The 351W is a Windsor class engine. It is made on the same factory line as our beloved 5.0. However, the 351 posseses several qualities that make it a desirable block for an engine buildup. The advantages of using a 351W vs a 5.0 (302):
Obviously, you get an extra 49 cubic inches of displacement. As the
saying goes, there is no replacement for displacement. Second, the
webbing in the lower half of the block is thicker, making the
block stronger. Third, the crank has bigger main and rods journals,
making the cranks more durable than their 302 counterparts.
FACTS: What you need to know/consider when you swap a 351W into a Fox3 platform chassis:
The 351 block is very similar to the 302. That means that almost all parts swap between a 302 and a 351. This includes: Heads, cam, lifters, timing chain, timing chain cover, water pump, engine mounts, and all sorts of other stuff. The bellhousing bolt pattern is the same as a 302, so all trannies that bolt to a 302 will bolt to a 351. However, there are some differences in the 351 that necessitate new parts:
1) The oil pan is different. Motorsports carries one. You can also get an oil pan of of an early eighties LTD Crown Vic. If you go the junkyard route, remember you also need a oil pan pickup tube, and a special main bolt that the pickup attaches to. The FMS pan is a pretty good deal, and if you shop around, you can get one for under $100, which comes with the dipstick, bolt, and pickup tube.
2) The internal balance of a 351W is the same as pre-81 302's (28.2 oz). The 5.0 HO has a 50 oz. unbalance, which means you cannot use the flexplate/flywheel or the harmanic balancer off of an HO engine. You have to get the correct pieces from a dealer/junkyard.
3) The deck height is higher, which means you need a different intake, since the 351W intake is wider. A 5.0 Upper will bolt to a 351W lower.
4) Also, a higher deck height means that the accessory bracket will need to be replaced. FMS sells the new bracket for about $50.
5) The higher deck height means the headers sit up higher than in a 302 powered Mustang. A special set is required for a 351.
6) A 351W will in all likelyhood not clear the stock hood. You will need a cowl hood for your car.
7) The distributor has a fatter shaft. You can obtain one from a 351W powered FI truck (if you are using FI) or any late 70's/early 80's car using the 351W and a Duraspark system if you are going to build a non-efi car.
Those are the major differences. As you can see, for about $1000 you can put a 351W in your Mustang. This is cheaper than a stroker, plus you wind up with a more reliable engine.
Tips: There are several things to look out for to ensure that your swap to a 351W is easier and more successful. They are as follows:
1) A high volume oil pump WILL NOT clear the FMS pan. If you want to run an HV pump, you must either modify the pan (which is what I did), or buy a Canton or similar pan, for many dollars more. The modifications just include cutting down the front drain bolt, and welding on a corner to the pan to clear the pump housing. It cost me $25 to get my pan welded.
2) Get new motor mounts. If your mounts are questionable already, the additional weight of the 351W will make them fail in a hurry. I recommend the 87-93 convertable mounts, which will work in any 79-93 Mustang.
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