| Author | Message | ||
| carl white (Cwmci9)
Registered Member Username: Cwmci9 Post Number: 1 Registered: 5-2009 Posted From: 72.23.107.13 Rating: N/A |
I need to replace the engine in my 79 mci 9. I would like to replace my 8v71 with a 8v71 turbo. I don't want to get into a great deal of modifications. Has anyone done this and what modifications are needed? I have access to a very good 8v71 turbo. any words of wisdom would be appreciated. Thanks Carl | ||
| Ralph Peters (Ralph7)
Registered Member Username: Ralph7 Post Number: 13 Registered: 3-2004 Posted From: 66.59.120.99 Rating: N/A |
I am going to do just that. My 8-71T from a fire truck, will not have a auto trans water /oilcooler, will use a air oil cooler. If your 8-71T has a trans oil cooler on it use it. I am not uesing the 24V. alt either. You may need to change/ exchange the bellhousing do to stater placement, it maybe at road level. Bellhousing exchange is only a hour job, air compressor,power steering pump, alt drive, on bus are different. But it is up to you what you want, if you want all bus items on engine you may need to exchange the rear gear huosing from your bus engine, I am not doing this. I am going with a new air cleaner/ you only need a 180 degree elbo, and a 90 degree exhaust an flex pipe. NO NEED to mod.engine compartment. Check my profile call or e-mail me. | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 219 Registered: 2-2007 Posted From: 205.188.116.203 Rating: N/A |
Carl, I don't know any thing about the MCI, but we just did one on an Eagle recently. We had to raise the floor about 4 inches, the rest was a snap. Had to use the bus bellhousing and there are several hours in that if you have that issue, ours came from a truck, and we kept the bus transmission. We didn't update the air cleaner and when we ran it into the first mountain the turbo literally sucked the steel mesh in and collapsed the old filter, shutting off the air, so you may need a boneyard air cleaner of large inlet and outlet dimensions.(8 inch in and out is my favorite or two 5's would be great too). The air compressor and starter also need to stay with their bellhousing, the starter was clocked different (changable) and the compressor also had a different clock, (not changable) as well as different bolt pattern. The truck bell and parts would have worked fine if we had used the 13 speed, but we thought it was to involved to change the shift linkage over and try to shorten an already short driveline, (You don't have that driveline problem), with everything else we were trying to do, so the 13 may still go in it in the future. The 05 gets around really well with the old 4 speed in it for now. REALLY WELL!!! If you can't raise the floor there are ways to remount the turbo at the back of the bus. You will need to fab some pieces for both the exhaust and the fresh air side of the turbo and lengthen the oil line to the turbo. Its been done before and its not real hard to do. | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1549 Registered: 12-2000 Posted From: 98.192.173.82  Rating: N/A |
Carl - FYI, the 8V71T was an option on the MC-9s, the charter company I worked for had two of them built that way from the factory. Next to the 4106s and 4905s in the fleet, these two were my favorite MCIs. Engine compartment construction looked identical - no raising of the blower compartment floor necessary, but they did use larger squirrel cage blowers with corresponding larger openings into the engine compartment. Wouldn't be surprised if they used thicker core radiators, too. One caveat: Make sure the oil return line from the turbo runs downhill all the way back into the block with minimum bends. Don't want any type of back pressure building up in this line. . . If this is mated to an HT-740, you'll be real happy with the results. With the right injectors, you'll have 370 hp, 100 more than currently, which will make a world of difference - especially if you live in an area with lots of rolling hills. Often, where you's have to catch 3rd because of a grade, you'll now be able to pull it in 4th. When climbing the long 6% grades like we've got out here on the Left Coast, you'll stay in 3rd a lot longer before having to drop to 2nd, if at all. Like all MCIs of this vintage, just make sure your cooling system is up to par, and keep an eye on the temp gauge, the turbo puts out quite a bit more heat. Interestingly, your fuel consumption will remain about the same, and in some cases, it might actually improve. Maybe. FWIW & HTH. . .  | ||
| Kevin Black (Kblackav8or)
Registered Member Username: Kblackav8or Post Number: 125 Registered: 8-2005 Posted From: 24.152.162.226 Rating: N/A |
Generally a 8V71 makes 318 horspower, the early T's made 335 and I can see 370 with the right combination of parts but where do you see 100 over stock unless you have an underpowered engine. Turbo's almost always improve fuel economy with other things being the same or upgrades being within reason. An aftercooler or Air to Air setup will help as well. The higher rated ones came with an Aftercooler. Make sure you add exhaust temp guages to monitor them. Non turbo engines generally didn't have them but most if not all turbo's do. Knowing when to back off will save your engine. | ||
| Glenn F Campbell (Gfcgfc1)
Registered Member Username: Gfcgfc1 Post Number: 16 Registered: 12-2008 Posted From: 68.3.224.234  Rating: N/A |
What about adding the turbo and related pieces to a 8v71 not doing the engine swap? | ||
| Ralph Peters (Ralph7)
Registered Member Username: Ralph7 Post Number: 15 Registered: 3-2004 Posted From: 66.59.120.99 Rating: N/A |
The 8-71 & 8-71T are different--T has lower compression- blower/aftercooler and a few other parts. IF you do a turbo/aftercooler and do not be extremly carefull driving the bottom is NOT going to last long, to much pressure on parts. You will have tons of torque at lower RPM but DD not ment to it that way, plus very high heat when tourque is needed. Also the $$$$ to do the turbo on non turbo is about 1500 for uaed patrs/ labor. Good used 8-71T better way to go. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1602 Registered: 12-2000 Posted From: 76.68.133.14  Rating: |
Hello Kevin. IIRC, stock 8V71 installed in MCI were set to 270 HP, SAE net, standard timed with ? 60 injectors. This made for a fairly bullet proof engine for a hired hand to abuse. There were some fleet owners out there who, at some point when the coach was in their hands, uprated to the 304 HP SAE net, 318 HP SAE gross. Advanced the timing, which is not a small adjustment, and bigger injectors. There are some who put it back later! This was typically considered the truck rating, with more gears available and a front mounted radiator to cool it with. There were trade offs, the extra 34 HP comes at a cost of moving the torque curve higher in the RPM band, not good for a 4 speed transmission, and run flat out down the interstate all day, they were a little more thirsty. The higher power setting also gave the driver more opportunity to destroy the engine, a 318 will reach destructive temps more readily if not driven correctly in the hills, being allowed to drop way down in the RPM with wide open throttle to avoid a shift, not a good thing when the guy driving doesn't care about anything more than his last paycheque... So, 8V71 is an engine name, 318 is a particular power set up for that engine. happy coaching! buswarrior | ||
| Joe Beleskey (Joebus)
Registered Member Username: Joebus Post Number: 29 Registered: 1-2001 Posted From: 74.13.40.100 Rating: N/A |
I replaced my 8v71 with a rebuilt 8v71T....75 injectors, 102 rads, fans and cages, changed muffler, and air cleaner. They say 375 hp. Sure has made a difference in my MC8. Had a heating problem (once) in New Mexico (on 70, my fault......pedal to the pin, and not watching the gauge. Soon as I backed off a little the temps went back to normal....never stopped | ||
| John and Barb Tesser (Bigrigger)
Registered Member Username: Bigrigger Post Number: 184 Registered: 9-2007 Posted From: 96.42.7.186  Rating: N/A |
My 2 cents worth: My experience with 8v71 in trucks (never had one in a bus) was that new from the factory in a 72 GMC mine had 60 injectors and was rated at 290 hp. The upgrade to 65 injectors brought it up to 318. The same motor 8v71T with a turbo was rated at 350 HP. When I rebuilt that one I had a guy who really knew Detroits and he put in White tag 75 injectors and tuned the motor to accept the extra fuel (I think he had to turn the pump faster), brought my Hp up to 350 on a dyno without a turbo. I had to be very careful about temp when I had my foot in it, but it would run. Just another option to think about if your rebuilding your 8V71N. | ||
| Larry Baird (Airhog)
Registered Member Username: Airhog Post Number: 158 Registered: 1-2001 Posted From: 173.58.244.205  Rating: N/A |
I put a 8V71T and RTO in my MC-7 great combo. This motor is rated at 350 HP and it made 343 on the dyno, all stock and a lot of new parts. The 400 Hp models have a INNER cooler. I could be wrong I have been married twice! | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 91 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
I turbo'd my non turbo 8V-71 engine. I still have the high compression pistons-they are two piece with the tight rings, so turboing hasn't been a problem. Also added an air to air intercooler, enlarged my radiator as large as I could go, installed an air to oil auxiliary trans cooler with 12v fan, extra venting, bigger air cleaner, turbo muffler, and bypass valve on the blower. Gets about the same 5-6 mpg, but now doesn't slow down but on the biggest of hills. Was well worth it. By the way, a turbo and non turbo engine have the same block, crank, connecting rods, except for the possible addition of the after cooler under the blower for the turbo (very small to be affective). I do have 15 misters for climbing long hills when it is over 90 degrees. Good Luck, TomC | ||
| John Lacey (Junkman42)
Registered Member Username: Junkman42 Post Number: 80 Registered: 3-2007 Posted From: 69.19.14.43  Rating: N/A |
Tom, could you post some pictures of Your turbo setup? I and probably others would appreciate it. Did You use standard brackets and manifolds etc? I am much interested in adding a turbo to My bus. I do not buy the compression change etc for the type of service I will put the engine through. Thanks in advance, John | ||
| Glenn F Campbell (Gfcgfc1)
Registered Member Username: Gfcgfc1 Post Number: 20 Registered: 12-2008 Posted From: 70.162.227.38 Rating: N/A |
I have wanted to do this since I got my coach.Very very motivated way to go TomC and please post photos and details Thanks , Glenn | ||
| Larry Baird (Airhog)
Registered Member Username: Airhog Post Number: 159 Registered: 1-2001 Posted From: 159.115.179.139 Rating: N/A |
Glenn, I'll look for the pictures of mine when I did the change or if you get to the coast look me up, things are a little different for a MC-7. Larry | ||
| Don Fairchild (Don_fairchild)
Registered Member Username: Don_fairchild Post Number: 23 Registered: 3-2007 Posted From: 66.17.9.74 Rating: N/A |
Larry Did your coach set over in Norco for a while. I used to see one over there that looks just like yours in a storage yard behind a house just off the I-15 Don | ||
| Larry Baird (Airhog)
Registered Member Username: Airhog Post Number: 160 Registered: 1-2001 Posted From: 71.102.15.105 Rating: N/A |
That was mine at Norco RV, my family owns that place and I was keeping it there. Larry | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1502 Registered: 10-2003 Posted From: 71.58.110.9  Rating: N/A |
There is no problem adding a turbo without going to those low compression pistons. Remember that the 8-71T or TA was designed to pull 80,000 up long grades or level with good durability. You aren't going to work your engine that hard. I would recommend that you spend the money for a quality pyrometer and monitor it when working the engine hard. Just keep it out of the max. critical temp and you will be fine. |
