Inliners International Forums General Discussion Engines Stock Rocker arm ratio

What is the stock ratio for a Chevy 250?
I was thinking of getting some stamped rockers with the roller tip. Thanks, Herb

1.75 is stock

Thanks Twisted, I thought they were 1.6.

Once again I want to say that the "W" motors '58 thru '65 348, 409 and Z-11 427 also all had 1.75 ratio rockers. Has anyone looked for these?

I know the 425hp/409s used some 315# springs , so they are pretty strong, I'm almost sure I have seen some in articles with the aluminum Harland Sharps.

Surely not all these have vanished from the face of the earth. They were of the standard Chevy design of stamped steel/ rocker balls, and threaded studs (hi-pos were pinned to the cast iron sockets to prevent stud pull-out)

Why not just use B.B.C. Big Block Chevy rocker arms, you can get those in all different ratios.
I have the old Crane 1.7 B.B.C. Gold aluminum rocker arms currently on my 250.
I plan on using 1.8 ratio BBC rocker arms for my 12 port.


MBHD

W.W.N. Well Why Not.

There is more to consider when choosing a rocker arm than just ratio. Just because a rocker has a certain ratio doesn't mean it will work. The geometry and spacing of the trunion to the pushrod cup and roller tip are actually more critical. Thats why most engines have their own unique rocker arms that are made for their own specific valve spacing relative to the rocker stud or rockers shaft. A custom SBC rocker for instance, with a 1.7 ratio will not work on a BBC, even though the BBC uses a rocker ratio of 1.7.

I'm using TLowes 1.75 rockers. My turbo cam is fairly mild with .544 lift but even at that at full lift there was clearance problems at the top of the push rod hole. The push rods are 3/8 and I opened the holes up to 5/8. Still had to take a die grinder to the tops of the holes. Also the bottoms had to be relieved about 3.5 inches under the head. TLowes rockers are for a BBC. Usually if theres a 409 anywhere on the box the price goes up.