thinking about putting 351w in a fox body

[Johnson1134]

im thinking about putting a 1978 351 windsow in a fox body will i run into any problems?

[Rick93coupe]

You need mustang specific headers made for a 351 in a fox body. The transmission will bolt up fine, you leaving the carb on it?

[Johnson1134]

yes it will stay carbed!

[Jeff88coupe]

351 headers and a 351 mustang oil pan are about all you'll need to make it fit then.

[bobtsgt]

In our 83GT we just put a 351w in and the stock hood still clears. Oil pan and headers are some biggies. Mac makes a nice set and you can get either a FMS pan kit or piece one together. Buying the kit may not be a bad idea for ya.

[Johnson1134]

so pan and headers that is all the trouble i will have?

[bobtsgt]

pretty much. I got some vert mounts which are suppose to be lower which will lower the engine to clear the hood. Don't know if they are lower or not but my hood closed down fine. The oil pan kit will save you time finding everything separate. The Mac headers on mine rubbed up against the steering shaft. You can dent in the header to make room. Might want to look at a radiator upgrade if you run too hot.

this might help you some http://www.fast351.com/cartech/

[Johnson1134]

thanks!

[85_SS_302_Coupe]

Here ya go....i didn't type this so i can't stand by it 100% but i've heard it's a pretty thorough checklist. Hope it helps. Sorry for such huge posts but i have no idea where to host a Word file...lol. Copy/save it all into a text file.

302 to 351W Swap In A Fox Body Mustang
Note: This FAQ was written for converting a T-5 5.0 efi Mustang to a T-5 351w efi Mustang. The conversion will be slightly different if starting with a 2.3l or carbureted Mustang OR converting to a carbureted 351w. Converting transmissions is beyond the scope of this document.

Background Info-

The major disadvantage of the 302 is its lack of strength at high power levels. Most will agree that at ~500hp the factory 302 block will try to split in half. For many the solution to this is an aftermarket 302 block.

Another alternative is to swap in a 351w block. There are 2 production blocks available; the 69-70 blocks had a deck height of 9.480”, and the 71 up blocks had a deck height of 9.503.” This is compared to the 302 deck height of 8.200” The 69-70 blocks also had thicker main webs and higher nickel content, making them significantly stronger. From 70 to 74 the 351w maintained the higher nickel content, but lost some of the material in the main webs. Another small reduction in the main web thickness occurred in 75, along with another reduction in Nickel content (supposedly), but after that the block remained basically unchanged until it ended production. From 1994 on, all 351w blocks were equipped with roller cams/lifters.

Getting Into the Nitty Gritty

Firing Order-
See Camshaft Section

Camshaft-
The specs of the cam will depend mostly on what your goals are for the motor. Cam spec selection is way beyond the scope of this FAQ. What you want to watch out for is selecting the correct base circle for the deck height and lifter combination, and using the stock 302 HO firing order (since you are most likely reusing the stock 302 computer). Probably the best thing you can do is ask the company you plan on purchasing the cam from, what would be appropriate for your application. They will need to know what year the block is and what lifters you plan on running. Additionally it may be helpful to have your rocker ratio available, and what piston you will be using if not stock.
Here is some unverified info on Ford 302 & 351w firing orders.
early 289 & 302 1-5-4-2-6-3-7-8
302HO & 351w 1-3-7-2-6-5-4-8 (this is all 83-93 Mustangs, and all 5.0 Explorers)

Pushrods-
Again, there are far too many options available to cover here. Check with the cam manufacturer on what length pushrod you will need. Or even better, you can use a pushrod length checker and measure them yourself.

Roller Lifters-
The stock 302 lifters can be swapped over to the 351w with a little machining and grinding. First the spider will require 2 holes to be drilled in the main valley. These holes will be drilled over the cam bearings, so great care should be taken not to damage the camshaft or bearings. Risk can be minimized by removing the camshaft, and drilling the holes before the cam bearing is installed. Some grinding will need to be done to allow the factory 302 dogbones to sit flush on the 351w block as well. A dremel is adequate to get the job done. Be patient and work slow; it is easier to remove material than put it back. Of course it would be best to do this work before having the block cleaned and prepped for assy. Ford Hydraulic Roller lifter (for both the 302 and 351w) part number is M-6500-302.
If all of this does not sound appealing to you then maybe some of the aftermarket roller lifters will be a better option. These tend to be fairly expensive however. Look for lifter pairs that have a link bar, connecting each pair of lifters.

Rocker Arms-
This will depend on the heads you select. All of the same rules that apply to selecting rockers for a 302 still apply to the 351w. Options to consider are Pedestal vs. Stud Mount, Roller vs. Non-Roller, and Brand.

Engine Mounts-
Stock 5.0 mounts will bolt up to the 351w. Aftermarket alternatives include solid mounts and polyurethane mounts. Convertible Engine mounts are supposedly reinforced & stronger. Another alternative is lowering engine mounts from HP Motorsports. These are solid and lower the motor ~¾”. Lowering engine mounts are useful for gaining hood clearance, but will also reduce clearance between the oil pan and stock k-member. This presents clearance issues with some aftermarket pans and stock k-members, but should be ok for the FRPP pan. The use of an aftermarket tubular k-member may help improve clearance.

Heads-
302 heads are the same as the 351w heads with the exception of the head bolt diameter. 302 heads have a 7/16” head bolt hole and the 351w has a ½” head bolt. Opening the holes can be done by hand, if done with care. It would be best to send this work to a machine shop however.

Exhaust Headers-
Stock 302 headers will bolt up the head of a 351w (since the heads are basically the same), but will not mate up to the factory 302 mid-pipe due to the extra width of the 351w. There are many aftermarket suppliers of 351w Fox Body headers including MAC, FRPP, Kooks, Hooker, and Hedman. The Ford shorty headers are p/n M-9430-A58.

Intake Manifold-
Since the lifter valley of the taller 351w is wider than the 302, a new lower intake is required. Aftermarket suppliers of 351w intakes are numerous. Most of these companies offer a 351w lower intake that will bolt up to the 302 upper intakes, which many Mustang owners may already have. Being able to reuse your current upper intake can present a significant $ savings.

Be cautious with intake height if you are trying to clear a stock hood. If the above mentioned drop motor mounts are not used then, another option is to cut down the upper intake. This is easier on the plastic box upper from Comp Cams, as the aluminum intakes will require cutting/welding followed my machining to square up the mating surface.

Shortening the upper intake will cause clearance issues between the TB and valve cover if the upper is trimmed more than ~¾”. Keep in mind that TrickFlow and many other aftermarket head companies have raised the valve cover flange up to .300” which will limit how much you can trim from the upper intake. Of course the use of tall aftermarket valve covers will be somewhat restricted as well. If you do plan on cutting the upper intake, be sure to do a full mock up with all parts that will be installed later. The part numbers for the Ford 351w Cobra manifold are as follows; Upper M-9424-D50 / Lower M-9461-D58.


Oil Pan-
The 351w is wider so a new oil pan is required. The lowest cost option is probably the FRPP 351w pan for Fox Body applications (M-6675-A58). Aftermarket companies have standard volume, high volume, drag race, and road race pans available. A pan specific pickup tube and dipstick will also be necessary. If using a main girdle and/or windage tray, be sure to select an oil pan that will clear these added components. If you can find them 351w equipped Crown Victoria and Grand Marquis had an oil pan that will fit in your Fox Body Mustang.

[85_SS_302_Coupe]

Oil pump-
The 351w oil pump is different from the 302 (mostly external). These are readily available in standard volume, high volume, and high pressure models. If a high volume oil pump is to be used, it is recommended that a high volume oil pan be used as well (most aftermarket pans seem to be 7qt).

Distributor-
The taller 351w does require a longer distributor. This can found from several stock Ford factory applications, mostly pickup trucks/vans. Some aftermarket suppliers do have electronic/TFI distributors available, such as MSD and Accel Be sure that the cam drive gear is appropriate for your application. Roller cams require a steel dist. gear.

Engine Management-
Any stock 302 computer will handle a mild 351w swap. The EEC-IV will be fine until the combination gets more dramatic with larger injectors, heads, intake, and cam. Aftermarket plug in style chips are not going to offer ideal performance. The best solution is to invest in a chassis dyno tune or an EEC-IV computer tuning system, such as a TwEECer.

Flywheel/Flexplate & Starter
The counter weight of the 5.0 is 50oz. The 351w counterweight is 28oz. You can reuse your 5.0 flywheel if you have it rebalanced at a machine shop. This is probably the easiest and most cost effective alternative. If purchasing new parts just make sure that the flywheel weight and starter tooth count are correct for the other components you already have. Ford flywheel M-6375-A302.

Harmonic Damper-
Again this must be matched to the 28oz. counterweight of the 351w. Another consideration here is getting the crank pulley to line up with the rest of the serpentine belt system. Many aftermarket dampers will come with an appropriate spacer for this application. FRPP does have a damper available specifically for this application (Damper M-6316-C351, and spacer M-8510-B351)

Fuel Injector Rails-
The stock 302 rails will not be wide enough to fit the wider 351w lower intake. If the flex line in the front and rear of the stock rails is removed and replaced with longer sections of high pressure fuel line the stock rails will work just fine. Simply cut out the stock flex line and replace it with high pressure fuel line, available from any parts store. A couple of hose clamps will secure the hose in place. It is also important to make sure the hose does not rub on anything.

Fuel Injectors-
Proper injector size will depend on the application. A mostly stock 351w will be ok with 19lb injectors, but with the addition of an intake & Throttle Body (with stock heads/cam) will most likely require 24lb injectors. Here is a link to my Fuel Injector Calculator...
http://www.freewebs.com/vristang/aut...rsformulas.htm

Fuel Pump-
A 190lph pump is recommended for mildly modified Mustangs. If an all stock 351w is being swapped in, then the stock fuel pump may be adequate. It should be noted that due to the re-circulating nature of the Mustang fuel system, installing a pump that is too large is not an issue. If in doubt, go with a larger fuel pump.


Heater Core Hoses-
The stock 302 routed the heater core coolant through metal tubes on the passenger side of the lower intake manifold. These metal tubes may or may not bolt up to the 351w lower intake. Either the tubes can be replaced with tubes from another application (junkyard parts), or heater hose can be used to replace the metal tubing. Just be careful that the hose will not bind or rub anywhere, especially the throttle linkage.


AC/PS-
This is the only stock 5.0 accessory bracket that requires modification. The original AC pump and Power Steering pump can be reused if an FRPP bracket is used. If using Power Steering only (without A/C), the FRPP part number is M-8511-A351. For both AC and PS applications the FRPP number is M-8511-B351.

Emissions-
Most emissions equipment can be swapped over, and will be required if the car is to pass emissions testing. The smog pump will present few challenges; mostly just routing of the hoses.

The EGR setup will depend on the application. The stock 302 routed the EGR gasses through the lower/upper intake. With some creativity the air passages on smog legal heads can be used for EGR. Several factory applications used a crossover pipe, which routed the exhaust gasses from the heads up to the EGR valve. These crossover pipes can be found on 351w equipped trucks and vans.

Hood-
The easy way to do it is get a taller cowl hood to replace the stock hood. This offers the aggressive look that many are looking for. If desired though, the 351w can clear the stock hood. Clearance will depend on engine mounts and intake manifold selection/modification. If necessary some of the bracing on the underside of the hood can be cut away, and the insulation mat can be removed. In general at least 3/4" will probably need to be trimmed off the height of the new 351w motor, but this will vary greatly with each combination. The reduced height can be achieved with lowering engine mounts (as mentioned under the engine mount section), or by shortening the intake manifold (as mentioned in the intake manifold section). There will be some mock-up needed for each application.


Miscellaneous-
Spark Plug Wires
Some Vacuum hoses may need to be lengthened or shortened
Accessory drive belt length will most likely change

Items Not Affected By the Conversion-
Transmission - Be sure to use the correct input shaft bearing in the crank
Bellhousing
Valve Covers
Belt Tensioner
Water Pump
Alternator
Clutch
Timing Cover
Radiator and hoses
Timing Chain
Oil Filter (the 351w uses the same part number)
Head Gaskets (same part numbers apply)


Desirable Upgrades-
3 core Radiator and Electric fan
Subframe Connectors
Tubular K-member (if clearance issues are feared)
Z-spec T-5 (or other high power upgrade)
Torque box Reinforcements
2.5” or larger exhaust
1 5/8 headers should be considered a minimum with 1 ¾ being ideal.

[85_SS_302_Coupe]

I was wondering myself though and i didn't see in that list, if the 302 alternator and power steering brackets will bolt to a 351....otherwise you'd have to get a serpentine setup off of a 351 unless you've got V belts and wanna keep'em.

[Rick93coupe]

Glad you guys remembered the oil pan, that one slipped my mind. Either way, as I'm sure your realizing, its a pretty straight forward swap, nothing too involved. If it were me, I'd invest in a set of heads for it before I dropped it in. There's been lots of guys who are confused as to why their 351 didn't run like what they THOUGHT it should run like. The heads in 78 were J-U-N-K! Even a standard old set of GT40's would wake it up considerably, like they put in the 351 lightnings. Still not ideal, but you get the picture.

[Rick93coupe]

I'm considering putting these on the boat motor once the car is finished. Worth looking into. IMO
http://www.tristatecylinderhead.com/catalog/product_info.php?cPath=41&products_id=43

[85_SS_302_Coupe]

Yeah i would honestly rather have an HO 302 vs. a bone stock "truck 351". It may make more torque but that's where the fun stops. Throw some GT40/GT40P heads on one or better yet get a set of the '69 351W heads and port'em out if you can't get aftermarket heads. There's also a lot of waking up to do with a 351 when you put the whole heads/cam/intake combo on one since in stock form they were really built for emissions.

[Johnson1134]

yeah i am going to take the 351 apart this winter and freshen it up!and go after market h/c/i.

[Johnson1134]

so if i go with a tremec trans it will work?

[85_SS_302_Coupe]

it'll be the same as with a 302, you just have to get the right bell housing for the trans and it'll bolt right up. The bolt pattern is the same in the back of a 351 as a 302.