6.7 Max RPM

[ALehman]

Does anyone know if a 6. 7 is safe to run over readline and by how much. I personally have taken it to 3500 when horsing around. I figured if its got an exhaust brake it hopefully has heavy valve springs. Any thoughts?

 

[mxaaron]

I'm not sure I understand why you would want to run it over redline. The powercurve flattens out, why would you do that???

 

[HBarlow]

Maximum horsepower is produced at 2900 rpm and falls off beyond that engine speed. Why overrev it?

The ECM will normally limit engine speed to about 3400 rpm.

The Cummins is a long stroke design with relatively heavy rods. It is not a short stroke high revving gas V8. It is possible to destroy it if you severely overrev it.

 

[Tinman]

I have the same question about my 5. 9. With the Smarty, it'll go to 3500. I don't want it to rev that high and I don't intentionally do it. But I just want to be sure that if I'm passing someone and I'm not looking at the gauges and it hits 3500 it's not gonna grenade. I wish I could limit it to 3000 max of engine life. I'm trying to decide if need springs or not.



ALehman: I'd say if your truck is stock, don't worry about it. But don't make a habit of going over 3200.

 

[ALehman]

Yea definitly stock, and don't intend to over rev but there ain't nothing to stop it. I know plenty of stock bottem end 12 valvers running 3200-3800. I mean thats why they put the govener springs and heavy valve springs in. I'm not debating that its not risky but if 12 valvers can do it, the 6. 7 is a lot stronger of a motor, they should be able too. Thats if they have heavy enough valve springs.

 

[MrLuckey]

Maximum horsepower is produced at 2900 rpm and falls off beyond that engine speed. Why overrev it?



The ECM will normally limit engine speed to about 3400 rpm.



The Cummins is a long stroke design with relatively heavy rods. It is not a short stroke high revving gas V8. It is possible to destroy it if you severely overrev it.

Is it really that high Harvey? I've had a long week and am too lazy/tired to check but I 'thought' I'd seen a chart that suggested it dropped off before that. I know mine (with or without smarty) doesn't seem like a happy girl above ~2500 rpm.

 

[DGamelin]

I am not sure about the 6. 7s but the in marine use they spin the 5. 9 up to 5500 RPMs. The grind of the cam is what decides your power band. If you want to spin one more them stock you are going to have go to a different grind cam and valve springs. Or like Harvey says it,s the power is just going to fall off.



_________________________

93 250 2wd xc 354 auto 269k

04. 5 3500 4wd qc dully 373 6speed 94k

 

[Tinman]

The bottom end can take quite a bit. Pullers routinely run up to 4k+ at extreme loads and boost with stock bottom ends. The real question is when springs are needed and perhaps pinning the damper. I do find it odd your stocker will go that high. Stock mine will touch 3500 with no load (floor it in park) but that's with no load or boost so I don't worry about that.



Apparently it's normal:



YouTube - Dodge Cummins 6. 7L - 6 Speed Automatic



For your listening and viewing pleasure:



YouTube - Cummins 4000 RPMs



YouTube - Dodge Cummins 4k 4000 rpm!!!!!!

 

[HBarlow]

Is it really that high Harvey? I've had a long week and am too lazy/tired to check but I 'thought' I'd seen a chart that suggested it dropped off before that. I know mine (with or without smarty) doesn't seem like a happy girl above ~2500 rpm.

Yes, here's the link to the ratings page on the Cummins website:

Cummins Every Time - Dodge Ram - 6. 7L Turbo Diesel

Every Cummins ISB since the 24 valve engines were introduced in late 1998 has had a horsepower band between 1500 or 1600 rpm to 2700 or 2900 rpm and a governed redline of about 3400 rpm.

Edit: Ooops. I opened and read the link I just provided and found I had forgotten. The max hp rpm of the ISB6. 7 installed in pickups is actually 3013 rpm not 2900 as I was thinking I remembered. The Cummins chart also shows that to be governed redline RPM!

The most important number with our Cummins inline six engines is max torque rpm which is 1600 rpm in almost all ratings. The ISB6. 7 in the pickup which produces max torque at 1500 rpm.