Convert from 8V-92 to Series 60

I am considering swapping our 8V-92TA to a series 60. Our coach is a 1990 40' Liberty Prevost. The throttle is by wire, not sure if it is the same as series 60. Does anyone know if the HT750 trans will mate ? Does the Allison HT750 ATEC system mate with the series 60 DDEC 4 ? Will the harness from the DDEC 3 on the 8V-92 work with the DDEC 4 series 60 ? Is the 8V-92 rotation the same as the truck Series 60 ?
Lots of questions, not sure if someone here knows the answers or I need to check with Detroit Allison.

I have seen 40' Prevost with the series 60 so I assume the clearance is there. There is a panel that can be removed in the floor behind the bed that looks like it would allow the clearance.

I know we will get some "why don't you just trade up to a series 60". But we love the floor plan, Liberty quality, colors and real wood bleached oak cabinets. All the newer coaches seem to have the laminates. Just not what we want. Also we have a series 60 engine available.

The 8V-92 runs great and has had the 500 HP upgrade. It runs circles around the series 60 coaches I have tested. Just concerned with the MPG and would like to swap engines prior to some lengthy travel.

Hi Robert,

This is a great set of questions to post on http://www.dieselenginetrader.com/di...es.cfm?catid=9.

Robert,

You need to drive a few more Series 60 coaches. I've had two since I had the 40' with the 8V92 and either one of them would hammer the 92 in every category - except sounding cool. Between the low end torque and the big fuel mileage improvement I would be hard pressed to own anything else.

As for the swap, I have to think you'll need to break out the chainsaw for the back closet.

Prevost was unable to install the Series 60 into a 40 footer until the shorter "World" transmission (the 6 speed) became available due to the increased length of the engine / transmission duo.

I also believe the tag axle geometry had to change, but I am not sure of that.

My reaction is that must be one hell of a Liberty that makes the swap justified compared to just going out and buying one with the Series 60 already in place. You should run the numbers. I am not sure you will escape interior changes as Jerry suggests. Our 87 Liberty had a north/south bed and the only impact of the higher Series 60 would have been to change the flat access cover under the bed to a "dog house", but if you have an east / west bed the cabintery across the back may also be affected.

I am not sure I buy into the theory that the Series 60 is a more powerful engine. It has more low end torque, but once the 8V92 comes alive (over about 1500 RPM) if does quite well. That may be attributable to the 5 speed transmission hanging in gear to 2100 compared to the 6 speed which will shift long before the engine is wound out unless you manually shift it. The only advantage I can see with the Series 60 apart from the low end torque getting you moving quicker from a stop is the fuel mileage, but the cost of converting will require a lot of miles of fuel savings to before those savings are realized.

Robert,

I know some "Bus Nuts" who have converted seated coaches to motor homes. Some of these bus nuts are incredibly talented. I have seen old buses turned into works of art. I have seen old 6V's and 8V's replaced with Series 50 and 60 engines and with Big cat engines. In every case, the owner said it was a lot of work and expensive to covert the engine over. Cooling, wiring, engine and transmission mounts, custom fabrication, possible vibration issues if not mounted correctly, the list goes on. I'm sure it can be done, I even saw one that used a manual transmission, if I remember correctly had 9 gears. But in every case the owner said it cost more then they had planned and took a lot longer to finish the job then they ever thought. Just a thought, how about having a "Hot Rod" 8V built and replace the engine you have now? Simple remove and replace, add water misters to the radiator to remove extra heat. Drive it like you stole it, and put the original engine back in when the hot rod engine melts down. That last line was "tongue in check":)

Whatever you decide, I sure it will be an interesting project,. Take lots of pictures and post often so we can follow along.

Robert, I am a long, long way from being very knowledgeable concerning Diesel engines, etc. but, in this change out you are contemplating, the knowledgeable guys are mentioning cooling. I replaced (recored) my radiator this past fall on my 8V92T and got by very cheap at $2000 final. If that gives you an idea on the associated costs, let alone the cost of the S60, then good luck.

Thanks for all the input, the 8V92 that is in it now is 500 HP and only has a little over 25000 miles. It was replaced by Detoit Allison by the previous owner because of a rear main leak and is a Reman, runs like new. All is documented. We would like to put alot of miles on the coach in the next few years and it looks like fuel is on a steady rise. The best mileage we have achieved is 6. And that was with a bit of a tail wind. Usually around
4-5. I keep hearing of 7-8 with S60 in a 40 footer. Does this sound accurate ?
I have a S60 470 HP which helps with the $$ part. The radiator is in excellent shape and oversized for a S60 according to what I read. I have a fab and machine shop at home. The bed is crossways so there would be a higher floor height behind it but the cabinet base starts at the top of the floor removal piece so I think they would remain untouched. I looked at a similar coach with a S60 and the floor is not an issue. My only hold up is the transmission concern, and wiring harness.
John mentioned a length difference between HT750 and World 6. If this is true then that would be the stumbling point untill I can find a trans.
The amount of work is not an issue since I am retired, we have some heavy dirt equipment and have built several street rods and hot boats. I have the equipment to handle lifting and positioning the heavy engines and trans.
As I said before, we love the coach, and also love the 40' length. We have looked at several 40 footers with S60's, the last one was at Parliament. Paul offered me a hell of a deal on it, but the interior was dark laminate and the conversion was different from our Liberty. We just have not found another 40' Liberty S60 that suits our taste. I know the engine swap is not like dropping a small block chevy in a 32 hiboy, but I think it would be a nice project if the trans and wiring can be figured out.

I do not know this to be a fact, but since Robert has the 500 HP 8V92 it is probable if the HP increase was a factory increase his cooling system has ample capacity. Detroit will not approve an engine installation (read that to mean stand behind any warranty coverage) unless they have approved the installation with respect to cooling.

My guess is the heat transferred to the cooling system from a Series 60 of similar HP is the equivalent of what the 8V92 puts out. The key to doing the swap, before any costs are considered is the physical space required for a taller, longer engine, and if the engine can be paired with a 6 speed transmission to make the fit. My brain is still wrapped around the tag axle configuration needing to change also, but I cannot be sure that is the gospel.

Thanks Jon, and sorry for the mis spelling earlier.
I appreciate the reply, you sound like you have had a lot of experience and that is what I was hoping to tap here. I never thought about the tag being an issue. I may have to crawl under the coach at Parliament.
The 500 HP upgrade was done by Jacksonville Detroit Allison and you are right, that was as high as the factory would allow for that configuration. They were the folks that told me the radiator for an 8V92TA actually had more cooling capacity than for a S60. I guess the 92 series create more heat because of firing each revolution ? I know they are more heat sensitive and have always kept a close eye on the pyrometers.
The front compartment in our coach has two boxes and ports for checking the ADEC and DDEC systems and the harness runs to the rear. I need to know if this harness will plug into a world trans and a DDEC4 ? I am thinking as I am typing this, I can check the DDEC4 on the S60 in my yard now and compare to the DDEC 2 on the 8V92.
I am searching online for a world trans to see what is available and what the plug looks like. Will also visit Detroit Allison tomorrow morning to see what they have to say. Maybe an adaptor or rewire new plugs if wires are the same.
I will also call Prevost in Jacksonville tomorrow to check on the tag axle issue.

As to your question about fuel consumption. I have heard some of the claims of 7-8 mpg, which sounds amazing to me. My S60 regularly performs at about 6.2 mpg. I have tried driving slower and several use combinations to see if I could improve this and found that I really couldn't, within a margin of error. I have a friend with the same basic coach as mine and regularly gets about 5.5 mpg. When you consider the thousands of gallons of fuel that you'll have to use to make up the difference I am not sure that it will pencil out.................