Rebuilding a Ford 351 Cleveland

Part 4: Ford 351C Cylinder Heads

Let's take a look at my cylinder heads. - Matt Hannes

Original Heads. As discussed earlier, my cylinder heads are the large open chamber style (Ford casting D3ZE-AA). Although there's nothing physically wrong with them (other than a lot of carbon build-up on the valves), I am replacing them with a set of earlier "quench" chamber heads. This is for two reasons. First, the quench heads promote better combustion with less detonation, although I will have to switch to flat-top pistons to keep the compression ratio reasonable.
Secondly, the D3ZE heads have fixed non-adjustable rocker pedestals. Since I plan to convert to a roller camshaft, most aftermarket conversion kits require the use of adjustable rocker pedestals. So I would have to have these heads machined to accept screw-in adjustable rocker studs. So I decided to see if I could track down a set of the quench heads.

"New" quench heads. I acquired a set of original Ford quench heads (casting D1AE-GA). These have the smaller wedge-shaped combustion chambers as seen here. They're 64 to 67cc which computes to a healthy 10.6 to 10.7 compression ratio with flat-top pistons. They also have the adjustable rocker arm studs which I will need for my camshaft conversion.
Quench chambers. The wedge chambers used on early Cleveland heads had excellent combustion properties but unfortunately were not emissions-friendly. The shape of these chambers cools the flame front and increases mixing, meaning less chance of detonation and more low-end torque.

In the glory days of leaded gas and no emissions tests, Ford offered these heads paired with pop-up pistons for an 11.1 compression ratio right from the factory.

Top view of the quench heads. Here we see the 7/16" diameter screw-in adjustable rocker studs and push rod guide plates. These are all Ford parts designed for use on high-revving Clevelands with mechanical camshafts. I'll need the adjustable studs and guide plates for my roller cam conversion.

Intake ports. Cleveland heads (and Boss 302 heads as well) are famous for their giant intake ports. Here we have a good look at a pair of them. The intake ports are 2.50"x1.75".

Exhaust ports. They are quite large at the mating face (2.00"x1.75") but are actually shallower further inside the casting.

Rocker studs and guide plates. My 1973 heads weren't equipped with these, and I'll need them for conversion to a roller cam, so finding a set of quench heads with these features in place will save some machining dollars.
Note: I later discovered that the Ford guide plates seen here would bind up my new CompCams valvetrain. I ended up having to replace the Ford guide plates with CompCams guide plates to get everything to align properly.

Continue to Part 5 - New Parts

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