Which GT40 heads?

dw89lx said:

Does anyone know how to tell which gt40 heads I have? Is there any markings that are visible on the outside of the heads. I bought the car with the heads already on. I went to change the spark plugs and found that the last guy that owned the car used Bosche 4449 plugs which are used on the stock heads. I was told that I should be using autolite 3924's. Now I'm wondering if the heads are even GT40's.

Click to expand...

jasonlee0704 said:

Collected from 2 different sources, Mustang Performance Engine Tuning and the Mustang 5.0 Technical Reference, here's how to distinguish between GT-40 castings.

OEM iron GT40 head:

has 3 vertical ribs cast into each end of the head
have "GT" cast into the right outboard corner

OEM iron GT40P head:

has 4 vertical ribs cast into the front of the head
has "GTP" cast into the head

SVO/FRPP aluminum GT40Y and GT40X head:

have "SVO" logo cast into the front of the head

Click to expand...

dw89lx said:

Well it looks like I got screwed!!! I wish I knew about the castings before I decided to buy the car. Where there any older gt40 heads without the lines or gt cast into the head?

Click to expand...