What are the differences between a sbc 350 and a sbf 351W?

Other than the obvious like the distributor is in a different position and the intake manifolds are different.........

For example, they share almost identical bore/stroke, but are the potentials similar out of the two?

What about the differences between the cylinder heads and cam configurations and such?

 

everything is differant as far as interchangeabliity goes. big differance on ford and most other engines compared to a SBC is the GMs 5 head bolts per hole and everyone else uses 4. less bolts allows for a little more room in designing ports and such.

 

Ede,

That's the kind of info I am looking for. I know that pretty much nothing is interchangable, but am just curious why one is considered a staple of the company (the 350 sbc) while the 351W is largely over looked. I was just curious as to why.

 

At one time, the 351W was in fact the staple engine in their lineup. It is still used in similar places: trucks, the Roush Mustangs IIRC, etc. It is the weapon of choice for NASCAR and other stock car racing.

In race-prepped form, the 351W usually produces slightly higher HP than a SBC, for the reasons ede cited. By the time you stick 5 bolts and 2 push rods through a head around every cylinder, there's not much room left for ports, especially on the intake side; with one less bolt (i.e. a square pattern around each cyl, rather than a pentagon), the intake port can be a good bit wider. The characteristics of the engines reflects that difference. The SBC (SB2 these days) produces slightly higher peak torque, but a slightly lower RPM compared to Brand F. You can watch the races and see this in action: the GM cars tend to come off the corner harder, the Brand F cars pull a little better down the straights.

 

The Early design Windsors also used a lighter crank with smaller journals, whereas the Cleveland and MC versions used a larger main and heavier crank, limiting the rate of spin-up to some extent. The Fords (both varieties) also used an oiling system that fed the mains and cam simultaneously.

I used past-tense terms, since that engine is history in the Ford lineup - too bad for them.

Factory SBCs fed the oil to the rear main and rear cam bearing first, then distribute it. A drill and plug can easily convert an SBC to priority main oiling, but the factory guys neglected to do that. Regardless, the lubrication system on the SBCs is generally more than adequate for most driving, and lubrication failures are rare unless some driver neglegence is involved.

The Fords also enjoy a slightly taller case and a little more cam clearance for stroking. The case is however, heavier as a result, but by design ovesight is actually a little weaker in the web areas.

There was also a firing order change part way through the line, so camshafts and other parts aren't as "universal" as with the SBCs.

As for the head bolt pattern, while the four-bolt pattern of the Fords allows for wider ports, the strength of the assembled case is reduced as compared to the SBC. Chevy builders can accomplish equal or better flows through taller ports at a higher angle, so unless "stock" rules apply, the flow differences are inconsequential. Aftermarket or custom heads can easily solve that discrepancy. The LT1 (and derivative Vortec family of SBCs) approached this problem and changed the port height and angle.

Incidentally, the LS1 family solved the port issue quite nicely by using non-siamesed intake ports, allowing whatever size the builder could imagine. Stock LS1 intake ports are very tall and relatively narrow, similar to what custom or aftermarket heads for SBCs are using. The LS1s seem to do quite well with them. The LS1 family also changed the head bolt pattern to six bolts surrounding each cylinder, but with two of that pattern raised well above the cylinder liner area and closer to the intake ledge. The familiar pentagon pattern is now gone.

 

So I can take a similar approach in a mild build up of my 351W as I would with a 350 sbc. I'm by no means even experienced or knowledgable, but am at least more familiar with SBC's.

I was curious though because in my experience, at least in stock form, the 351W doesn't seem to be as capable as a 350 sbc. I'm talking about carbed trucks though, not performance cars. I'm almost topped out in stock form in my 83 Bronco (and I have the H.O. factory option) at 75 mph, and right now I'm running 3.55 gears.

Now I know that it was designed with a 55 mph speedlimit and is supposed to be an off road. But in a similar counter of a Chevy, it seemed to be much more powerful on the highway.

So I can attribute the general gutless performance to the factory settings, not just to the fact that the engine is just hands down inferior.

One interesting thing in aftermarket parts is that brand F produces rather inexpensive parts like heads and cams and such. The other brands like edelbrock, holley and such are more expensive for brand F, especially with the 351W than a sbc, and it seems that the information regarding this engine is much less readily available.

 

One last question:

If the 351W is a decent powerplant, then why did Ford quit using them?

Sounds to me like it's fairly universal in its application, being used in trucks and sports cars, so I don't get it.

 

Probably for reasons that have nothing to do with how good of a job it does at producing power....

• emissions
• CAFE
• labor contract at the plant that built them
• replaced by a new design that's cheaper to produce

and so forth...