gas mileage
01-20-2007, 09:32 PM
#2
On The Tree
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ok well how bout this question...
-sb 350
-700r4 tranny
-4.11 rear end
-holley 750 carb vacum secondary (front primaries are 68's)
-hp is around 275 at the rear wheels
Why is my gas mileage 9 city if a feather it???
I thought I should be getting better... could it be because of my rear end gears??
-sb 350
-700r4 tranny
-4.11 rear end
-holley 750 carb vacum secondary (front primaries are 68's)
-hp is around 275 at the rear wheels
Why is my gas mileage 9 city if a feather it???
I thought I should be getting better... could it be because of my rear end gears??
01-21-2007, 12:20 AM
#3
TECH Apprentice
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I first thoughts when seeing your 4:11's and a 700r4 which has a really low first gear. So the gears are prolly not helping at all.look into a set of 3:55's if your thinking about changing, or possibly higher. The 750 holley is probly a big factor too. Im pretty sure they are jetted high from the factory. You could go down a couple of jet sizes or a smaller carb. With 275 RWHP I think the engine would do better with a smaller 650 cfm sence the demand for higher amounts of fuel isnt there.
I had a similar setup in a 69 chevelle and made the switch from a new 750 holley to a new edelbrock 650 and it was night and day. much crisper throttle response and no loading up or backfire( no more blowing powervalves)
try jetting down the holley first and maybe a smaller fuel pump cam for the holley as well. a smaller fuel pump cam will dump less fuel everytime you feather the throttle.
hope this helps, Josh.
I had a similar setup in a 69 chevelle and made the switch from a new 750 holley to a new edelbrock 650 and it was night and day. much crisper throttle response and no loading up or backfire( no more blowing powervalves)
try jetting down the holley first and maybe a smaller fuel pump cam for the holley as well. a smaller fuel pump cam will dump less fuel everytime you feather the throttle.
hope this helps, Josh.
01-21-2007, 10:58 PM
#5
Staging Lane
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Sounds like your using a lot of fuel.....lol, are you running fat? The gears shouldn't really be killing you that bad though. It just sounds to me that there is a fuel delivery issue and that maybe its running way to fat. How are the converters? Plugs, wires, distibutor? Something just doesn't seem right.