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Dodge Cummins Diesel - First-Gen Performance

Big Horsepower For Your '89-'93 Cummins Diesel

Jason Sands
Feb 1, 2009
Photographers: Jason Sands, Jeremy Torgensen, Brian Block
Photo 2/9   |   A shortcut to power is a P7100 injection pump swap. Unless you have a donor engine or access to a Cummins junkyard, many people find it easier to source a complete second-gen engine from a '94-'98 1/2 Dodge and drop it in.
As newer and flashier trucks became available, many people forgot about the older '89 to '93 Dodges. There's no doubt that this early 5.9L Cummins is a workhorse, but can it make power? The answer is, yes it can, and we've provided some suggestions on how it can be done. We'll go over the parts you need to really pump up your first-gen, compile a list of resources that are VE-pump friendly, and even give you a mini buyer's guide. Let's make some power!
The Basics
In 1989, Dodge introduced its 160hp Cummins-powered Ram 3/4-and 1-ton trucks into the market. They were non-intercooled, and actually made about 200 hp, rather than the advertised 160 hp. They were available with either a five-speed Getrag manual transmission, or a 727 Torqueflite three-speed automatic. In stock form, both the automatic and manual transmission-equipped trucks were gearing-limited, giving them a top speed of about 75 mph. The Cummins 12-valve engine was fitted with a Bosch VE rotary pump, which hid some free modifications that could give these early trucks more power. In the next few years, the Dodges gained an intercooler and an extra gear in the transmission, but other than those two changes, the '91 1/2-'93 models were virtually the same as '89-'91 1/2 trucks.
If you're going to try to build a 5.9L Cummins with a VE injection pump to make more than 400 horsepower, you'd better have some big injectors. The Bosch rotary pump only puts out about 17,000 psi of pressure versus more than 25,000 psi for '03-and-newer common-rail injection systems. This means that since there is no way to up the pressure to increase the amount of fuel that is sprayed into the engine, more volume (larger injectors) is your only solution.
Lucas Prince of Darkness injectors (commonly referred to as POD's) are a good starter injector, although they are smoky, and your mileage may suffer. Dynomite Diesel also offers injectors for first-gens that are a bit more expensive, but they make for a great daily-driver injector, and can still make good power. For those sled pulling guys who aren't worried about smoke or EGTs, custom six-hole injectors with .016-inch or .018-inch orifices (referred to as 6x16s or 6x18s) are available from places like Scheid, Buddha Power, and New Era Diesel.
Photo 6/9   |   First-gen Dodges lead hard lives, but with some easy upgrades, trucks like this one can make 300 horsepower or more.
Injection Pump
There are some simple tweaks you can perform to the VE injection pump to get an extra 100 hp. In the last few years, people have started making custom parts for these pumps to increase their fuel output even more. Brian Block, one of the original VE gurus, designed a 14mm injection pump head that can flow a lot more fuel than the stock version. The upside to the 14mm is a 100-horsepower increase over stock; to date, the only VE trucks over 600 horsepower at the wheels have used Brian's pump heads. Rocken-Tech is another company that builds parts for the VE, and their 4mm cam plate and 14mm head have also been used successfully at power levels over 400 hp. With either of these 14mm heads, an ultra-high-flow lift pump is necessary to maintain injection pump longevity.
Unfortunately, there aren't that many cheap turbochargers out there for the early 5.9L Cummins. A popular upgrade is to fit a Holset HX35 off of '94-'98 1/2 trucks onto the earlier models. An HX40 from an 8.3L Cummins will also work, but the HX35's seem to be a little stronger. Compressor upgrades for the stock Holset WHC-1 are also an option, and are available through Gillett Diesel Service and High Tech Turbo. Any of these turbochargers will be an upgrade over the stock 56mm turbo. Turbo Auto Diesel out of Phoenix, Arizona, also offers a line of turbochargers that can support 400-500 horsepower or more, for less than $1,000.
If you want to step beyond 500 hp, then it is time for twins. An HT3B or S400 off of a semitruck can be used as a low-pressure turbo in conjunction with an HX35 or upgraded WHC1 if you or a friend knows how to fabricate, but the turbo system probably won't spool right without a small exhaust housing, big injectors, and a 14mm injection pump head.
Intercooled vs. Non-Intercooled
If you plan on towing, it's easier and cheaper to start off with a later, '91 1/2-'93 intercooled truck. The intercooler will keep EGTs in check, and the extra Overdrive gear will help fuel economy. Oddly enough, non-intercooled trucks had much larger injectors, which means they can still make decent power on a set of stockers. Power Stroke intercoolers can be made to fit first-gens, although water injection also does a good job of cooling the incoming air. If you find a screaming deal on an earlier model, go for it. If not, hold out for an intercooled truck.
The 727 Torqueflite and 518 Overdrive transmissions available in '89-'93 Dodges are actually pretty strong. A shift kit, upgraded flexplate, and converter are a good idea, as is using the best clutches available. If you're shooting for 500 hp, include a steel planetary in your parts list. Since these transmissions don't have lock-up converters, parts will be cheaper, and transmission shafts will be less likely to break. Expect to pay anywhere from $1,000-$2,000 in parts for a rebuild (including the price of the converter) plus whatever labor rate your transmission shop charges. If you have a manual transmission, it's most likely a Getrag 360, which is pretty stout. An upgraded clutch may be needed, but that's about it. If you decide to greatly increase your horsepower, an NV4500 out of a second-gen truck can also be swapped in.
P7100 Injection Pump Swap
One of the most common questions when it comes to first-gen trucks is, "How hard is it to P-pump it?" The P-pump in question is the Bosch P7100 injection pump, which came on '94-'98 1/2 Cummins-powered Dodge Rams and offers much greater fueling and rpm capabilities. Depending on who you ask, the swap is either really hard, or fairly easy. If you're patient and good at collecting parts, the whole swap can be done with used parts for about $1,000. You'll need a P7100 injection pump, drive gear, injector lines, a '94-'98 1/2 front cover, second-gen injectors, and a new lift pump. You'll also need all the transmission and throttle linkages, or you'll have to fab your own. Most people we talked to said that the parts hunting was the most difficult part of the swap.
Overdrive Transmission Swap
The other question we hear all the time is, "Can I put a later Overdrive transmission in my truck?" The answer again is yes, and the 47RH found in '94-'95 Dodges is the best choice due to it's lack of electronics, although later 47RE's found in '96-'03 1/2 trucks can also be used. For the transmission swap you'll need the transmission, a new flexplate and converter, a shortened driveshaft, a new transmission crossmember, and a new engine-to-transmission adapter plate, as well as a second-gen starter.
First-Gen Mini Buyer's Guide
Scheid Diesel (800) 669-1593
Dynomite Diesel (360) 794-7974
New Era Diesel (740) 819-0457
Injection Pumps
Scheid Diesel (800) 669-1593
Brian Block (502) 633-1515
Rocken-Tech (707)-658-1915
Ponci's Diesel Center (707) 725-3307
High-Tech Turbo (801) 304-0700
Turbo Auto Diesel (602) 272-5311
Gillett Diesel Service Inc. (801) 571-7780
Transmissions and Converters
J&H Performance (530) 245-0176
Goerend Tranmission Inc. (563) 778-2719
Spec-Rite Torque Converters (530) 243-8300



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