Chevy to Cummins Conversion

We have finished installing the "93 Cummins motor into the "94 Chevy 3500 and everything works just fine. I have 2 questions: First, do you guys think the easiest way to connect the gauges would be to install a set of auxillary gauges on the dash? Second, since there is no room for an AC compressor up front, none that I can visualize anyway, do any of you know of some way to install an AC system on this truck? I appreciate all comments.
 
If I'm not mistaken, using sending units would require the services of the computer. This truck will not be dependent on a computer of any kind, by choice. The Cummins motor had brackets for the compressor, but there is no room between the motor and the Chevy frame for a compressor. We might be able to mount it up higher if we can utilize existing bolts. This is a new experience for both of us. Thanks.
 
I did a 1997 Chevy truck motor swap, put carbureted big block in it. On those the gauges don't work through the ecm. You should be able to get the factory GM sending units and with the help of a wiring diagram wire the factory gauges to work.
 
Report back with fuel mileage.

Guy at work put a cummins in a 1995 ? Ford F250 4x4 he claims like 24-26 mpg empty ? which I find hard to believe.
 
I think mechanical guages are going to be the way for you to go.I have a pair of 12 valve Cummins Dodges,and the weirdest things can upset the instruments.If my oil pressure starts acting up at a hot idle it means the battery terminals need checking.There are a couple of feed wires for functions that hang off the batteries,and just a little corrosion upsets everything.I don't usually bother to check the fuel mileage on mine,they mostly work towing short distances or plowing snow.I did get 28 MPG on a trip to pick up an engine one time.Those Cummins engines are way better on fuel than my 4 cylinder Rangers.That 93 engine should be a pre-intercooled engine,I have no idea how they were on fuel.I understand the later engines can be pretty horrid on fuel too.
 
So do I. 4X4s almost always have lower gear ratios in the rear end, plus they're heavier. However, 24-26 mpg is certainly not unreasonable. I have a "93 D-350 with a 5.9 Cummins up front. It has over half a million miles on it and still gets 23 or better depending on how fast I drive.
 
Is yours an automatic or a standard? I've heard of people getting as high as 26, but never 28. Is yours pure stock? And is it a dually? I have driven a "93 D-350 with a 5.9 for about 15 years now. Has a 5 spd. Getrag. Gets about 23 with about 500K on it. It came with an intercooler. We put one in the "94 Chevy. I think I took it out of a "91 D-250. Incidentally, the "93 I have been driving finally stopped shifting the other day. I think it's the clutch. Haven't had time to look yet. It has hauled 20K# loads over hill and dale for a long time. It deserves a break.
 
My engine is stock.I did up the fuel line size to 1/2 inch,changed the timing just a hair,went to almost a straight pipe,just use a resonator in the rear.I did change to a different air filter too.I have a 3.54 rear(I think,I can't quite remember on that).I have am automatic overdrive that I have done quite a lot to.Some heavier parts and revalving,had to add a little box to change the shift points.The biggest thing I've changed in the trans is the torque converter.It bites very positively,with minimal slippage.The stock engine really use a little more power to carry that torque converter on takeoff.I rarely check the mileage I get,usually in the low-mid 20's.I went to southern Conn.to pick up a chipper engine and that was when I actually got 28MPG.1850 RPM gives me about 68 MPH./i held it there from the time I left until I got there.No cruise control.
 
M Mike: I have a factory 1990 Dodge W350 with a five speed in it. I commonly get 20-21 MPG with 4.10 rear ends. I know of several fellows that have 2wds that get 25+.
 
"If I'm not mistaken, using sending units would require the services of the computer."

Nope.

A '94 Chevy truck would have an oil pressure sender and 2 temp sensors, the oil sender operates the gauge directly, as does one of the temp sensors (the one in the LH head), (the temp sensor near the t-stat keeps the 'puter informed of coolant temp).

Simply adapt the old oil pressure sensor and correct engine coolant sensor to the Cummins, (using reducer bushings, if needed), and hook them up to the main wiring harness, the gauges won't ever know there's a Cummins under the hood, and will work as before.

Having seen a couple of engines ruined by a melted or worn-though plastic oil gauge line, or a worn-through or cracked/broken steel or copper line, I'd stick with the electric gauges.

Yep, the drivers/operators should have noticed the loss of oil pressure (and oil) in time, but it doesn't always work that way in the real world!
 
I suppose if you drove 35-45 mph you could get that kind of mpg. When I cruise on the Interstate with my '96 PowerStroke I run 70-75 mph and get 18-19 mpg. If I could replace my 3.55 gears with 3.08's (frt & back) I could get a little better mpg.
The 300-6 powered F-150's I had got 12-14 mpg running 65 so I'm happy.
 
Thanks heaps. My "93 D-350 has both stock and auxillary gauges. So I get 2 oil pressure readings plus exhaust gas temperature, fuel pressure and turbo boost.
 
the old 12 valves will do it, my 94 dodge cummins got 28 mpg running I 80 from colorado to iowa and back
 
I can get 22 out of my 7.3 PSD fairly regular in the summer if I don't drive it stupid. I have gotten 23 before, but I don't check it real often.
 
If the 94 Chevy you are doing the swap into was a diesel then the tachometer would have been signaled off the alternator.

I put 7.3 into a 3500 HD for a customer and used the Chevy alternator, was surprised to see the tachometer functioning when we initially started it up.

As far as the other gauges go you can do a look up on the standard ignition website or others to find the value/range of the sensors that came with the Chevy then determine if the ones in the Cummins are compatible.
If they are not then you should be able to cross reference a sensor with the right value and thread size to match things up.
 

You can use the factory Chevy sending units to get the gauges working. 12v Cummins blocks and heads use standard pipe threads. You can install the water temp sender in the front of the head or in the left back corner using a reducing bushing, if your Chevy oil sending unit won't fit down on the side of the block move it over to the oil filter, there's a pipe plug there that should be same size as your Chevy sender.

I put a 97 12v p pump engine in my 04 F-450, had to get adaptor to use the Ford sending units but the ages work fine.

There's a company called Auto World that offers several different brackets for Cummins conversions, I got brackets from them that allowed me to reuse my factory Ford alternator.
They offer several different brackets for installing AC and likely know what brackets and compressor you need.
You can email them or call them up, very nice folk to talk to and very informative.

You can find them at cumminsdieselrepowers.com

The early Cummins with V44 injection pump get the best fuel mileage, but around here only a few report over 20 mpg, Ky hills and hollows with plenty of curves
My F-450 is a heavy (9500 lbs) 4x4 dually and I've never ran a tank of fuel through it that it wasn't hooked to a trailer at some time, so far I have a running average of 13 mpg, not bad for a rig that averages 26k lbs + when loaded.
I'd like to see 18 mpg empty average but won't complain if it does anything over 16 mpg. It's not stock, has upgraded turbo, injectors and pump work making over 300 hp so I'm not expecting big fuel milage numbers
 
Thanks heaps for the info. Like you, my "93 D-250/350 really varies in mpg depending on the load. I've been down to close to 11 when pulling my
gooseneck with 2 tractors on it in mountainous terrain. One tractor on my 8 x 16 trailer will get it down to about 16. 23 by itself. Torquiest truck I
ever owned.
 
Walter,
The Cummins stock Air-condition pump will fit. I am running B5.9TD on the similar year truck. Stock pump is lower right front. Requires one of two modifications. My AC is awesome.
Problem, there is not enough room to install bolt up front.
1. trim bolt hole on right of pump, for slot fit, install bolt and then pump. Tighten bolts with wrench.
2. drill hole in frame and insert bolt and tighten with socket and extension
3. install without one bolt, but, you would never be happy as a mechanic.
My choice at the time: (1) modify pump with slot hole and install.
My rationale was the pumps do not have a core (lifetime warranty), so who cares.

Wayne
 
Walter,
As for gages, I used the "W" terminal on the alternator. The dodge alternator does not have one, but a wire soldered to the un rectified windings gets it the same. If your tachometer is not spot on calibrated, change the pulley size to get RPMs right. Also, a GM alternator, (the one on your old truck) will bolt right on and work just fine. Find pulley to match same size, same rib.
I used dodge truck AC brackets and pulleys.
My engine was not out of a Dodge truck, but ironically an International roll back truck. My engine only turns 2500 RPM. Don't seem to need more RPM. I connected oil, temperature and other gages to what looks like Cummins sending units and spent not a dime on conversion there.
My problem was distance from radiator to engine. No Dodge or Cummins fan setup will work. I used a snub adapter and an 18" flex fan, made shroud, and it cools fine. My fan is full time engaged. BTW- My intercooler is down low, not in front of radiator.

My next modification is to put a 94-95 dodge intercooler imbedded in the radiator support. This will require a total front end pull for brackets, cushions and trim for fitting. I have 400K on the engine, and I will pull it for a gasket overhaul, front and rear main and paint. Still runs fine, and doesn't go thru a lot of oil. F & R rear main leaks seem to account for oil usage. I may put in 2 quarts oil in 10,000 miles.

My Chevy Cummins conversion made the Truck so much better. However, because my fan and AC loads the serpentine, I get about 70K and it is time for new belt and water pump. Learn from w-pump failure, and its a check and a 70K service. Starter has to be pulled and solenoid lubed, but that is at 100K and common for gear reduction starters.

I have had no fuel problems, at 200K did the lift pump. Replaced the crankcase vent (root to my Rear and Front main leaks). Adjusted valves and drove the crap out of this old truck like it is a new one. Few who aren't commercial pullers will pull more miles than I have with a pickup. I constantly pulled trailers with her.

She is still on my farm used often, with a tired old paint job.

When I do the front end, I am converting to SRW flatbed, cab paint, changing from 4:10 to 3:73 F&R diffs and using to pull my RV again.
Best truck I have ever owned.
I have a 2004 Dodge 3500 4x4 dually, 6 speed, which is a fantastic truck, but my Cummins Chevy will pull just as good, and grunt down low better. But the dodge wins on brakes.

Good luck with the conversion.

Wayne
 
I really appreciate this info Wayne. I also have a "91 D-250 with only 73K on the 5.9 Cummins motor. Body is trashed. My neighbor has a "91 D.350 dually regular cab with a 318 up front. Great body. Said he would take $700 for it. Not run in years. Bad Getrag tranny. Kind of thinking about putting the Cummins that's in my "91 in it. Wonder how much trouble that would be other than motor mounts, moving the exhaust pipe, adjusting the drive shaft and another tranny?
 
Walter,
Swap gages, components and likely most stuff needed is right there. Probably very little fabrication.

Wayne
 
Bob, doesn't this depend on the Chevy still having the original wiring harness? We don't have it. We took the truck on a test run today. Got it up to about 60mph. For some strange reason the wire coming from the temperature sending unit and going to the auxillary temp. gauge shorted out near the firewall. Plus we still can't get the speedometer to work. We installed the "Cable X Box" but just can't seem to get the wiring right. I'm about to just install a GPS speedometer and be done with it. But then I won't have cruise control. Also, there is absolutely no room under the hood for an AC compressor. I hope to figure out some alternative means to provide cool air for the cab. It gets really hot down here in the summer.
 

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