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Gearheads
906 Vortec heads and old school tunnel-ram
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<blockquote data-quote="swampratt" data-source="post: 3106894" data-attributes="member: 15054"><p>I may have got lucky I have seen no cracks yet ...Knock on wood.</p><p></p><p>So i spent 1 hour and 35 minutes porting them.</p><p>I blended the bowls and reduced the exhaust guide boss diameter and raised the roof on the exhaust port .100"</p><p>I could go much more.. but that will help a tick.</p><p>I roughed up the intake runners where I blended them.</p><p>and smoothed the exhaust port.</p><p></p><p>No chamber stuff and I did not mess with the entry of the intake runner and nothing inside the intake runner.</p><p>Just bowl work.</p><p>I will take the sharp edge off the chamber edge though.</p><p></p><p>I did order a vortec intake.</p><p>I may just replace the heads on my 57 and it runs a single 4 barrel.</p><p>Be nice too see a back to back vs ported 305 heads.</p><p></p><p>I found out the retainer to guide seal clearance falls in at .470"-.480" My cam is .454".</p><p>But if I replace the factory seals with viton 35-305V16 seals which I have on hand I am rewarded with .520" clearance before the retainer hits the top of the seal.</p><p></p><p>I also have different retainers that add another .040".</p><p>Not that I need it.</p><p></p><p>Now I did not know the exhaust runner floor was raised in these Heads The runner floor at the exit is .250" raised</p><p> The top of the runner is in the same location as the older heads.</p><p></p><p>Yea the exhaust side flows the same as all smogger gm exhaust ports..BUT by raising the floor in the head and leaving the exhaust runner on the exhaust manifold large you get a huge anti reversion deal happening at the exhaust port.. which will actually make that exhaust more efficient than what the "Flow" numbers lead you to believe.</p><p></p><p></p><p>Oldsmobile manifolds were larger than the ex runner in the head.</p><p>And i always ported my manifolds or headers to mimic that anti reversion step.</p><p></p><p>I never tested it back to back but it makes me sleep better at night. <img src="/images/smilies/smile.png" class="smilie" loading="lazy" alt=":)" title="Smile :)" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="swampratt, post: 3106894, member: 15054"] I may have got lucky I have seen no cracks yet ...Knock on wood. So i spent 1 hour and 35 minutes porting them. I blended the bowls and reduced the exhaust guide boss diameter and raised the roof on the exhaust port .100" I could go much more.. but that will help a tick. I roughed up the intake runners where I blended them. and smoothed the exhaust port. No chamber stuff and I did not mess with the entry of the intake runner and nothing inside the intake runner. Just bowl work. I will take the sharp edge off the chamber edge though. I did order a vortec intake. I may just replace the heads on my 57 and it runs a single 4 barrel. Be nice too see a back to back vs ported 305 heads. I found out the retainer to guide seal clearance falls in at .470"-.480" My cam is .454". But if I replace the factory seals with viton 35-305V16 seals which I have on hand I am rewarded with .520" clearance before the retainer hits the top of the seal. I also have different retainers that add another .040". Not that I need it. Now I did not know the exhaust runner floor was raised in these Heads The runner floor at the exit is .250" raised The top of the runner is in the same location as the older heads. Yea the exhaust side flows the same as all smogger gm exhaust ports..BUT by raising the floor in the head and leaving the exhaust runner on the exhaust manifold large you get a huge anti reversion deal happening at the exhaust port.. which will actually make that exhaust more efficient than what the "Flow" numbers lead you to believe. Oldsmobile manifolds were larger than the ex runner in the head. And i always ported my manifolds or headers to mimic that anti reversion step. I never tested it back to back but it makes me sleep better at night. :) [/QUOTE]
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