toobroketoretire

The ratios of G.M. "stamped steel" rocker arms can vary a lot because the rocker arms came from different vendors that used different tooling. As such its not uncommon to find rocker arm ratios that can vary from 1.30 to 1.50 on the same engine. Which means the net valve lift can vary from .390" to .450" or a whole 1/16" difference. When I changed over to full roller rocker arms on my 454" recently I found the OEM rocker arms had three different slot lengths and those with the shortest slots were actually hitting the studs on the UP side.

Its always recommended to trash your OEM rockers and buy quality rocker arms from one of the major vendors. The Summit Racing and Chevrolet Performance rocker arms may be okay but I have never checked them for accuracy so I can't comment on them.

Strokemyaxe

Is it possible a po had work done on the car by a bubba mechanic? Because this sounds really crazy coming from GM. Even in the 60's and 70's.

marc1973

I bought the summit brand full roller rockers 1.5 ratio and read up that scorpion makes them for them, when i got them i looked at t9ns of pics and they look exactly like scorpion rockers just with no logo, have had them on for about 4k miles and have no issues yet

toobroketoretire

You see, G.M. doesn't make hardly any parts but rather has vendors make the parts. Small blocks are notorious for having different ratio rocker arms because the vendors used different tooling. All of my rocker arms were OEM but yet they had 3 different slot lengths. As alloys vary and heat treatments vary the quality varies a LOT.