Engine/Transmission (1994 - 1998) 12V budget power, need help with defueling

[Texas Diesel]

Story: 98 12V 5 speed, wonderful ride. Everyone that drives/rides in it says wow. Son wants to sell his Dakota and buy a 98 12V , a three Cummins family.



Gauges: Oil temp and post turbo pyro mounted in the Jake Brake.



Mods: OEM plate full-forward, AFC housing: full-forward, Star wheel, full forward then back for smoke control, wastegate: doesnt have one, no kitty, no muffler.



Problem: Runs like a scalded dog till 2500RPM then starts to drop off. Has OEM 3k gov springs.



Question: What is making it defuel? Gov springs?

 

[RBratby]

oem gov springs start defueling at about 2200 rpms. put in 3k gsk and you will notice a huge difference in power above 2500 rpm.

 

[Cooker]

Correct. The OEM springs start defueling much sooner than 3k RPM's even though they will rev to 3k you are getting little to no additional fuel after 2500 RPM. It sounds like you need a 3k GSK then you will have full fueling to 3k.

 

[Texas Diesel]

ok, thats what I thought. I dont need heavy exhaust springs with 3k gov springs do I?

 

[EGaskamp]

No you don't need heavier exhaust springs.

 

[Jim Fulmer]

If a guy is on a real tight budget you might try a set of 3K's with that stock plate (ask Piers on this one) I really don't know how it will work with that plate..... something I haven't tried!



Jim

 

[Forrest Nearing]

do the GSK and grind that plate!

 

[Texas Diesel]

need info!! Grind plate???

 

[Howard Durand]

If you are using an exhaust brake you should already have heavy duty exhaust valve springs.

 

[Texas Diesel]

The pacbrake came with a hole drilled in the restrictor plate, the instructions ( I think) said it was ok with OEM springs but if I wanted to block the hole off I had to install HD exhaust springs. Realizing that Cummins increased the size of the cam lobe and tappet (follower or whatever) on the 24V's I wanted to stay away from increasing the stress on the valve train.



ISB upgrades:



"... Wider camshaft lobes and tappet faces as well as longer pushrods reduce valvetrain wear and stress... "



http://www.dodgeram.org/tech/dsl/mt_2_feb98/Cyl_head.htm



Please correct me if I am wrong.

 

[Texas Diesel]

Please correct me if I am wrong.



Anyone disagree? Do I need heavy valve springs?

 

[BV]

Originally posted by Tejas Deezul



Please correct me if I am wrong.



Anyone disagree? Do I need heavy valve springs?

If you want to use the EBrake to it's full potential or install a 4k GSK then you will need the heavy springs.

 

[JohnE]

My contact at Cummins said stock valve springs are good for around 3,600 rpm. Using an exhaust brake should include the heavier springs. As long as you put in heavier springs may as well go for all 12 places.



This is my opinion, but I found a GSK with stock plate is a very poor combination. It put my peak hp at 3,100 which is way above where I want to run. Switched to a #4 plate and all the peaks are in a good range.

 

[BPonci]

Some Pacs have two holes in the valve. One for 60# and both for stock springs. Check the classifieds for plates. The 3k springs are a great add on.

 

[DHorstman]

I installed just the 3K springs for a couple of days. It did make a noticeable difference as far as driveability. Wider rpm band was nice. Then I installed the #6 plate .



So far my stock springs have help 3600 rpm. Although I try to keep it at a max of 32-3300 untill I can install some new valve springs.



Best $300 I've spent so far.