Redline on 12 valve

[RBrunson]

Do any of you guys have an idea what the bottle neck might be to reaching the redline of 3000 rpm. With auto locked out of overdrive it will go like stink up to 65mph and tac at 2500 rpm and it hits the wall, no more go unless you shift into od. It feels like it could pull a lot more out of it. Only mods are DD #2 fuel plate in stock position AFC forward and K&N.

 

[Todd G]

I would post this in the 12 valve forum first. The governor is what's stopping the revs. You can adjust the high-idle screw for about 500 more rpm's or you can buy the governor spring kit and 60lb. intake and exhaust springs for about 3800 rpm. (much better)

 

[Dieselnerd]

I would almost be willing to bet that your throttle is not opening all the way. Have someone step on the pedal while you watch the linkage. Watching the coil springs behind the bellcrank, they should go all the way to the stop and then the spring goes a little past to ensure WOT. Can be stretched throttle cable or out of adjustment. I had to put a spacer behind my accelerator pedal with the new style cable to get it to open all the way.

 

[MikeR]

Stock truck with the auto? 30lb springs that's all you'll get. For higher RPM call Piers and a get new spring set.

 

[Steve St.Laurent]

Moving to 12v forum for better exposure.

 

[SlyBones]

My 97, stock, would rev to 3000 in third locked on the freeway. Just not real strong. A grade would pull the rev limit down. As the govenor cuts back on the fuel you can watch he boost drop. A little trick Piers told me to watch for. -- Down in the 2200-2300 range I would have full boost and as it revs up there is a point where the truck would still rev, but all of a sudden the boost would start falling off. Thats the govenor kicking in. Never went past 3000, thats the high idle adj limit.



Now of course, it can rev to 3000 and hold full boost the whole way. Another little trick... ...

 

[Dieselnerd]

MikeR, I beg to differ. Mine has always gone up to 3000 RPM both when stock and after modifications. Several friends also go to 3000. My fuel doesn't even start to cut back until about 2650 or so which is apparent on the boost gauge. It does continue to roll and after awhile on a long flat stretch it will get up to 3000 in OD with the pedal to the metal. A good test is to leave the truck in park or neutral and put your foot to the floor to see where your governor is set. It should go to 3000 or very close. Don't worry, it won't over rev. If it doesn't you may still have a throttle that doesn't open all the way. A friends '98 12 valve only revved to 2500 in neutral and while he had his foot to the floor I pushed on his bellcrank and it went to 3000. His was not opening all the way. My throttle did not open all the way when new from the factory and it was the first adjustment I made.

 

[Forrest]

Not all 12 valvers are created equal

My 96 started fueling back at 2300 or so. Thanks to the SOTN, not for very long! Pop out the old governor springs & plop in the SOTN springs & walla, easy reving. I did it for towing, where I wanted more airflow & more fuel in a lower gear for more power & lower EGT. Guess what, it works.

 

[Cooker]

Can we rev these things at 3000 for an extended period of time? What is the safe max RPM for extended periods (several minutes)?



-Ryan

 

[DRR-24V]

I had the identical thing as Dieselnerd. New throttle cable=2500 RPM and with a spacer under the end of the cable it now hits 2800+

 

[Dieselnerd]

Ryan, they will not hurt themselves with the stock governor springs. It's safe to run them all day long with your foot to the floor. That's how they were designed.

 

[drawson]

My truck run real hard right to 2750 and then the power and torque go through the floor. A governer spring kit is in my future.

 

[Josparkz]

revved - out

I hit 2750, and that's it. Revved out. 105 m. ph. in o. d. But I think that is o. k.

 

[MikeR]

Dieselnerd,



Maybe it's because Cummins did something different for '97 and newer,but my stock '95 with 30lb springs can not and will not rev to 3000. there's nothing wrong with the throttle either.

 

[RHARVEY]

I had the lift pump replaced on my 97 a few weeks ago by a Cummins dealer. I know that when its not under load its a different story but when the mech. started the truck to check it out and to check the pump, when he stomped the throttle she spun real quick to 3500 rpms. He didn't hold it there but he did run it up there a couple of times...



Rick

 

[R.ebel]

High Idle

For the '97 model trucks the high idle (no load) setting is 3400 rpm. Under load defueling will start at 2700 rpm

 

[The patriot]

I was curious, so I held it to the floor in 3rd gear today. I got to 3250 rpm. I held it there for about 10 seconds just to be sure it wasnt the needle jumping. It stayed at 3250.

I have never adjusted anything that would effect this.

Oh yea, it starts cutting back fuel at about 2700- 2800 rpm.

Eric