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Why is my 408 not making power?

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Old 12-16-2007, 10:08 AM
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Originally Posted by Asmodeus
I can tell you exactly why your car is down on at least some of it's power. Your cam is horrible. You're missing 20 degrees on the exhaust side, and you need to advance the ICL about 8 or 9 degrees. You have huge CC runners with crappy low flowing exhaust ports in the L92 heads. You need to open the intake valve a LOT sooner to compensate for the low velocity intake, and you either need more duration on the exhaust or more lift on the valve, either way, there's no way you can be clearing the entire combustion chamber through that exhaust port with a 2 degree split. The intake/exhaust ratio on those is only slightly above 60% iirc. Katech is running a 233/277 in their L92 headed budget 427. I would go at least with a 236/260 on yours and try to get the ICL around 105-106. (not the LSA, the ICL.) The heads are very different from cathedral port heads, you cannot use the same thinking as any old LS1-2-6 motor.
I didn't relize this, thanks for the info.
Old 12-18-2007, 03:40 AM
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That cam sux *****. Where did u get it? Also, I don't think you need that wiode a split, but around 8* is enough. I would have thought at least 260-268@0.050
Old 12-18-2007, 08:44 AM
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Originally Posted by MNR-0
That cam sux *****. Where did u get it? Also, I don't think you need that wiode a split, but around 8* is enough. I would have thought at least 260-268@0.050
What reasons do you have to support an 8 degree split is enough on L92 heads? Maybe you should call Katech and tell him even though he's building engines for GM's racing divisions, that his 233/277 cam in his street attack 427's making 650hp is too big of a split and he'd have better luck with a smaller split.

What about the recangle port L92 head makes it want a cam that is generally seen in Cathedral port heads with completely different intake-exhaust flow ratios?

I'd just like to hear your thoughts about this as it pertains to valve events.




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