Best year of the 12 valve?

[Marcus2000monster]

So I maybe selling the 24 and buying a 12 valve Cummins in the near future. What is the best year of the 12 valve? Any other tips or advice also appreciated

[Guest 04Mach1]

If you want a 4 door quad cab 1998 is your only option. I've always liked the p7100 6BT the best which you'll find in the 94-98. 

[Dmaney]

Yup the 98 12V quad cab with the 5spd is supposed to be the unicorn truck. Didn't the 97 and 98 have something different done with the injection pumps compared to 94-96? Seems like I remember reading that somewhere.

[GSP7]

I almost bought a nice clean '97 but had 4:10 gear, beige interior, 15 years ago but wanted a quad cab so I then found my 99 with black/dark gray interior

 

I wish I would have bought the 97 too. It was very clean

[Guest 04Mach1]

It feels like the cab of my 97 extended cab is a little more roomy than my 01 quad cab. I've never measured or researched the cab dimensions but it's just the feeling I get when sitting in them  I do know access to the back seat is quite easier in the 01.

[GSP7]

25 minutes ago, 04Mach1 said:

I  I do know access to the back seat is quite easier in the 01. 

 

I most always sit in the front seat while driving

 

 

.

[Guest 04Mach1]

17 minutes ago, GSP7 said:

 

I most always sit in the front seat while driving

 

 

.

I do too however with kids and dogs the backseat of the 01 is much more accessible.

[Mopar1973Man]

On 7/13/2018 at 5:46 PM, Marcus2000monster said:

So I maybe selling the 24 and buying a 12 valve Cummins in the near future

 

I've got to ask why? Why are you willing to give up the 24V for 12V?

 

All I can say is make sure you buy the tools for the p-pump. Timing is rather tough without the dial indicator. Then when there is issues there is no diagnostic port to help you. Yes, I know the 1996 and up have a port but there are no electronics on the engine to help you on diagnostics. 

[Dmaney]

3 hours ago, Mopar1973Man said:

 

I've got to ask why? Why are you willing to give up the 24V for 12V?

Everyone thinks they are more reliable! 

[Mopar1973Man]

31 minutes ago, Dmaney said:

Everyone thinks they are more reliable! 

 

I always loved the comment. But always loved when the 12V craps the bed and leaves them on the side of the road now you guessing.

 

Did it run out of fuel?

Is the lift pump pumping enough pressure?

Did the fuel solenoid burn up?

Is the fuel shutoff arm up or not?

Is the p-pump timing still on or do the gear just slip?

Did the fuel heater just fail and now sucking air?

 

All these questions are my typical checklist for the broke down person along the road. The bad part is most people can't do anything about most of it. Like lift pump problems most people don't install a fuel pressure gauge on a 12V. Fuel solenoid typically a no-brainer but most people don't know it. Then people out here broke down don't have the luxury of waiting days for a quality fuel shutoff solenoid so they get raped by the local part store. Then have guys that think they know how to time the pump end up not getting the nut on tightening and having the gear slip and now stuck in the middle of nowhere.

 

[Guest 04Mach1]

4 hours ago, Dmaney said:

Everyone thinks they are more reliable! 

More reliable is ehhh not so much. The simplicity of the 12 valve is what is sought after. Timing a 6BT engine is very easy especially after you've done it a few times and timing procedures are different according to what CPL the engine is, each CPL has it's own procedure and has a lot to do with the many different cams Cummins used in the 6BT engines. Lets just say the Dodge 6BT is detuned compared to what you would find in the commercial market like school buses and F750 dump trucks, etc... Fuel shut off solenoids don't fail too often that I've noticed. Lift pump issues, well has Cummins ever had a good lift pump? If the fuel heater ever fails on my 97 I will switch it over to either what you would find in the commercial application or an Airdog.

 

As far as timing slipping, use loc-tite retaining compound as Cummins instructions state, it's a common issue for the person winging it without Cummins instructions, once somebody removes the gear from the P7100 and doesn't reapply retaining compound to the gear and non-keyed shaft the fuel pump timing will eventually slip no matter how tight the nut on the end of the P7100 shaft is.

 

My last 6BT rebuild in a  96 F750.

 

 

Edited July 16, 2018 by 04Mach1

[GSP7]

Yeah ,,, those 12 valves suck !

 

 

 

You'all are just being mean and hateful and stuff

 

 

.

Edited July 16, 2018 by GSP7

[Guest 04Mach1]

20 minutes ago, GSP7 said:

Yeah ,,, those 12 valves suck !

 

 

 

You'all are just being mean and hateful and stuff

 

 

.

I wouldn't say they suck. I very much like the 6BT engine because of it's simplicity. Reliability is dependent on the abuse it gets during use and how well it's maintained. You'd be surprised how many people who own a Cummins Dodge don't get simple things like valve adjustments done in the increments Cummins states.  Instead they wait until the engine is mis-firing because the valves are so tight they can't close completely. Or how many starve the fuel pumps and injectors of fuel because they don't change filters regularly and run the tank close to empty all the time.

[Dieselfuture]

6 hours ago, 04Mach1 said:

like valve adjustments done in the increments Cummins states.  Instead they wait until the engine is mis-firing because the valves are so tight they can't close completely.

Could you elaborate more on this please

[Mopar1973Man]

2 hours ago, Dieselfuture said:

Could you elaborate more on this please

 

8 hours ago, 04Mach1 said:

You'd be surprised how many people who own a Cummins Dodge don't get simple things like valve adjustments done in the increments Cummins states.  Instead they wait until the engine is mis-firing because the valves are so tight they can't close completely.

 

In other words. 

 

Intake range is 0.006 to 0.015" Typically set for 0.010"

Exhaust range is 0.015 to 0.030" Typically set for 0.020"

 

To find people that don't know how to properly use a feeler gauge. 

 

Edited July 16, 2018 by Mopar1973Man

[Guest 04Mach1]

5 hours ago, Dieselfuture said:

Could you elaborate more on this please

Valves on solid tappet engines will get tighter from valve stem stretch and the valve beating itself into the head. Stiffer valve springs accelerate this happening. IIRC typical initial valve adjustment should happen around 100,000 miles for Cummins. Failing to adjust valve lash as they get tighter will cause valves to not close all the way usaully accompanied by white smoke and mis-firing.Valve lash getting tighter is normal which is why routine adjustment is required.

 

If valve lash gets looser the likely cause is worn camshaft, bent push tubes, worn tappets, worn rockers, or worn valve bridges all of which are caused by dirty lubricating oil. If valve lash is looser than spec and a recent adjustment hasn't been done further inspection should be done to find what is wearing.

[Dieselfuture]

4 hours ago, 04Mach1 said:

Valves on solid tappet engines will get tighter from valve stem stretch and the valve beating itself into the head. 

Did not know that, I would of thought it would even out with wear and stay same not get tighter

[Guest 04Mach1]

4 hours ago, Dieselfuture said:

Did not know that, I would of thought it would even out with wear and stay same not get tighter

You'll see valve stem stretch the most with new valves. When you hear the term "dropped valve" it's referring to the valve stem or the valve head breaking and the valve head drops into the cylinder which causes expensive damage. 

 

 

 

 

[Dieselfuture]

8 minutes ago, 04Mach1 said:

When you hear the term "dropped valve"

I heard that before but always thought it happened because of wear on keepers or something, didn't think that hard I guess. Thanks for explaining it.

[Guest 04Mach1]

Have another Detroit DD15 with a dropped valve today. This one lost about half of an intake valve head on cylinder 1. Beat the crap out of the piston, caused the cylinder liner to crack, and trashed the turbo on it's way out. Up to about a $15,000 repair as of now. I'll try to remember to get pictures when I pull the piston and liner.

 

Seems like dropped valves are pretty common on EPA13 and GHG17 Detroit Diesel engines. At least the Cummins ISX just eats cams rather than choking on valves.