| [GMCnet] Gas Mileage Test [message #218010] |
Mon, 12 August 2013 13:36  |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma:
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Senior Member |
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Good Afternoon
I know this subject gets talked about a lot, but I need to share my recent experience.
I have the 403 engine with a 3:70 final drive and Dick Pattersons rebuilt carb and his springfield iginition setup for my coach and for towing my trailer with the Harley in it, about 2,000 lbs for trailer and Harley.
My normal average gas mileage is right around 9 MPG since I put in the 3:70 final drive 3 years ago and I keep lunatic records.
This past week I took a trip up to Northern Wisconsin towing the trailer and Harley and decided to do a gas mileage test, since I had the whole day to travel there I decided to travel as close to 60-63 MPH as I could for the entire trip. I filled the tanks as full as I could get them and headed out, stayed at 60 nearly the entire time for 313 miles, then refilled the tanks to the same level.
RESULT: 7.53 MPG....... I thought...what the hell ?????
On the way home I decided to drive faster like I normally do and try to keep it at a consistent 70-73 MPH. Before I started out I filled the tanks again and traveled 353 miles home and then filled the tanks right to the top again.
RESULT: 9.78 MPG......
I don't have a tach or a vac gauge so I don't have that data.
Any ideas on what's going on here? Best I can figure is that the SWEET SPOT for my setup must be in the later higher speed & RPM range.
Comments or Thoughts???
The good ole GMC never fails to blow my mind and confuse me even more. These machines are weird !
Thanks
Ray
Ray & Lisa
78 Royale "Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMC-Royale@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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