6v92 vs 8v71

[TomC]

You can run either a single or dual turbos mounted anywhere that is convenient-closer to the engine the better.  Rebuild your 8V-71 with turbo pistons and run a mild 65-75 injector for maximum engine life and fuel mileage.  Good Luck, TomC

[GM0406]

What about cooling down with water injection?  Bill T.

[mccarlk]

hi tom, do you know what kind of hp i will have with a 75 injector,and a turbo, will i have to limit the amount of boost?

[TomC]

I have 9G75 injectors in my 8V-71 and had it dynoed.  It came out at 375hp and 1125lb/ft torque with the air to air intercooler.  Without any kind of intercooler or aftercooler look for more like 350hp and 950lb/ft torque with the same injectors.  Good Luck, TomC

[mccarlk]

    Tom      ,  can i bump the hp to around 400, with the 1100 ft torgue? what would i need to do?

[TomC]

Detroit's last version of the 8V-71TA with 80 injectors was 400hp with 1200lb/ft torque.  You would need to rebuild your present engine up to a turbo spec engine, then you could just get the exact specs of this engine for the injectors (7G80), turbo pistons (17:1 compression verses the 18.7:1 you have now), bypass blower valve, fuel modulator (keeps the injectors from opening until you have turbo boost-otherwise you get a big black smoke cloud each time you push on the go pedal), increase your radiator, muffler and air cleaner, and install an air to air intercooler.  Sounds like alot, but it still is the cheapest and easiest way to go to get a turbo engine into your bus.  As stated before, you could run one turbo or two smaller, it doesn't matter.  If you have room on the sides of the engine, maybe two smaller 4-71 turbos would be the way to go.  Good Luck, TomC

[Busted Knuckle]

Detroit's last version of the 8V-71TA with 80 injectors was 400hp with 1200lb/ft torque.  You would need to rebuild your present engine up to a turbo spec engine, then you could just get the exact specs of this engine for the injectors (7G80), turbo pistons (17:1 compression verses the 18.7:1 you have now), bypass blower valve, fuel modulator (keeps the injectors from opening until you have turbo boost-otherwise you get a big black smoke cloud each time you push on the go pedal), increase your radiator, muffler and air cleaner, and install an air to air intercooler.  Sounds like alot, but it still is the cheapest and easiest way to go to get a turbo engine into your bus.  As stated before, you could run one turbo or two smaller, it doesn't matter.  If you have room on the sides of the engine, maybe two smaller 4-71 turbos would be the way to go.   Good Luck, TomC

mccarlk you should give Don Fairchild a call he is who built Tom's current set up and in my honest opinion (which will buy a gallon of fuel if ya add $5 to it!) the guru of hot rod 8V71's. (or any 2 stroke for that matter!) And the twin turbo set up would look way cool too!
  BK 

[RJ]

Tom,  can i bump the hp to around 400, with the 1100 ft torgue? what would i need to do?

McCarlk -

There is nothing wrong with the stock power output of the 8V71.  It was the industry's reliable work-horse for over 20 years.  Sure they were slow in the mountains, but reality-check time:  we're driving a BUS here, for goodness sake - not a BMW!

If you hot-rod your 8V71 and keep the same transmission, be prepared.  That gearbox will NOT stand up to the high-hp V-8, as it's a medium-duty model.  Putting 1100 ft/lbs of torque into it could very easily leave you stranded along the roadside with a blown transmission.

The HT-740 will take the high HP & torque of a hot-rod motor, but will NOT fit with the V-8 in your 5A.

As I said before: "The best "bang-for-the-buck" in your MC-5a would be a 6V92TA bolted to an HT-740 Allison."

Or simply reinstall the stock 8V71 with that 600 series Allison, sit back and enjoy a reliable and dependable ride - what's the hurry, anyway?

FWIW & HTH. . .




PS:  Another thought:  Putting in a high hp motor will also increase your fuel cost all the time, not just when you're climbing Rocky Top.  Gotta pay to play!

[mccarlk]

the engine i have is from a 80 5c with a manual, will the bell housing on the engine accept the auto?

[TomC]

It should-or you can change the bell housing to fit the automatic. Good Luck, TomC

[makemineatwostroke]

If you are going to use the 644 with that bellhousing you need a drop down adapater plus a 15/16 spacer ring and if you can find a sae 2 bellhousing for a MCI which I doubt you still would need the spacer

[mccarlk]

where can i find the adapter i need?  the original engine is long gone

[blue_goose]

Check any large truck salvage yard. 
Jack

[mccarlk]

good morning guys, great news for me, i went out to check the trans and it has the adapter plate still on it, this bus is great, best deal i have ever got, there must be thousands apon thousands, was done by someone very in to detail, oak, corion every where, before the engine was blown up the people just put new rads, new alcoas and tires, batterys, air bags , brakes, new steering box, velvac mirrors, comfort air mattress with the heaters, list gos on , holy crap im so excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Busted Knuckle]

good morning guys, great news for me, i went out to check the trans and it has the adapter plate still on it, this bus is great, best deal i have ever got, there must be thousands apon thousands, was done by someone very in to detail, oak, corion every where, before the engine was blown up the people just put new rads, new alcoas and tires, batterys, air bags , brakes, new steering box, velvac mirrors, comfort air mattress with the heaters, list gos on , holy crap im so excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

KWEL! It sounds as though you've found the proverbial "needle in the hay stack!!"  While not usually the case it is great to hear of it when someone actually hits a good deal! It musta been the straw that broke the previous owners heart & wallet when the blew! Hang in there and enjoy it! But keep in mind that theses things are expensive toys, and from time to time ya gotta spend some to keep 'm happy!   BK