#11
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Quote:
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#12
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When they were 425hp in 1965, that was with the more streamlined Corvette exhaust manifolds that also fit & were used on full-size L78 cars that year. They became 375hp when fitted with Chevelle, Nova, Camaro log-style manifolds. It would interesting to see an exhaust manifold comparison on the dyno.
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1962 Biscayne O-21669 MKIV/M-22 1962 Bel Air Sport Coupe 409/1,000 |
#13
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What were the final numbers?
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#14
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For comparison here is an original 1969 L/78 restoration engine I rebuilt last year. All stock except Comp/Cam replacement cam, EDM lifters,+030 TRW pistons and run with shop headers. Fifteen minute break in & one dyno pull 38 deg timing pump 92 octane. We did not jet or do any other tuning as this is the original motor from a SS 1969 Chevelle.
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#15
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Yikes! Thanks for all of the input. We were able to coax a few more HP after re-jetting. Then we put the shop carb on and it woke up! 446 hp at 5700.
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#16
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I built a 66 L78 all stock except for a little head work. It made 444 @ 6000 rpm with headers and a 3247 Holley carb.
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1970 Z28 Citrus green CW 3:73 1970 Ls6 Cy 3:31 14K miles 1968 Biscayne L72 M22 952 actual miles. 1966 Biscayne L72 3:73 1966 Chevelle L78 M22 4:56 |
#17
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L78...
Impressive numbers from the "baby rat'...especially some of the torque figures. So, this begs the question...'if the L78 makes those numbers...what does it's big brother, the L72 really make? I would assume well north of 450hp...
-wilma
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02 Berger 380hp #95 Lots of L78 Novas Join National Nostalgic Nova! 70 Orange Cooler 69 Camaro |
#18
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That is a very impressive torque curve from a stock L78 IMO.
__________________
65 Corvette Coupe L78 67 427/390 Vette Coupe unrestored 67 L-79 Vette roadster (Top Flight) 69 L71 Roadster Survivor 69 L46 Roadster Survivor (Sold) 69 Z/28 RS 69 Dodge Charger R/T 70 W30 442 Auto Air Survivor 2016 Z06 Coupe M7 70 AAR Cuda (Sold) 69 L78 Chevelle |
#19
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every 427/425 that I have had done developed between 490 and 505 hp through headers with stock carb & dist.
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#20
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Quote:
I installed a 3910 on my 496 for the initial dyno tests and the engine picked up somewhere around 20 when I swapped to a 3418 (`67 L88 855 vacuum secondary). During the last series of tests, the engine picked up another 30+ when I replaced the L88 carb with a 4781 850 double pumper, and another 20 when I switched to a 1000 HP (I built & calibrated myself). That's over 60 HP just in the carbs. The factory carbs are good, but they do leave room for improvement. Comparing them to a newer "race" type carb really is an apples to oranges comparison. |
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