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Don't say headers don't make any difference, anybody who has seen a 427 Camaro/Chevelle exhaust manifold and been to a dyno room and swapped on a set of headers, knows they are worth 40-70 hp.
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That is very correct, but if you are running exhaust manifolds hooked up to a 1969 exhaust system and then bolt on headers on that same 1969 exhaust system, you "might" get 10 horse. I does not matter how big you make the funnel at the top, it still has to flow through the bottom!
Todays exhaust systems are light years ahead of yesteryears systems. I know some of the 1969 articles are great to look back on, but there are some articles up to and including 2006 that would show that 2.5 madrel bent pipes with todays excellent mufflers and a X pipe will outflow open headers. Actually, 1969 highwater marks in a lot of sporting events or records for lack of a better term have all been broken up to and including 2006!
Seat time is everything. period. I have to smile when I read some of those ZL-1 tests. Dick and the boys were even doing 6000rpm neutral to low gear drops in the column shift cars trying to get ets!
So Gonzo.... are we in agreement that ZL-1/L88 would get a varience in vaccumm reading of between 5 and 6 @900rpm????
Did you get a reading off your stable L88 yet????
Peter