Cummins 5.9 Pulling Tractor October 16, 2020 10:46AM
I have brought this class up before, but for those who are unfamiliar, see the following list of key rules;

7k and 8k # weight classes
18.4 x 38 Non cut tires
360 in3 limit
3000 RPM limit
Rotary injection pump
Single 3LM466 max turbo size (smaller allowed)
No water injection or intercoolers
No speed limits
Stock intake and exhaust manifolds

We are running a Cummins 5.9 that complies to the rules above. We have improved the fuel system and the turbo, but we are running a totally stock 1990 Cummins 5.9 short block and head.

I am concerned with pre-turbine temperatures, we are seeing 1800 F, so far the turbo is holding up, but we have had head gasket issues immediately under the exhaust ports. The compression rings in the head gasket are holding.

Like everyone I would like more power, but we have maxed out the fuel pump and we are not "rolling coal" so I do not see what we can do differently.

I have been considering the following, but I have concerns that any of them would make a significant difference given the rule limits.

1) Reduce compression by using different pistons or by cutting the existing pistons.

2) Change rocker arm ratios to increase lift and duration using the stock camshaft.

3) Change camshaft .to change lift, duration and overlap.

4) Any other ideas?

From what I have read, given the rule limitations, there is little to be gained by any of these changes in terms of power gain or pre-turbine temperature reduction.

What do the experts on this site believe?


Re: Cummins 5.9 Pulling Tractor October 16, 2020 11:21AM
How bout a shot of H2O?

Re: Cummins 5.9 Pulling Tractor October 16, 2020 12:25PM
What exactly have you done to the fuel system and which turbo are you running? I’m not a fan of 3LM classes, there’s way better Box chargers out there, but is what it is.
What injection pump? VE or Roosamaster? There’s tricks for both.
What injectors? 6x.016” Seemed to be the sweet spot years ago with the rotary pumps.
Timing? A little more with drop EGT’s, but will put more heat on the pistons and increase cylinder pressure which will require some other tricks to keep a head gasket in.

Don’t mess with the rocker arms, lots of good runners out there on stock rocker arms.
A better cam will help more more air and such, not sure if it will drop your temps much. Your running probably at the hottest fuel air ratio right now.

How much power do you think you are making? Track speed? Realistically the rotary pumps don’t fuel well above 3000 rpms anyway. The stock VE with some tweaks and injectors will easily make 360ish HP, more is possible, but takes more to find it.

Re: Cummins 5.9 Pulling Tractor October 16, 2020 12:55PM
I am trying to avoid making this a discussion on the fuel and air systems, they are as good as I can afford.

I am trying to get some insight into engine changes that would benefit the engine from a power and pre-turbine standpoint.


Re: Cummins 5.9 Pulling Tractor October 16, 2020 01:37PM
Do some head work stock heads dont flow crap and get a cam

Edited 1 time(s). Last edit at 10/16/2020 01:39PM by Lewis Conner.

Re: Cummins 5.9 Pulling Tractor October 16, 2020 01:58PM

What cam or whose cam would you suggest?

Re: Cummins 5.9 Pulling Tractor October 16, 2020 02:02PM
Vogel out of Effingham Illinois. Cams are cheap and so is headwork.

Re: Cummins 5.9 Pulling Tractor October 17, 2020 12:32AM
How can you avoid not making this a discussion about fuel and air ? It takes fuel and air to make power ! You are worried about exhaust temps , it takes extra fuel to cool it down ! ( since your not allowed to use water ) putting a bigger cam and doin head work is not goin to work without more fuel .

Re: Cummins 5.9 Pulling Tractor three days ago
Vogel cant do diesel cams for a cummins because of a contract with shied

Re: Cummins 5.9 Pulling Tractor three days ago
Ok then go through schied to get a vogel cam.... I've had others but Vogel is the only one I trust.

Re: Cummins 5.9 Pulling Tractor three days ago
I agree that fuel and air are critically important in this situation, I am saying that what I have is what I have, I am looking for input on things other than fuel and air.

Re: Cummins 5.9 Pulling Tractor three days ago
A camshaft and a light cleanup under the valves

Re: Cummins 5.9 Pulling Tractor three days ago
Head work as well as a cam will lower egts. Valve reliefs for the cam will likely lower your compression ratio enough. It will all help. Get your piston tops ceramic coated. I think there is more then little to gain, people wouldn’t do it if you didn’t gain anything.

Re: Cummins 5.9 Pulling Tractor three days ago
Could you run a AMBAC 100 pump?

Re: Cummins 5.9 Pulling Tractor two days ago
Yes you can run the AMBAC pump, but I am not sure how to adapt it to the Cummins.

Re: Cummins 5.9 Pulling Tractor yesterday, 02:38AM
Call eric at no limit mfg on the cam. His cams are top notch. He has an off the shelf cam that works very well in a 12v. It makes very good power and toque on the dyno also.

Re: Cummins 5.9 Pulling Tractor sixteen hours ago


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