I heard you can drill and tap a 351 to use that spider for a roller cam?
You can, but this is a separate issue from the valvetrain stress introduced by a small base circle cam/stock 302 lifters.
The first section of this has the block/cam info you need...
302 to 351W Swap in a Fox Body Mustang
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.
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:
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 ***** 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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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