4bt Cummins Mini Build Thread

Seeing how there are several Cummins enthusiasts on here, I figured I would start a thread on the 4BT Cummins I have. I bought it over the summer for $600 at a tractor show. I didn't have high hopes for it to run, but I took the gamble. Last week, I got it running.

https://youtube.com/shorts/f_nZfoxRlmI?si=O-mviORHB089Yq32

One issue with this particular engine is, it doesn't have an AFC (air fuel control) on the injection pump, so if this engine was in a vehicle and you come upon a hill and stop the pedal, it would belch black smoke and egt's (exhaust gas temps) would rise. Of course, you could learn to drive it to avoid that, but the AFC is nice.

These engines came with multiple injection pumps, stationary engines, like generators, have one speed pumps, so as soon as it starts, it goes right up to the set rpm, no good for anything but its intended purpose. Of course, it can be swapped out, but involves a timing gear cover change, sourcing an injection pump and new injection lines.

Some engines like mine, have throttle controlled injection pumps that were used in machinery, like skidders, so the AFC wasn't needed. Okay, but still not great.

The last were used in bread trucks or the like and those have an AFC. The later ones even came with a P-pump on them. Those are the best.

Here is my injection pump a non-AFC Bosch VE pump, like what is used on 89-93 Dodge trucks. The throttle is on top, the mechanical shutoff is on the side and the electronic shutoff is in the back.



And I bought this rough VE pump core off ebay for $100. It has the AFC on it, so I'll take the top off and swap it onto my injection pump. It's even the same color!



I already built one of these pumps for my 1985 GMC C2500 with an 89 Cummins in it.

 

The plan is to build it like I did to my GMC. I'll do a fuel pin, governor spring, which brings it up to 3200 RPM instead of 2500, crank the fuel screw in a turn, some prince of darkness injectors and a bigger turbo, probably an HX35 which is the stock size on 6BT cummins, but bigger than the dinky thing on this engine. Should run real nice then. My GMC runs amazing with the same fuel mods. Of course that has a much bigger turbo. The most expensive thing will be the turbo, but I can probably find a decent used one for $500 or so. All in all, I will have less than $1000 in these power mods. The engines are very cheap to build.

Also, this engine does not have a vacuum pump or power steering pump. That assembly bolts on under the injection pump. Luckily, there is a block-off plate there on the timing gear cover. I just have to take that off and bolt the vacuum pump and power steering pump on. I already have one of those assemblies in stock too.

 

Fuel pin and governor spring

https://www.dieselpowerproducts.com...MIxrPa8ciphAMVlVhHAR0lUwIbEAQYASABEgLQ0PD_BwE

POD injectors

https://www.ebay.com/itm/364460272614?chn=ps&_trkparms=ispr=1&amdata=enc:1aYRI14X5SEOPIMhepVNC-w27&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=364460272614&targetid=1644837434363&device=c&mktype=pla&googleloc=9001644&poi=&campaignid=20125739985&mkgroupid=149128855676&rlsatarget=aud-1297930287258la-1644837434363&abcId=9312975&merchantid=762071043&gad_source=1&gclid=EAIaIQobChMIq-m_rsmphAMVkXJHAR0IPQDHEAQYASABEgJIrfD_BwE

And HX35 turbo. Wow, way cheaper than I thought for a new one! I suspect this little 4 banger will make 250HP after all this and a butt load of torque. Stock, it makes 110HP iirc.

https://www.summitracing.com/parts/...MItN7Q7MmphAMVxmFHAR1bAAINEAQYAyABEgJml_D_BwE

 

Careful with the wording or this will be another Thanksgiving Dinoslip thread. Otherwise I'm excited to see how this pulls. One of the guys when I was in college was a farmer who returned to school to buy a ton of tools at student price... and build a 5.9 for his 6 speed manual transmission dually.........

When it was finished and had a few miles he stopped by the house to see my roommate. When he left he did the most impressive burnout I've ever seen or heard and it had a 30' gooseneck car hauler in tow. Now I've been to a tractor pull or two and this topped em all.
He did the works on that motor. From ported head to pistons and rods. He spent the time on the details and was rewarded.

 

The 6 cylinder in my GMC was originally 160HP and with the same mods, it brought it up to 350HP. The internet said it was a 350HP build anyways, so it must be true.

I pulled the top of the donor pump off. It had the factory 2500 RPM governor spring still.



Just some minor corrosion, but not bad. Pulled all the pieces out and cleaned it up.

 

a bit off topic, but do you happen to have any info on that '85? sounds like an awesome truck.

 

1985 C2500 with a 1989 Cummins and 4L80E and 14 bolt full float with posi-traction. It is my drag racing truck and hot rod diesel. I will be pulling this engine out to replace it with a P-pump Cummins for more power. I am at the max fueling capabilities of the VE pump. I would like to get up to 500hp. I plan on putting the VE cummins in my 1955 Chevy 4WD.









The little sneaky sneak air intake.



I need the HP to spin these bad boys, 33.5x17s.



They'll tuck real nice under the bed of the truck.

 

Installed the new pump top and tuned it in. Still runs good.