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redgoat's 1967 GTO

2021 January
of the Month

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does anyone know if you can change the rocker arm ratio from 1.5 to 1.6 on a basically stock 69 400 to increase the lift.  I have done this on chevrolet motors in the past but am new to the pontiac motors and don't know how well this works. thanks in advance

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Here are a couple of articles on this very subject. Rocky Rotella and Jin Hand are established Pontiac enthusiasts and writers. 

https://www.hotrod.com/articles/hppp-1110-high-ratio-rocker-arms-install/

https://pontiacstreetperformance.com/psp/RockerArms.html

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Thank You

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  • 3 months later...

It all depends on the clearance you have at the valves. All Pontiacs have around .420 lift and most have non adjustable valve trains except on RA2 & 4 & 455SD engines. While they will physically fit on the engine rocker stud, Pontiac did a few things to ensure their 400 RA4 engines didnt blow up with 1.6 rockers. The push rod holes typically need to be enlarged to ensure the pushrod doesn't contact the head. And adjustable rocker studs are will be necessary so you can lash the valves. The factory valve springs will bind if not replaced, and the taller springs need their location milled to accept tall springs to prevent binding.  Other than that its a go. 1.6 are hard on pushrods, many replace theirs with better ones. The best working fix is a cam with more lift ground into the cam, and then use 1.5 rockers for reliability.  1.6 rockers will add about 3 degrees of duration and around .040 " lift to a stock cam. Dropping them on a stock motor will very likely result in a broken valve springs, bent pushrods, and a walk home...

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