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Topic: Dynoed today, got ?'s

in Forum: C3 Engines


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Dynoed today, got ?'s

Posted: 8/16/07 5:43pm Message 1 of 6
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Redwingvette
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Waterford, MI - USA
Joined: 9/13/2002
Posts: 1750
Vette(s): 1973 Red coupe
First time evr on a dyno. It showed that my Holley 4175 vac sec Spreadbore carb runs way to rich.
In the air/fuel ratio 10's throughout the curve. I new it was rich but now I have a reason to fix it, well make it better.
So what do you guys recommend I do to solve this issue. The guy who ran the test suggested I drop 3 sizes in the jets. Is that a good idea? Do I change both the primaries and secondaries? He also said if I do this i should see a big jump in gas mileage, from 17mpg to maybe as high as 24mpg



Brian - NCM Lifetime Member

73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System

Dewitt radiator and dual electric fans
Borgeson Steering box
 


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Dynoed today, got ?'s

Posted: 8/16/07 7:37pm Message 2 of 6
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
I wouldn't hold my breath about getting that big a jump in fuel mileage, tho it will help to lean her out a bit.
Most folks that run dynos usually have a good idea of what may or may not help peak power outputs. You have good HP/Tq numbers...pretty dang impressive.
It is definitely too fat in the mid range...seems to be just dumping fuel down there from 3000rpm up. At that rpm, the secondaries should be coming into play. Up to 3 grand, it looks good at 14:1(approx), but then it starts loading up. I would suggest you leave the primaries where they are, and maybe drop the secondaries a size or two...or three. Ya don't want it to lean out too much, or it'll start melting stuff...
Just my 2c...



Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Dynoed today, got ?'s

Posted: 8/16/07 8:38pm Message 3 of 6
rearn2go72
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Bladenboro, NC - USA
Joined: 1/22/2006
Posts: 1058
Vette(s): 1972 conv., sunfire yellow, blk interior, blk vinyl and convertible top. Off frame restoration with American Speed 383 stroker engine producing 500hp plus a 200hp NOS system. MSD ignition. Hooker super competition headers with chambered exhaust.
[QUOTE=Adams' Apple]I wouldn't hold my breath about getting that big a jump in fuel mileage, tho it will help to lean her out a bit.
Most folks that run dynos usually have a good idea of what may or may not help peak power outputs. You have good HP/Tq numbers...pretty dang impressive.
It is definitely too fat in the mid range...seems to be just dumping fuel down there from 3000rpm up. At that rpm, the secondaries should be coming into play. Up to 3 grand, it looks good at 14:1(approx), but then it starts loading up. I would suggest you leave the primaries where they are, and maybe drop the secondaries a size or two...or three. Ya don't want it to lean out too much, or it'll start melting stuff...
Just my 2c...
[/QUOTE]

That Joel never ceases to amaze me. Is there ANYTHING that guy doesn't know something about? Clap



Dynoed today, got ?'s

Posted: 8/16/07 9:14pm Message 4 of 6
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Jack of all trades...master of NONE!


Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Dynoed today, got ?'s

Posted: 8/16/07 10:15pm Message 5 of 6
deeboy59
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visalia, CA - USA
Joined: 10/27/2006
Posts: 641
Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition

 JOEL'S DEAD NUTS ON ! Thumbs%20Up  IF YA LEAN IT OUT TO MUCH, SHE'S GONNA RUN HOT ON YA !




Dynoed today, got ?'s

Posted: 8/17/07 12:50am Message 6 of 6
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Redwingvette
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Waterford, MI - USA
Joined: 9/13/2002
Posts: 1750
Vette(s): 1973 Red coupe
I was taught to watch the plugs and they will tell the story. I was also told to make changes in jets by the 2's. I have to take the carb apart to see what size jets are in there and then go buy a couple of sets to try.
Thanks for the replies.



Brian - NCM Lifetime Member

73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System

Dewitt radiator and dual electric fans
Borgeson Steering box
 


in Forum: C3 Engines


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