I just spent a day digging what's supposed to be a 68 Thunderbird 429 out of a friends shed. I have been told that the heads on this Engine will really improve the performance of a 460. The casting numbers on the heads are C8VE-E. Can anybody tell me about these heads? are they a good performance swap? I also have heard that the 429's are a lot better on gas than the 460's. any comments?
Thanks
Craig

 

the reason theyd improve performance is because theyll raise your compression... if you have d3ve heads they have big chambers (95-99cc) and the c8ve heads have small chambers (72-77 cc) turning the stock 8.5ish-1 compression to 10.5ish-1 the reason i say -ish is because chamber volume on factory heads will vary a bit. the heads actually flow almost exactly the same. thats also the main reason they get better mileage- higher compression means better efficiency- up to the point of detonation. the 31 ci displacement difference doesnt make that much difference in mileage because what they were installed in was big and heavy... if you install a 429 and a 460 in a big heavy vehicle the mileage could be the same or slightly worse with the 429... if its a lighter vehicle then the 429 would win out on mileage... with a heavy vehicle you need more torque and thats what displacement gives you.