Jeep Strokers

What are stock 4.0 rods balanced, shot peened, fluxed with ARP bolts good for HP/TQ?

I don't know the numbers but I haven't heard of anyone managing to break a 4.0L rod unless he hydrolocked the engine. They're very strong and 400hp shouldn't be a problem.

Thats good to hear because the 2nd rebuild of this **** due to the cam failure is already eating my budget big time. This rendition of the engine should make someplace near 400 N/A. CNC ported head, solid lifter cam, KB forged pistons, ARP bolts, 8mm valves w beehives, headers, 3" system, 30# injectors, of course a custom tune and other parts. My worry is that I had planned a mild boost setup for the street just to have fun with. I figure the motor 350+ N/A + 7psi should make near 500? thus I dont want to snap the rods like twigs and be doing all this again for a 3rd time.

If they are polished and shot peened properly it will make them stronger, I don't know why everyone is so set on having to have ARP bolts???, the stock bolts are stronger than the rod!, I've NEVER! seen any broken rod bolts (in ANY engine), the rod always fails at the big end between the bolt and the beam.

IH 392 wrote:I don't know why everyone is so set on having to have ARP bolts???

Because they're cheap insurance.

Ok even funnier that you mention the bolts, Titan engines although they failed to setup my head properly (seat pressures over 135 on seat and near 290 open) killing my engine and cam. They did ship the forged piston stroker kit with new 4.0 rods and some brand of bolts (forgot name) that are supposedly just as strong as ARP. In my case I would love not to spend another 400 on rods/bolts etc and risk pressing the bastards off the pistons again. I did have the rods fully shot peened and the entire assy spin balanced during the 1st installation so if I change the rods I would also lose my balancing and have to redo that as well.

Let me answer this question, you guys know my plans and the build specs, would you be comfortable with a properly prepped and balanced set of 4.0 rods in this setup under boost? I dont plan to spin the holy >>>> out of the engine but the cam grind and head should make great power to 6200RPM. Most of its life im certain it will live below 3k, especially once I have the turbo installed as the TQ curve should be more than enough to pass most traffic without even having to lay into it.

I meant to say let me ASK this question of you guys...

And isnt it rod bolt stretch that leads to failure? vs flat out shearing?

superstingray77 wrote:And isnt it rod bolt stretch that leads to failure? vs flat out shearing?

If the bolts are stretched the installer over torqued them in the first place!, the rod will fail before the bolts do, AMC/Jeep 6cylinder rods are cheap cast not forged.
Real high HP engines use "cap screw" rods, they have WAY! more meat in the transition area at the big end than a bolt type rod.
Also real high performance engines (think NASCAR) the bolts aren't torqued at all!, they measure the actual bolt stretch with a dial indicator, the "torque" we're given for production engines is a "general" amount of the actual "stretch" the engineers figure in during the design.