Right or left-hand rotation?

[Craig R]

I am looking for a repower for my MC5c and I have just heard from a fella who says he has a sweet running DD 6v92N with 150K original miles bolted to a V-Drive in a '68 GM -- he doesn't know if it's a transit or a highway coach. He says it's a right-hander like I need. How do you get a right-hand engine hooked to a V-Drive -- other than a VR730? How can I tell for sure from long distance? Would the model and serial numbers help?
Craig

[roadrunnertex]

If it's in a GMC "V" Drive Coach it's a L/H roation engine.
jlv

[Jerry Liebler]

Craig,
    If it's in a GMC v drive the chances are very high that it's a LH rotation, however, if the transmission is a ZF it's definitely a RH.  Also Voith made a 'v'drive transmission that uses a RH engine and you already know about the VR730 & VR731.  Some RTS and Flxible transits used the Voith and ZF transmissions.
Regards
Jerry 4107 1120

[Craig R]

Thanks, guys, for the info. Would any of these transmissions (VR-, Voith, or ZF) have been OE in a '68 GM?  If not, how likely would it have been that they replaced a southpaw V-drive with one of these when the repower was done? Would a SN &/or mod. # clear up the identity of this engine?
Craig R

[littlehouse]

My quesrion is how hard is it to change the rotation, if it's that good an eng. is it something
that can be done.

Ray with the littlehouse

[luvrbus]

craig if you are going to repower find youself a 6v92ta a 6v92n would not be a big improvement over a 8v71 and if its LH you have to get a RH crank and cams for the 92 engine

[Jerry Liebler]

Craig,
     I'm quite sure GM only used their Allison  automatics in 68 especially.  It's not very likely that the trans and engine were changed to an rh as this would involve modifications to the cradle.  It's not to practicle to rererse the rotation as it requires changing the cam drive gears and the camshafts. 
Regards
Jerry 4107 1120

[Dallas]

Ummm, overlooking the transmisson problem,

There wasn't a 92 series in '68.

Be careful what you buy.  the valve covers and accessories on a 6V71 willl fit on a 6V92 and the same goes for a 8V71/8V92. Including the valve covers.

I'm not certain about the 6V92, but the 8V92 is only about an inch longer than the 8V71. The surest way to tell for certain is to get the serial number and carry it to your favorite high dollar engine mfg, or email it to DDA or simply call Detroit.

If you buy without checking, I have a really good 46 chev school bus I can let you have for a little bit of nothing! It has a factory original RTOO 14613 and a 16V53!  Just make me an offer!

I wouldn't sh*t ya, your one of my favorite tu*ds!

                       

[Craig R]

Thanks loads! Every one of you guys is a peach; You're a whole flat of peaches! Especially you, Dallas. That '46 skoolie sounds like just the thing to haul tourists around the Brooklyn Bridge -- I bought THAT last week. Would you consider a timeshare on an Arizona oceanfront in trade?

I'm not replacing an 8V71, Luvrbus. I was pushing my tubular home around with a 6V71.

How about the Allison VR-730 & VR-731 mated to an RH engine, Jerry? Would that require cradle modification?

[TomC]

You can mate the VR-731 to either the Cummins ISM or Detroit series 50.  With the ease at which a Detroit 8V-71 can be reversed (the only thing you have to replace is the oil pump), don't EVER use an 8V-71 right hand with the reverser VR-731-it just doesn't make sense.  Since the VR-731 is longer with its' reversing gear, you'd have to modify the engine mounts.  Good Luck, TomC

[Craig R]

I'm sooo confused! Luvrbus says, "if its LH you have to get a RH crank and cams for the 92 engine". then Jerry says, "It's not too practicle to reverse the rotation as it requires changing the cam drive gears and the camshafts". Now Tom says, "a Detroit 8V-71 can be reversed [with ease] (the only thing you have to replace is the oil pump)". What am I missing? Are the internal workings of the 8V71 so different from those of the 6V92 that the former is a breeze to reverse while the latter is a nightmare?

[Happycampersrus]

To change from RH to LH rotation on a V71 or a V92 series engine will require quite a bit of work.

(1) The camshafts are different between RH & LH engines even though they rotate the same direction on both engines. The cam lobes are located in different places. if you try to use the cams from a RH in a LH engine it won't turn over because of the valves contacting the pistons. Bill Gerrie over on the other board tried to reverse a 8v71 without changing the cams and had it lock up. Also the idler gear and the crankshaft gear has to changed or the cams will be spinning backwards.

(2) On the 92 series the crankshaft depends on the serial # if it can reverse direction or not. A easy way to tell is if the oil passages are drilled straight through (can you see through it?) you CAN reverse the direction of the crank.

If you cannot see through the crankshaft, the passages are drilled at an angle to improve oil flow. That crankshaft is designed for a specific rotation do NOT try to reverse it.

As far as I know from looking and reading ALL 71 series cranks can be reversed.

(3) The oil pump is crank driven, so that has to be changed. Plus you have to swap the bypass valve to the other side of the block.

(4) The starter will have to be replaced.

I bought my bus with a tired 6v71 LH and was given a 6v92 RH that needed rebuilt. I have personally done this conversion and had success, but I am a heavy equipment mechanic by trade. If you are not a mechanic, I would advise you to buy the PROPER rotation engine to begin with as it is not as simple to reverse an engine.

Check out this thread.
http://www.busnut.com/bbs/messages/233/13788.html

HTH,
Dale

[luvrbus]

Craig  if i confused you i am sorry but i had a mci 5 with a 8v71 and a 4 speed manual  in it and wanted a auto transmission and i bought a 6v92ta and a aliison from a mci 9 cheaper than i could buy the parts and transmision to install it on the 8v71 like dave said just shop to you get a good buy on what you need there are a lot of 6v92s out there and they have plenty of power in a 35 ft bus

[buswarrior]

Hello.

As far as reversing a motor, Bill G will tell you, he'll not participate in doing one again.

This from a guy who has been tinkering and doing what others said was impossible for over 20 years, back before we had this internet resource or the books.

This is a guy who....... just built a DDEC IV 6V92 and ATEC V731 swap for his GM fishbowl, taking out the 8V71/V730 combo he installed way, way back to replace the original 6V71/VH that it came with from transit when he got it circa 1980....

Because he wanted to...

I'll go with his advice: Lots of motors out there, look harder, go find what you need.

Offer a commision and see how quick your friends on here will find what you need and have it shipped right to you.

happy coaching!
buswarrior

[Happycampersrus]

I have the tools and equipment and I won't reverse another one either. To much involved for money you THINK you will save.

FWIW Bill Gerrie is my hero. He has helped me out of a jamb a couple of times with my Fishbowl.

Dale