[xXJakeXx]

Ok so i about **** myself today when i started researching about this engine thats in my 1966 mustang and why someone would put it in it. The serial to the engine is D8XE-6015-A3A And it says 78 0n the block and as well on the heads under the valve cover. Does anyone know why the horsepower was killed so much and what on the engine mainly decreased it? Heads compression? I know it was emssions related.

Thanks,
Jake.

[rotorr22]

Originally, the automobile manufacturers rated their engines in much the same way most dyno shops do today, that is, without any accessory loads or restrictions imposed by stock induction systems. Starting around '72 or '73 they tested to an SAE spec that included said. Further emissions related modifications to the cam timing and compression ratio further degradated horsepower. Mid to late 70's Ford engines were the worse of the worse for power output. Put some good heads on a '78 shortblock, along with a good cam and induction and you can gain a lot of power!

My guess as to why someone put a '78 302 in your '66 is that they got it cheap or had it setting around.

[xXJakeXx]

I already picked up a beefy but streetable crane cam and the engine has a 289 performance edelbrock intake, and a 4 bbl edelbrock 600 cfm carb. The heads are restricted as well? If i were to get heads off a older year like 67 68? what should i go with cast iron wise, cant afford aftermarket aluminum. Or should i save the headache and pick up a 351w from a buddy of mine? Thank you for the info.

Jake.

[BLUEMAX]

Im not sure what it takes to install a 351 in your body style, but if it is mostly a street car Im sure going with a nicly built 302 would be plenty of power. Also dont forget if you're looking at heads, factory iron heads have ALOT of weight to them and by the time you go through them (valves, guides, valve job, springs and so on)
you could have a way better performing aluminum head.