Why wont my pontiac 400 rocker arms fit on a 389 head?

  • Thread starter Thread starter mechtech212
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mechtech212

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I have rebuilt a 1974 pontiac 400 and used a set of heads from a previous 389. I wanted to take advantage of the incresed compression ratio. When I put the new rocker arms on the 389 heads they would not work. I found that the studs on the 389 heads a 1.5" long compared to the 400 heads which are 1.75" long. What is the difference between the heads? rocker arms, push rods etc?
 
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