I have a 1987 Chevy 1/2 ton "show" truck.
Currently I have a carbrated SBC 350, turbo 400 transmission, and 2.73 gears (yes 2.73 not 3.73). I get around 13 miles to the gallon and run 15's in the quarter mile. Because I would like to have better gas mileage I thought of putting a Vortec 350 (multi point fuel injection) engine in my truck. To do this I would have to buy a 96 or newer chevy truck that is already equipped with the engine, transmission, and electronics, you can pick up a wreck vehicle with this engine for roughly $2500. if you look. But for my question.

I found a 91 Dodge with a Cummins diesel and a 5 speed (could be 6 speed not sure but it is a manual tranny not auto), the truck is still drivable but the front-end needs work, brakes need work and body is rough so I can get the truck pretty cheap from the guy. The engine and tranny are great, it has 150,000 miles on it.

If I was to put this Cummins and the 5 speed tranny what would I expect as far as gas mileage and what would my quarter mile times be any rough figures with this stock engine? I would like to 18-20 MPG when I drive the truck on the road. I don't really care what kind of mileage I get racing but I would like to have a 14 second possibly 13.5 but 14 is a good number. Can I get this good of gas mileage and still have a truck that will run 14's in the quarter? What can be done to the older Cummins? I have heard turbo's and bigger injectors? What kind of money would be spent doing this?

I know this engine weighs a lot but since the front of the truck will be on airbags I figure I can get big enough airbags to support the weight. As far as the actual swap I don't think it will be to big of a deal since my dad is a welder/machinest. How much electronics will be involved? I haven't put much thought into the brakes but I have heard there isn't enough vacuum to work my power brakes, any idea what I will have to do there? I plan on using my stock power steering pump, but the alternator from the dodge.

As far as the rear end goes I will start with a chevy 12 bolt rear end, but if I have trouble with it I have a Dana 60 with 4.11 gears I will but in the truck. What rear end gears would yall suggest for this truck to get the gas mileage but still run good in the quarter?

As far as the transmission I really don't like the idea of a 5 speed, is there and how hard is it to find an automatic transmission that will bolt to the Cummins engine?

Any information or suggestion are welcome, I am leaning towards the Cummins more than the vortec, but if the diesel engine isn't what is in my best interest I will go with a vortec.

Also what would be the advantages to a 94+ engine?

 

A 13.5 sec cummins is nothing. Tweak the injection pump, add a new fuel plate, turbos, injectors, and there you go. Go and find yourself a 47re transmission from a wrecked dodge, have it sent to any of the big tranny companies (DTT, ATS, Suncoast, Goerend) and have them build it up for ya. You can expect probably 18 to the gallon with it running 13.5s. I'd stick with a set of 3.54 gears since you'll need all the rpm you can. This sounds like a fun project. Let us know how it comes out.

 

If I was wanting good mileage and quick times I would keep the 350 and put a r4-700 or another 4 speed auto in it.

 

Welcome,


I am with barry on this one. The money spent on this conversion either way, could be used to increase your mileage some with less work. You could try to add holly projection and/or a tranny upgrade.

If you decide to go the diesel direction it WILL be alot of work, and with a getreg tranny it may be difficult to get in the 14 or less range.

good - luck



P.S. To get better answers about a 91 cummins try doing some looking around in the first gen. area. just my .002

 

Drop an LS1 in that truck if your gonna stay with a gasser. Lots of power and good mileage.

 

i have a plan, but i am using a 55 to 59 chevy half ton short narrow bed[with stacks of course] shooting for 11 seconds quarters and 30 mpg. the reason for me using a old truck is to beat emmision testing. i don't know what you would have to do to get it by where you live but it is another thing to check out.
but it would be alfull easy to get a good set of heads[vortecs can be picked up for 200 a set] and cam for you motor now and make a world of differance with a 700 r4 tranny. for very little money outlay.

 

A Dakota was mod'd some time ago ...

http://www.turbodieselregister.com/f...ght=12v+dakota

Wasn't he gettin 30+ mpg?

 

i imagine the gears in the truck arent helping though either. 2.72....... figure out what your cruising speed is and your rpms at that speed my guess is you are out of the efficiency range of the cam and therefore making the engine work to get going and keep going

 

With the 5 speed and the 2.73 gears you can expect mid to high 20's on the highway. It will not be a drag truck but you can easily make it as quick as it is now. Check out the 1st gen forum for info on pump tuning and other power parts. Since this is a show truck, not a working truck the rear axle will be OK as long as you don't go around dumping the clutch. There are absolutely no electronics involved in getting it running. If you want intake heaters (only needed for starting in sub - 20 degree weather) and a "water-in-fuel" idiot light there will be some wiring needed.

If you want a drag truck, find a '94 - '98 automatic equipped truck and build as BigBlue suggested. You will need the Dana 70 out of the donor truck to hold the power.

 

I am not keeping the engine I have, it just isn't ever going to get good gas millage, it was TBI when I bought the truck and the TBI had its issues. I took the TBI off the truck and put a carbrator on it. I had 3.48 gears in the truck with a 700R4 but I blew the overdrive and 3rd out racing the truck, then put a turbo 350 in the truck that was rebuilt for a dirt track car so it had a shift kit but the torque converter didn't lock in so I was runing HIGH RPM's and getting 10mpg so I put the 2.73 gears in the truck and got 11.5 mpg. The turbo 350 went out so I put a turbo 400 in the truck, I guess it has a locking torque converter cuz it lowered the rpm's alot in drive and caused me to get 13 mpg. The truck has vortec heads right now, electric fans. The carbrator is a quadrajet.

How much would an auto transmission cost for a dodge out of the junk yard? I never have had much luck out of auto transmissions I have had 2 turbo 350s and a 700r4 to go out in my truck and a 60e4 or whatever that new electronic transmission was went out in my mothers tahoe when I was pulling a trailor, it was a big trailor but that tahoe went through 2 transmissions from 98 when we bought it till 2001.

I could expect 20 miles to the gallon and what q/m times with the stock 91 cummins engine? Also what does a turbo, injector and fuel plate?

How does the injectors work if there is not electrical? I never have worked with a deisel so I don't know much about it. I have been going to pop the hood and look around at my dads 87 Ford truck, just an old welding truck.

Anybody know for sure if I will have enough room getting the engine in my truck? What kind of work will be involved? I know the motor mounts, fuel system, transmission mount, cluch if I put a maunal tranny, all of the front acessories(water pump, altinator, power stearing), any electrical if there is any. I will probally put the radiator from the dodge in my truck. I will have to make sure the air bags willl hold the front end. Have a new drive shaft built.

Is there anything else that I am missing, its always the little stuff that get ya. Will the stearing columb clear the engine?

When I first get the eninge in I will just be worried about getting the bugs out and hoping for good gas millage. I would like to have an auto so I don't have to do any cluch work.
As far as the transmission goes what would be better for quarter mile an auto or a manual?
I really don't want to tied $2000. up in an auto just to get the same results as I would with a manual.

 

what you want to do would have to be a labor of love. i did it in a 1/2 ton dodge which was as easy a swap as i have ever done. last tank of fuel was 19.8 longest drive was 7 mi. one way. runs 8.70s 1/8 mi. with a weak cylinder. by all means use auto. rarely use anything but 3rd gear on street. smokes street tires at will to 40 mph. forget gasser dragracing gears with a diesel they wont work you will run out of rpms. see my sig.

 

There is a Travelall in Polson Mt. running 3.08 Dodge axles with a automatic OD and a mildly turned up 90 non intercooled motor getting 25-28.

 

One of the things I've seen mentioned by people who put a Cummins in a Chevy is that they had to notch the front crossmember. I doubt you'll have any steering column issues putting an inline 6 in place of a V-8. With the '91 motor turned up and the manual trans, I think you could get mid 15's out of the truck. And automatic would knock half a second off that.

The injectors are mechanical. The injection pump sends a shot of fuel under high pressure to the injectors. When the pressure at the injector is high enough, the injector "pops off" and the fuel is injected.

 

Notching the front cross member is for oil pan clearance, correct? Any advantages to having a 5 speed tranny such as fuel millage?

What is the difference in a 5 speed and 6 speed tranny are they both overdrives just more space in the 5 speed, or is the 6 speed a double overdrive?