351 Swap Information
Written By: Ric Reppert
Here is the list that I wrote up from my
experience building my motor. This list includes what you will need depending on
if your building a mild daily driving 351w or a racing 351w. There is a big
difference between parts. But here is what you need to swap from a fox bodied
5.0 to your new 351w.
Little history on 351's... the 69-74
blocks are said to be the strongest due to the extra webbing in the block. 94
and newer blocks are all roller blocks. They are the ones to look for if you
want to make it a roller block. Even if you cant find one you can easily make
the older blocks roller. When swapping parts between these engines (302 and
351), the most confusion surrounds the camshafts. Camshafts will interchange,
but the 351W has a different firing order (1-3-7-2-6-5-4-8) compared to the
289/302 Non-HO (1-5-4-2-6-3-7-8). Compounding the situation, the '82-and-later
302 HO engines use the 351W firing order.
As for on the block to fit into a fox
bodied Mustang, you will need a double hump oil pan and pickup tube. Canton &
FRPP are two companies who make 351 swap pans. The FRPP ones are 5qt where as
the other brands are usually 7qt.
Internally you cannot use the parts
from your 302, except for your camshaft, which will probably be too small
anyways depending on the rest of your combo. Connecting rods cannot be
reused... they need to be 5.956". The crank is a 3.5" stroke crank which is also
different then the 302. If your going with a higher hp motor you may want to
look into getting a crank from Scat. Summits cranks are made by Scat, but if I
am correct, cost more. Do not buy the cranks you see for $200 off Ebay. Keep
in mind your building a larger motor, think big. And keep in mind " You get
what you pay for ".
Your upper intake will work if it is a
Cobra upper intake, but you will need a 351 gt40 lower intake if your using EFI.
But if you are building a racing motor you will want to use a different intake
setup, Trick Flow makes a nice R series 5.8L intake. There are other companies
as Edelbrock and what not that sell 351 intakes. Your 302 heads will bolt up
but the bolt holes will have to be drilled from the 7/16" they are now to 1/2".
But there again if your building a larger 351 you want to go with aftermarket
aluminum heads to lighten your front end up and let more air move through them.
I suggest TrickFlow heads. Other companies are AFR, Edelbrock, and more. You
will also a need 351w distributor by such makers as MSD or Accel, your 302
distributor will not work. A 28oz balancer and 28oz flywheel are required, you
cannot use your 302 50oz flywheel and balancer. You can get these parts from
Summit Racing or even AutoZone.
Next you need an accessory drive
bracket, depending on what you have on your car you will either need one for
power steering and AC or just PS depending on what you have on your car and what
you don't have, both of these can be bought from Summit Racing. Your current
alternator bracket will work with the new setup. You will need 351 swap
headers, by such companies as Mac, BBK, Hooker, Kooks, etc, your
stock/aftermarket 302 headers wont work.
As for your stock Mustang fuel rails,
they wont stretch far enough to go over the lower intake unless you cut out the
cross over and replace it with braided lines, otherwise those will need
to be replaced. If your replacing them get the 1/2" ones. If your building a
high horse powered motor, you want to upgrade to larger fuel rails anyways. As
for injectors, the pretty much depend on how much your building this up. I ran
a 393 stroker with 30#'s but they were towards their limit. To figure out
roughly what size injectors you should need you can use this formula - "motor
horsepower ÷ 8 (= xxx) x .50 (= xxx) ÷ .85 = "injector size". This will give
you a close idea of what injectors to use. For your mass air meter (calibrated
for new injectors), you should upgrade to a larger mass air meter. But keep in
mind bigger is not always better with this. A mild 393 will run fine on a 75mm
MAF. Others run 80mm MAF's with no problems. Do some research and check out
other people's setups.
As for the electronics, you can
reuse all you electrical stuff. Your computer will be ok for the 351 but you
should upgrade and either get a custom chip or Tweecer program. I ran my 393
for 1500 miles without a chip just running off stock Cobra computer with out
problems. But a tune and custom chip gained a good amount of HP and TQ.
Pretty much everything else can be used.
You should replace your motor mounts as well while you have it out. The 351w is
a lot heavier and is also 1" higher so keep that in mind, you will need at least
a 1.5" hood, but that depends on your combo. With the TFS R intake you at least
a 2.5" hood and it still may hit a little. Your intake can make you need a
bigger hood. But as for all your pulleys and accessory stuff goes (i.e.. water
pump, AC, PS, alternator), they will all fit. Your upper Cobra intake, cam,
heads, etc can all be used but may not be enough to make the numbers your
looking for. Same clutch and drive train can be used. But you may want to
upgrade them. But if you don't have the money at the time I would hold off. I
ran a WCT5 on my 393 for awhile, not track or slicks though.
Any other questions e-mail me anytime (
Don't forget to send pictures of the engine and car when its done. Good luck.
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