
lower the engine farther than the '66 mounts. They are better for
clearance, but worse for ground clearance. Low profile intake manifolds
air cleaners are generally required if you don't use a hood scoop.
to leave enough clearance to account for the engine rocking in its
I use an Edelbrock F-351 intake and 14"x3" drop base air cleaner on my
with room to spare. The local club member with the 351W in his Shelby
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
are in order. The first tip is obvious but easy to overlook. Many
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
the proper clearance. The second tip is handy when it's difficult to
socket on the plug. Cut a U-shaped opening into the side of the socket.
opening can be aligned with the plug to gain clearance. Since the
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
for additional clearance. Also, Accel makes plugs that are
shorter than standard plugs. If you still can't get a socket on, try
and bending a box-end wrench to fit. The final tip can help get the
started in tight spaces. Push a piece of rubber hose over the end of
sparkplug and use it to position the the sparkplug at the hole. Simply
the hose to start the plug.
Specially modified tools can also come in handy elsewhere. I bent
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
electronic ignition to extend sparkplug life. However, I'd stay away
platinum plugs. Under the right circumstances, platinum plugs can
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
below). You can compensate for the increased front end weight by
stiffer and/or taller springs in front. You may also want to increase
spring rate or add a traction device to handle the increased torque.
the Early Mustang Suspension FYI for details.
Of course, you can also lighten the load by using aluminum heads, an
water pump, a lightweight starter, tube headers, a fiberglass hood,
battery or by deleting heavy accessories like air conditioning and power
steering. On the 351C in my '66 fastback, I have no power
aluminum intake, tube headers, a lightweight starter, and a relocated
(trunk mounted). I expect my front end weight isn't that much different
a '66 289 Mustang with cast iron intake and exhaust manifolds and maybe a
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
on this car had sagged and had to be port-a-powered apart. The 351W
dyno tested with both Torker II and Performer intake manifolds. The
II, with a one inch spacer, made the most power but would not fit under
hood so the Performer intake was used instead. The car was fitted with
steering and a C4 automatic, both of which are not supposed to work with
JBA headers. Power steering bracket lengthening was required. A
radiator was used.
2. "Old Favorite", Super Ford, November 1991.
This article covers a 351W swap into a 1966 fastback using JBA headers
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,
the other hand, is more involved. The Cleveland heads are wider than
Windsor counterparts, making the shock tower clearance problem more
difficult. Special swap headers or extensive shock tower
are required. Sparkplug access and adequate cooling will be more
The 351C is also generally more expensive to modify these days and is
25 lbs heavier than the 351W, which is already 65 to 75 lbs heavier than
On the plus side, the 351C has a lower deck height, so hood clearance
be a bit better. The 351C also has better flowing factory heads and
crank, rods, and main caps. It will take more work than a 351 swap, but
results can be impressive.
Three list members have voiced their experience with 351C into 64-66
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
towers were sludge hammered out it looked pretty sad. The car is fast
hell, and a real sleeper. The hardest part of driving it is not
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
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
-> This I would say physically fits, but not really. By the time
-> 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
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
work with that swap, but I don't know how they'd run them. The
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
of pulling the motor) would have been to cut holes through the
-> > exhaust system. I've been told that the only headers
-> custom > made by JBA and have a list price of $899.
Cyclone used to sell some, Hooker still does. They're substantially
If you really, *really* want the Cleveland in there, check into the
Crites big block conversion. They sell modified A-arms and shock
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
give you plenty of working room around the engine."
My results were much better than either of these. I used special
headers (from Total Performance) which ended up requiring a lot of
but the final product is very strong. The headers are individually
and slip-fit into the header collectors, with two of the tubes passing
the engine and into the opposite side collector. The swap headers are a
big (1 7/8" diameter primaries, 3 1/2" collectors) but they are the only
available for the 4V heads (1 3/4" primaries are available for the 2V
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
close to fitting into the collectors. There was steering linkage and
pan interference, as well. After several trial fits, all the tubes
re-bent and a couple of sections grafted on. Still, the shock towers
to be slightly massaged (heated with a torch and rapped with a body
repainted and undetectable) to get everything to fit. When I called
Performance to express my displeasure, I was informed that 5 out 10
get them to go together without too much trouble, 3 out 10 have trouble
eventually get them to fit, while the last 2 just give up! Besides
Performance, Mustangs Unlimited and Sacramento Mustang also carry 351C
headers. Their telephone numbers are listed above.
A re-located oil filter was necessary, as was a larger radiator. I used
larger 3 core unit from a V8 Maverick with A/C. This radiator has
mounting points so I had to move the pick-up points. This set-up
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,
when I installed a high stall speed converter, it was immediately apparent
heat load had increased. I added an auxiliary tranny cooler but it
helped much. It sits in front of the radiator and just seems to
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
cross flow unit which requires cutting the radiator support opening to
the (much larger) radiator dimensions. I've not pursued this much since
plan to switch to a Tremec 5 speed manual, which should reduce the heat
considerably. If, after the tranny swap, I still have cooling problems,
plan on opening up the radiator support and and fitting a late model
cross flow radiator. Wrapping the headers with Thermo-Tec might
but that would be a real chore with my swap headers.
One other radiator note. The stock 289 radiator has both the inlet and
outlet on the same (passenger) side. 351C, 351W, and late model 5.0
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
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
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.
are no messy emissions hoses or accessories to clutter up the bay. With
few customized sparkplug wrenches, the sparkplugs can be changed
loosening the motor mounts and jacking up the engine (unlike my Dad's
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,
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
351C 25.5 29.0 29.0
351M-400 26.0 29.0 29.0 575
This is consistent with my experience (and other published numbers). As
check, I weighed several sets of heads and got the following weights:
50.0 lbs 289/302 - complete
56.5 lbs 351C 2bbl open chamber -
58.0 lbs 351C 2bbl open chamber -
complete except for rockers
60.0 lbs 351C 4bbl closed chamber
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
pair of heads, figure on 25 lbs extra for Cleveland heads. A
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
lbs more than a 351W (525 lbs vs 550 lbs). The 302 Boss weight
seems high compared to a 302W, especially considering it's aluminum