Can You Really Put GM LS Heads On A Ford Small Block?

Technically, with enough cutting and welding, you could probably make any combination of block and heads work for at least a few minutes. Slicing and dicing a set of Chevrolet LS or LT V8 heads to fit on a Ford Windsor 302 or 351 wouldn't even be the weirdest Chevy head on a Ford block project out there. A guy named Ken Hutchison cut the end cylinders off of a couple of LS heads and welded up a single inline-six head for a Ford 300.

But, what's astonishing about the LS/LT-head-to-Windsor-block swap is how much lines up. The Chevy small block V8 famously has a bore center spacing of 4.4 inches, while a Ford Windsor V8 has a nearly identical bore center spacing of 4.38 inches. Both use 10 head bolts that are in roughly the same location. The pushrod paths are also relatively close. It's almost as if, feeling the rage after papa GM had the audacity to allow a Lotus-designed V8 made by a marine engine company into the Corvette ZR-1, Chevy engineers were taking no chances making the next generation small block V8 as stout as it could be. So, maybe, when creating the LS, they copied a little homework to meet the C5 deadline?

Well, probably not. Pushrod engines are already pretty similar to each other, especially when their pre-existing bore center spacings are almost identical and use the nearly-ubiquitous 90-degree V angle. The truth is, mating up LS and LT heads to a Ford Windsor small block still requires a metric butt ton of work to yield a usable engine.

The first hurdle to overcome is that the LS head bolt holes aren't quite in agreement with the Windsor block. To get them to line up, you have to oval out the holes in the heads. It appears, according to GMTgearHDs' "351LS" project involving a 351W truck block and 317 LS 6.0-liter truck heads, that just the outside sets of holes need this treatment, as the middle six line up close enough. 

A 302W/L83-LT-head build by fabricator Mark McDonald and his son Corbin was documented by Hot Rod, and they used a Windsor head gasket as a template on the head to line up the holes starting in the center. Some coolant passages matched up reasonably well, and some had to be filled and redrilled. Unused passages in the head were blocked off. Since the heads came from a 5.3-liter L83 GM truck engine with direct injection, the DI ports were filled in preparation for a conversion to port fuel injection. 

According by Tecmotion's video, the existing pushrods will go through, though they're the wrong length and custom pushrods are necessary. There's also the issue of valve angle differences (15 degrees in LS/LT heads versus 20 degrees for Windsor heads) with the valvetrain. Tecmotion popped the stock LT rockers in to find they were dang close, and they theorized that a builder could add clearance for the pushrod in the head. Still, changing valve angles willy-nilly is asking for valvetrain geometry headaches. 

Now, zero intake manifolds fit this Ford-Chevy chimera, necessitating a custom build. Also, Chevy heads need a dry lifter valley, which means the Windsor block's exposed wet lifter valley must be blocked off. And then there are potential lubrication and oil passage problems to solve.

This all sounds like a lot of work when Ford Windsor V8s famously already have heads. While this may seem like an extension of the "because it's there" ethos espoused by George Leigh Mallory as he prepared to climb Mount Everest, and we all know some engineers like to do difficult projects just because they can, there's a good reason to give LS/LT heads on a Windsor the old college try (that reason is money). 

The aluminum L83 heads that the McDonalds picked up were from a flood-damaged pickup truck, and they scored both of them for $280. The stock intake ports flow 253 cubic-feet-per-minute (cfm) with 0.6 inches of valve lift. Over at Ford Performance Parts, a set of aluminum "X2" Street Cruiser 302/351 heads are $1,250 each and flow 230 cfm at 0.6 inches of lift. So, saving $2,220 on heads with superior breathing sounds like a pretty compelling reason to give the swap a shot. 

Still, to make this work, you'd better be a fabricator or be really good friends with a fabricator who will cut you a serious discount. Neither the McDonald nor the GMTgearHDs engine seems to be running yet, so there isn't any pudding to look through for proof at this point. Perhaps an LS-headed Windsor is a viable way to get Boss-351-Cleveland-level breathing and performance(if you're interested, here's the difference between Ford's 351 Cleveland, Windsor, and Modified engines), or it could be a years-long fabricating nightmare that ends in a leaking, ill-running engine with perpetual performance deficiencies. The LS and Windsor V8s sure are close in design, but as anyone who's ever had a lottery ticket with every number being one away from the winning results will tell you, sometimes close isn't close enough.