My stock pushrods measure 6.905, I'm replacing the valvetrain and have a question. When I look through parts catalogs depending on the supplier they list both 6.875 and 6.905. Why would there be 2 different length pushrods for the same motor?
Most of the manufacturers only list one or the other, I haven't found a manufacturer that sells both. 351 push rods are like 8" big diff from 302s. And the 5.0 roller motor rods are shorter by about 1/2".
Just as 78CobraII was suggesting- The 302 uses 2 different pushrods. The early 302 uses the shorter rod and the later 74-77 uses the longer pushrod. They are in direct relation to the deck height of the block. So if you use '74-77 heads on a 289 or early 302, use the pushrods correct to the engine, not the heads, and vice versa for a 289 head on a '74-'77 302.
I have a '71 block (D1 block) in the garage and it's the same deck hgt. as the '69 block in another rig i have. I haven't seen a D3 coded block in a car yet, just D2s but have seen D3TE blocks in trucks, but havent verified their deck height but assume from lots of other material, that the deck height change was poineered in the new D4 ('74) blocks. Right around '78, the blocks were reversed back to the short deck height while the combustion chambers were drastically increased to 69cc to maintain the crap-o compression ratio. I just built a '79 block and it's nice and tight to the deck just like the 68-72 302's were.