A K5 Cummins Conversion: The saga continues...

[MaxPF]

So, last time I updated the thread I was about to get some exhaust going. It's just your basic 3" aluminized system,starting with a downpipe:



I decided to reuse my Magnaflow muffler:



It really tones down the exhaust and eliminates any in-cab drone despite being a straight-through design:



Complete exhaust system:



Gotta wrap the downpipe to keep the heat down:



A few installed pics. I had to route the exhaust on the outside of the trans crossmember due to lack of clearance inside:











And, of course, the honkin' 4" tip!

[MaxPF]

Since the exhaust was now good to go, I needed some intake plumbing. I was leery of all the Chinese silicone couplers out there, so I opted for Gates couplers used for MD/HD trucks and equipment. I got simple straight couplers that I could cut to length for areas where little flex was needed:



I also needed one flexible coupling on each side, so I got a pair of ring-retained hump hoses:



Note the "Made In USA" on the hoses I also got some constant-tension t-bolt clamps to retain the hoses.

I also needed tubing. Some of the stuff I found was ridiculously expensive. I ended up using Chinese aluminum u-bends because I could actually afford them. I made a simple bead tool to put a bead on the ends, and after some , , , and I ended up with these:



Starting at the turbo:



Through the core support:





Into and out of the intercooler:



Back through the core support:



Around the extra-wide diesel radiator, which other swappers assured me COULD NOT be done:





A hump hose mid-pipe:



And finally into the intake elbow:



I had to use regular hose clamps here because the constant tension clamps were too wide. In case your wondering, yes, it does clear the master cylinder. Barely:



There was one other minor thing I wanted before I threw the batteries in and took it for a spin. I wanted a place to tee both positive battery cables off to the starter. A piece of Delrin, a 3/8" Allen bolt, and an hour of lathe time later yielded this:





It's mounted to the front of the drivers side battery tray stand. Following that was some uninteresting and still unfinished wiring and installation of the air cleaner (which I lost the pics to somewhere ), and it was ready to drive! Yay! So, how did that go? Stay tuned to find out...

[notchbackgta]

I would like to see your bead tool. They are usually pretty expensive to buy and I will need one eventually

[MaxPF]

I will have to see if I have a pic of it. It's seriously redneck, but it gets the job done.

[Dieselwrencher]

Man, I still can't see yor pics even with google chrome. Is your bead tool a modified 3 jaw vice grips?

[MaxPF]

Do you have Dropbox blocked? That's where my pics are hosted.

[MaxPF]

So, the initial drive showed a few issues. Most were simple fixes of minor things, but one major problem was a random failure to crank. I had a starter relay mounted on the fender. and from that relay a 14 gauge wire snaked down to the starter along the main battery cable, a distance of perhaps 7-8 feet total. It seems this length of 14 gauge had too much resistance and gave marginal voltage at the starter solenoid terminal as well as some heating of the wire.

The immediate idea for a solution was to run a larger wire, but that meant threading a 12 or 10 gauge wire through an already-mounted loom. Instead, I close to eliminate the relay from the fender and connect the ignition switch start wire directly to the wire going to the starter. I then moved the relay to the frame rail adjacent to the starter, and used the starter wire going to the starter to instead actuate the relay. The relay switches power directly from the main battery terminal on the starter, protected with an inline fuse, to the solenoid terminal when the key is in the start position. The wire on the fuse holder is 12 gauge, while the other wire is 14 gauge. Since resistance increases with length, and the wires are kept very short with this arrangement, there have been no more failure-to-crank issues. Here's some pics before I put convolure tubing over all the wires:



I put a reverse-biased 50V Schottky diode between the starter wire and the ground wire. When the relay opens, the energy stored in the magnetic field of the solenoid has to go somewhere. Normally, it arcs across the relay terminals as they open, which will eventually cause the relay to fail. The diode allows the reverse current to travel harmlessly to ground with no arcing, where it is dissipated as heat in the solenoid winding.



Here's the installed relay and fuse:



This setup engages the solenoid without fail, even when the batteries are too weak to give more than a half-crank to the engine. The weak batteries were caused by my alternator losing a diode, which is a story for later time .

[MaxPF]

Quite a bit has happened since the last update. I have been chasing an intermittent bump-induced driveshaft vibration for several months. Despite rebuilding the CV and replacing the output bearings in the t-case the vibration persists. :gaah: I will get it figured out one of these days.

My batteries finally went Tango Uniform I was originally set on running a pair of group 24 flooded deep cycles because, frankly, I believe properly maintained QUALITY deep cycles will outlast AGMs. However, that plan got thwarted when I discovered that Sam's Club had group 34/78 Deka AGMs (labeled Duracell) for only $105 during a Christmas sale!



Sign me up on that deal! I eventualy plan on moving the batteries out of the engine bay and into the rear of the truck, so hopefully getting them out of the engine bay heat will increase their lifespan. When I do that I will make the battery boxes capable of accepting group 31's.

Not long after that my third Autozone alternator decided to windmill the pulley and spit the belt off. Swell. At this point my option was to fix the pulley and keep running the Zoner alternator, or put this in it's place:



I scored a pair of these off of Ebay for $165 each. Normally, these are $525 alternators, but these had been dropped and had broken back covers and some dings, hence the discount.



$525 you say?!?! Why so expensive? Simple answer:



This alternator can crank out 240A CONTINUOUSLY. And they are made in USA. Unlike mere mortal alternators that have six rectifier diodes that are heat-sinked to the case, these bad boys sport 12 rectifiers in their own heat sink, which is still mounted to the case for further head sinking.It also has dual fans:




I ordered new rear covers for them, as well as an 8 rib pulley and a 7 rib pulley. They 8 rib pulley is for mine, while the 7 rib pulley is destined for Todd's Jeep. These alternators have 7/8" shafts, and it seems 6 rib alternators are not made for that size shaft, so the 7 rib jobbie will be used on the LS motor with it's 6 rib belt. Here they are, ready to go:





10 hours of machining and wrenching later, I ended up with this:



What is not noticeable in the above pic is that the AC hoses and lines are gone. This was pre-planned even before the alternator debacle. I evacuated the refrigerant and capped the compressor, condenser, and receiver. In the next few days I will remove the glower/evaporator box from under the hood and the HVAC box from under the dash. This will get replaced by a unit that fits entirely under the dash. The purpose of removing the factory HVAC stuff is to make the room needed to fit the HE351VE variable geometry turbo that I have acquired Not to mention I have always disliked that crap cluttering the engine bay. It will also make room for another item I have just ordered, but I am keeping hush-hush for now

[MaxPF]

But wait! There's more! Another item on the to-do list for the New Year was new tires.

I had originally intended on running the same 37" BFG KO2's that Todd is running on his Jeep. However, perusal of the reviews on this tire revealed a disturbing trend; it seems they wear rapidly when they are on a heavy vehicle. I had already noticed the weight on the front end of my truck has not been kind to the 35" KO's I was running, and I most certainly did not want to pay $1500 for tires that would only last 20,000 miles. :whaa:

A buddy of mine with a Cummins-swapped old-school Suburban had the same issues with KO's and ended up switching to Toyo M55's. The M55's are designed for heavy trucks that routinely run down unpaved roads, so they are tough and designed to wear well. My buddy has been running them for over three years and has nothing but praise, so I was sold. Sadly, the biggest size available is 33" and I want 37's So, I did some more looking. As it turns out, Toyo's sister company Nitto recently introduced a new tire geared toward the same type of use as the M55. It is called the Exo Grappler AWT, and unlike the M55 it is available in a 37" version. 37x13.5x17 to be exact, so it is an inch wider than the typical 37" radial. It's E load rated, and guys running them on 3/4 and 1 ton trucks report 30,000+ miles with plenty of tread left. And, they only cost $15 more per tire vs the BFG's. Sounds good to me, so I had Discount order a set of four. They arrived in due course, and looked better in person than on Nitto's web page:



Mounted on my H2 rims:





Like the KO2's, the Exo's are severe snow service rated, which will come in handy during those December hunts when a snow storm rolls in:



Here's the tread:



And finally, installed on the truck:



So far I have put about 100 miles on them, and they are night and day compared the the 35" KO's they replaced. They are responsive, and despite their E load rating they soak up the road bumps better than the BFG's they replaced. They are also smoooooth, which I attribute both to the quality of the tire and the 10oz of Dynabeads in each tire instead of conventional balancing. It will be interesting to get them off-road and see how they work and how they wear, but so far I like 'em a lot.

One side benefit is that the 37" tire actually improves my gearing. The engine seems happier cruising down the freeway, and I no longer need 5th gear on the surface streets. It will be interesting to see if/how much my fuel economy is impacted by the new rubber.

[1972K20]

Sounds like fun. I've got a Dana 60F and Dana 70HD rear I'll be getting into soon.

[MaxPF]

Originally Posted by 1972K20

Sounds like fun. I've got a Dana 60F and Dana 70HD rear I'll be getting into soon.

Dana axles are my least favorite to set up. If you want to save yourself a lot of grief, either buy or make setup bearings for the carriers and inner pinion bearing. And buy, rent, beg, borrow, or build a case spreader. And never, EVER spread the case more than .010".

[lower50's]

Cool I have been throwing around the idea of a cummins swap in my '87 K5 Jimmy that we bought in Mesa 3 years ago.

[MaxPF]

Originally Posted by lower50's

Cool I have been throwing around the idea of a cummins swap in my '87 K5 Jimmy that we bought in Mesa 3 years ago.

If you choose to do so, plan on boxing or otherwise reinforcing the frame from at least the front body mounts forward and replacing your axles with one ton units.

[lower50's]

Yes sir. Good idea. They are a very heavy motor.