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Re-power AM General Cliff Potthoff 1-3-03  
I have a converted 40 foot AM General that I am considering repowering. It now has a non turbo 8v71 with a V730 Auto. Axle gears are 463 and with 12 X 22.5 tires, and tops out at about 70 and 2300rpm. It pulls down on the hills. I am ok with the 65 to 70 cruise, but would like to do better on the hills. Does anyone have any experience with replacing the 8V71 with a 6v92Turbo in the AM General bus? Any info on difficulty, cost, transmission problems with more power etc. will be greatly appreciated. Thanks
Re: Re-power AM General Joel 1-10-03  
Have you considered adding a turbo to the 8-71. The power output is about the same as a very hot 6-92, and the overall cost is a lot less! Most of your local heavy truck wreckers will probably have standard turbo unit and the exahaust connections.
Re: Re-power AM General Frank Zsitvay 1-29-03  
No, do not add a turbo to a normally aspirated 8V71. The 8V71 and 8V71T are two different engines in enough ways that it is not economically feasible to change one into the other and expect it to work reliably.

The 6V92TA was the standard power for later versions of the AM General built by Flyer. However, you probably won't climb hills much faster with it at sea level. At 6000' the 6V92TA will not lose power and smoke like the 8V71 because of the turbo.

The V730 transmission has a maximum rating of 350 horsepower, which is what a 6V92TA or an 8V71 will do with big injectors. A real tame 8V92 would fit, but if you resisted the urge to keep it tame you would risk breaking the V730.

Before you give up your 8V71 with its distinctive acoustic signature, you might want to visit a Detroit Diesel technician and have him look over your engine. You may be able to install bigger injectors or modify the injection timing to produce more power.

By the way, the reason why the 6V92TA superceeded the 8V71 has to do with emissions, fuel economy, and repair costs. Generally, the 6V92TA is cleaner, uses less fuel and is cheaper to repair than the 8V71, although it doesn't sound as nice IMHO.

-Frank
Re: Re-power AM General Frank Zsitvay 1-29-03  
Oops - the sentence that reads " A real tame 8V92 would fit, but if you resisted the urge to keep it tame you would risk breaking the V730" should read " A real tame 8V92 would fit, but if you failed to resist the urge to beef it up you would risk breaking the V730."

That's more clear...
Re: Re-power AM General cliff Potthoff 2-3-03  
Thanks for the info. It confirms what I recently heard from the service manager at the local Stewart and Stevenson. He has a in excess of 20 years experience with the 71/92 series Detroits, and he recomends against changing to a 6V92. He said that I may gain a couple of mph's on the hills but I may also have trouble keeping things cool. He recommends giving my old 71 a physical to determine proper function of injectors and injector timing. That is what i will now do. thanks again.

Cliff Potthoff
Re: Re-power AM General Mark 2-5-03  
Hello,
I have a Caterpillar 7155 Transmission that is used in AM General trucks that I purchased at a auction sale. Rebuilt in the crate for $1000.00. If this would help with you transplant please let me know. 16 speed - air shift - automatic.
Re: Re-power AM General cliff potthoff 2-8-03  
Thanks for the info, but I doubt that I could use it. Since it came from a truck it is most likely is set up for a tee drive (straight in to the differential). The bus application uses a v-drive. the engine sits cross-wise and the drive train goes through a set of beveled gears before the torgue converter. This set up requires the input to the tranny to rotate in left-hand rather than a right hand direction.
Re: Re-power AM General BILL 8-24-06  
Do you have a7155 trans made by catipiller
Re: Re-power AM General Gregg 2-28-03  
Hey Cliff, dont give up on the 8v71. I have a fully converted 1977 40ft wide body am general with the same exact drive train and I pull a 12,000 lb enclosed trailer and do 40mph up donner summit in Nevada. I have no 65 injectors and it doesnt black smoke at all,even floored on flat ground and just a light haze of black when floored at 6000 feet. funny though, it goes about the same speed up the hill without the trailer. I checked into the turbo and there are a few guys that will set up your naturally asparated 8v71 with a turbo kit but it will be a very brittle engine when your finished and you will only gain around 60 horses. In order to do it right and make it basicly bullet proof you would need to change the pistons and liners and the blower, ect, ect, to the tune of about $12,000. its just not worth it. you can gain 30 hp for about $1100 with just a set of 70 injectors but it will devestate your fuel mileage and you will blacken the wind shields of the cars behind you.I talked with a guy who did the conversion from an 8v71 to the 6v92 and he told me that he "thinks it helped a little on the hills" but the bus sat so long durring the swap that he couldnt realy tell the difference. he also said the increase in power he got, if any, wasnt worth the amount of work and money he spent on it. also if considering an 8v92 also consider a different radiator because yours is barely enough to keep the 8v71 cool in hot weather on a long hill and you would need to figure out a completely different cooling fan system because its a totaly different system on the front of the 92. If I were you and the 8v71 isnt worn out I would have the size of the injectors checked because I was told some transit buses came with size 60 injectors and get the injectors timed by someone who realy knows what they are doing and just leave it alone and be happy with what you have. that is unless money and time are in endless supply! if you want to talk with someone who realy knows thier stuff call In line diesel in sacramento CA. they can make a Detroit sing and always have 3 or 4 busses running and backed in the bays at thier shop. I would love to talk with you or other Am General owners. maybe we can compare notes. shoot me an email at pinktangerinee@aol.com. Gregg
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