[VAC] Re: Vintage Puller

[Harvey Barlow]

Bob,   I hope this mechanic friend of yours doesn't also tell you about the UFO he saw over San Diego recently.   All the carburetor adjustments in the world will not change the run mixture.  The needle valves on the base of the carburetor are air bleed valves which control air bleed at idle speed.  When the engine is running at operating speed fuel is controlled by the jets installed.  It is possible to lean or richen the mixture by changing jets but except for race car mechanics who do this continually on race engines, it normally requires a sophisticated machine to "sniff" the exhaust mixture while running the truck on a rear wheel dynamometer in order to do much more than an educated guess.   Beware if the guy also tries to sell you a device that fits into the neck of the carburetor which will atomize the fuel air mixture thereby giving you an additional 4 mpg.  It is your truck and your money of course, if it makes you happy having this guy tune your truck, I'm happy also.   Harvey         ----- Original Message ----- From: Bob Kiger To: Multiple recipients of VACList Sent: Thursday, June 14, 2001 10:13 AM Subject: [VAC] Re: Vintage Puller My approach is going to be to put on the exhaust and then take the puller into the carb guy with one mandate.  Do everything to fuel flow and vacuum to increase gas mileage.  He is a wiz and has already told me that he will set the carb on the margin to get a couple of miles more per gallon.  That might reduce performance a bit, but as I mentioned the truck is so hot at the low end that I could sacrifice a little performance. The numbers are staggering in terms of operating costs.  Even 1mpg is 10% increase in fuel economy.  I would not be pursuing this if I had a modern puller that was getting 20mpg or just a regular passenger car with 25+mpg.  I am still aiming for 14-15mpg and will know by next week. Thanks for all your advice. Bob At 04:54 AM 6/14/01 -0500, you wrote: Bob, ----- Original Message ----- From: Bob Kiger At 05:59 PM 6/13/01 -0500, you wrote: Dual exhaust systems will improve high rpm horsepower, but in some cases, will reduce low speed torque.  >  Why is this Harvey?<   I can't remember the details sufficiently to provide a convincing explanation; the thought comes from books and magazine articles I have read on building and dyno testing performance engines.  I think it is because of the scavenging effect of increasing exhaust flow that leans the incoming fuel air mixture because of more complete removal of the exhaust gasses from the prior power stroke.  It is a known fact that gasoline engines such as small block Chevys used in pickup truck engines have smaller intake and exhaust valves than high rpm horsepower engines used in Corvettes, Camaros, etc. for the same reason.   >Hope I can prove you wrong on the gas mileage thing.  Only time will tell.>   I hope you can also but I must have read 100 test articles on those old trucks back in the '60s and '70s, some factory stock and others testing aftermarket products advertised to improve performance and efficiency.  I have never read of one that attained much more than 10 mpg in documented testing.   Harvey 1966 Airstream "Safari"  WBCCI #2857 1966 Ford F-250 "Camper Special" Mira Mar Mobile Community Oceanside, California