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#1
05-24-2001, 05:59 PM
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I have a 428 h.o. motor in my 69 SJ,it is stock with long branch exhaust manifolds,how high rpm is it safe to rev it to? 6000 6500? I think it is the fastest motor Pontiac ever built except the 63 S>D> motor.What do you guys think?
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#2
05-24-2001, 05:59 PM
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I have a 428 h.o. motor in my 69 SJ,it is stock with long branch exhaust manifolds,how high rpm is it safe to rev it to? 6000 6500? I think it is the fastest motor Pontiac ever built except the 63 S>D> motor.What do you guys think?
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#3
05-24-2001, 06:15 PM
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Even though it has the bore like a 455, it still has a 4" stroke and 3.25" main bearing diameter which causes friction. I thinking if still has the original rods and rod bolts along with stock cam and .407"/.407" lift that 5200-5500 max is about as far as you would want to go. The 428 HO is a very potent combination but I think the cam is limiting you. As far as the most potent since the 421 SD, I think the RA II 400 and RA IV 400 would have to get the nod there. The cam was a major role in their performance.
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