My427stang wrote:True statement, a GT head is better described as a "small port truck head drilled for unibody car exhaust manifolds"
They are absolutely nothing special. D2TE-A (truck only) and C8AE-H (truck and car) are identical and on almost every truck out there from 68+
I disagree with that statement completely. First off, the ports are smaller but it was an efficiency design, not a truck design. On a mild engine the smaller port made for better velocity and fuel atomization which makes for much more efficient engine operation. The smaller ports actually helped improve power in the lower RPM ranges that cars usually operate at. THe C8AE-H (and C8AE-I) heads are a very good mild head up to about 5000 RPM but at that point they fall off fast. The other thing I disagree with is the C8AE-H and the D2TE-A heads are only similar. The D2TE-A head is actually a significant improvement over the C8AE-H with slightly better port design and the chamber changes make for a significantly better combustion process. It is all about efficiency. These heads were a big improvement over the earlier larger port heads because they were designed to improve the combustion process and they do a great job. That is not to say that the earlier heads can't be better, it is to say that in stock applications, the later heads perform the task they were designed for much better from the factory. BTW, the D2TE heads are worth a few HP on the dyno over a C8AE-H with no mods at all! Finally, to the issue of GT heads, A GT head is the same as a truck head of the same year as far as the casting goes. It has the same ports and chambers, the same valve sizes etc... What makes it a GT head is the exhaust side is drilled with a different bolt pattern to fit GT manifolds (truck manifolds will not bolt on) and they have different valve springs. There is no potential power gain from running a GT head over the truck head. Hawkrod
As you can see in the pics below, the C8AE-H and the D2TE-A heads do have different chamber designs (it is a common misconception that they are the same, probably because very few people have actually bothered to look due to the lopo nature!):