i'm very confused after reading all these threads regarding broken rods. Are the rod failures from running high boost say 6-8# over stock or is it more related to the horsepower level being produced? like is it that they can only handle up to(for example perposes)400rwhp or is it they can only handle up to 15-17lbs of boost? also how does the the boost bypass play into this? some have told me it doesn't do anything except dump boost when you redline doing a burnout other have said it will save your engine when at high boost level...

 

Horsepower matters, Boost is just a measuerment of the cylinder pressure.

 

Actually 'killa...boost is a measure of restriction.

 

Torque is a measurement of the twisting ability of the motor. It comes from the pressure in the combustion chambers times the bore * the bore * stroke. All this load goes thru the rods making its way to the back of the crank.

HP is torque * RPM / 5450 So the higher the RPM that you make this torque, the higher the HP. But you also get a streaching load on the rods as the pistons come up to top dead center between exhaust and intake. This load causes the rods to stretch about .001" for every 1000 RPM.

Note: This is why you should never run the snot out of a motor that has been babied its whole lift. The pistons bounce off the ring ware pattern in the cylinders.

Bottom Line:
The loads on the rods go up with the RPM^2 due to the stretch, They go up linear with the pressure. Also remember, the loads and temps go up huge with detonation.

Hope this helps.

Andy

 

what im trying to figure out is if you run 17# of boost with bare minimum mods(chip) and someone else runs everymod possable but with stock boost(no nos) and you both have the same hp and trq numbers is the more boost more likely to cause the rods to break? what im wondering is do the rods break specifically from high boost or is it a certain hp trq level that the rods can't hold.
is a high boost combo more likely to break a rod, a nos combo with stock boost, or if possable a naturaly aspirated 5.4 l engine more likely to break a rod if they all make the same power and torque and are other wise the same....so confused

 

Possibly, if you rephrase the question........ "Is it the stretch of the rod or the compression of the rod that causes the breakage", you may get a more clear answer. I wonder if oil "windage" contributes to rod failure too?? Whaddaya think guys?

 

If FORD would put good rods in the engines they wouldn't.For an ertra $250 they could make the bottom end of the engine much more solid.The pistons in the L are already forged,just get a set of manley rods or?????????it gets real ugly!!!!!!
Take the engine get ie balanced,your off and running,
J MAN

 

Basically the rods break cause they are junk!!!!

 

They are not junk. The bottom end in these engines is good for 500 HP. You exceed that, you take your chances.

 

Is that 500hp at the flywheel, crank or at the wheels? Remember that the blower eats about 80-100 hp at these HP ranges. The trans eats about 75 hp.

Andy

 

I say freeze them.

http://www.google.com/search?q=cache...operties&hl=en

http://www.cryogenicprocessing.com/

 

Yeah those wimpy rods won't cut it...gotta get those MANLEY rods

Hey SVTbolt......i think i should just freeze the whole truck.....

 

99 SVT Bolt
If you read the sales adds for the cryo process, I think you'll find that it really only works on tool steels or highly alloyed steels.

The lower down the food chain the material is the less effective cryo is. Since our rods are made out of pressed metal particles mixed with a binder, I really don't think it would do any good.
IMHO Dale