The biggest restriction to the 351W and all windsor motors is the exhaust manifold, namely the 351W with it's increased displacement, the 302 get's away with it because the smaller engine doesn't notice the restriction as much. The problem is right at the entrance for each port, the port in the manifold gets squeezed sideways right at the entrance, the manifold itself is very restrictive with it's 90 degree bends into the main section of the manifold, i see no other reason for this other than to make the exhaust manifold stronger at the flange, who knows but it sure impedes airflow out of the heads. I have a E150 with a 351W and i am hoping a pair of shorty smog hedders will slip in there and let me hook up the factory Y-pipe with minimal hassle but i am sure some pipe work will have to be done, just don't know how much.

The other lesser but equally important restriction is the intake manifold itself, there are plenty of very expensive options but all you really need to do is send the manifold and have it 'extrude honed', they force a very thick and abrasive substance through the manifold and it removes a layer of material from the inside of the manifold as it is being forced through, this is considerably less expensive than going with an aftermarket manifold and to be honest i don't want intake runners as big as the aftermarket but i do want to improve on the factory design, not a lot of material needs to be removed to let that manifold breathe and as an added bonus the inside of the manifold is very smooth after the extrude honing operation.
After you have improved flow on both sides of the head and you're still not happy with the 5.8 then it is time for a pair of TFS Twisted Wedge 185's, the 170's belong on a 302 and are too small for a 351cid engine.
The 351W will make 300hp with these mods and you don't need to change the cam but S/D (speed density) MAF is a little bitchy and enjoys 112 LSA or less, TFS has you covered there too and if i was using their heads i would damn sure use their camshaft since it is designed to work in harmony with the twisted wedge heads.. Have fun..

 

The exhaust manifolds for the first Windsor small block Ford was designed to primarily fit between the shock towers of the Falcon. There was really no consideration for efficient flow. Of course, if you think about how they have to package the engine under the hood, the primary consideration is how to make all its parts fit into a limited space. That's true for all passenger cars, with the remarkable exception of the Boss 429 Mustangs, where the shock towers were modified to make room for the heads.

 

There's one thing I don't understand about the TFS Heads:

On every "Twisted Wedge" Head I looked up was the note "Trick Flow Pistons Required"
But nobody here seemed to do that.

Is ist just a marketing strategy or just a matter of camshaft lift?

 

Wow, all that information and he completely missed the other bottleneck in the exhaust ports, the Thermactor bumps. 30 minutes with a porting bit and they're history. Then he also missed the stock throttle body, which is the same part used on both the 300 six and the 302. As for the TFS 170's being too small for a 351, that's kinda strange considering the stock heads somehow seem to work, up to a point.

 

normally i would take the time to prove you wrong but you were really rude to me so i will not contribute any more of my worthless info to your site, you seem to know it all so have at it and have a great day, i will not bother posting since i MISS so much stuff.. what an ******* you are.. all the people that loved reading my articles will no longer have that opportunity thanks to people just like you..

 

Gee, I though guys came here to get questions answered, not to read articles that lack pertinent information.