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Old 03-14-2018, 03:49 PM   #1
MONTE
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C20/cummins 12 valve

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 donít work. I also found a crack on the housing unit. Would I need to replace it?
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Last edited by MONTE; 03-19-2018 at 07:33 PM.
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Old 03-14-2018, 11:01 PM   #2
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

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Old 03-14-2018, 11:35 PM   #3
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Re: C20/cummins 12 valve

Thanks for the info. Hopefully I can get the correct 1 or get my refund for the pump.
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Old 03-16-2018, 09:20 AM   #4
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Re: C20/cummins 12 valve

Some pics
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Last edited by MONTE; 03-19-2018 at 07:37 PM.
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Old 03-16-2018, 09:26 AM   #5
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Re: C20/cummins 12 valve

more pics
Few upside down, not sure why...
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Last edited by MONTE; 03-19-2018 at 07:30 PM.
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Old 03-19-2018, 07:16 PM   #6
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

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Old 03-19-2018, 07:22 PM   #7
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Re: C20/cummins 12 valve

Im going with the automatic for now until I find a good manual transmission. The truck is a longhorn, it's in great condition.
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Old 03-19-2018, 07:38 PM   #8
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-20-2018, 12:12 AM   #9
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Re: C20/cummins 12 valve

My truck is a big block 402 8 lug, I need to look and see what it has.
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Old 03-24-2018, 10:52 AM   #10
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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.
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Old 03-26-2018, 10:21 PM   #11
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-27-2018, 01:46 AM   #12
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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.
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Old 03-29-2018, 06:04 PM   #13
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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.
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Old 03-29-2018, 06:59 PM   #14
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Re: C20/cummins 12 valve

Quote:
Originally Posted by Peanutbutter View Post
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.
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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-29-2018, 07:02 PM   #15
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Re: C20/cummins 12 valve

Quote:
Originally Posted by MONTE View Post
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.
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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-30-2018, 12:09 AM   #16
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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?
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Old 03-30-2018, 05:13 PM   #17
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Re: C20/cummins 12 valve

Which expansion plugs?
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-30-2018, 06:33 PM   #18
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Re: C20/cummins 12 valve

Core plugs/freeze plugs.
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Old 03-30-2018, 10:45 PM   #19
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 03-31-2018, 09:52 PM   #20
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Re: C20/cummins 12 valve

Got the KDP today.
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Old 01-15-2019, 11:31 PM   #21
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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. Iím going to remove the injectors/clean and torque back to specs, hopefully that fixes the leak.
Iíll try to post a video of it running.
This is what Iíve 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.
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Last edited by MONTE; 01-16-2019 at 01:33 AM.
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Old 01-16-2019, 07:52 PM   #22
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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.
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 01-16-2019, 11:13 PM   #23
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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.
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Old 01-17-2019, 08:32 PM   #24
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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?
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1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread
1976 K30 CC SWB Build Thread

Tired of spark plugs? Check this out.
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Old 01-19-2019, 11:36 AM   #25
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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.
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