2 351Ws to get or not to get

alludethis · Sep 16, 2006

My g/f was talking to a guy today who has 2 351 Windsor blocks he's trying to get rid of. They are both still in vehicles so i would be getting the engines and vehicles for 500-700 dollars, i guess he isnt sure how much he wants to get rid of them for. My question is, are they worth that much? 1 is running and the other is not. I was reading on here that there is clearance issues with the 351 in the fox body stangs? Also, they are carburated, how hard is it to switch them to FI? Does anyone know the HP rating on a stock 351W and if they are good for supporting boost?

90_Red_LX · Sep 16, 2006

A 351W block will hold around 650 hp or so. A lot stronger than a 302 block. A 351W will work with efi, you just need a new lower intake since the valley or w/e is wider. Can't remember what you call it technically. But you need a new lower. Other than that the efi will work with it. The stock hood won't clear with a 351w. You'll probably have to run a 2.5" cowl at the very least. I think the oil pan from the stock motor will work fine but I'm not sure. The 351 oil pan won't work I know though. It's pretty much a straight bolt in, and worth the money imo though. You can make plenty of power, and gobs more torque with a lot milder setup than a 302 based motor. And the block is a lot stouter.

Hickfied · Sep 17, 2006

You need a double hump oil pan for the 351. Depending what vehicle it is in, it may have one. A 5.0 oil pan will not work on a 351.

2000xp8 · Sep 17, 2006

IMO, not worth it.

If they were already built for performance, i'd agree, but a standard 351 really doesn't do much if anything that a 302-347 won't.

To take advantage of a good 351, you need a set of heads correctly matched. victors, tfs cnc's, afr 205's, so if you aren't prepared to shell out $2000 for heads, don't bother.

85_SS_302_Coupe · Sep 17, 2006

Eh....any mod that'll make a 302 run stronger will make a 351W run stronger. More cubes is never a bad thing. As for needing heads.....2000xp8 is right on that, but if you compare two engines, say a 347 and 351W, and lets say they both have good flowing/matching aluminum head setups and both are running around equal numbers since they're similar in cubes....when you get bored with how the 347 is running, the only thing you can do is get a power adder. When you get bored with your aluminum head 351W, you can still stroke the crap out of it AND get a power adder.

Cubes do still matter in the performance world...even Ford finally realised it when they put the 5.4 in the Shelby. It's just too bad they should have already been using the 5.4 in the GT.

vristang · Sep 17, 2006

It sounds like it would be worth the money, as most yards will get ~ $700 for a single 351w long block. You will have to dispose of the vehicle bodies though. Consider that cost as well.

Yes, stock heads will strangle a 351w.
But, if you put a cam in an otherwise stock 351w, it will run better than the 302 with same cam/heads.

You can get the 351w to clear a stock hood. I did, but most go with a cowl hood.

The oil pan and lower intake must be swapped. Not all 5.0 upper intakes will bolt up to a 351w lower however.
What intake do you have now?

The stock efi electronics/computer will handle the 351w very well. Converting a non efi 351w block to efi is pretty much a bolt on conversion.

We have no idea what your current car is.
Year/computer
engine mods
other mods

I'll put up my FAQ too. That should give you a good idea of the considerations.

jason

vristang · Sep 17, 2006

http://www.freewebs.com/vristang/fox351wswapfaq.htm

302 to 351W Swap In A Fox Body Mustang

VRISTANG

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 basic 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 351w is supported by the aftermarket nearly as well as the 302, but can handle much more power than the 302. Some common safe power numbers given for the 351w are usually in the 600-700hp range.

351w Casting Numbers
The casting numbers are on the passenger side near the starter location. You will have to turn the block upside down to see them.

The year will be designated by the first 2 digits of the casting number.
The first digit is the decade and will be a letter. C=1960's, D=1970's, E=1980's, and so on. The second digit will be a number and specifies the year of the decade. Some examples follow:
D1=1971
E9=1989
F4=1994

Getting Into the Nitty-Gritty

The 351w Engine Block -
69-70 - High Nickel content and thicker main webs (These are the only Production Ford 9.480" Deck Height 351w blocks)
71-74 - Reduced Nickel content thinner main webs (71-up had 9.503" Deck Height)
75-91 - Reduced main web thickness
92-On - Lifter Bores were lengthened to accept roller lifters

There were some 351w Mexican blocks as well. These are desirable due to their higher nickel contents. A Mexican block can be identified by the useless looking knobs cast into the block on either side of the timing cover. Mexican blocks were supposedly used on some US vehicles, but they are a very rare find.

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 lifter combination and using the stock 302 HO firing order (since you are most likely reusing the stock 302 computer).

69-91 351w blocks -
Option 1) Standard Base Circle Cam / Aftermarket Linked Bar Hydraulic Roller Lifters
Option 2) Small Base Circle Cam / 302 HO Roller Lifters

92 & Later 351w blocks -
The Standard Base Circle Cam can be used with 302 HO Roller Lifters.
A Small Base Circle Cam is not needed in these blocks.
(The 92 and later "roller" blocks will have a F4TE casted into the block near the starter)

If using solid lifters (either flat tappet or roller) then a standard base circle cam can be used on any year 351w block.

If in doubt, ask the company you plan on purchasing the cam from (or better yet a reputable engine builder) 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.
NOTE: Small Base Circle Cams are known to be less than ideal, as they are weaker. Also, there are not as many cam profiles available for the Small Base Circle Cams, so your Off The Shelf Cam selection will be limited. If possible, it is recommended to avoid the Small Base Circle Cams.

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 (see the cam discussion above) 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 may 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 assembly. 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 & shorter. Another alternative is lowering engine mounts from either Year One or HP Motorsports (HPM). 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 with aftermarket oil pans. Moroso is another potential source for solid motor mounts.
Un-Confirmed –
From 87-90 the convertible Mustang had the “captured” mount design, while the Hardtops had the standard design. The captured style mounts are said to be ½” to 1” lower, and to be stronger.
In 90 and later Mustangs, ALL were equipped with the captured design.
Aftermarket Prothane mounts are said to mimic the design of the early Hardtops. While the Energy mounts are said to mimic the convertible “captured” mounts.

Heads-
302 heads are basically 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 to 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 their 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 by 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 oil rails are 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, the 351w equipped Crown Victoria and Grand Marquis had an oil pan that will fit in your Fox Body Mustang.

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.

Distributor-
The taller 351w does require a longer distributor. This can found from several stock Ford factory efi 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 to moderate 351w swap. The EEC-IV will be fine 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, but may affect durability. 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. However, 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.

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, in fact 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.

GSP393 · Sep 17, 2006

Thanks for posting that FAQ. I'm building a 393 stroker from a 74 351W block. I'm swaping the efi for a Wieand Stealth intake and a Holley 800cfm. Also I plan to keep my stock hood. The info there helped answer my clearance questions.

85_SS_302_Coupe · Sep 17, 2006

GSP393 said:
Thanks for posting that FAQ. I'm building a 393 stroker from a 74 351W block. I'm swaping the efi for a Wieand Stealth intake and a Holley 800cfm. Also I plan to keep my stock hood. The info there helped answer my clearance questions.

Not sure if that's going to fit under the stock hood....reason is, i used to run a stealth on my 302 and if it wasn't for the scoop on my hood, it wouldn't have fit. I'm not running a drop-base breather though, but i am only running a little 2 inch tall breather too.

GSP393 · Sep 17, 2006

I'll measure everything I want to run on the 351 and see what I come up with. I could use the lower engine mounts and maybe even a tubular K-memeber if I have to. I might even have to cut out the inner hood brace. I've got a trick idea I'm thinking about doing, so the stock hood would be necessary. I'm not even near my car or my parts, so I can't do much for the time being.

Thanks for the advice.

85_SS_302_Coupe · Sep 17, 2006

GSP393 said:
I'll measure everything I want to run on the 351 and see what I come up with. I could use the lower engine mounts and maybe even a tubular K-memeber if I have to. I might even have to cut out the inner hood brace. I've got a trick idea I'm thinking about doing, so the stock hood would be necessary. I'm not even near my car or my parts, so I can't do much for the time being.

Thanks for the advice.

The only 351W i've ever seen fit under a stock hood was an EFI setup running a spider style/elbow intake that was VERY short, and it also had a tubular K which was something like 3/4 inch engine drop. I did have a carbed 351W in my old '83 and i had it under the stock hood, but i had a plain old Performer intake, no carb spacers and i ran one of those crappy triangle foam breathers which are really close to the carb but they're a fire hazard.

alludethis · Sep 17, 2006

well i already have a cowl hood on it so clearance isnt a problem. This seems to be alot more stuff than I can do myself so i dont know if it is even worth getting them. Do I have to swap everything over to the 351 from my stock 302 or what? Cant I just build the 351 as its own engine rather than swapping everything over? Or just put the 351 in the car as is? It just seems like its alot more work than i thought it would be, and i dont know that i would do it right.

vristang · Sep 17, 2006

alludethis said:
well i already have a cowl hood on it so clearance isnt a problem. This seems to be alot more stuff than I can do myself so i dont know if it is even worth getting them. Do I have to swap everything over to the 351 from my stock 302 or what? Cant I just build the 351 as its own engine rather than swapping everything over? Or just put the 351 in the car as is? It just seems like its alot more work than i thought it would be, and i dont know that i would do it right.

The swap is not that hard, if you plan ahead.

The writeup I did is an attempt to be comprehensive, so don't let its size spook you.

Read through it one item at a time, and decide what you want to do with each component.
Odds are you already have done some work on the 302, so some of the parts can just swap over.

Since you are going carb'd, and already have a cowl hood the swap should be pretty straight forward.

I suggest getting a performance car cam, as the 351w truck cams that are common in used motors are not ideal for street cars that want to rev.

jason

alludethis · Sep 17, 2006

well actually Im not going carbed. I want to stay FI. Im just not understanding why I have to swap stuff over from the 302, cant i just build the engine itself and get just the parts for the 351 and leave the 302 parts out of it.

vristang · Sep 17, 2006

alludethis said:
well actually Im not going carbed. I want to stay FI. Im just not understanding why I have to swap stuff over from the 302, cant i just build the engine itself and get just the parts for the 351 and leave the 302 parts out of it.

I suppose you could do that, but most of the parts that would go on the 351w are the same as those used on the 302.
You would end up buying parts that you already have.

I guess I should ask what parts we are talking about, as that will make a big difference in this discussion.

jason

Aliate X · Sep 17, 2006

my friend made 763rwhp on his turbo 351. Holds fine.

alludethis · Sep 17, 2006

pretty much the more technical stuff like the harmonic dampner, also grinding the lifters. Also as far as heads and stuff, they wont fit to the 351 so i have to get new ones. I just dont want to mess it up and ruin 1 or both of the motors. I mean how much are heads going to run me? Before I knew i could get the 351, i was going to go with GT40 heads and maybe an aftermarket or ported intake and a blower. Can i still do the same thing with the 351?

vristang · Sep 17, 2006

alludethis said:
pretty much the more technical stuff like the harmonic dampner, also grinding the lifters. Also as far as heads and stuff, they wont fit to the 351 so i have to get new ones. I just dont want to mess it up and ruin 1 or both of the motors. I mean how much are heads going to run me? Before I knew i could get the 351, i was going to go with GT40 heads and maybe an aftermarket or ported intake and a blower. Can i still do the same thing with the 351?

The heads from your 302 will bolt onto the 351w block. The only difference is that the 351w used a larger head bolt. So, if you want to use heads originally setup for a 302 on a 351w you need to enlarge the head bolt holes from 7/16 to 1/2 in. If your good with a drill motor you can do this yourself.
The same is true of the GT40 heads. Just enlarge the bolt hole and they are a direct swap onto the 351w.

The lower intake is wider on the 351w so you need to decide what block you are going to use, before you purchase an intake manifold.
Note also that some companies like Trickflow offer the upper manifold for sale, so that you don't have to buy a complete separate upper and lower when you do the 351w swap. You just buy the 351w lower.

It would be best to run an aftermarket intake, heads, and cam. However, I ran stock 302 heads on my 351w for several months.
It is not the end of the world to do this.

There is no reason why you can't run boost on a 351w.
In fact most supercharger kits for the 302 will fit the 351w.

jason

vristang · Sep 17, 2006

OOPPPSSS!!!!

Forgot about the damper.

Use the one from the 351w. The damper counter balance must match the counter weight of the crank.

dastang2 · Sep 17, 2006

i got a cheap oil pan for a 351 if you want it, needs some sandblasting though. comes with dipstick and pickup tube.

2 351Ws to get or not to get

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