[arbys]

If I were to replace the 326 HO 4 speed in my 66 LeMans would you go with a 389 or a 400? What advantages does the 400 have over the 389?

[Mr Twister]

I like 400 engines, but the 389 would be more "period correct"

[b-man]

Eleven cubic inches plus a better cylinder head and valvetrain design.

The availability of pistons that are reasonably priced is a big advantage for the 400 engines, good 389 pistons are scarce and expensive in comparison.

[Kenth]

1963 and earlier 389 blocks wont hold the starter.
1964-66 389´s may be bored out to 400 std.

400´s is still plentiful, 389´s is not.

[Sirrotica]

65 and 66 389 have thin wall cast blocks, plus the connecting rods were strengthened in 1967 over 1966 by adding a rib on the big end next to the rod bolt.

Then there's what Bart said about the heads, and valvetrain being improved also. Unless you needed to have a 389 for class rules, I would go for a 400, hands down.

[geeteeohguy]

A '66 326 HO 4 speed LeMans is a rare enough bird (and way cool) that I would leave it alone. Put an 068 cam in it and bolt on a tri-power and you're all set.

[65madgoat]

I vote leave the 326 HO in and build that up some. But if you must, just go to a 400 stroker then.

[rohrt]

https://www.youtube.com/watch?v=JTCZYSLh1rk