The usual MPG question...
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
The usual MPG question...
Im really curious as to what MPG this set up should get. I think it has around 10.5:1 compression.
428 bored 40 over with edelbrock rpm intake + full serpentine kit w/AC and PS and electric fans, mildly ported heads, 270 cam, MSD with blaster coil and ign box (vacume advance), holley 770 aluminum street avenger, 410 gears, c6 auto.
Full length headers with 3" ex.
428 bored 40 over with edelbrock rpm intake + full serpentine kit w/AC and PS and electric fans, mildly ported heads, 270 cam, MSD with blaster coil and ign box (vacume advance), holley 770 aluminum street avenger, 410 gears, c6 auto.
Full length headers with 3" ex.
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
lol im getting 6.98 right now and really id like at least ten... There has gotta be something that needs adjusting cuz its still not running optimal. Maybe the operating temp is to low like the shop suggested. It runs at 180 but ive been told 195-200 is optimal for the 428.
Senior User
Joined: Mar 2013
Posts: 274
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From: aouth east idaho
How long ago was the rebuild? Is bet that you have more than one thing wrong. Could be everything is slightly out of adjustment. Gap the plugs. Make sure timing is good. Make sure MSD is set up right etc...... Good thing about these old engines is with enough reading you can do it all yourself.
More Turbo
Joined: Oct 2011
Posts: 636
Likes: 5
From: down a red dirt road
play with the carb jetting, a 770 is huge, maybe swap a 600cfm onto it and see how that does.
i had a 460 auto with a 750 summit double pumper that seemed to get pretty good mileage once i jetted down some. did even better with the 600 i put on before i sold it. it had the 3.55 gears in it tho...
i had a 460 auto with a 750 summit double pumper that seemed to get pretty good mileage once i jetted down some. did even better with the 600 i put on before i sold it. it had the 3.55 gears in it tho...
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
Engine is less then a month old. And what's weird is it runs well off the 770 and if anything the plugs look lean vs black and rich. I need to swap in a different bushing in the distributor and go to 18 degrees on the timing is what the shop told me. Right now I'm at 10 degrees. And I'm sure there is something else like power valve maybe or something.
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
Whats even worse is its running lean. Saw the headers glow red tonight. Creepy when all you see is red in the fender well gap between the frame and inner skirt.lol Tomorrow its going in to have the timing adjusted and carb tweaked and tuned.
I would have no problem changing the gears but its a 4x4 so that means it has to be done front and back. $$$X2 -.-
I would have no problem changing the gears but its a 4x4 so that means it has to be done front and back. $$$X2 -.-
Lead Driver
Joined: Jun 2006
Posts: 5,650
Likes: 977
From: Near Yosemite CA
Quick question,,,, did you calibrate your speedo, or see if it is off? 4.10's/35" tires not stock,,, going to slow down your speedo, you could be going further than your odometer is saying, 60-65 miles for every 50... are you taking that into account?
Cargo Master
Joined: Sep 2005
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10mph is not a good answer, you need to run the measured mile a couple of times and see what % you are off. I'm guessing number dummy can hook you up with a part # once you know the % and the gear you currently have.
Postmaster
Joined: Oct 2010
Posts: 4,656
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From: Northern and Southern Cal
I'm figuring a lot of guys don't take wheel size into account, so your not alone.
There are plenty of speedo gear sites on the net.
I searched and found a local to me shop that will lengthen my speedo cable and adjust the gearing.
Good luck.
There are plenty of speedo gear sites on the net.
I searched and found a local to me shop that will lengthen my speedo cable and adjust the gearing.
Good luck.