12 Valve Performance Advice

[campbell2j]

I'm a new owner of a used Dodge Cummins diesel pick-up, and a recently inaugurated TDR member. My truck was purchased after I retired so that my wife and I could plan on towing a camper with "diesel ease", however, my first towing experience with the truck left me disappointed. My truck is a 1998 12 valve, long bed, extended cab, 2-wheel drive, automatic transmission model with 135,000 miles. It starts and runs great and transmission seems to shift well and properly. My disappointment comes from my towing an approximately 4000 pound load in mountainous North Carolina terrain, the truck would barely maintain 50 mph on a hill, and that was with the overdrive turned off! I was under the impression that these trucks would literally accelerate up hills while towing a decent load, but not my truck. To my knowledge my truck is completely stock, and based on the appearance of the engine bay, I believe that is correct. Am I expecting way too much of a stock 180 hp/420 ft pounds 1998 12 valve engine????
Thanks to any and all for the advice.

 

[GrantP]

When I bought my 97 I thought it was a dog compared to the powerstroke I owned previously. If you add a fuel plate and 3k governor spring kit it won't defuel so quickly and be around 600 torque very affordably. You'll be shocked at the difference. You'll need to add an EGT gauge so you don't melt a piston while towing...and start saving for a built transmission to handle it.

My guess is that at 50 mph in third you were defueling already, the springs fix that. It's been a long time since I drove a stock 12V but I recall it started falling on it's face around 2300 rpm or so. If you live in an area requiring the "snap idle" emissions test well, let's just say it gets fun with the springs.

 

[campbell2j]

When I bought my 97 I thought it was a dog compared to the powerstroke I owned previously. If you add a fuel plate and 3k governor spring kit it won't defuel so quickly and be around 600 torque very affordably. You'll be shocked at the difference. You'll need to add an EGT gauge so you don't melt a piston while towing...and start saving for a built transmission to handle it.

My guess is that at 50 mph in third you were defueling already, the springs fix that. It's been a long time since I drove a stock 12V but I recall it started falling on it's face around 2300 rpm or so. If you live in an area requiring the "snap idle" emissions test well, let's just say it gets fun with the springs.

Many thanks Grantp, would you advise the #10 fuel plate then?

 

[GrantP]

I went with a #6 but if you're towing regularly I'd do something more conservative, I really had to watch the EGT gauge on long hills when pulling. I think the #10 is a good choice and your trans may live a little longer for it.

Actually, since this is a "new to you" truck do the regular maintenance on it first. There have been many complaints on this forum over the years of poor performance and it just turns out to be a clogged fuel filter. Make sure you have a good baseline and build from there.

 

[crabman]

Installing the #10 plate & spring kit will really wake up the 12V. I suggest you add 2 gauges for sure, EGT & Fuel pressure with optional 3rd, boost pressure. The EGT so that you do not damage engine and the FP which will help you diagnose any problems. I also suggest that you view the following link and print it out to help you with any fueling problems. This link is one of the best explanations for 12V fueling systems.
http://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

 

[campbell2j]

GrantP and crabman
Many thanks for your responses and suggestions. The first thing I did upon taking possession of the truck was new fluids and filters all around, just to establish a maintenance baseline, so the fuel filter SHOULD not be the culprit. I think it will be boost, EGR, and fuel pressure gauges first, then #10 fuel plate, 3k governor springs , and maybe a new adjustable OFV.
Thanks again for your time.

 

[fest3er]

1. Adjust the valves; if they're tight or loose, performance could be adversely affected.
2. Add 8 oz. cetane boost and 8 oz. fuel treatment (like Stanadyne); 40 cetane is really too low.
3. Verify tire pressure is adequate; low pressure is contra-indicated.
4. Verify brakes are not dragging (at least not excessively).
5. Verify torque converter clutch is not slipping. (Going up hill locked in D, RPM shouldn't change as you mash down on the go pedal.)
6. Verify that you get about 18-20 PSI boost at full fueling. (Remember that you will lose a *tad* of power when you push the pedal past the breakover.) If not, you might have a fuel supply problem. Definitely a supply problem if you smell #2 under the hood or see fuel dripping.

If that's all OK, get 1-4 replacement bolts for the AFC housing; at least one is a 'break-off' when cinched down. Then slide the AFC housing full forward, then back, oh, ¼". And twerk it for smoke control from there. That'll be about the best you can do without spending money. If you want more power and no TCC slipage, get your checkbook out. You'll want 215 HP injectors at least, and maybe a better torque plate. There's a good chance the stock TC clutch will slip with the added power, so you may want a better aftermarket TC and valve body.

Oh, you didn't say if you have 3.54 or 4.10 rear gear. I suspect you may have 3.54 if the best you could do going up hill was 40 MPH in D. What's the RPM at 40 with the TC locked? Rule of thumb: you should be able to reach about 70 in D with the TCC engaged (about 3k RPM) with 3.54 rear end. 40 MPH should be around 1700 RPM with 3.54 gear (or about 2k RPM with 4.10 gear).

With the ATS TC and VB, 215HP injectors, 3k GSK, and the AFC housing near full forward, I hauled a 3k-4k# trailer up I70W west from Denver in OD at 70-75 MPH and around 1100-1200° EGT. A few years ago, I put the original 180HP injectors back in while the 215s were being 'freshened up'. The truck was very nearly a dog; I was glad to get the 215s back in. (Oh, mine's a '98 12V, club cab, long bed, auto, 4WD, 315k miles now.)

 

[campbell2j]

Many thanks for all the good advice, fest3er. I addressed all of the maintenance areas before putting the truck on the road, so I should be good to go in that respect. Based on your description of the symptom, I don't believe the TC is/was slipping during my towing event. I can't say what my boost pressure was as I don't have the appropriate gauge installed yet. I have not seen 215hp injectors referenced, I have seen 100hp versions in a lot of discussions, is that how they are specified?. I also was able to find the build sticker under the hood on my truck, it says that I have a Spicer 70 limited slip diff with 3.5 axle ratio, so I would take from that info that I have the 3.54 gearing (which is good because I did not note the rpm's during the hill towing). I consulted with a local diesel speciality shop yesterday and was advised by them that my truck should tow better than I described in stock form, and that they suspect a fuel issue as well, believe I will pursue that and see where it goes.

 

[GrantP]

I have not seen 215hp injectors referenced, I have seen 100hp versions in a lot of discussions, is that how they are specified?.

215 injectors refers to the manual transmission version of your truck rated at 215 hp rather than your 180 hp automatic, they are different injectors. You can make plenty of power with your stock injectors, unless they need replacement I wouldn't worry about them.

 

[campbell2j]

That is great news, GrantP, at this point in the process I'd rather keep it as simple as possible, and not really needing to upgrade the injectors is a very good thing.
Thanks