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Old 12-30-2008, 09:12 PM   #7 (permalink)
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Originally Posted by midnight rumbler View Post
Couple things I noticed today.....

Today compared to yesterday was lot cooler +11 Yesterday compared to -6 today. My vacuum gauge yesterday was at 20 and today it is at 16. Is cold a factor when it comes to reading vacuum gauges?


When I am at 60km/h my trucks RPM's are at 2200 and at 100km/h they are at 3000 RPM's. This is a 5.7 TBI 1989 350 with a 3 spd tranny. Seems a little high if you ask me although this truck is a cube van and is meant to haul.

Is there anyway I can lower the RPM's drastically without putting in a 4spd or swapping gears yet maintain driveability and increase fuel mileage?

I am not sure what the factory gears are in the rear-end on this truck. Something I will have to look into
The reason you're seeing the difference in vacuum in colder weather is because it is putting more load on the engine therefore lowering vacuum.

One thing that can be done to change the gearing and is very simple is go to a larger wheel and tire.

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