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bent rods again

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Old Nov 6, 2015 | 10:42 AM
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Default bent rods again

Hey guys i took the truck out for a quick hit last night. Ended up spiking 20psi and busting rev limiter 3 times. Pulled over and heard the rods tapping the crank.

Compression test shows 3 rods hurt so far. Would rev limiter hurt rods at that power? Log showed 4 degress knock on 2 rev limiter hits. Ill have it tore down this weekend for more info.
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Old Nov 6, 2015 | 11:52 AM
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Was this the stock PCM rev limiter? Stock PCM pulls fuel and not spark, so that might of made it go lean. Not saying that did the rods in, but probably didn't help the pistons / rings either.
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Old Nov 6, 2015 | 12:23 PM
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Yea stock pcm with hptuners. Dam thing revs so fast its hard to catch a shift just right. May have to go to a higher gear to help. Its currently got 3.73s
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Old Nov 6, 2015 | 12:24 PM
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Wow, I didn't know the stock PCM pulled fuel. That's not good.
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Old Nov 6, 2015 | 01:28 PM
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Not a damn thing wrong with pulling fuel as a rev limiter. Almost every ecu will do this including aftermarket, although they give you the option of fuel, spark or both.

Pulling fuel is a wrong term anyway, it simply doesnt fire the fuel injector for all power cycles in order to control rpm. It doesnt actually reduce the amount of fuel going into the cylinder on any given firing event.
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Old Nov 6, 2015 | 01:39 PM
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Hmmm. Well what would you think the problem could be? Timing was safe at 13°. Also spraying a single nozzle of water meth at 10psi.
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Old Nov 6, 2015 | 01:40 PM
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Iat temp was 105°
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Old Nov 6, 2015 | 01:47 PM
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20psi at what rpm to start? I have bent rods with tractor like torque more then high rpm hp.

Also yes a fuel cut will not hurt anything no reason to change the GM strategy.
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Old Nov 6, 2015 | 01:49 PM
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No idea what the problem or cause is.

Not saying that in some shape or form you hitting the limiter was good....but shutting fuel down is a perfectly normal approach and the very reason OEM's use fuel is so unburnt fuel doesnt get dumped into the catalytic convertors etc.

But even some aftermarket dont like chucking lots of fuel into the cylinder during a limiter either, so even if they have the option of using a spark shutdown, they still choose fuel.
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Old Nov 6, 2015 | 01:51 PM
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Did you pedal it when it hit the limiter? Lot of spark maps leave high timing numbers at low load high rpms. This and lean coditions getting in and out of the throttle can be destructive. The ecu can only correct so fast. If this wasn't the case, than ignore my response.
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Old Nov 6, 2015 | 02:26 PM
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I bent a set of rods last season following a pass that i ran through the traps on the limiter.
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Old Nov 6, 2015 | 02:35 PM
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From the logs it starts making boost around 2800 rpm. So im pretty sure 20psi was around 5k.

I just very well may have pedald it when the limiter hit. The sum bitch popped back so hard it kinda worried me to stay in it lol. I geuss leason learned. Do u think its worth it to throw another set of floating rods in it on the cheap? Pistons should be fine. No specks on plugs. Oil looks good no metal.
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Old Nov 6, 2015 | 02:38 PM
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What plugs and gap do u guys recommend. Ngk br7ef? Limiter was at 6800 by the way. I may move it up to 7400 so im not right at the shift withthe limiter. Thoughts?
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Old Nov 6, 2015 | 02:44 PM
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Gen 3 or 4 rods? My 5.3 lives on a Daily driven diet of 20 lbs and pump gas @ 12 degrees of timing.

Last edited by JoeNova; Nov 6, 2015 at 04:34 PM.
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Old Nov 6, 2015 | 02:51 PM
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Gen 4 rods was in it.
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Old Nov 6, 2015 | 02:56 PM
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I'd set the limiter well above your shift point/trap rpm, 500 rpms or so. It's there in case if a F&@k up during a shift or if something comes apart (like a driveshaft or trans). Avoid hitting the limiter if you can. As far as pedaling it, no reason to just cruising around or racing for that matter unless you REALLY think it's gonna make a difference. If it kills the tires, just let off. Let John Force tear up his parts. Lol!! I cringe every time I see these guy's video of a burnout and they're in and out of the throttle 30 times. Then a week later they wonder why their ***** blown up. But hey whatever, it's their stuff.
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Old Nov 6, 2015 | 03:10 PM
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Well thats the thing the truck has very good suspension. Alot of time and money in it. Caltracs, relocated shocks etc. With a 275 radial outback it will hook up and run from a 30mph dig. Havnt tried from a stop just yet. Its actually hooking and running better than i thought for the power its making on the street. Awesome!!
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Old Nov 7, 2015 | 12:03 AM
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Got it torn down tonight. Rods 7 and 8 were bent pretty bad. 1 and 4 was slightly bent just enough to scuff the bottom of pistons.

Im thinkin if 7 and 8 was bent pretty bad is there a possiblity that those cylinders are hotter as ive always heard of? Coolant steam tubes are blocked at rear only on the front. I may run a 4 corner one this time around. Im also running the tbss intake. I wonder if distribution could be.suffering toward the rear cylinders exspecially on the meth. Thoughts?
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Old Nov 7, 2015 | 08:16 AM
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Are you sure the water/method kit is not the problem and your not on the verge of hydrolocking it? Just a thought
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Old Nov 7, 2015 | 08:26 AM
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Originally Posted by watman02
Are you sure the water/method kit is not the problem and your not on the verge of hydrolocking it? Just a thought
I have seen trucks actually suck water in the intake and hydro lock. It always kills the 7&8 rods first. Ouch!
Attached Thumbnails bent rods again-photo935.jpg   bent rods again-photo63.jpg   bent rods again-photo466.jpg  
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