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 maybe 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 long 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 surprised 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.  Hedmann has recently 
stepped in to fill the void with 351W swap headers but make sure they are 
compatible with your heads.  Some aftermarket Windsor heads have raised
exhaust ports and may not quite fit.

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.

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

   Their catalog claims that power steering brackets are required for 
   any 64-70 Mustang using any style header and power steering.

   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).  

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 64-66 Mustang, Comet, Falcon, and 70-76 
   Maverick and Comet applications.  They might be sourcing the headers 
   from Total Performance (or their supplier) 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
   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. 
   Also list 64-66 351C Mustang swap headers in 2V or 4V flange.

4. Tubular Automotive
   PO Box 279
   248 Weymouth St
   Rockland MA 02370

   Lots of swap headers for Fords, including 351C into '65-'66.
   Darkhorse Performance carries Tubular Automotive headers.

   Darkhorse Performance
   16617 SE 134th 
   Renton, WA 98059
   425-277-3893 fax

5. Pro Mustang Performance 
   2070 Del Amo Blvd
   Torrance, CA 90501

   Custom 351C into '65-'66 Mustang swap headers.
6.  Hedman Hedders
    16410 Manning Way
    Cerritos, CA 90703
    310-921-7515 fax

    Hedman has recently introduced two sets of 351W headers specifically 
    designed for swaps into 64-73 Mustangs:

    P/N 88660 - Full Length - 1 5/8" primaries with 3" collectors
    P/N 88650 - shorty

Note: a couple of guys have had real trouble swaping in aftermaket headed 
(Dart, TW) 351W's.  Here's what one said:
* Unless you are a masochist, DO NOT put Dart heads on your early Mustang, 
particularly the '65-66. They are great heads BUT the plugs are seriously 
relocated, enough for you to go to "custom headers" which are more
aggravating than I'd care to discuss.  Fox Mustang owners will gladly take your Darts if
you're reading this a little late in the game; they can use 'em all day
long.I recommend Edelbrock Performer RPMs or GT-40 Aluminums for early car folks.
They go right on there, pretty as you please. 

I did talk to Bill Mitchell, maker of the Dart heads, recently, and he 
admitted that the relocated plugs were giving people problems. He said my 
circa 1995 heads were "old" and that the new batch of heads has the stock 
locations for the plugs again. So, get the *new* Darts. 

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.
Hooker may also make a header that will fit the early Mustang chassis.
Here's what one individual (David Cole) on the web had to say.  "On the headers:
Hooker Super Comps. Part #6208. These are 1 3/4" headers with 32" tubes. I have
well over 400 rwhp in my 383-W and they are plenty big enough.  These are engine
swap headers to let you put the 351-W in an early Mustang. They fit 65-70
Mustangs. I have them in my 69, but they are designed to fit the earlier cars also.
Before I bought them I called Hooker. They told me that these headers were designed
to be able to fit a 65 Mustang with a 351W and C-6. Anything else is cake. I
have seen them installed in a 65 and a 66 and they fit well. True, plugs are a
little tight to get to, but it is workable.  These headers are available mailorder
for around $360. Hedman also makes a set. I had some but refused to install them
due to poor quality."

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 (28.2 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.  My swap headers fit with only a little clearancing on my
Lakewood scattershield.

Another tip is to install 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 K&N air cleaner on my 
351C with room to spare.  A 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 be 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 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 spark plug life.  However, I'd stay away from
platinum plugs.  Under the right circumstances, platinum plugs can have
remarkably long 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 accessories.  

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 shock tower modifications are required.
Sparkplug access will be tight.  The swap headers will have a 90 degree 
bend coming out of the port so exhaust flow will be hurt some.  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 351W 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 sledge 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 fenderwells.

-> > 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). The approach is sound but the fit quality was pathetic.  Initially the 
headers were bolted to a spare block for a trial assembly.  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
tapped 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, others have swap headers that
will do the job.  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 fitting a late model style 
cross flow radiator.   Wrapping the headers with Thermo-Tec might also help,
but they can turn the headers brittle over time.

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.

One other problem I ran into is the steering box.  The '65-'66 Mustangs
have an integral shaft steering box and there's no way to remove it with
the 351C in place.  Instead of pulling the engine, I just used a cutoff
wheel and cut the firewall area above the steering shaft.  Pulled and
replaced the box then Mig welded the piece back.  The trickiest part was
keeping the interior from catching fire (used a helper with wet towels 
to keep things cool).  Before swapping the engine in, you may want to 
rebuild your steering box or, better yet, swap to the non-integral shaft 
set up of the '67-'70 Mustangs.  

I've re-worked the suspension to match the increased power of the 351C-4V,
so I didn't have any of the traction problems Darius Rudis described 
.  Subframe connectors, Monte Carlo brace, and
export brace are highly recommended.

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 spar kplug 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.


>Dave told me that he tried to get a 351C into a pre-'67 Mustang and 
>that you could even jump up and down on the thing and it wouldn't go 
>into the engine bay. Now as I'm wanting to put a Clevor in said space, I 
>have to wonder if it won't be the same brand of fun.

If I remember correctly, Dave tried to put the engine in with the factory
iron manifolds.  You'd have to hack the hell out of the shock towers to
make it fit that way.  With the swap headers, it will slide in, assuming 
your shock towers haven't sagged towards each other.  I saw one 351W swap 
where they had to port-a-power the towers apart for clearance.  The biggest 
drawback with the swap is the headers have to make an abrupt 90 degree bend 
at the exhaust port.  It's got to kill exhaust flow but it's the same with 
351W swaps I've seen.  I've also heard that guys with aftermarket Windsor 
heads on 351W's have trouble with the commonly available swap headers.  

You'll need a big radiator to keep 430 cubes cool.  The stock radiator 
is tall and narrow but the grill opening is short and wide.   Dump the
stock radiator and cut the radiator support out to the width of the 
grill and mount up a Howe or Griffin circle track radiator.

The extra deck height *and* the wider Cleveland heads may make for
trouble.  I bet you'd be looking at some re-work of the headers.  Things 
are tight to begin with.  


>Dan, there's always a lot of questions about this swap. I think your 
>personal experiences would be quite helpful posted here. I know that I 
>would be interested.  I've never attempted this swap, but get a lot of 
>questions about it. 

Okay, I've posted my swap info below.  It includes notes about both
351C's and 351W's.  Some of the info is outdated now and I've put in
notes to myself to update it here and there where I need to add updates 
but you should be able to follow it.  
>One misconception is that the Cleveland doesn't fit without cutting the 
>shock towers.  I've seen at least two of these swaps, using stock exhaust 
>manifolds, that required no cutting.  

The only ones I've seen that did not require notching the shock towers
were the ones that used custom headers.  No way mine would have gone
in with stock manifolds.  One big variable is shock tower sag.  I've 
seen one 351W swap that needed the towers porta-powered back apart before 
the engine would go in. 

The Mustang Illustrated article that I mentioned earlier mentions they
will be swapping the 351C into a '65 or '66 Mustang using swap headers
and a swap kit from Pro Mustang Performance.  It will be interesting to 
follow that story.

Dan Jones

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