413 vs 400 engine swap

[dardal@xxxxxxxxxxxxxxx]

Phil, the 67 heads (915 I think) had the smaller size exhaust valves (1.60)
while the 906 heads had 1.74".  It appears that in flat out performance, the
later heads will do better.

Also, people keep on saying that the compression ratio was higher in 67 than
68-70.  However, the factory specs was 10.1:1 for all these years (or at least
until 69).  I think that the argument is that the 915 heads had smaller
combustion chamber, but my guess is that if Chrysler posted a 10.1 compression
ratio on the later engines, it was achieved by redesigning the piston or using
thinner head gaskets.

D^2 

Quoting Phil Patterson <hilljack7@xxxxxxxxxxxxx>:

> Just a note on the heads, the 67 440 heads are very desireable, having the
> earlier small combusion chamber combined with the larger valves and improved
> intake port and larger exhaust valve size of the 68 and later heads. I think
> you would see a difference in performance, especially if you go to the
> trouble of having a good 3 angle valve job done while you're freshening them
> up.
> Don't forget to check the guide to valve stem clearance when rebuilding!
> Phil <><