C10 Suburban Cummins
 

I got a 12 valve for my next project and I have a few questions for you guys. Donor engine is from a 1989 dodge. It was missing the vacuum pump/power steering. Went out to the junkyard and found one but it don’t work. I also found a crack on the housing unit. Would I need to replace it?

Re: C20/cummins 12 valve
 

Yes, I'd say replace that gear housing or have it welded properly. Those early 1st gens had a diaphragm type vacuum pump and the whole assembly is shorter than the later vane type vac pump setups. You can get the later vane style like you have to work with some mods to the throttle bracket. I'd rather have the later set up anyway.

C10 Suburban Cummins
 

Thanks for the info. Hopefully I can get the correct 1 or get my refund for the pump.

C10 Suburban Cummins
 

This was the original idea for my project.

C10 Suburban Cummins
 

more pics

Re: C20/cummins 12 valve
 

Monte, very cool! That looks like a pretty clean truck. It also appears to be a Longhorn from what I can see from the pics. Do you plan to use that 727? If so you better try to get rear end gears near 3.08 or so.

C10 Suburban Cummins
 

Im going with the automatic for now until I find a good manual transmission. The truck is a longhorn, it's in great condition.

Re: C20/cummins 12 valve
 

If you can find a D60 with 3.54 gears from one of these trucks, that would help. Your truck probably has 4.10s unless it was a big block truck.

Re: C20/cummins 12 valve
 

My truck is a big block 402 8 lug, I need to look and see what it has.

Re: C20/cummins 12 valve
 

Cooler heater exchanger/converter oil cooler

Where do I find a replacement cooler or do I need it ?
What setup are you guys using?
Would I need to replace the metal line or can I use rubber hoses for the coolant?
They are all rusted.

Re: C20/cummins 12 valve
 

That is the torque converter heat exchanger. On a Texas truck with a 727 I'd just toss it and put a good after market cooler in front of the radiator.

Re: C20/cummins 12 valve
 

When I go down this road again I will put a block off plate on the gear housing and belt drive a common ps pump and go hydraboost. The marriage vacuum pump and ps pump can be a real pain if you get a bad shaft and seal on the ps pump. As long as you have the gear housing off make sure you put a fix on the killer dowl pin or it may destroy the whole motor. I was lucky, dowl pin fell down and instead of going between the two gears it got caught between the gear and tin cover, when I pulled the timing cover it looked like you had shot it with a 45 ACP from the inside out. Could'nt figure out where all the oil was coming from.

Re: C20/cummins 12 valve
 

Thanks for all the information guys. First time working on diesels for me.
Got a few parts today:
Gear housing
Expansion plugs
Water inlet seal
Water pump
Changing all the gaskets other than manifold and head.
Waiting on the Killer dowel pin to come in.

Re: C20/cummins 12 valve
 

The power steering pumps have a drive coupler that is pressed on the pump shaft. That is a wear item and can be purchased with a new or reman pump. I can't tell you how many of these vac/ps pumps I've resealed and have no issues with them. I have had some severly worn ones I've had to source odd parts for but I still wouldn't hang a different pump off the side and run another belt to drive it. You can run hydroboost with a non hydroboost pump. You just have to either t the return or add a return to your reservoir on the pump.

Re: C20/cummins 12 valve
 

Buying those parts from Mopar sounds pricey. Make sure you replace the oil cooler gaskets. I'd go ahead and do the cooler too if it has a lot of miles on it. Those early ones are known to leak and cause headaches. Make sure if your crankshaft has a groove worn in it that you get a seal with a wear sleeve other wise you will be having leaks again. That goes with the rear main seal too.

Re: C20/cummins 12 valve
 

I'll look into the oil cooler next.
Looks like a reman one will run about $200-$300.
Should I apply any type of permatex with the expansion plugs or just press them in?

Re: C20/cummins 12 valve
 

Which expansion plugs?

Re: C20/cummins 12 valve
 

Core plugs/freeze plugs.

Re: C20/cummins 12 valve
 

Red lock tite is what I use but usually I put in billet ones. You could use permatex rated for coolant though.

Re: C20/cummins 12 valve
 

Got the KDP today.

Re: C20/cummins 12 valve
 

Finally moving on the Cummins.
Found a Getrag transmission to go with it.
Got it running on a stand after a few rounds.
Was going to put it in a suburban I found in Portland, Oregon but the guy backed out. Saved me a 2400 mile roadtrip. So the search continues for a c20 suburban.
Injectors keep leaking from the top bolt. I’m going to remove the injectors/clean and torque back to specs, hopefully that fixes the leak.
I’ll try to post a video of it running.
This is what I’ve done:
KDP fixed
New front housing
New vacuum pump
Water pump
Gasket replacements
Thermostat
Crush washers
Oil line for vacuum pump
Throttle rod
Just ordered the fuel pin and 3200 spring from the hungry diesel.

Re: C20/cummins 12 valve
 

Are you sure the return bolts are leaking? Fuel can travel up the body from the nozzle and come out around the retaining nut and make it look like the return line is leaking.

Re: C20/cummins 12 valve
 

I don't think it's the return line. Removed all the injectors today reinstalled them. Looks like that fixed the problem for 3 of them. I can see bubbles around the retaining nut. I torqued them back to 44. I might take it another pound or 2. Hopefully that will fix that issue.

Re: C20/cummins 12 valve
 

The problem isn't the retaining nut torque. Your nozzles are leaking past the threads where the nozzle nut screws on to the body. I'm guessing by the looks of the paint on the body these are used or original to the engine?

Re: C20/cummins 12 valve
 

Cool project and nice longhorn! Are you looking for a suburban in general or one to put the cummins in instead of the longhorn?

Are you going to check your head for cracks? Some of the non IC 6BT's have them.

Re: C20/cummins 12 valve
 

I’m looking for a suburban for it. Cummins engine was going into the C20 but a few members recommended that I keep it all stock, plus the 20 is running. Good suburbans are hard to find. So many scams.

I removed the injectors today and gave them a good cleaning. Hopefully this will fix my leaks.
Attachment 1866320

Attachment 1866321

Re: C20/cummins 12 valve
 

Looks like it worked!!! No more fuel leaks.

Re: C20/cummins 12 valve
 

Worked on the engine today but found another issue.
Looks like oil in my exhaust and all my injectors starting leaking again.
This engine was sitting for 10-15 years. Any suggestions where to start?

Re: C20/cummins 12 valve
 

You just need to get your injectors rebuilt with new nozzles. The are you cleaned is not where the diesel leak is coming from. On the turbo, the turbine shaft seals are more than likely stuck and allowing oil to go past and into the exhaust. That turbo is not that great so if I were you I would just get a new or rebuilt HX35w. It really depends how much you want to spend.

Re: C20/cummins 12 valve
 

I just ordered a new set of injectors from THD.
Will the HX35w be a bolt on or will I need to change some things?

Re: C20/cummins 12 valve
 

The HX35 bolts right on. But, you won't be able to reuse your stock intake cross over without an adapter boot. IMO I'd just put an intercooler on and put a different intake horn on and be done with it.

Re: C20/cummins 12 valve
 

Did a little shopping this morning.
Attachment 1869004

Re: C20/cummins 12 valve
 

Almost got all the parts.Attachment 1869054

Re: C20/cummins 12 valve
 

I think I got everything I will need.
Attachment 1869321

Re: C20/cummins 12 valve
 

How can I make this work?
Attachment 1869486
Do I need to change this wastegate?
Attachment 1869487
Is this the correct way to have it setup?
Attachment 1869488

Re: C20/cummins 12 valve
 

Monte, you have a 2nd gen upper there not a 1st gen style. I have a chrome one I'd sell reasonably. You won't be able to use that 1st gen upper with a 2nd gen intercooler tube so either way you will have to modify something. Either you modify the throttle bracket or you modify/build the intercooler tube. Here's a pic of what a 1st gen intercooled upper intake looks like.

Re: C20/cummins 12 valve
 

Just keep in mind there is really no correct way on what you’re doing, after all a cummins in a c series truck will never be “correct.” Now on that note you can go wrong on things, but as long as you don’t bottle neck the charge coming from the turbo to the intake you’re fine. My setup is an he351 and comes out 2.75” to a 3” pipe, 3” in and out duramax intercooler and then a modified P-pump intake horn. Silicone couplers/boots are available in many different sizes and step ups. I found the p-pump horn with a 24v plenum plate was the easiest way to clear the brake master cylinder.

Re: C20/cummins 12 valve
 

Thanks for the input guys.
I did a little shopping today San Diego and found Getrag speedometer adaptor.
Sucker was hard to find.
Attachment 1875795

Re: C20/cummins 12 valve
 

Then I found this beast!
Attachment 1881635

Attachment 1881636

Re: C20/cummins 12 valve
 

Nice find! Looks like a fun road trip as well.