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Discussion Starter · #1 ·
Greetings. First time posting. I'm gearing up to attempt a Cummins 6BT swap into my motorhome. It currently has a carburetored 460 with a C6 transmission. Right off the bat everyone needs to know that I'm inspired by and following Joz's posts closely. It appears to be a similar conversion. I have 1992 1st gen, 12 valve engine coupled with a 2015 6 speed Allison 1000 from a Duramax. I am also working closely with Dave and KC from CA Conversions (CAC). They've been great. However, I am still trying to wrap my head around this conversion.
I have built a test bed to run the engine and trans combo and have figured out that a 1997 cluster works with the '92 PCM so I have all the original instrumentation. Yes, I am mounting the Dodge cluster in the Ford dash. Aux gauges will be EGT, Trans temp, Boost & Low Fuel Pressure. Currently waiting for injector pump and injectors to be rebuilt and upgraded to 230hp. Looking forward to hearing feedback and help with avoiding potential pitfalls as I take on this challenge. Will follow up with photos soon.
 

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Have you got the transmission mounting and functions worked out? The Duramax is a bit higher revving diesel than the Cummins so it's torque converter may or may not be ideal for your swap. Cummins engines came with Allisons. Late model 3.9's had the Allison 1000 5 speed.
 

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Discussion Starter · #5 ·
Have you got the transmission mounting and functions worked out? The Duramax is a bit higher revving diesel than the Cummins so it's torque converter may or may not be ideal for your swap. Cummins engines came with Allisons. Late model 3.9's had the Allison 1000 5 speed.
Thanks for the input char1355. I am working with Dave at CAC and they have a custom torque converter for this application. They also have an Allison stand alone controller that does not use GM software but Allison stuff. I admit that I don't know much about all that and I'm trusting them to know their stuff. As far as the mounts are concerned, I know it's going to be a challenge. I need to get the engine and trans as low as possible to minimize how much I will need to cut the dog house area for the trans to clear. We'll cross that bridge when we get there. Note: WE 😂🤣
 

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Discussion Starter · #6 ·
I'm still figuring out how to post pic's so please bear with me. Still waiting patiently for the pump and injectors. I want to run the engine and trans before tearing into the motorhome.
 

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Discussion Starter · #7 ·
Anyone out there have experience with Real Gaskets? I ordered a Cummins oil pan gasket and was surprised to see it arrive as 4 piece gasket. I then ordered one from Real Gaskets because it looked thicker and stronger, knowing that the oil pan has to be installed after the engine. Maybe someone has input?

 

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I see you already have the transmission mounted. You could have swapped the bellhousing on the transmission for an SAE3 type and used stock Cummins engine adapter parts. What you have there looks very nice. I'd guess that is cheaper than going the Cummins way. That billet tappet cover looks nice. There is an option where you can eliminate the vent hoses. There are valve covers with the vents built in. They were used on industrial engines. They were designed so the oil stays in the engine and the air is vented into the air cleaner. Can also just vent them to a catch can. Guys doing a 6bt use 2 of them. Here's what they look like. For posting photos, if they are stored on your computer it's easy. If you look at the bottom of the page there are a bunch of icons. Click on the one that looks like a paper clip. It's labeled attachment. Go to the photo on your computer and double click it. It will post it like the one I just did. If you want the photo to appear in the post, then click on it to copy and paste it where you want it.
 

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The oil pan gasket for a B series engine is a single piece item. The one you got sounds like the one used on the common rail engines. Those don't fit a B series. They use a different block. 1989-2002 use the same pan gasket. 2003 and up are different. Cummins part number for the gasket is 3959052. You can also use Felpro, Mahle, or a zillion other brands. The standard pan gasket isn't very fancy. Some guys use gasket shellac on those. You have a ton of bolts to hold it. Here's a good video showing the process.
 

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Discussion Starter · #10 ·
Thank you char1355. I wasn't aware of the bell housing swap option. I would have liked to see it as currently I have to use a Ford 6.0 starter and its located on the passenger side. This may be a problem when it comes to the exhaust as space is limited. This project is getting out of hand with the $$ so I have to try make this work. I am still thinking of plugging the holes and going with the vented valve covers. The only reason I went with the billet cover was because of the problems that Joz had with his. I do like the idea of allowing oil vapors to escape from the top rather than to side.

On a side note: I intend to keep and use this motorhome for long distance towing so I want it to be as reliable and durable as possible. Most of the upgrades I've done are from "monkey see, monkey do" so if there's something odd looking please feel free to point it out. The bright paint is to brighten up an otherwise dark engine bay. Easier to see what you're doing.
Thanks again.
 

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Discussion Starter · #11 ·
I have a question on brakes and I know it's probably not the right place but here goes. Hydroboost brakes? The motorhome has miserable brakes. I have a Dana 80 from a 1997 Dodge 3500 dually that I want to swap into the Ford and maybe add hydroboost. Any input will be appreciated. Is it worth it? What power steering pump and boost unit?
 

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Most do change to hydroboost on brakes. It's a good system and has been around for a long time. Also, that brake booster takes up a lot less space. On that you have a couple options. The Dodge units used a combo power steering pump/vacuum pump. The ones from about 1994-2002 are the best. After that they didn't use an engine driven vacuum pump. If you pick up one those combos it will bolt up to your engine. The power steering pump is a Saginaw unit an very dependable. The pump reservoir will have 2 return line ports. One return from the steering gear and one from the hydroboost unit. They need separate returns. Also, an in line filter is recommended for the line coming out of the steering gear. Hydroboost units are very sensitive to contamination so you want to keep the fluid clean. The second part of the puzzle with be the booster unit. Ford used hydroboost systems in F450/550 trucks starting around 1987 or 1988. It may be possible to fit one of those units to your van. Been a while since I looked at these but the E series vans may have had one also which could be fitted to your van. Second option would be to adapt a Dodge booster. A couple of things to look for should you pick up used parts. The vacuum/power steering combo has a small support brace that attaches to the engine block. That part is required or the unit will likely break. There is also an oil line and fitting that sends oil to the vacuum pump. If you shop for used units, be aware there were 3 styles of those combo units. The first style used only about 2 years had 2 diaphragm vacuum pumps along with the power steering pump. Not a good design. Don't recommend that one. The second and third designs both use a better vacuum pump. I believe the first of those had a 3 piece vacuum pump and the second was 2 piece. Those pumps often need a tune up and rebuilding one is not rocket science. A company here in North Carolina named Gould Gear and Electric makes the best rebuild kit. Has all the seals and even special tools needed. Here's one of their videos which is worth watching if you plan a rebuild.
As far as hoses and fittings go, you can probably use a mix of the Ford and Dodge hoses. You'd have to work that out. Now there is a second option which does not include the vacuum pump. There is a power steering pump only system that was used on the Cummins 4bt that can be used. It is designed for hydroboost with 2 returns. Any vacuum requirements such as heater/ac controls or cruise control can be done with an electric vacuum pump. That's what Dodge and I believe Ford also did. You mentioned the word "Cost" and unfortunately there is nothing free. The '96 up Dodge combo units seem to be selling for around $300 for used ones. Those are usually missing the oil line and that little brace I mentioned which may cost around $100 or a tad more. And of course, when buying used parts you never know whether they need rebuilding. The vacuum pump rebuild kit is $60 or they will rebuild it for you for $299 exchange. A power steering seal kit is around $15. Then there's the hydroboost unit. It will be in the area of $200 or more. So just a guess but to do a complete system is probably in the $700-800 area. Now you might find all the parts you need in a salvage yard for far less. Now the optional power steering pump without the vacuum pump isn't going to be cheap either. The OEM Cummins adapter was discontinued about 20 years ago. It has been reproduced. The kit not including the power steering pump is $525. For the pump you use one from a GM truck with hydroboost. Sorry for a long response but there's no simple fix and definitely not a cheap one.
Now another item you mentioned was the starter location. The aftermarket adapters all have them on the passenger's side. Do you plan on a turbo upgrade? The early engines used an H1C turbo which was OK but there are far better ones. In 1994 they changed to the WH1C and in 1995 the HX35W came into play. These were far superior to the old H1C. You will have to have an intercooler with any of those. There are a number of different exhaust manifolds out there. One that may be of benefit came on Ford and Freightliner trucks with the 6bt. Puts the turbo closer to the engine block which may help with side clearance. Not sure about starter clearance. With those van chassis it's like putting 10 lbs in a 5 lb sack. LOL.
 

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Discussion Starter · #13 ·
Wow char1355, thank you so much. I'll need a little time to process all this great info. The unit does already have a vacuum pump set up with the little bracket. I'm now on the search for the right pump and booster. Off to Napa again😂
 

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There were at least 4 stand alone vacuum pumps offered on the B series engine. Three were belt driven and one gear driven. One belt driven one uses a pump that requires an oil feed and drain. Here's a photo of a 4bt with one of those. That pump was expensive when new and it has been discontinued years ago. The second style was the same diaphragm type used on the Ford diesels in the '80's and '90's. That pump is easy to find but I've never been able to narrow down the mounting bracket. Don't know if it was Cummins of aftermarket. Cummins didn't list those pumps on the engine build sheet but they did sell them. Do you have the serial number of you engine? If so, I can look it up and double check to be sure. Both those pump drive from an accessory V belt. The third type was also the diaphragm type but driven by the same 8 groove belt as the other engine accessories. That one was used on the 2003-2007 Dodge for the exhaust brake system.
 

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Discussion Starter · #15 ·
I have the 3 piece pump as mentioned in the video. I ordered a seal kit and new vanes from Geno's. I also have a power steering pump on hold at NAPA from a 97 Dodge. It has 2 returns. I want to make sure it fits first. I thought I could simply plug one of the returns for now and research which hydroboost and master cylinder is best suited.
 

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OK. You engine is a CPL 1351 built June 26, 1991 at the Consolidated Diesel Company in Rocky Mt. NC. It is classed as a 91.5 model because it had the intercooler. Also, has an improved head with 7mm injectors. The injectors are 6x.009 units and have a 145 degree spray angle and pistons with smaller bowls to fit that. All this was done mainly for smog control. The earlier 4x.012 injectors and injection pump actually have more power potential. A common upgrade to your engine is 5x.012 injectors. Your turbo is the basic H1C. A better performing turbo would be a WH1C or HX35W. Those are a much better design. Although the engine is rated at 160 HP it would not take a lot to get to 250-300 HP. Upgrade the turbo and injectors and adjust the injection pump settings and you'd have a fire breathing dragon. Always keep in mind that as the HP goes up so does the torque. In stock form you have 400 lb ft. Your engine would have had the 3 section vacuum pump. As far as I know the '97 power steering pump should bolt right up to your vacuum pump. If in question, email the guys at Gould Gear and Electric in Murphy NC. They can tell you for certain. As for the master cylinder choice that can be a real hair puller. The Ford F Superduty (F450) from 1988-1998 had a master with a 1.31" bore. Those trucks had 4 wheel disc brakes. Regular trucks with the standard rear brakes got a cylinder with a 1.13" bore. When 1999 came around everything went nuts. Ford changed the master cylinder almost every year and in one year they changed it twice. If it would fit, that first series would be fine and less complicated. Does your axle have rear discs? One thing I'll caution you about if you go hydroboost. Should you buy a unit at the parts store it will probably be missing one vital part. The little push rod that goes between the booster and master usually doesn't come with it and trying to find one is truly like hunting hen's teeth. Been there and done that. Took me over a year to find the specs on that darn little rod and then had a company in Michigan who specializes in hydroboost make me a couple. If you find a used unit in a salvage yard you can swap it for a rebuilt unit but be sure and keep that rod, spring, and retaining clip. The spring and retaining clip you can get but that rod is tough. One thing good about your 2015 Allison 1000 is it has a much higher torque input rating than previous models. It will handle 765 lb ft of input so you are safe with most any sane engine mods you want to make. VE injection pumps will only go so high before they run out of steam.
 

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Discussion Starter · #18 ·
WOW! You really know your stuff. Thanks for taking the time to explain it all. It's great for me to have that ground level info. I have just received the pump and injectors and will be installing them soon. 230 HP is expected. I am still waiting for the vacuum pump rebuild kit and the upgraded torque convertor. I have the exhaust manifold that you spoke of and am trying to figure out the return. The pressure side should be easily made up at the hose shop. Thank char1355. your input is appreciated.
 

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When you speak of the return are you talking about the exhaust pipe routing? That can be a challenge on those van chassis. You should plan on a minimum of 3" exhaust pipe. Some systems go as large as 4". Below are some photos of various exhaust elbows that may come in handy when you get into tight fitting. 230 HP should be very good for your application. That was the power level of the most powerful 12 valve used in road applications. It was used in medium duty trucks and buses. Are you upgrading the turbo? That old H1C sort of struggles for much power above stock. The factory 230 HP used the HX35W. That turbo is as common as dirt in the marketplace. Caution, beware of the cheap knock offs. The genuine Holset turbo is the better way to go. If you find a good used one you can install a rebuild kit. If you should do that remember the nut on the end of the turbine shaft turns clockwise to loosen. Guys sometimes forget that and break the shaft.
 

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Hey Sid. Glad my thread is still useful.
Don't take the issues I had with the gasket as something that you'll have to deal with. Tens of thousands of the engines are still on the road with no issues like I experienced. I've owned 4 more 6BT's since then with no issues.
@char1355 is right (about a ton of stuff) - the pushrod on the hydro boost can be tricky. I seem to remember that I had to shorten mine.
Good luck with your build. You're in good hands here.
 
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