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406 / 421 sbc builds

Old 01-10-2019, 01:04 AM
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94Sylvan- I have never had engine on a dyno but an educated guess would be peak power at about 5500-5600 rpm. Currently I am propped it about 5400 running a 23p Mirage. I would like to send the prop back to the shop to see if they can give me an extra hundred RPM.

As for the choice on rocker ratios, ultimately the decision was mine. I did a lot of reading and talked with a couple of custom cam guys that spoke of similar philosophies of having a higher lift on the intake and longer duration on the exhaust. The only way to get this with the cam that had I selected was by using split rocker ratios. The other factor that influenced my decision was the length of my exhaust tails. I have an Eddie Marine exhaust that originally came with short SS tales. I had them lengthened about 3 1/2” which was all that would fit with my setup. They are still not as long as many performance exhaust tails. I have been fortunate that I have not experienced any reversion but at the time I was building the engine we suspected that it was very close to the edge. The use of a larger rocker ratio could have made exhaust reversion problem that much worse.
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Old 01-10-2019, 10:57 PM
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I have 427s making 652 hp. Big roller cams so exhaust has to be dry to tips. Dart blocks, Afr heads, Howard cams. Builder is white performance.
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Old 01-10-2019, 10:58 PM
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Old 10-08-2020, 01:41 AM
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Originally Posted by ttrm007 View Post
I have 427s making 652 hp. Big roller cams so exhaust has to be dry to tips. Dart blocks, Afr heads, Howard cams. Builder is white performance.
what howard grind did you go with? How big are the heads? I'm building 421's for my Formula, aiming for turn-key reliable 500-550hp with ability to make 600 hp if i can keep the drives together.
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