Performance mods for a rock buggy? BACK FROM THE DEAD!

[oldestof11]

I would put in at least new headbolts torqued down to 125ft lbs or even 130ft lbs. That should hold.

[PToombs]

Along with a new head gasket!

[Deathrod]

Someone else would probably know better then me....but don't you need #60 lb valve springs to run those high rpms?

[oldestof11]

110.

I can get pictures from a p-pump 12sec drag truck that lost OD and had just 60lbs springs. The exhaust kissed each piston when he revved that motor to 4400 rpms....

[Jeep-hauler]

110.

I can get pictures from a p-pump 12sec drag truck that lost OD and had just 60lbs springs. The exhaust kissed each piston when he revved that motor to 4400 rpms....

110's eh? This could get expensive. Maybe I should just be happy with a 3200 spring until I get it sorted out.

[oldestof11]

Cummins Performance Parts has 110's for just under $500...

[ellis93]

Cummins Performance Parts has 110's for just under $500...

"Just" 500$ huh
You just made that sound like 5$ Jon

[Jeep-hauler]

Cummins Performance Parts has 110's for just under $500...

"Just" 500$ huh
You just made that sound like 5$ Jon

Yeah, pocket change.

I don't know, the 4k spring like a slippery slope. Heavier valve springs, maybe new retainers, might as well buy heavy-duty pushrods while your at it .

How well does the VE fuel at that RPM? Who here is running one?

I think I might take some of the earlier advice and keep it mild at first and see if the drivetrain stays together, then start hot-rodding it.

[PToombs]

With all the torque of a cummins down low, why do you think you need to wind the snot out of it? I understand if you need to stab it quick and get over a rock or something, but I just don't see the need for a 4k rpm truck. That makes things very expensive in a cummins, if you need that kinda rpms, put in a small block chevy or something.

[AHineman]

I agree with Pete. Torque and gearing are where its at. Winding it up that far puts you past your peak for both horsepower and torque anyways.

[oldestof11]

With rock crawling, torque can help getting started in 3rd gear but the quick stab and high RPM's are needed to launch up the rock.

Torque is not going to help climb this wall...

http://www.youtube.com/watch?v=wir8f8KN ... re=related

[Tacoclaw]

You can get wheel speed with gearing, you don't have to wind the engine up that high. It'll be a tough dance to pick the perfect ratio to compliment the Cummins.

[Jeep-hauler]

I don't mind RPM discussion at all. I'm listening to all ideas, that's why I started the thread.

That said, I think gearing is going to be key in making it work. I've ran 4.88 and 5.13:1 ratios in my Jeeps with 35-37" tires, so I'm thinking 4.10's or 4.56 gears with 39-40 tires should work with the Cummins torque.

And I don't wheel like these Southern guys. We call that "rock bouncing" not crawling.

http://www.youtube.com/watch?v=wir8f8KN ... re=related

[oldestof11]

Also, the less gearing in the axles means more torque placed on the trans and transfer case.

I would go 4.56's or 4.88's.

The fact that you have a manual is what is hard. With an auto, you can still have 3 or 4 forward gears with no disconnect of power transmission. With a clutch, if you need another gear, you have to disconnect the engine to get another one...

I would not really do head studs because the gearing will be helping to keep cylinder pressures down.

[Deathrod]

Well whenever you get it done bring it down to the Hammers!!! That body could use a few major dents