I am trying to put 66 389 rocker arms on my 72 400 heads. I was wondering if this interchange is possible. I thought that all the rocker arms were the same but apparently I was wrong. Is there supposed to be a spacer under the rocker or somthing that I am missing of my 400 heads sot he rocker has somthing to rest on?

I am trying to put 66 389 rocker arms on my 72 400 heads. I was wondering if this interchange is possible. I thought that all the rocker arms were the same but apparently I was wrong. Is there supposed to be a spacer under the rocker or somthing that I am missing of my 400 heads sot he rocker has somthing to rest on?

The rockers are the same, but the pushrods are different. I believe the later heads use longer pushrods.

'61 -'67 (except '67 061, 670, 97 & 997 heads) used the 8.715" pushrod.

'67 and later (except 256/301) used the 9.145" pushrod.

The special Ram Air II/IV/V and early Super Duty engines used various different lengths and diameters.

You need pushrods that match your '72 heads, 9.145".

1966 389 and 1972 400 rockers are NOT the same!
The 389`s rockers are shorter, as are the push rods.
This is due to different valve angle in the heads.
The rocker is not resting on anything, it´s hold in place by the end of the valve stem and the push rod.

I did get the later pushrods. I just wasnt sure if the rockers would work.