Does anyone know what the stock rocker arm ratio is for a 454? I looked for a set on summitracing.com and they're all 1.7 and a few 1.8's. I though it was 1.5 but is that sbc?

1.7

Yeah, 1.7 is stock for a big block.

So if I bought roller tips that were 1.72 ratio, would that drastically change the lift? I have a 560 lift edelbrock cam, stock valve springs.

do the math.
560 divided by 1.7=cam lift. Cam lift times 1.72 = new valve lift.

do the math.
560 divided by 1.7=cam lift. Cam lift times 1.72 = new valve lift.

566.58.

Is that too much for stock valve springs

Depends if they're singles or duals and they're open/closed pressures.

Depends if they're singles or duals and they're open/closed pressures.

singles. I dont know what open/closed pressures is. They are just stock valve springs

.560 plus stock bbc valve springs equals spring bind/cam death. All the factory springs had far too much spring rate, giving them weak seat pressure and stupid (350#+) open pressure, or simply not enough room for even .500" for the newer stuff. Check your installed height and buy the appropriate single spring.

.560 plus stock bbc valve springs equals spring bind/cam death. All the factory springs had far too much spring rate, giving them weak seat pressure and stupid (350#+) open pressure, or simply not enough room for even .500" for the newer stuff. Check your installed height and buy the appropriate single spring.

Now thats good to know

You might see some benefit from going to a 1.72 ratio rocker arm. Several years ago on the Corvette Forum (where some members are more anal about factory originality) there was a thread about rocker arm ratio on small blocks. One of the engine gurus measured a boatload of stock rocker arms he had and found that they averaged 1.37, which he attributed to sloppy manufacturing tolerances. If this holds true for big block rockers you might find that a presumably more accurate 1.72 aftermarket rocker will give a 10% improvement in lift rather than the 1% difference if the actual factory ratio was a true 1.70.

Full roller rockers on a big block are always the way to go for durability. Stay away from 1.8 rockers on a flat tappet cam, the small footprint lifter and big rocker ratio is already taxing the camshaft, and big block Chevs are by far the most difficult engine to successfully break in a camshaft.

Fwiw, 348/409/427 "W" engines have 1.75 to 1 ratio rockers.

pdq67