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Need some professional advice Al 9-11-03  
I have a 1961 GMC Bus Conversion which is very nice but I would like to know how to get more fuel mileage than it gets now. It has a 6-71 detroit with a 4 speed. It will get around 9 to 9 1/2. I saw something on messages where someone said referring to someone else to put a 10 speed road ranger in theirs and and they would get about 18 mpg.I would like to have a automatic. I possible but would prefer to get the most mileage, and don't mind shifting the gears. It has a blower on it now but dont know what size, would like also to have it turbocharged, with the blower if that is possible. But everyone I have talked to says leave it alone like it is. But if it wouldn't cost a fortune I would like to have it rebuilt totally with more power somehow. It runs great but has no power going up a hill.
Re: Need some professional advice Ron 11-12-03  
Al, I put a 6V71 in a 1949 Courier 100,previously had a gas engine. Because of the different engine rpm's,I HAD to change final gearing. I took circumferance of tire in feet divided into 5280 feet per mile for rev's per mile. Then figured miles per hour that was realistic and had ring & pinion changed based on max engine rpm(2200 in my case) Gear shop said I was wrong, but I cruised fine on the prairies at 70-72 mph. I think mileage was likely 8-9 mpg. The rockies were something else! Clark 5spd had a big gap from 3rd to 4th, meaning some hills were 3rd gear flat out at 20mph.
Bus weighes 28000lb, engine has 219hp injectors. Cost to change gears, probably 15 years ago was $500 Can.
Re: Need some professional advice silverhawk 9-12-03  
I had a 6-71 and didnt get that kind of mileage. At 9 to 10 you get more than any one I know. I had a cruise control put on mine and it would keep it going down the road but couldnt go up hills at all. You put in higher gears an overdrive or whatever you will probably lose mileage as the engine will have difficulity keeping a speed without the pedal on the floor all the time. Leave your gearing as is, the mileage is good, and the higher revs are not necessairly bad for the engine. More power is nice but be prepared to pay for it in mileage.......Ron......
Re: Need some professional advice Mark O. 9-13-03  
9 to 9.5 MPG? WOW! What are you complaining about? Most coach operators are happy if the MPG is over 5 MPG.

As far as 18 MPG goes, someone is really selling you a line. It takes a certain amount of BTU's to move a given amount of pounds. Unless you are going downhill all the time or you can shed about 20K pounds the physics will never allow 18 MPG.

As far as changing transmissions goes, you have a V-drive in your GM bus. A Road Ranger will not fit in your configuration. An automatic will cost your about 10% in your MPG.

All 2-cycle DD have blowers (superchargers). The blower is what allows the 2-cycle engine to operate. A turbo can be added and many later model 6-71's came from the factory with them. It will require a lot of plumbing changes to get the air into the engine and the exhaust through the turbo and out the back. It will also require some changes in timing and perhaps different injectors.

At 9 to 9.5 MPG I would be happy and not try to change anything.

Mark O.
Re: Need some professional advice TVP 10-27-03  
Hhhmmm....63 mph ??? I'm pretty sure all the OTR GMC's had the highway gearing and would run 78 mph.. downhill :)... and get the mileage you mention....

TVP
Re: Need some professional advice al 9-14-03  
I mostly average 9 to 9 1/2. I was just hoping to get something better if possible. It want run out but only at 63mph. I was hoping for something to change the gears and get better milage. But if you say leave it alone, I guess I will, everyone I talk to says leave it like it is. Ron I thank you for your time.
Re: Need some professional advice al 9-14-03  
Mark O. Thank you. I really beleave in the algae X system I have on the bus, I get about average 2 mpg better with the system on the bus, plus I have a gates pump and extra return fuel lines so I run it thru the system more often than it says. It cleans the fuel and gets all the crap out of it so to speak. I met the man in Orlando at the detroit place and they can show you something that will change your mind about diesel fuel. It runs the combustion chamber clean as a whistle so to speak.
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