Dumb 427 question
Thread Starter
Melting Slicks
Joined: Apr 2010
Posts: 2,790
Likes: 108
From: On the coast North of SF bay
Dumb 427 question
I know there's a simple explanation as to why the Z06 427 (small block) gets great mileage and the old 427's (big blocks), don't. The difference is fairly significant but not too obvious to this guy.
Anyone?
Anyone?
Burning Brakes
Joined: Aug 2007
Posts: 812
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From: Atascadero California
Safety Car
Joined: Apr 2006
Posts: 4,254
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From: Anaheim Hills, Ca
Lot's of reasons: Fuel injection, electronic ignition that includes knock sensors, high compression that is allowed by the use of F.I. and knock sensors for retarding spark, more efficiently flowing heads, lighter weight internals, more efficient combustion chambers, and lot's more that I'm forgetting right now!! Basically, the engine just runs so much more efficiently.
Instructor
Joined: Jan 2010
Posts: 120
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From: NJ
so, what would the mileage be if you dropped an aluminum block ZL-1 big-block into an otherwise unmodified C6 with manual trans? How about if you rigged it for fuel injection as well?
More importantly, how incredible would it sound?
More importantly, how incredible would it sound?
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Le Mans Master
Joined: Sep 2004
Posts: 5,116
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From: Livonia MI
Lots of stuff already covered here, but you gotta realize the different times. 427's of the past had no concern for milage/emissions, and were really just 660 lb boat anchors. Many were running around with 4.11-4.56 axles feeding 1:1 top tranny gears. A modern LS7 is 430 lb pushing a 3130 lb car with 0.50 tranny top gear and 3.42 axle. The heads flow 360 cfm intake with factory cam. Just a few more numbers to get an idea.
Melting Slicks
Joined: Jan 2004
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From: Henderson Nevada
Tech Contributor
Joined: Oct 1999
Posts: 41,055
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From: Charlotte, NC (formerly Endicott, NY)
There was something different about the old BB block configuration that affected the efficiency of the engine. The NASCAR teams were some of the first to document the difference. Back in the 70s when NASCAR was cutting back on engine sizes the teams had the choice of going with the big block engine or the small block engine to get the same displacement. The small block engines produced more power and got better mileage than the big block versions given bore/stroke were the same.
Bill
Bill
Team Owner
Joined: Jun 2001
Posts: 26,714
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From: Houston, TX
Actually, while there were a lot of good answers, the real answer was never addressed. I know this is going to shake the world, but the government is largely to thank. Yes - I'm not kidding either. Buy requiring that cars start meeting much more stringent EPA tests, they were forced to make the cars much more efficient to reduce emissions. That is what truly spurred the move towards much more advanced computer controlled ignition, fuel injection etc. CAFE was icing on the cake.
Race Director
Joined: Dec 2010
Posts: 18,097
Likes: 1,593
Actually, while there were a lot of good answers, the real answer was never addressed. I know this is going to shake the world, but the government is largely to thank. Yes - I'm not kidding either. Buy requiring that cars start meeting much more stringent EPA tests, they were forced to make the cars much more efficient to reduce emissions. That is what truly spurred the move towards much more advanced computer controlled ignition, fuel injection etc. CAFE was icing on the cake.
Le Mans Master
Joined: Feb 2002
Posts: 5,394
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From: cumming ga
z51vett