Some 1 who knows tell me what is happening to cause or rods to break in our trucks looks like what i have read is 5-7-8 are the 1s that go.AND Detonation

 

Detonation (whether by excessive timing or lean conditions) cause elevated cylinder pressures. These pressures resist the top area of the piston from extending fully to the top of the bore and the excess stress is then transfered to the rod. The rods, being relatively weak powdered metal (sintered) consrtuction experience incressed compressive loading and fail (fracture) as soon at there is a change in angular motion to allow the stress to concentrate at the center of a bending radius of the rod beam.

Or at least that's what I think...

Herb

 

In case you didn't know our connecting rods are LONG. Between detonation, increased boost and hi rpms breakage is inevitable. The fact that they are powdered metal doesn't help either.

 

#7 seems to be the most often one to go (or go first)
I'd say #7, #8, #5 (same order we seem to burn plugs) ???

I was most def 1320 ft away from sending #7 flying myself

Most will agree I took it apart at the right time, prob didn't have another run in it.

BTW
Herb, I am impressed

 

Thanks Rob - experience teaches well, unfortunately!

Herb

 

Rob,

What do you think caused the wear on the bearings? Weak rods had nothing to do with scuffs in the bearings like that, would they? Or were the rods flexing, and thats what caused the scuffs?

I'm wondering if you ran your built motor like you did your stock one (same timing, nitrous, A/F....), Would the same thing have happend to the new bearings?

 

Long arm (stroke) motors traditionally do not like a lot of RPM.
They make good torque but it is a trade off.

 

Increased cylinder pressure caused from more boost/nitrous in the cylinder will do that. Another thing is that our motors aren't built very tight from the factory. I bet in Robs case it was the timing he was running.

 

my 2-6-7-8 all went out to lunch
and yeah the rod only has one place to go when the piston cant go any farther up the cylinder
also i think with the increse in pressure the piston can **** in the cylinder and well we know what happens after that

 

Good reading guys thanks ,so if i reading everything right if i dont hammer the truck with the kennebell on it should last me til i get my bottom end built.Or just buy 1.

 

This confuses me. Boss330 Has a 4v 5.4 that he revs to 7k I belive with no problems.

 

I agree

Sharpshooter

Unfortunately another known issue with our stock motor is not enough oil getting to the #7 journal, most say it's due to design,
"and" the oil pump. I had some Crank work done, and we used a high vol and diff oil pump in my case.....

 

Couple things I don't like from a detonation standpoint on these Gen 2s.
People don't seem to question the octane!
Folks it's not a constant just cause the sticker on the pump says 93 octane.

Also, These heads have sharp corners from the machining done. Those sharp edged are nothing but a detriment to high combustion temps and detonation.

Rich

 

Will a high volume oil pan help in that matter? Such as a Moroso pan with baffles installed.

TB

 

ditto...... octane is #1.


Whitelighting I am that some 1....... whats happening to cause our rods to break is we mod the hell out of our trucks.

"nothing" will cause your rods to break if you dont mod your truck and you run the correct octane.....

of course 99% of us mod our engines (except for Tim I cant afford a built lower end Skelton ) so I'm sure your modded. Save up for a built lower end and you wont have to worry about those rods anymore.