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Is there any difference between C6AE U and C7AE A heads 14 bolt? I've been told that U was the end of C6 and A is the start of C7 castings. I've read different assembly plants used a variety of casting numbers depending on what was available, even pulling engines off other assembly lines like Fairlane GT. Every book I read has different info.
 

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390GT heads for 1966-67 could be C6AE-J, C6AE-L, C6AE-R, C6AE-U, and C7AE-A. There may be one or two others. Note that all of these castings were available on any FE these two years. The GT did not get a special casting. It was simply drilled for the Fairlane/Mustang exhaust manifolds, and the GT also got a valve train suitable for the GT camshaft (stiff springs, etc).
 

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Both of those are low performance heads used on everything from 352 to granny's 428 station wagon. The C7AE-A heads were used on Shelby GT500 428 engines, not because they were anything special, but because they had the 14 bolt pattern in 1967 so the Mustang / Cougar exhaust manifolds would fit.

The C6AE-U was used only in 1966. There is precious little difference between the two, perhaps the exhaust ports on the C7AE-A heads are a little more restrictive but basically both are crap from a performance standpoint the way they came from Ford.

Either can be ported and have bigger valves installed for improved performance, but the cost will approach or surpass modern aluminum heads that are better right out of the box.

Is there any difference between C6AE U and C7AE A heads 14 bolt? I've been told that U was the end of C6 and A is the start of C7 castings. I've read different assembly plants used a variety of casting numbers depending on what was available, even pulling engines off other assembly lines like Fairlane GT. Every book I read has different info.
 

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Discussion Starter #4
Thank you for your reply. Were all heads cast at the same foundry? I have a 67 GT390

S code. All the casting dates are 66 though the car was built in 67. I've seen several 67s original drive train with a variety of cast numbers. Ford didn't make it easy on FE motors
 
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