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LS conversion

F-ingrob

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Im thinking of doing a LS conversion
In my 87 K5
I already got rid if the throttle body and stock motor due to lack of power and towing capability
The new motor has plenty of pkwer but now i want fuel economy
What are some milages you guys are seeing
With an LS
Thinking of a LS 5.3
I have 35" tires and 4.56 gears with a 700R4
Thanks for any input
 

1977k5

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What is your new motor that has the power you want?

Gen III-V GM motors make good power, but aren't miracles for economy. What are you seeing now vs. what are you hoping for?
 

F-ingrob

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What is your new motor that has the power you want?

Gen III-V GM motors make good power, but aren't miracles for economy. What are you seeing now vs. what are you hoping for?
I would like better than 10-12 MPH
i have a late model SBC roller cam dont remember the grind
aluminum heads
thorly headers holly 650 double pumper rpm intake
 
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ZooMad75

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I'm running a 5.3/700r4 with 4.10's and 35s. Prior to the camper install I saw as high as 18mpg, average 13-15. Post camper install the best I've seen is 16, but average is around 12. Going to go up in gearing to keep the 5.3 in the sweet spot. It's just out of the powerband at highway speed in OD.
 

jkroberts

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My 5.3 and 4l60e with 4.10's and 35's saw 18mpg highway and about 11 city, when I jumped to 4.56 I got 17/13, and now with 5.38's and 37's I got 16/13. Pretty consistent too as long as I keep my foot out of it
 
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