The GT40 story is complex. The first cars had the 289s.
They were homologated in Group 4 as Ford built enough of them to comply with Group 4.
After failing to win in 64 and 65 Ford had a re-think and came out with the Group 6 Mk2 with the 427. This won Le Mans in 66. It was prepared by the Shelby team.
In 67 Ford came out with the Group 6 MkIV also with the 427 and it won Le Mans.

In 68 the organisers decided to bring in a 3 litre capacity limit for Group 6. There was no capacity limit in Group 4 as long as you built the 25 cars required. The Mk2 and MkIV were no longer eligible so Ford pulled out and left the John Wyer team to run the old 289 powered GT40 in Group 4.
Somehow they won in 68 and 69. It was these cars that had the Gurney Weslake rocker covers.

- thanx for the history

Not a bad effort on the rocker covers then, Harry...........

_________________
1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.

Hi Morris 1100
Let me tell you a little about the GT40 heads the Gurney Weslake were a modified 289 [recast head] they took away the short turn radius, or the ski hump as the yanks would say and called them GT40 heads once again these heads flowed more air on the flow bench but they lacked that low down torque and mid range torque because of lack of air speed around the valve throat and direction of air onto the valve these heads are very rare now and bring very good money.
Graham Russell

_________________
"It's better to be not informed than ill-informed"

Thanks Graham, I did know a bit about the GT40 Weslake heads, I am just not sure if they were used as often as claimed. Ford was doing a lot of stuff on their own and Weslake had a habit of falling short of what they promised.

I was in Shelby's workshop in the early 90s and was shown one of the tunnel port Trans-Am heads, you could almost fit a tennis ball down the ports! Pity they didn't work like they planned.

Hi Morris1100
No different to the 4V clevo heads fill the bottom of the port up 3/4 of an inch and it brings them to life.
Graham Russell

_________________
"It's better to be not informed than ill-informed"