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Old 06-16-2018, 01:03 PM   #182
Purcell69
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Join Date: Jul 2013
Location: Central OK
Posts: 521
Re: 57 GMC, frame swap, 4wd, 454 big block, 4 speed

Quote:
Originally Posted by Old57 View Post

I did play hooky from work yesterday afternoon and got the 32 gallon square body Suburban tank mounted. I'm hoping to get 300 miles per tank out of the big block...
It can be done depending on how aggressive the cam is and what your overall gearing works out to relating to engine RPM at highway speed. At 9.375 MPG, you would be bone dry at the 300 mile mark.

I've had two 454 powered trucks that would consistently get me 12 mpg. One was a bone stock 1994 C3500 with TBI. The other was a 1978 C10 using a 454 I'd built, hooked to a TH-400 automatic and a 3.07 geared rear axle on 31" tall tires. The carb was a Holley 3310 750 CFM vacuum secondary carburetor with the heaviest secondary spring Holley offered to keep the motor as lean as safely possible. The motor was built for torque and towing so it didn't need to spin fast.

4wd may cost you a bit, but the lighter truck body may be enough to offset that, hopefully. It's going to be close.

-Joe
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