302 Cleveland

As has been mentioned before, the 302C engine was unique to Australia. Effectively, it was short stroke - 3” as opposed to 3.5” - 351C engine, which used a different crank and shorter rods. Early in its life in the XA and XB Falcon range and ZF and ZG Fairlanes, the 302C was available only as a two barrel carbed engine, but later, when Ford introduced the XC Falcon and ZH Fairlane, they swapped to a four barrel carburetor. This was primarily an emissions driven change and the carb fitted was the Carter Thermoquad which is a spreadbore type of carb with small primaries and larger secondaries. Again, there was some logic to Ford’s move as it redesigned the inlet manifold to take the Thermoquad but could use it on both 351C and 302C.

The most interesting thing about the 302C engine is that fact the Australian heads that were fitted to it are different from the Australian heads fitted to 351C engines. The 302C 2V heads are closed chamber heads - sometimes called quench design - and have a chamber size significantly smaller than that of the Aus 351C 2V head. The chamber size for the 302C is 58cc, in comparison with 74cc for the 351C. The difference between the two is compensated for in the actual difference in the combustion chamber size between the shorter stroke 302C and the longer stroke 351C. Considering the engines as fitted to cars, for example an XB, the actual compression ratio is 9.4 to 1 for the 302C and 9.1 to 1 for the 351C.

Now, the closed chamber quench design of the 302C head is more efficient, so it would theoretically be a good idea to fit the 302C heads to the 351C block and rods ? The problem is that the compression ratio for an engine configured like this hits 11 to 1. Great in the days of high octane petrol, not so good now. It can be done, and done successfully, but it has to be watched carefully for detonation. The other side of the coin, of course, is that if you put 351C heads on your 302C engine, then you get awful compression, and it is a waste of time.

To illustrate. This is a 351C open chamber head.



And this is a 302C closed chamber head.